remove incomplete union mounts / jffs2 patches. will be replaced by updated versions once they're ready - should fix #6375

SVN-Revision: 18822

target/linux/generic-2.6/patches-2.6.31/230-union_mounts.patch

@@ -1,5203 +0,0 @@
---- /dev/null
-+++ b/Documentation/filesystems/union-mounts.txt
-@@ -0,0 +1,187 @@
-+VFS based Union Mounts
-+----------------------
-+
-+ 1. What are "Union Mounts"
-+ 2. The Union Stack
-+ 3. Whiteouts, Opaque Directories, and Fallthrus
-+ 4. Copy-up
-+ 5. Directory Reading
-+ 6. Known Problems
-+ 7. References
-+
-+-------------------------------------------------------------------------------
-+
-+1. What are "Union Mounts"
-+==========================
-+
-+Please note: this is NOT about UnionFS and it is NOT derived work!
-+
-+Traditionally the mount operation is opaque, which means that the content of
-+the mount point, the directory where the file system is mounted on, is hidden
-+by the content of the mounted file system's root directory until the file
-+system is unmounted again. Unlike the traditional UNIX mount mechanism, that
-+hides the contents of the mount point, a union mount presents a view as if
-+both filesystems are merged together. Although only the topmost layer of the
-+mount stack can be altered, it appears as if transparent file system mounts
-+allow any file to be created, modified or deleted.
-+
-+Most people know the concepts and features of union mounts from other
-+operating systems like Sun's Translucent Filesystem, Plan9 or BSD. For an
-+in-depth review of union mounts and other unioning file systems, see:
-+
-+http://lwn.net/Articles/324291/
-+http://lwn.net/Articles/325369/
-+http://lwn.net/Articles/327738/
-+
-+Here are the key features of this implementation:
-+- completely VFS based
-+- does not change the namespace stacking
-+- directory listings have duplicate entries removed in the kernel
-+- writable unions: only the topmost file system layer may be writable
-+- writable unions: new whiteout filetype handled inside the kernel
-+
-+-------------------------------------------------------------------------------
-+
-+2. The Union Stack
-+==================
-+
-+The mounted file systems are organized in the "file system hierarchy" (tree of
-+vfsmount structures), which keeps track about the stacking of file systems
-+upon each other. The per-directory view on the file system hierarchy is called
-+"mount stack" and reflects the order of file systems, which are mounted on a
-+specific directory.
-+
-+Union mounts present a single unified view of the contents of two or more file
-+systems as if they are merged together. Since the information which file
-+system objects are part of a unified view is not directly available from the
-+file system hierarchy there is a need for a new structure. The file system
-+objects, which are part of a unified view are ordered in a so-called "union
-+stack". Only directories can be part of a unified view.
-+
-+The link between two layers of the union stack is maintained using the
-+union_mount structure (#include <linux/union.h>):
-+
-+struct union_mount {
-+       atomic_t u_count;               /* reference count */
-+       struct mutex u_mutex;
-+       struct list_head u_unions;      /* list head for d_unions */
-+       struct hlist_node u_hash;       /* list head for searching */
-+       struct hlist_node u_rhash;      /* list head for reverse searching */
-+
-+       struct path u_this;             /* this is me */
-+       struct path u_next;             /* this is what I overlay */
-+};
-+
-+The union_mount structure holds a reference (dget,mntget) to the next lower
-+layer of the union stack. Since a dentry can be part of multiple unions
-+(e.g. with bind mounts) they are tied together via the d_unions field of the
-+dentry structure.
-+
-+All union_mount structures are cached in two hash tables, one for lookups of
-+the next lower layer of the union stack and one for reverse lookups of the
-+next upper layer of the union stack. The reverse lookup is necessary to
-+resolve CWD relative path lookups. For calculation of the hash value, the
-+(dentry,vfsmount) pair is used. The u_this field is used for the hash table
-+which is used in forward lookups and the u_next field for the reverse lookups.
-+
-+During every new mount (or mount propagation), a new union_mount structure is
-+allocated. A reference to the mountpoint's vfsmount and dentry is taken and
-+stored in the u_next field.  In almost the same manner an union_mount
-+structure is created during the first time lookup of a directory within a
-+union mount point. In this case the lookup proceeds to all lower layers of the
-+union. Therefore the complete union stack is constructed during lookups.
-+
-+The union_mount structures of a dentry are destroyed when the dentry itself is
-+destroyed. Therefore the dentry cache is indirectly driving the union_mount
-+cache like this is done for inodes too. Please note that lower layer
-+union_mount structures are kept in memory until the topmost dentry is
-+destroyed.
-+
-+-------------------------------------------------------------------------------
-+
-+3. Whiteouts, Opaque Directories, and Fallthrus
-+===========================================================
-+
-+The whiteout filetype isn't new. It has been there for quite some time now
-+but Linux's VFS hasn't used it yet. With the availability of union mount code
-+inside the VFS the whiteout filetype is getting important to support writable
-+union mounts. For read-only union mounts, support for whiteouts or
-+copy-on-open is not necessary.
-+
-+The whiteout filetype has the same function as negative dentries: they
-+describe a filename which isn't there. The creation of whiteouts needs
-+lowlevel filesystem support. At the time of writing this, there is whiteout
-+support for tmpfs, ext2 and ext3 available. The VFS is extended to make the
-+whiteout handling transparent to all its users. The whiteouts are not
-+visible to user-space.
-+
-+What happens when we create a directory that was previously whited-out? We
-+don't want the directory entries from underlying filesystems to suddenly appear
-+in the newly created directory.  So we mark the directory opaque (the file
-+system must support storage of the opaque flag).
-+
-+Fallthrus are directory entries that override the opaque flag on a directory
-+for that specific directory entry name (the lookup "falls through" to the next
-+layer of the union mount).  Fallthrus are mainly useful for implementing
-+readdir().
-+
-+-------------------------------------------------------------------------------
-+
-+4. Copy-up
-+===========
-+
-+Any write to an object on any layer other than the topmost triggers a copy-up
-+of the object to the topmost file system. For regular files, the copy-up
-+happens when it is opened in writable mode.
-+
-+Directories are copied up on open, regardless of intent to write, to simplify
-+copy-up of any object located below it in the namespace. Otherwise we have to
-+walk the entire pathname to create intermediate directories whenever we do a
-+copy-up. This is the same approach as BSD union mounts and uses a negigible
-+amount of disk space.  Note that the actual directory entries themselves are
-+not copied-up from the lower levels until (a) the directory is written to, or
-+(b) the first readdir() of the directory (more on that later).
-+
-+Rename across different levels of the union is implemented as a copy-up
-+operation for regular files. Rename of directories simply returns EXDEV, the
-+same as if we tried to rename across different mounts. Most applications have
-+to handle this case anyway. Some applications do not expect EXDEV on
-+rename operations within the same directory, but these applications will also
-+be broken with bind mounts.
-+
-+-------------------------------------------------------------------------------
-+
-+5. Directory Reading
-+====================
-+
-+readdir() is somewhat difficult to implement in a unioning file system. We must
-+eliminate duplicates, apply whiteouts, and start up readdir() where we left
-+off, given a single f_pos value. Our solution is to copy up all the directory
-+entries to the topmost directory the first time readdir() is called on a
-+directory. During this copy-up, we skip duplicates and entries covered by
-+whiteouts, and then create fallthru entries for each remaining visible dentry.
-+Then we mark the whole directory opaque. From then on, we just use the topmost
-+file system's normal readdir() operation.
-+
-+-------------------------------------------------------------------------------
-+
-+6. Known Problems
-+=================
-+
-+- copyup() for other filetypes that reg and dir (e.g. for chown() on devices)
-+- symlinks are untested
-+
-+-------------------------------------------------------------------------------
-+
-+7. References
-+=============
-+
-+[1] http://marc.info/?l=linux-fsdevel&m=96035682927821&w=2
-+[2] http://marc.info/?l=linux-fsdevel&m=117681527820133&w=2
-+[3] http://marc.info/?l=linux-fsdevel&m=117913503200362&w=2
-+[4] http://marc.info/?l=linux-fsdevel&m=118231827024394&w=2
-+
-+Authors:
-+Jan Blunck <[email protected]>
-+Bharata B Rao <[email protected]>
-+Valerie Aurora <[email protected]>
---- a/fs/autofs4/autofs_i.h
-+++ b/fs/autofs4/autofs_i.h
-@@ -130,6 +130,7 @@ struct autofs_sb_info {
- 	int reghost_enabled;
- 	int needs_reghost;
- 	struct super_block *sb;
-+	struct vfsmount *mnt;
- 	struct mutex wq_mutex;
- 	spinlock_t fs_lock;
- 	struct autofs_wait_queue *queues; /* Wait queue pointer */
---- a/fs/autofs4/init.c
-+++ b/fs/autofs4/init.c
-@@ -17,7 +17,16 @@
- static int autofs_get_sb(struct file_system_type *fs_type,
- 	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
- {
--	return get_sb_nodev(fs_type, flags, data, autofs4_fill_super, mnt);
-+	struct autofs_sb_info *sbi;
-+	int ret;
-+
-+	ret = get_sb_nodev(fs_type, flags, data, autofs4_fill_super, mnt);
-+	if (ret)
-+		return ret;
-+
-+	sbi = autofs4_sbi(mnt->mnt_sb);
-+	sbi->mnt = mnt;
-+	return 0;
- }
- 
- static struct file_system_type autofs_fs_type = {
---- a/fs/autofs4/root.c
-+++ b/fs/autofs4/root.c
-@@ -179,6 +179,12 @@ static void *autofs4_follow_link(struct 
- 	DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d",
- 		dentry, dentry->d_name.len, dentry->d_name.name, oz_mode,
- 		nd->flags);
-+
-+	dput(nd->path.dentry);
-+	mntput(nd->path.mnt);
-+	nd->path.mnt = mntget(sbi->mnt);
-+	nd->path.dentry = dget(dentry);
-+
- 	/*
- 	 * For an expire of a covered direct or offset mount we need
- 	 * to break out of follow_down() at the autofs mount trigger
---- a/fs/compat.c
-+++ b/fs/compat.c
-@@ -847,6 +847,9 @@ static int compat_fillonedir(void *__buf
- 	struct compat_old_linux_dirent __user *dirent;
- 	compat_ulong_t d_ino;
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	if (buf->result)
- 		return -EINVAL;
- 	d_ino = ino;
-@@ -918,6 +921,9 @@ static int compat_filldir(void *__buf, c
- 	compat_ulong_t d_ino;
- 	int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 2, sizeof(compat_long_t));
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	buf->error = -EINVAL;	/* only used if we fail.. */
- 	if (reclen > buf->count)
- 		return -EINVAL;
-@@ -1007,6 +1013,9 @@ static int compat_filldir64(void * __buf
- 	int reclen = ALIGN(jj + namlen + 1, sizeof(u64));
- 	u64 off;
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	buf->error = -EINVAL;	/* only used if we fail.. */
- 	if (reclen > buf->count)
- 		return -EINVAL;
---- a/fs/dcache.c
-+++ b/fs/dcache.c
-@@ -18,6 +18,7 @@
- #include <linux/string.h>
- #include <linux/mm.h>
- #include <linux/fs.h>
-+#include <linux/union.h>
- #include <linux/fsnotify.h>
- #include <linux/slab.h>
- #include <linux/init.h>
-@@ -157,14 +158,19 @@ static void dentry_lru_del_init(struct d
- }
- 
- /**
-- * d_kill - kill dentry and return parent
-+ * __d_kill - kill dentry and return parent
-  * @dentry: dentry to kill
-+ * @list: kill list
-+ * @greedy: return parent instead of putting it on the kill list
-  *
-  * The dentry must already be unhashed and removed from the LRU.
-  *
-- * If this is the root of the dentry tree, return NULL.
-+ * If this is the root of the dentry tree, return NULL. If greedy is zero, we
-+ * put the parent of this dentry on the kill list instead. The callers must
-+ * make sure that __d_kill_final() is called on all dentries on the kill list.
-  */
--static struct dentry *d_kill(struct dentry *dentry)
-+static struct dentry *__d_kill(struct dentry *dentry, struct list_head *list,
-+			       int greedy)
- 	__releases(dentry->d_lock)
- 	__releases(dcache_lock)
- {
-@@ -172,13 +178,78 @@ static struct dentry *d_kill(struct dent
- 
- 	list_del(&dentry->d_u.d_child);
- 	dentry_stat.nr_dentry--;	/* For d_free, below */
--	/*drops the locks, at that point nobody can reach this dentry */
-+
-+	/*
-+	 * If we are not greedy we just put this on a list for later processing
-+	 * (follow up to parent, releasing of inode and freeing dentry memory).
-+	 */
-+	if (!greedy) {
-+		list_del_init(&dentry->d_alias);
-+		/* at this point nobody can reach this dentry */
-+		list_add(&dentry->d_lru, list);
-+		spin_unlock(&dentry->d_lock);
-+		spin_unlock(&dcache_lock);
-+		__shrink_d_unions(dentry, list);
-+		return NULL;
-+	}
-+
-+	/* drops the locks, at that point nobody can reach this dentry */
- 	dentry_iput(dentry);
-+	/* If the dentry was in an union delete them */
-+	__shrink_d_unions(dentry, list);
-+	if (IS_ROOT(dentry))
-+		parent = NULL;
-+	else
-+		parent = dentry->d_parent;
-+	d_free(dentry);
-+	return parent;
-+}
-+
-+void __dput(struct dentry *, struct list_head *, int);
-+
-+static void __d_kill_final(struct dentry *dentry, struct list_head *list)
-+{
-+	struct dentry *parent;
-+	struct inode *inode = dentry->d_inode;
-+
-+	if (inode) {
-+		dentry->d_inode = NULL;
-+		if (!inode->i_nlink)
-+			fsnotify_inoderemove(inode);
-+		if (dentry->d_op && dentry->d_op->d_iput)
-+			dentry->d_op->d_iput(dentry, inode);
-+		else
-+			iput(inode);
-+	}
-+
- 	if (IS_ROOT(dentry))
- 		parent = NULL;
- 	else
- 		parent = dentry->d_parent;
- 	d_free(dentry);
-+	__dput(parent, list, 1);
-+}
-+
-+/**
-+ * d_kill - kill dentry and return parent
-+ * @dentry: dentry to kill
-+ *
-+ * The dentry must already be unhashed and removed from the LRU.
-+ *
-+ * If this is the root of the dentry tree, return NULL.
-+ */
-+static struct dentry *d_kill(struct dentry *dentry)
-+{
-+	LIST_HEAD(mortuary);
-+	struct dentry *parent;
-+
-+	parent = __d_kill(dentry, &mortuary, 1);
-+	while (!list_empty(&mortuary)) {
-+		dentry = list_entry(mortuary.next, struct dentry, d_lru);
-+		list_del(&dentry->d_lru);
-+		__d_kill_final(dentry, &mortuary);
-+	}
-+
- 	return parent;
- }
- 
-@@ -199,19 +270,24 @@ static struct dentry *d_kill(struct dent
-  * Real recursion would eat up our stack space.
-  */
- 
--/*
-- * dput - release a dentry
-- * @dentry: dentry to release 
-+/**
-+ * __dput - release a dentry
-+ * @dentry: dentry to release
-+ * @list: kill list argument for __d_kill()
-+ * @greedy: greedy argument for __d_kill()
-  *
-  * Release a dentry. This will drop the usage count and if appropriate
-  * call the dentry unlink method as well as removing it from the queues and
-  * releasing its resources. If the parent dentries were scheduled for release
-- * they too may now get deleted.
-+ * they too may now get deleted if @greedy is not zero. Otherwise parent is
-+ * added to the kill list. The callers must make sure that __d_kill_final() is
-+ * called on all dentries on the kill list.
-+ *
-+ * You probably want to use dput() instead.
-  *
-  * no dcache lock, please.
-  */
--
--void dput(struct dentry *dentry)
-+void __dput(struct dentry *dentry, struct list_head *list, int greedy)
- {
- 	if (!dentry)
- 		return;
-@@ -252,12 +328,35 @@ unhash_it:
- kill_it:
- 	/* if dentry was on the d_lru list delete it from there */
- 	dentry_lru_del(dentry);
--	dentry = d_kill(dentry);
-+	dentry = __d_kill(dentry, list, greedy);
- 	if (dentry)
- 		goto repeat;
- }
- 
- /**
-+ * dput - release a dentry
-+ * @dentry: dentry to release
-+ *
-+ * Release a dentry. This will drop the usage count and if appropriate
-+ * call the dentry unlink method as well as removing it from the queues and
-+ * releasing its resources. If the parent dentries were scheduled for release
-+ * they too may now get deleted.
-+ *
-+ * no dcache lock, please.
-+ */
-+void dput(struct dentry *dentry)
-+{
-+	LIST_HEAD(mortuary);
-+
-+	__dput(dentry, &mortuary, 1);
-+	while (!list_empty(&mortuary)) {
-+		dentry = list_entry(mortuary.next, struct dentry, d_lru);
-+		list_del(&dentry->d_lru);
-+		__d_kill_final(dentry, &mortuary);
-+	}
-+}
-+
-+/**
-  * d_invalidate - invalidate a dentry
-  * @dentry: dentry to invalidate
-  *
-@@ -689,6 +788,7 @@ static void shrink_dcache_for_umount_sub
- 					iput(inode);
- 			}
- 
-+			shrink_d_unions(dentry);
- 			d_free(dentry);
- 
- 			/* finished when we fall off the top of the tree,
-@@ -951,6 +1051,10 @@ struct dentry *d_alloc(struct dentry * p
- 	INIT_LIST_HEAD(&dentry->d_lru);
- 	INIT_LIST_HEAD(&dentry->d_subdirs);
- 	INIT_LIST_HEAD(&dentry->d_alias);
-+#ifdef CONFIG_UNION_MOUNT
-+	INIT_LIST_HEAD(&dentry->d_unions);
-+	dentry->d_unionized = 0;
-+#endif
- 
- 	if (parent) {
- 		dentry->d_parent = dget(parent);
-@@ -981,8 +1085,10 @@ struct dentry *d_alloc_name(struct dentr
- /* the caller must hold dcache_lock */
- static void __d_instantiate(struct dentry *dentry, struct inode *inode)
- {
--	if (inode)
-+	if (inode) {
-+		dentry->d_flags &= ~(DCACHE_WHITEOUT|DCACHE_FALLTHRU);
- 		list_add(&dentry->d_alias, &inode->i_dentry);
-+	}
- 	dentry->d_inode = inode;
- 	fsnotify_d_instantiate(dentry, inode);
- }
-@@ -1513,7 +1619,9 @@ void d_delete(struct dentry * dentry)
- 	spin_lock(&dentry->d_lock);
- 	isdir = S_ISDIR(dentry->d_inode->i_mode);
- 	if (atomic_read(&dentry->d_count) == 1) {
-+		__d_drop_unions(dentry);
- 		dentry_iput(dentry);
-+		shrink_d_unions(dentry);
- 		fsnotify_nameremove(dentry, isdir);
- 		return;
- 	}
-@@ -1524,14 +1632,14 @@ void d_delete(struct dentry * dentry)
- 	spin_unlock(&dentry->d_lock);
- 	spin_unlock(&dcache_lock);
- 
-+	shrink_d_unions(dentry);
- 	fsnotify_nameremove(dentry, isdir);
- }
- 
- static void __d_rehash(struct dentry * entry, struct hlist_head *list)
- {
--
-- 	entry->d_flags &= ~DCACHE_UNHASHED;
-- 	hlist_add_head_rcu(&entry->d_hash, list);
-+	entry->d_flags &= ~DCACHE_UNHASHED;
-+	hlist_add_head_rcu(&entry->d_hash, list);
- }
- 
- static void _d_rehash(struct dentry * entry)
-@@ -1550,6 +1658,7 @@ void d_rehash(struct dentry * entry)
- {
- 	spin_lock(&dcache_lock);
- 	spin_lock(&entry->d_lock);
-+	BUG_ON(!d_unhashed(entry));
- 	_d_rehash(entry);
- 	spin_unlock(&entry->d_lock);
- 	spin_unlock(&dcache_lock);
-@@ -2182,7 +2291,9 @@ resume:
- 		struct list_head *tmp = next;
- 		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
- 		next = tmp->next;
--		if (d_unhashed(dentry)||!dentry->d_inode)
-+		if (d_unhashed(dentry)||(!dentry->d_inode &&
-+					 !d_is_whiteout(dentry) &&
-+					 !d_is_fallthru(dentry)))
- 			continue;
- 		if (!list_empty(&dentry->d_subdirs)) {
- 			this_parent = dentry;
---- a/fs/ext2/dir.c
-+++ b/fs/ext2/dir.c
-@@ -219,7 +219,8 @@ static inline int ext2_match (int len, c
- {
- 	if (len != de->name_len)
- 		return 0;
--	if (!de->inode)
-+	if (!de->inode && ((de->file_type != EXT2_FT_WHT) &&
-+			   (de->file_type != EXT2_FT_FALLTHRU)))
- 		return 0;
- 	return !memcmp(name, de->name, len);
- }
-@@ -255,6 +256,8 @@ static unsigned char ext2_filetype_table
- 	[EXT2_FT_FIFO]		= DT_FIFO,
- 	[EXT2_FT_SOCK]		= DT_SOCK,
- 	[EXT2_FT_SYMLINK]	= DT_LNK,
-+	[EXT2_FT_WHT]		= DT_WHT,
-+	[EXT2_FT_FALLTHRU]	= DT_UNKNOWN,
- };
- 
- #define S_SHIFT 12
-@@ -341,6 +344,18 @@ ext2_readdir (struct file * filp, void *
- 					ext2_put_page(page);
- 					return 0;
- 				}
-+			} else if (de->file_type == EXT2_FT_FALLTHRU) {
-+				int over;
-+				unsigned char d_type = DT_UNKNOWN;
-+
-+				offset = (char *)de - kaddr;
-+				over = filldir(dirent, de->name, de->name_len,
-+						(n<<PAGE_CACHE_SHIFT) | offset,
-+						123, d_type);
-+				if (over) {
-+					ext2_put_page(page);
-+					return 0;
-+				}
- 			}
- 			filp->f_pos += ext2_rec_len_from_disk(de->rec_len);
- 		}
-@@ -448,6 +463,30 @@ ino_t ext2_inode_by_name(struct inode *d
- 	return res;
- }
- 
-+/* Special version for filetype based whiteout support */
-+ino_t ext2_inode_by_dentry(struct inode *dir, struct dentry *dentry)
-+{
-+	ino_t res = 0;
-+	struct ext2_dir_entry_2 *de;
-+	struct page *page;
-+
-+	de = ext2_find_entry (dir, &dentry->d_name, &page);
-+	if (de) {
-+		res = le32_to_cpu(de->inode);
-+		if (!res && de->file_type == EXT2_FT_WHT) {
-+			spin_lock(&dentry->d_lock);
-+			dentry->d_flags |= DCACHE_WHITEOUT;
-+			spin_unlock(&dentry->d_lock);
-+		} else if(!res && de->file_type == EXT2_FT_FALLTHRU) {
-+			spin_lock(&dentry->d_lock);
-+			dentry->d_flags |= DCACHE_FALLTHRU;
-+			spin_unlock(&dentry->d_lock);
-+		}
-+		ext2_put_page(page);
-+	}
-+	return res;
-+}
-+
- /* Releases the page */
- void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
- 		   struct page *page, struct inode *inode, int update_times)
-@@ -472,9 +511,10 @@ void ext2_set_link(struct inode *dir, st
- }
- 
- /*
-- *	Parent is locked.
-+ * Find or append a given dentry to the parent directory
-  */
--int ext2_add_link (struct dentry *dentry, struct inode *inode)
-+static ext2_dirent * ext2_append_entry(struct dentry * dentry,
-+				       struct page ** page)
- {
- 	struct inode *dir = dentry->d_parent->d_inode;
- 	const char *name = dentry->d_name.name;
-@@ -482,13 +522,10 @@ int ext2_add_link (struct dentry *dentry
- 	unsigned chunk_size = ext2_chunk_size(dir);
- 	unsigned reclen = EXT2_DIR_REC_LEN(namelen);
- 	unsigned short rec_len, name_len;
--	struct page *page = NULL;
--	ext2_dirent * de;
-+	ext2_dirent * de = NULL;
- 	unsigned long npages = dir_pages(dir);
- 	unsigned long n;
- 	char *kaddr;
--	loff_t pos;
--	int err;
- 
- 	/*
- 	 * We take care of directory expansion in the same loop.
-@@ -498,55 +535,97 @@ int ext2_add_link (struct dentry *dentry
- 	for (n = 0; n <= npages; n++) {
- 		char *dir_end;
- 
--		page = ext2_get_page(dir, n, 0);
--		err = PTR_ERR(page);
--		if (IS_ERR(page))
-+		*page = ext2_get_page(dir, n, 0);
-+		de = ERR_PTR(PTR_ERR(*page));
-+		if (IS_ERR(*page))
- 			goto out;
--		lock_page(page);
--		kaddr = page_address(page);
-+		lock_page(*page);
-+		kaddr = page_address(*page);
- 		dir_end = kaddr + ext2_last_byte(dir, n);
- 		de = (ext2_dirent *)kaddr;
- 		kaddr += PAGE_CACHE_SIZE - reclen;
- 		while ((char *)de <= kaddr) {
- 			if ((char *)de == dir_end) {
- 				/* We hit i_size */
--				name_len = 0;
--				rec_len = chunk_size;
-+				de->name_len = 0;
- 				de->rec_len = ext2_rec_len_to_disk(chunk_size);
- 				de->inode = 0;
-+				de->file_type = 0;
- 				goto got_it;
- 			}
- 			if (de->rec_len == 0) {
- 				ext2_error(dir->i_sb, __func__,
- 					"zero-length directory entry");
--				err = -EIO;
-+				de = ERR_PTR(-EIO);
- 				goto out_unlock;
- 			}
--			err = -EEXIST;
- 			if (ext2_match (namelen, name, de))
--				goto out_unlock;
-+				goto got_it;
- 			name_len = EXT2_DIR_REC_LEN(de->name_len);
- 			rec_len = ext2_rec_len_from_disk(de->rec_len);
--			if (!de->inode && rec_len >= reclen)
-+			if (!de->inode && (de->file_type != EXT2_FT_WHT) &&
-+			    (de->file_type != EXT2_FT_FALLTHRU) &&
-+			    (rec_len >= reclen))
- 				goto got_it;
- 			if (rec_len >= name_len + reclen)
- 				goto got_it;
- 			de = (ext2_dirent *) ((char *) de + rec_len);
- 		}
--		unlock_page(page);
--		ext2_put_page(page);
-+		unlock_page(*page);
-+		ext2_put_page(*page);
- 	}
-+
- 	BUG();
--	return -EINVAL;
- 
- got_it:
-+	return de;
-+	/* OFFSET_CACHE */
-+out_unlock:
-+	unlock_page(*page);
-+	ext2_put_page(*page);
-+out:
-+	return de;
-+}
-+
-+/*
-+ *	Parent is locked.
-+ */
-+int ext2_add_link (struct dentry *dentry, struct inode *inode)
-+{
-+	struct inode *dir = dentry->d_parent->d_inode;
-+	const char *name = dentry->d_name.name;
-+	int namelen = dentry->d_name.len;
-+	unsigned short rec_len, name_len;
-+	ext2_dirent * de;
-+	struct page *page;
-+	loff_t pos;
-+	int err;
-+
-+	de = ext2_append_entry(dentry, &page);
-+	if (IS_ERR(de))
-+		return PTR_ERR(de);
-+
-+	err = -EEXIST;
-+	if (ext2_match (namelen, name, de)) {
-+		if ((de->file_type == EXT2_FT_WHT) ||
-+		    (de->file_type == EXT2_FT_FALLTHRU))
-+			goto got_it;
-+		goto out_unlock;
-+	}
-+
-+got_it:
-+	name_len = EXT2_DIR_REC_LEN(de->name_len);
-+	rec_len = ext2_rec_len_from_disk(de->rec_len);
-+
- 	pos = page_offset(page) +
- 		(char*)de - (char*)page_address(page);
- 	err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
- 							&page, NULL);
- 	if (err)
- 		goto out_unlock;
--	if (de->inode) {
-+	if (de->inode || (((de->file_type == EXT2_FT_WHT) ||
-+			   (de->file_type == EXT2_FT_FALLTHRU)) &&
-+			  !ext2_match (namelen, name, de))) {
- 		ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
- 		de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
- 		de->rec_len = ext2_rec_len_to_disk(name_len);
-@@ -563,7 +642,60 @@ got_it:
- 	/* OFFSET_CACHE */
- out_put:
- 	ext2_put_page(page);
--out:
-+	return err;
-+out_unlock:
-+	unlock_page(page);
-+	goto out_put;
-+}
-+
-+/*
-+ * Create a fallthru entry.
-+ */
-+int ext2_fallthru_entry (struct inode *dir, struct dentry *dentry)
-+{
-+	const char *name = dentry->d_name.name;
-+	int namelen = dentry->d_name.len;
-+	unsigned short rec_len, name_len;
-+	ext2_dirent * de;
-+	struct page *page;
-+	loff_t pos;
-+	int err;
-+
-+	de = ext2_append_entry(dentry, &page);
-+	if (IS_ERR(de))
-+		return PTR_ERR(de);
-+
-+	err = -EEXIST;
-+	if (ext2_match (namelen, name, de))
-+		goto out_unlock;
-+
-+	name_len = EXT2_DIR_REC_LEN(de->name_len);
-+	rec_len = ext2_rec_len_from_disk(de->rec_len);
-+
-+	pos = page_offset(page) +
-+		(char*)de - (char*)page_address(page);
-+	err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
-+							&page, NULL);
-+	if (err)
-+		goto out_unlock;
-+	if (de->inode || (de->file_type == EXT2_FT_WHT) ||
-+	    (de->file_type == EXT2_FT_FALLTHRU)) {
-+		ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
-+		de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
-+		de->rec_len = ext2_rec_len_to_disk(name_len);
-+		de = de1;
-+	}
-+	de->name_len = namelen;
-+	memcpy(de->name, name, namelen);
-+	de->inode = 0;
-+	de->file_type = EXT2_FT_FALLTHRU;
-+	err = ext2_commit_chunk(page, pos, rec_len);
-+	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
-+	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
-+	mark_inode_dirty(dir);
-+	/* OFFSET_CACHE */
-+out_put:
-+	ext2_put_page(page);
- 	return err;
- out_unlock:
- 	unlock_page(page);
-@@ -616,6 +748,70 @@ out:
- 	return err;
- }
- 
-+int ext2_whiteout_entry (struct inode * dir, struct dentry * dentry,
-+			 struct ext2_dir_entry_2 * de, struct page * page)
-+{
-+	const char *name = dentry->d_name.name;
-+	int namelen = dentry->d_name.len;
-+	unsigned short rec_len, name_len;
-+	loff_t pos;
-+	int err;
-+
-+	if (!de) {
-+		de = ext2_append_entry(dentry, &page);
-+		BUG_ON(!de);
-+	}
-+
-+	err = -EEXIST;
-+	if (ext2_match (namelen, name, de) &&
-+	    (de->file_type == EXT2_FT_WHT)) {
-+		ext2_error(dir->i_sb, __func__,
-+			   "entry is already a whiteout in directory #%lu",
-+			   dir->i_ino);
-+		goto out_unlock;
-+	}
-+
-+	name_len = EXT2_DIR_REC_LEN(de->name_len);
-+	rec_len = ext2_rec_len_from_disk(de->rec_len);
-+
-+	pos = page_offset(page) +
-+		(char*)de - (char*)page_address(page);
-+	err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
-+							&page, NULL);
-+	if (err)
-+		goto out_unlock;
-+	/*
-+	 * We whiteout an existing entry. Do what ext2_delete_entry() would do,
-+	 * except that we don't need to merge with the previous entry since
-+	 * we are going to reuse it.
-+	 */
-+	if (ext2_match (namelen, name, de))
-+		de->inode = 0;
-+	if (de->inode || (((de->file_type == EXT2_FT_WHT) ||
-+			   (de->file_type == EXT2_FT_FALLTHRU)) &&
-+			  !ext2_match (namelen, name, de))) {
-+		ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
-+		de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
-+		de->rec_len = ext2_rec_len_to_disk(name_len);
-+		de = de1;
-+	}
-+	de->name_len = namelen;
-+	memcpy(de->name, name, namelen);
-+	de->inode = 0;
-+	de->file_type = EXT2_FT_WHT;
-+	err = ext2_commit_chunk(page, pos, rec_len);
-+	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
-+	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
-+	mark_inode_dirty(dir);
-+	/* OFFSET_CACHE */
-+out_put:
-+	ext2_put_page(page);
-+	return err;
-+out_unlock:
-+	unlock_page(page);
-+	goto out_put;
-+}
-+
- /*
-  * Set the first fragment of directory.
-  */
---- a/fs/ext2/ext2.h
-+++ b/fs/ext2/ext2.h
-@@ -102,9 +102,13 @@ extern void ext2_rsv_window_add(struct s
- /* dir.c */
- extern int ext2_add_link (struct dentry *, struct inode *);
- extern ino_t ext2_inode_by_name(struct inode *, struct qstr *);
-+extern ino_t ext2_inode_by_dentry(struct inode *, struct dentry *);
- extern int ext2_make_empty(struct inode *, struct inode *);
- extern struct ext2_dir_entry_2 * ext2_find_entry (struct inode *,struct qstr *, struct page **);
- extern int ext2_delete_entry (struct ext2_dir_entry_2 *, struct page *);
-+extern int ext2_whiteout_entry (struct inode *, struct dentry *,
-+				struct ext2_dir_entry_2 *, struct page *);
-+extern int ext2_fallthru_entry (struct inode *, struct dentry *);
- extern int ext2_empty_dir (struct inode *);
- extern struct ext2_dir_entry_2 * ext2_dotdot (struct inode *, struct page **);
- extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, struct inode *, int);
---- a/fs/ext2/inode.c
-+++ b/fs/ext2/inode.c
-@@ -1176,7 +1176,8 @@ void ext2_set_inode_flags(struct inode *
- {
- 	unsigned int flags = EXT2_I(inode)->i_flags;
- 
--	inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
-+	inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|
-+			    S_OPAQUE);
- 	if (flags & EXT2_SYNC_FL)
- 		inode->i_flags |= S_SYNC;
- 	if (flags & EXT2_APPEND_FL)
-@@ -1187,6 +1188,8 @@ void ext2_set_inode_flags(struct inode *
- 		inode->i_flags |= S_NOATIME;
- 	if (flags & EXT2_DIRSYNC_FL)
- 		inode->i_flags |= S_DIRSYNC;
-+	if (flags & EXT2_OPAQUE_FL)
-+		inode->i_flags |= S_OPAQUE;
- }
- 
- /* Propagate flags from i_flags to EXT2_I(inode)->i_flags */
-@@ -1194,8 +1197,8 @@ void ext2_get_inode_flags(struct ext2_in
- {
- 	unsigned int flags = ei->vfs_inode.i_flags;
- 
--	ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|
--			EXT2_IMMUTABLE_FL|EXT2_NOATIME_FL|EXT2_DIRSYNC_FL);
-+	ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|EXT2_IMMUTABLE_FL|
-+			 EXT2_NOATIME_FL|EXT2_DIRSYNC_FL|EXT2_OPAQUE_FL);
- 	if (flags & S_SYNC)
- 		ei->i_flags |= EXT2_SYNC_FL;
- 	if (flags & S_APPEND)
-@@ -1206,6 +1209,8 @@ void ext2_get_inode_flags(struct ext2_in
- 		ei->i_flags |= EXT2_NOATIME_FL;
- 	if (flags & S_DIRSYNC)
- 		ei->i_flags |= EXT2_DIRSYNC_FL;
-+	if (flags & S_OPAQUE)
-+		ei->i_flags |= EXT2_OPAQUE_FL;
- }
- 
- struct inode *ext2_iget (struct super_block *sb, unsigned long ino)
---- a/fs/ext2/namei.c
-+++ b/fs/ext2/namei.c
-@@ -54,15 +54,16 @@ static inline int ext2_add_nondir(struct
-  * Methods themselves.
-  */
- 
--static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, struct nameidata *nd)
-+static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry,
-+				  struct nameidata *nd)
- {
- 	struct inode * inode;
- 	ino_t ino;
--	
-+
- 	if (dentry->d_name.len > EXT2_NAME_LEN)
- 		return ERR_PTR(-ENAMETOOLONG);
- 
--	ino = ext2_inode_by_name(dir, &dentry->d_name);
-+	ino = ext2_inode_by_dentry(dir, dentry);
- 	inode = NULL;
- 	if (ino) {
- 		inode = ext2_iget(dir->i_sb, ino);
-@@ -230,6 +231,10 @@ static int ext2_mkdir(struct inode * dir
- 	else
- 		inode->i_mapping->a_ops = &ext2_aops;
- 
-+	/* if we call mkdir on a whiteout create an opaque directory */
-+	if (dentry->d_flags & DCACHE_WHITEOUT)
-+		inode->i_flags |= S_OPAQUE;
-+
- 	inode_inc_link_count(inode);
- 
- 	err = ext2_make_empty(inode, dir);
-@@ -293,6 +298,78 @@ static int ext2_rmdir (struct inode * di
- 	return err;
- }
- 
-+/*
-+ * Create a whiteout for the dentry
-+ */
-+static int ext2_whiteout(struct inode *dir, struct dentry *dentry,
-+			 struct dentry *new_dentry)
-+{
-+	struct inode * inode = dentry->d_inode;
-+	struct ext2_dir_entry_2 * de = NULL;
-+	struct page * page;
-+	int err = -ENOTEMPTY;
-+
-+	if (!EXT2_HAS_INCOMPAT_FEATURE(dir->i_sb,
-+				       EXT2_FEATURE_INCOMPAT_FILETYPE)) {
-+		ext2_error (dir->i_sb, "ext2_whiteout",
-+			    "can't set whiteout filetype");
-+		err = -EPERM;
-+		goto out;
-+	}
-+
-+	if (inode) {
-+		if (S_ISDIR(inode->i_mode) && !ext2_empty_dir(inode))
-+			goto out;
-+
-+		err = -ENOENT;
-+		de = ext2_find_entry (dir, &dentry->d_name, &page);
-+		if (!de)
-+			goto out;
-+		lock_page(page);
-+	}
-+
-+	err = ext2_whiteout_entry (dir, dentry, de, page);
-+	if (err)
-+		goto out;
-+
-+	spin_lock(&new_dentry->d_lock);
-+	new_dentry->d_flags &= ~DCACHE_FALLTHRU;
-+	new_dentry->d_flags |= DCACHE_WHITEOUT;
-+	spin_unlock(&new_dentry->d_lock);
-+	d_add(new_dentry, NULL);
-+
-+	if (inode) {
-+		inode->i_ctime = dir->i_ctime;
-+		inode_dec_link_count(inode);
-+		if (S_ISDIR(inode->i_mode)) {
-+			inode->i_size = 0;
-+			inode_dec_link_count(inode);
-+			inode_dec_link_count(dir);
-+		}
-+	}
-+	err = 0;
-+out:
-+	return err;
-+}
-+
-+/*
-+ * Create a fallthru entry.
-+ */
-+static int ext2_fallthru (struct inode *dir, struct dentry *dentry)
-+{
-+	int err;
-+
-+	err = ext2_fallthru_entry(dir, dentry);
-+	if (err)
-+		return err;
-+
-+	d_instantiate(dentry, NULL);
-+	spin_lock(&dentry->d_lock);
-+	dentry->d_flags |= DCACHE_FALLTHRU;
-+	spin_unlock(&dentry->d_lock);
-+	return 0;
-+}
-+
- static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
- 	struct inode * new_dir,	struct dentry * new_dentry )
- {
-@@ -392,6 +469,8 @@ const struct inode_operations ext2_dir_i
- 	.mkdir		= ext2_mkdir,
- 	.rmdir		= ext2_rmdir,
- 	.mknod		= ext2_mknod,
-+	.whiteout	= ext2_whiteout,
-+	.fallthru	= ext2_fallthru,
- 	.rename		= ext2_rename,
- #ifdef CONFIG_EXT2_FS_XATTR
- 	.setxattr	= generic_setxattr,
---- a/fs/ext2/super.c
-+++ b/fs/ext2/super.c
-@@ -1062,6 +1062,13 @@ static int ext2_fill_super(struct super_
- 	if (EXT2_HAS_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_HAS_JOURNAL))
- 		ext2_warning(sb, __func__,
- 			"mounting ext3 filesystem as ext2");
-+
-+	/*
-+	 * Whiteouts (and fallthrus) require explicit whiteout support.
-+	 */
-+	if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_WHITEOUT))
-+		sb->s_flags |= MS_WHITEOUT;
-+
- 	ext2_setup_super (sb, es, sb->s_flags & MS_RDONLY);
- 	return 0;
- 
---- a/fs/Kconfig
-+++ b/fs/Kconfig
-@@ -58,6 +58,14 @@ source "fs/notify/Kconfig"
- 
- source "fs/quota/Kconfig"
- 
-+config UNION_MOUNT
-+       bool "Union mount support (EXPERIMENTAL)"
-+       depends on EXPERIMENTAL
-+       ---help---
-+         If you say Y here, you will be able to mount file systems as
-+         union mount stacks. This is a VFS based implementation and
-+         should work with all file systems. If unsure, say N.
-+
- source "fs/autofs/Kconfig"
- source "fs/autofs4/Kconfig"
- source "fs/fuse/Kconfig"
---- a/fs/libfs.c
-+++ b/fs/libfs.c
-@@ -133,6 +133,7 @@ int dcache_readdir(struct file * filp, v
- 	struct dentry *cursor = filp->private_data;
- 	struct list_head *p, *q = &cursor->d_u.d_child;
- 	ino_t ino;
-+	int d_type;
- 	int i = filp->f_pos;
- 
- 	switch (i) {
-@@ -158,14 +159,25 @@ int dcache_readdir(struct file * filp, v
- 			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
- 				struct dentry *next;
- 				next = list_entry(p, struct dentry, d_u.d_child);
--				if (d_unhashed(next) || !next->d_inode)
-+				if (d_unhashed(next) || (!next->d_inode && !d_is_fallthru(next)))
- 					continue;
- 
-+				if (d_is_fallthru(next)) {
-+					/* XXX Make up things we can
-+					 * only get out of the inode.
-+					 * Should probably really do a
-+					 * lookup instead. */
-+					ino = 100; /* XXX Made up number of no significance */
-+					d_type = DT_UNKNOWN;
-+				} else {
-+					ino = next->d_inode->i_ino;
-+					d_type = dt_type(next->d_inode);
-+				}
-+
- 				spin_unlock(&dcache_lock);
- 				if (filldir(dirent, next->d_name.name, 
- 					    next->d_name.len, filp->f_pos, 
--					    next->d_inode->i_ino, 
--					    dt_type(next->d_inode)) < 0)
-+					    ino, d_type) < 0)
- 					return 0;
- 				spin_lock(&dcache_lock);
- 				/* next is still alive */
---- a/fs/Makefile
-+++ b/fs/Makefile
-@@ -52,6 +52,7 @@ obj-$(CONFIG_NFS_COMMON)	+= nfs_common/
- obj-$(CONFIG_GENERIC_ACL)	+= generic_acl.o
- 
- obj-y				+= quota/
-+obj-$(CONFIG_UNION_MOUNT)	+= union.o
- 
- obj-$(CONFIG_PROC_FS)		+= proc/
- obj-y				+= partitions/
---- a/fs/namei.c
-+++ b/fs/namei.c
-@@ -33,6 +33,7 @@
- #include <linux/fcntl.h>
- #include <linux/device_cgroup.h>
- #include <linux/fs_struct.h>
-+#include <linux/union.h>
- #include <asm/uaccess.h>
- 
- #define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
-@@ -229,16 +230,17 @@ int generic_permission(struct inode *ino
- }
- 
- /**
-- * inode_permission  -  check for access rights to a given inode
-+ * __inode_permission  -  check for access rights to a given inode
-  * @inode:	inode to check permission on
-  * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
-+ * @rofs:	check for read-only fs
-  *
-  * Used to check for read/write/execute permissions on an inode.
-  * We use "fsuid" for this, letting us set arbitrary permissions
-  * for filesystem access without changing the "normal" uids which
-  * are used for other things.
-  */
--int inode_permission(struct inode *inode, int mask)
-+int __inode_permission(struct inode *inode, int mask, int rofs)
- {
- 	int retval;
- 
-@@ -248,7 +250,7 @@ int inode_permission(struct inode *inode
- 		/*
- 		 * Nobody gets write access to a read-only fs.
- 		 */
--		if (IS_RDONLY(inode) &&
-+		if ((rofs & IS_RDONLY(inode)) &&
- 		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
- 			return -EROFS;
- 
-@@ -276,6 +278,18 @@ int inode_permission(struct inode *inode
- }
- 
- /**
-+ * inode_permission  -  check for access rights to a given inode
-+ * @inode:	inode to check permission on
-+ * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
-+ *
-+ * This version pays attention to the MS_RDONLY flag on the fs.
-+ */
-+int inode_permission(struct inode *inode, int mask)
-+{
-+	return __inode_permission(inode, mask, 1);
-+}
-+
-+/**
-  * file_permission  -  check for additional access rights to a given file
-  * @file:	file to check access rights for
-  * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
-@@ -404,15 +418,10 @@ do_revalidate(struct dentry *dentry, str
-  * Internal lookup() using the new generic dcache.
-  * SMP-safe
-  */
--static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
-+static struct dentry *cache_lookup(struct dentry *parent, struct qstr *name,
-+				   struct nameidata *nd)
- {
--	struct dentry * dentry = __d_lookup(parent, name);
--
--	/* lockess __d_lookup may fail due to concurrent d_move() 
--	 * in some unrelated directory, so try with d_lookup
--	 */
--	if (!dentry)
--		dentry = d_lookup(parent, name);
-+	struct dentry *dentry = d_lookup(parent, name);
- 
- 	if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
- 		dentry = do_revalidate(dentry, nd);
-@@ -421,6 +430,208 @@ static struct dentry * cached_lookup(str
- }
- 
- /*
-+ * Theory of operation for opaque, whiteout, and fallthru:
-+ *
-+ * whiteout: Unconditionally stop lookup here - ENOENT
-+ *
-+ * opaque: Don't lookup in directories lower in the union stack
-+ *
-+ * fallthru: While looking up an entry, ignore the opaque flag for the
-+ * current directory only.
-+ *
-+ * A union stack is a linked list of directory dentries which appear
-+ * in the same place in the namespace.  When constructing the union
-+ * stack, we include directories below opaque directories so that we
-+ * can properly handle fallthrus.  All non-fallthru lookups have to
-+ * check for the opaque flag on the parent directory and obey it.
-+ *
-+ * In general, the code pattern is to lookup the the topmost entry
-+ * first (either the first visible non-negative dentry or a negative
-+ * dentry in the topmost layer of the union), then build the union
-+ * stack for the newly looked-up entry (if it is a directory).
-+ */
-+
-+/**
-+ * __cache_lookup_topmost - lookup the topmost (non-)negative dentry
-+ *
-+ * @nd - parent's nameidata
-+ * @name - pathname part to lookup
-+ * @path - found dentry for pathname part
-+ *
-+ * This is used for union mount lookups from dcache. The first non-negative
-+ * dentry is searched on all layers of the union stack. Otherwise the topmost
-+ * negative dentry is returned.
-+ */
-+static int __cache_lookup_topmost(struct nameidata *nd, struct qstr *name,
-+				  struct path *path)
-+{
-+	struct dentry *dentry;
-+
-+	dentry = d_lookup(nd->path.dentry, name);
-+	if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
-+		dentry = do_revalidate(dentry, nd);
-+
-+	/*
-+	 * Remember the topmost negative dentry in case we don't find anything
-+	 */
-+	path->dentry = dentry;
-+	path->mnt = dentry ? nd->path.mnt : NULL;
-+
-+	if (!dentry || (dentry->d_inode || d_is_whiteout(dentry)))
-+		return !dentry;
-+
-+	/* Keep going through opaque directories if we found a fallthru */
-+	if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry))
-+		return !dentry;
-+
-+	/* look for the first non-negative or whiteout dentry */
-+
-+	while (follow_union_down(&nd->path)) {
-+		dentry = d_hash_and_lookup(nd->path.dentry, name);
-+
-+		/*
-+		 * If parts of the union stack are not in the dcache we need
-+		 * to do a real lookup
-+		 */
-+		if (!dentry)
-+			goto out_dput;
-+
-+		/*
-+		 * If parts of the union don't survive the revalidation we
-+		 * need to do a real lookup
-+		 */
-+		if (dentry->d_op && dentry->d_op->d_revalidate) {
-+			dentry = do_revalidate(dentry, nd);
-+			if (!dentry)
-+				goto out_dput;
-+		}
-+
-+		if (dentry->d_inode || d_is_whiteout(dentry))
-+			goto out_dput;
-+
-+		/* Stop the lookup on opaque parent and non-fallthru child */
-+		if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry))
-+			goto out_dput;
-+
-+		dput(dentry);
-+	}
-+
-+	return !dentry;
-+
-+out_dput:
-+	dput(path->dentry);
-+	path->dentry = dentry;
-+	path->mnt = dentry ? mntget(nd->path.mnt) : NULL;
-+	return !dentry;
-+}
-+
-+/**
-+ * __cache_lookup_build_union - build the union stack for this part,
-+ * cached version
-+ *
-+ * This is called after you have the topmost dentry in @path.
-+ */
-+static int __cache_lookup_build_union(struct nameidata *nd, struct qstr *name,
-+				      struct path *path)
-+{
-+	struct path last = *path;
-+	struct dentry *dentry;
-+
-+	while (follow_union_down(&nd->path)) {
-+		dentry = d_hash_and_lookup(nd->path.dentry, name);
-+		if (!dentry)
-+			return 1;
-+
-+		if (dentry->d_op && dentry->d_op->d_revalidate) {
-+			dentry = do_revalidate(dentry, nd);
-+			if (!dentry)
-+				return 1;
-+		}
-+
-+		if (d_is_whiteout(dentry)) {
-+			dput(dentry);
-+			break;
-+		}
-+
-+		if (!dentry->d_inode) {
-+			dput(dentry);
-+			continue;
-+		}
-+
-+		/* only directories can be part of a union stack */
-+		if (!S_ISDIR(dentry->d_inode->i_mode)) {
-+			dput(dentry);
-+			break;
-+		}
-+
-+		/* Add the newly discovered dir to the union stack */
-+		append_to_union(last.mnt, last.dentry, nd->path.mnt, dentry);
-+
-+		if (last.dentry != path->dentry)
-+			path_put(&last);
-+		last.dentry = dentry;
-+		last.mnt = mntget(nd->path.mnt);
-+	}
-+
-+	if (last.dentry != path->dentry)
-+		path_put(&last);
-+
-+	return 0;
-+}
-+
-+/**
-+ * cache_lookup_union - lookup a single pathname part from dcache
-+ *
-+ * This is a union mount capable version of what d_lookup() & revalidate()
-+ * would do. This function returns a valid (union) dentry on success.
-+ *
-+ * Remember: On failure it means that parts of the union aren't cached. You
-+ * should call real_lookup() afterwards to find the proper (union) dentry.
-+ */
-+static int cache_lookup_union(struct nameidata *nd, struct qstr *name,
-+			      struct path *path)
-+{
-+	int res ;
-+
-+	if (!IS_MNT_UNION(nd->path.mnt)) {
-+		path->dentry = cache_lookup(nd->path.dentry, name, nd);
-+		path->mnt = path->dentry ? nd->path.mnt : NULL;
-+		res = path->dentry ? 0 : 1;
-+	} else {
-+		struct path safe = {
-+			.dentry = nd->path.dentry,
-+			.mnt = nd->path.mnt
-+		};
-+
-+		path_get(&safe);
-+		res = __cache_lookup_topmost(nd, name, path);
-+		if (res)
-+			goto out;
-+
-+		/* only directories can be part of a union stack */
-+		if (!path->dentry->d_inode ||
-+		    !S_ISDIR(path->dentry->d_inode->i_mode))
-+			goto out;
-+
-+		/* Build the union stack for this part */
-+		res = __cache_lookup_build_union(nd, name, path);
-+		if (res) {
-+			dput(path->dentry);
-+			if (path->mnt != safe.mnt)
-+				mntput(path->mnt);
-+			goto out;
-+		}
-+
-+out:
-+		path_put(&nd->path);
-+		nd->path.dentry = safe.dentry;
-+		nd->path.mnt = safe.mnt;
-+	}
-+
-+	return res;
-+}
-+
-+/*
-  * Short-cut version of permission(), for calling by
-  * path_walk(), when dcache lock is held.  Combines parts
-  * of permission() and generic_permission(), and tests ONLY for
-@@ -467,10 +678,11 @@ ok:
-  * make sure that nobody added the entry to the dcache in the meantime..
-  * SMP-safe
-  */
--static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
-+static int real_lookup(struct nameidata *nd, struct qstr *name,
-+		       struct path *path)
- {
--	struct dentry * result;
--	struct inode *dir = parent->d_inode;
-+	struct inode *dir = nd->path.dentry->d_inode;
-+	int res = 0;
- 
- 	mutex_lock(&dir->i_mutex);
- 	/*
-@@ -487,27 +699,36 @@ static struct dentry * real_lookup(struc
- 	 *
- 	 * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
- 	 */
--	result = d_lookup(parent, name);
--	if (!result) {
-+	path->dentry = d_lookup(nd->path.dentry, name);
-+	path->mnt = nd->path.mnt;
-+	if (!path->dentry) {
- 		struct dentry *dentry;
- 
- 		/* Don't create child dentry for a dead directory. */
--		result = ERR_PTR(-ENOENT);
--		if (IS_DEADDIR(dir))
-+		if (IS_DEADDIR(dir)) {
-+			res = -ENOENT;
- 			goto out_unlock;
-+		}
- 
--		dentry = d_alloc(parent, name);
--		result = ERR_PTR(-ENOMEM);
-+		dentry = d_alloc(nd->path.dentry, name);
- 		if (dentry) {
--			result = dir->i_op->lookup(dir, dentry, nd);
--			if (result)
-+			path->dentry = dir->i_op->lookup(dir, dentry, nd);
-+			if (path->dentry) {
- 				dput(dentry);
--			else
--				result = dentry;
-+				if (IS_ERR(path->dentry)) {
-+					res = PTR_ERR(path->dentry);
-+					path->dentry = NULL;
-+					path->mnt = NULL;
-+				}
-+			} else
-+				path->dentry = dentry;
-+		} else {
-+			res = -ENOMEM;
-+			path->mnt = NULL;
- 		}
- out_unlock:
- 		mutex_unlock(&dir->i_mutex);
--		return result;
-+		return res;
- 	}
- 
- 	/*
-@@ -515,12 +736,170 @@ out_unlock:
- 	 * we waited on the semaphore. Need to revalidate.
- 	 */
- 	mutex_unlock(&dir->i_mutex);
--	if (result->d_op && result->d_op->d_revalidate) {
--		result = do_revalidate(result, nd);
--		if (!result)
--			result = ERR_PTR(-ENOENT);
-+	if (path->dentry->d_op && path->dentry->d_op->d_revalidate) {
-+		path->dentry = do_revalidate(path->dentry, nd);
-+		if (!path->dentry) {
-+			res = -ENOENT;
-+			path->mnt = NULL;
-+		}
-+		if (IS_ERR(path->dentry)) {
-+			res = PTR_ERR(path->dentry);
-+			path->dentry = NULL;
-+			path->mnt = NULL;
-+		}
- 	}
--	return result;
-+
-+	return res;
-+}
-+
-+/**
-+ * __real_lookup_topmost - lookup topmost dentry, non-cached version
-+ *
-+ * If we reach a dentry with restricted access, we just stop the lookup
-+ * because we shouldn't see through that dentry. Same thing for dentry
-+ * type mismatch and whiteouts.
-+ *
-+ * FIXME:
-+ * - handle union stacks in use
-+ * - handle union stacks mounted upon union stacks
-+ * - avoid unnecessary allocations of union locks
-+ */
-+static int __real_lookup_topmost(struct nameidata *nd, struct qstr *name,
-+				 struct path *path)
-+{
-+	struct path next;
-+	int err;
-+
-+	err = real_lookup(nd, name, path);
-+	if (err)
-+		return err;
-+
-+	if (path->dentry->d_inode || d_is_whiteout(path->dentry))
-+		return 0;
-+
-+	if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry))
-+		return 0;
-+
-+	while (follow_union_down(&nd->path)) {
-+		name->hash = full_name_hash(name->name, name->len);
-+		if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
-+			err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
-+							    name);
-+			if (err < 0)
-+				goto out;
-+		}
-+
-+		err = real_lookup(nd, name, &next);
-+		if (err)
-+			goto out;
-+
-+		if (next.dentry->d_inode || d_is_whiteout(next.dentry)) {
-+			dput(path->dentry);
-+			mntget(next.mnt);
-+			*path = next;
-+			goto out;
-+		}
-+
-+		if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry))
-+			goto out;
-+
-+		dput(next.dentry);
-+	}
-+out:
-+	if (err)
-+		dput(path->dentry);
-+	return err;
-+}
-+
-+/**
-+ * __real_lookup_build_union: build the union stack for this pathname
-+ * part, non-cached version
-+ *
-+ * Called when not all parts of the union stack are in cache
-+ */
-+
-+static int __real_lookup_build_union(struct nameidata *nd, struct qstr *name,
-+				     struct path *path)
-+{
-+	struct path last = *path;
-+	struct path next;
-+	int err = 0;
-+
-+	while (follow_union_down(&nd->path)) {
-+		/* We need to recompute the hash for lower layer lookups */
-+		name->hash = full_name_hash(name->name, name->len);
-+		if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
-+			err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
-+							    name);
-+			if (err < 0)
-+				goto out;
-+		}
-+
-+		err = real_lookup(nd, name, &next);
-+		if (err)
-+			goto out;
-+
-+		if (d_is_whiteout(next.dentry)) {
-+			dput(next.dentry);
-+			break;
-+		}
-+
-+		if (!next.dentry->d_inode) {
-+			dput(next.dentry);
-+			continue;
-+		}
-+
-+		/* only directories can be part of a union stack */
-+		if (!S_ISDIR(next.dentry->d_inode->i_mode)) {
-+			dput(next.dentry);
-+			break;
-+		}
-+
-+		/* now we know we found something "real" */
-+		append_to_union(last.mnt, last.dentry, next.mnt, next.dentry);
-+
-+		if (last.dentry != path->dentry)
-+			path_put(&last);
-+		last.dentry = next.dentry;
-+		last.mnt = mntget(next.mnt);
-+	}
-+
-+	if (last.dentry != path->dentry)
-+		path_put(&last);
-+out:
-+	return err;
-+}
-+
-+static int real_lookup_union(struct nameidata *nd, struct qstr *name,
-+			     struct path *path)
-+{
-+	struct path safe = { .dentry = nd->path.dentry, .mnt = nd->path.mnt };
-+	int res ;
-+
-+	path_get(&safe);
-+	res = __real_lookup_topmost(nd, name, path);
-+	if (res)
-+		goto out;
-+
-+	/* only directories can be part of a union stack */
-+	if (!path->dentry->d_inode ||
-+	    !S_ISDIR(path->dentry->d_inode->i_mode))
-+		goto out;
-+
-+	/* Build the union stack for this part */
-+	res = __real_lookup_build_union(nd, name, path);
-+	if (res) {
-+		dput(path->dentry);
-+		if (path->mnt != safe.mnt)
-+			mntput(path->mnt);
-+		goto out;
-+	}
-+
-+out:
-+	path_put(&nd->path);
-+	nd->path.dentry = safe.dentry;
-+	nd->path.mnt = safe.mnt;
-+	return res;
- }
- 
- /*
-@@ -623,11 +1002,8 @@ static __always_inline int __do_follow_l
- 	touch_atime(path->mnt, dentry);
- 	nd_set_link(nd, NULL);
- 
--	if (path->mnt != nd->path.mnt) {
--		path_to_nameidata(path, nd);
--		dget(dentry);
--	}
--	mntget(path->mnt);
-+	if (path->mnt == nd->path.mnt)
-+		mntget(nd->path.mnt);
- 	cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
- 	error = PTR_ERR(cookie);
- 	if (!IS_ERR(cookie)) {
-@@ -715,7 +1091,7 @@ static int __follow_mount(struct path *p
- 	return res;
- }
- 
--static void follow_mount(struct path *path)
-+void follow_mount(struct path *path)
- {
- 	while (d_mountpoint(path->dentry)) {
- 		struct vfsmount *mounted = lookup_mnt(path);
-@@ -780,6 +1156,7 @@ static __always_inline void follow_dotdo
- 		nd->path.mnt = parent;
- 	}
- 	follow_mount(&nd->path);
-+	follow_union_mount(&nd->path);
- }
- 
- /*
-@@ -790,35 +1167,55 @@ static __always_inline void follow_dotdo
- static int do_lookup(struct nameidata *nd, struct qstr *name,
- 		     struct path *path)
- {
--	struct vfsmount *mnt = nd->path.mnt;
--	struct dentry *dentry = __d_lookup(nd->path.dentry, name);
-+	int err;
-+
-+	if (IS_MNT_UNION(nd->path.mnt))
-+		goto need_union_lookup;
- 
--	if (!dentry)
-+	path->dentry = __d_lookup(nd->path.dentry, name);
-+	path->mnt = nd->path.mnt;
-+	if (!path->dentry)
- 		goto need_lookup;
--	if (dentry->d_op && dentry->d_op->d_revalidate)
-+	if (path->dentry->d_op && path->dentry->d_op->d_revalidate)
- 		goto need_revalidate;
-+
- done:
--	path->mnt = mnt;
--	path->dentry = dentry;
--	__follow_mount(path);
-+	if (nd->path.mnt != path->mnt) {
-+		nd->um_flags |= LAST_LOWLEVEL;
-+		follow_mount(path);
-+	} else
-+		__follow_mount(path);
-+	follow_union_mount(path);
- 	return 0;
- 
- need_lookup:
--	dentry = real_lookup(nd->path.dentry, name, nd);
--	if (IS_ERR(dentry))
-+	err = real_lookup(nd, name, path);
-+	if (err)
-+		goto fail;
-+	goto done;
-+
-+need_union_lookup:
-+	err = cache_lookup_union(nd, name, path);
-+	if (!err && path->dentry)
-+		goto done;
-+
-+	err = real_lookup_union(nd, name, path);
-+	if (err)
- 		goto fail;
- 	goto done;
- 
- need_revalidate:
--	dentry = do_revalidate(dentry, nd);
--	if (!dentry)
-+	path->dentry = do_revalidate(path->dentry, nd);
-+	if (!path->dentry)
- 		goto need_lookup;
--	if (IS_ERR(dentry))
-+	if (IS_ERR(path->dentry)) {
-+		err = PTR_ERR(path->dentry);
- 		goto fail;
-+	}
- 	goto done;
- 
- fail:
--	return PTR_ERR(dentry);
-+	return err;
- }
- 
- /*
-@@ -845,6 +1242,8 @@ static int __link_path_walk(const char *
- 	if (nd->depth)
- 		lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
- 
-+	follow_union_mount(&nd->path);
-+
- 	/* At this point we know we have a real path component. */
- 	for(;;) {
- 		unsigned long hash;
-@@ -913,6 +1312,44 @@ static int __link_path_walk(const char *
- 		if (err)
- 			break;
- 
-+		/*
-+		 * We want to create this element on the top level
-+		 * file system in two cases:
-+		 *
-+		 * - We are specifically told to - LOOKUP_TOPMOST.
-+		 * - This is a directory, and it does not yet exist on
-+		 *   the top level.  Various tricks only work if
-+		 *   directories always exist on the top level.
-+		 *
-+		 * In either case, only create this element on the top
-+		 * level if the last element is located on the lower
-+		 * level.  If the last element is located on the top
-+		 * level, then every single element in the path
-+		 * already exists on the top level.
-+		 *
-+		 * Note that we can assume that the parent is on the
-+		 * top level since we always create the directory on
-+		 * the top level.
-+		 */
-+
-+		if ((nd->um_flags & LAST_LOWLEVEL) &&
-+		    ((next.dentry->d_inode &&
-+		      S_ISDIR(next.dentry->d_inode->i_mode) &&
-+		      (nd->path.mnt != next.mnt)) ||
-+		     (nd->flags & LOOKUP_TOPMOST))) {
-+			struct dentry *dentry;
-+
-+			dentry = union_create_topmost(nd, &this, &next);
-+			if (IS_ERR(dentry)) {
-+				err = PTR_ERR(dentry);
-+				goto out_dput;
-+			}
-+			path_put_conditional(&next, nd);
-+			next.mnt = nd->path.mnt;
-+			next.dentry = dentry;
-+			nd->um_flags &= ~LAST_LOWLEVEL;
-+		}
-+
- 		err = -ENOENT;
- 		inode = next.dentry->d_inode;
- 		if (!inode)
-@@ -962,6 +1399,25 @@ last_component:
- 		err = do_lookup(nd, &this, &next);
- 		if (err)
- 			break;
-+
-+		if ((nd->um_flags & LAST_LOWLEVEL) &&
-+		    ((next.dentry->d_inode &&
-+		      S_ISDIR(next.dentry->d_inode->i_mode) &&
-+		      (nd->path.mnt != next.mnt)) ||
-+		     (nd->flags & LOOKUP_TOPMOST))) {
-+			struct dentry *dentry;
-+
-+			dentry = union_create_topmost(nd, &this, &next);
-+			if (IS_ERR(dentry)) {
-+				err = PTR_ERR(dentry);
-+				goto out_dput;
-+			}
-+			path_put_conditional(&next, nd);
-+			next.mnt = nd->path.mnt;
-+			next.dentry = dentry;
-+			nd->um_flags &= ~LAST_LOWLEVEL;
-+		}
-+
- 		inode = next.dentry->d_inode;
- 		if ((lookup_flags & LOOKUP_FOLLOW)
- 		    && inode && inode->i_op->follow_link) {
-@@ -1029,6 +1485,7 @@ static int path_init(int dfd, const char
- 
- 	nd->last_type = LAST_ROOT; /* if there are only slashes... */
- 	nd->flags = flags;
-+	nd->um_flags = 0;
- 	nd->depth = 0;
- 	nd->root.mnt = NULL;
- 
-@@ -1172,61 +1629,437 @@ static int path_lookup_open(int dfd, con
- }
- 
- static struct dentry *__lookup_hash(struct qstr *name,
--		struct dentry *base, struct nameidata *nd)
-+				    struct dentry *base, struct nameidata *nd)
-+{
-+	struct dentry *dentry;
-+	struct inode *inode;
-+	int err;
-+
-+	inode = base->d_inode;
-+
-+	/*
-+	 * See if the low-level filesystem might want
-+	 * to use its own hash..
-+	 */
-+	if (base->d_op && base->d_op->d_hash) {
-+		err = base->d_op->d_hash(base, name);
-+		dentry = ERR_PTR(err);
-+		if (err < 0)
-+			goto out;
-+	}
-+
-+	dentry = cache_lookup(base, name, nd);
-+	if (!dentry) {
-+		struct dentry *new;
-+
-+		/* Don't create child dentry for a dead directory. */
-+		dentry = ERR_PTR(-ENOENT);
-+		if (IS_DEADDIR(inode))
-+			goto out;
-+
-+		new = d_alloc(base, name);
-+		dentry = ERR_PTR(-ENOMEM);
-+		if (!new)
-+			goto out;
-+		dentry = inode->i_op->lookup(inode, new, nd);
-+		if (!dentry)
-+			dentry = new;
-+		else
-+			dput(new);
-+	}
-+out:
-+	return dentry;
-+}
-+
-+/*
-+ * Restricted form of lookup. Doesn't follow links, single-component only,
-+ * needs parent already locked. Doesn't follow mounts.
-+ * SMP-safe.
-+ */
-+static int lookup_hash(struct nameidata *nd, struct qstr *name,
-+		       struct path *path)
-+{
-+	int err;
-+
-+	err = inode_permission(nd->path.dentry->d_inode, MAY_EXEC);
-+	if (err)
-+		return err;
-+	path->mnt = nd->path.mnt;
-+	path->dentry =  __lookup_hash(name, nd->path.dentry, nd);
-+	if (IS_ERR(path->dentry)) {
-+		err = PTR_ERR(path->dentry);
-+		path->dentry = NULL;
-+		path->mnt = NULL;
-+	}
-+	return err;
-+}
-+
-+static int __hash_lookup_topmost(struct nameidata *nd, struct qstr *name,
-+				 struct path *path)
-+{
-+	struct path next;
-+	int err;
-+
-+	err = lookup_hash(nd, name, path);
-+	if (err)
-+		return err;
-+
-+	if (path->dentry->d_inode || d_is_whiteout(path->dentry))
-+		return 0;
-+
-+	if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry))
-+		return 0;
-+
-+	while (follow_union_down(&nd->path)) {
-+		name->hash = full_name_hash(name->name, name->len);
-+		if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
-+			err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
-+							    name);
-+			if (err < 0)
-+				goto out;
-+		}
-+
-+		mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+		err = lookup_hash(nd, name, &next);
-+		mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
-+		if (err)
-+			goto out;
-+
-+		if (next.dentry->d_inode || d_is_whiteout(next.dentry)) {
-+			dput(path->dentry);
-+			mntget(next.mnt);
-+			*path = next;
-+			goto out;
-+		}
-+
-+		if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry))
-+			goto out;
-+
-+		dput(next.dentry);
-+	}
-+out:
-+	if (err)
-+		dput(path->dentry);
-+	return err;
-+}
-+
-+static int __hash_lookup_build_union(struct nameidata *nd, struct qstr *name,
-+				     struct path *path)
-+{
-+	struct path last = *path;
-+	struct path next;
-+	int err = 0;
-+
-+	while (follow_union_down(&nd->path)) {
-+		/* We need to recompute the hash for lower layer lookups */
-+		name->hash = full_name_hash(name->name, name->len);
-+		if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
-+			err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
-+							    name);
-+			if (err < 0)
-+				goto out;
-+		}
-+
-+		mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+		err = lookup_hash(nd, name, &next);
-+		mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
-+		if (err)
-+			goto out;
-+
-+		if (d_is_whiteout(next.dentry)) {
-+			dput(next.dentry);
-+			break;
-+		}
-+
-+		if (!next.dentry->d_inode) {
-+			dput(next.dentry);
-+			continue;
-+		}
-+
-+		/* only directories can be part of a union stack */
-+		if (!S_ISDIR(next.dentry->d_inode->i_mode)) {
-+			dput(next.dentry);
-+			break;
-+		}
-+
-+		/* now we know we found something "real" */
-+		append_to_union(last.mnt, last.dentry, next.mnt, next.dentry);
-+
-+		if (last.dentry != path->dentry)
-+			path_put(&last);
-+		last.dentry = next.dentry;
-+		last.mnt = mntget(next.mnt);
-+	}
-+
-+	if (last.dentry != path->dentry)
-+		path_put(&last);
-+out:
-+	return err;
-+}
-+
-+int hash_lookup_union(struct nameidata *nd, struct qstr *name,
-+			     struct path *path)
-+{
-+	struct path safe = { .dentry = nd->path.dentry, .mnt = nd->path.mnt };
-+	int res ;
-+
-+	path_get(&safe);
-+	res = __hash_lookup_topmost(nd, name, path);
-+	if (res)
-+		goto out;
-+
-+	/* only directories can be part of a union stack */
-+	if (!path->dentry->d_inode ||
-+	    !S_ISDIR(path->dentry->d_inode->i_mode))
-+		goto out;
-+
-+	/* Build the union stack for this part */
-+	res = __hash_lookup_build_union(nd, name, path);
-+	if (res) {
-+		dput(path->dentry);
-+		if (path->mnt != safe.mnt)
-+			mntput(path->mnt);
-+		goto out;
-+	}
-+
-+out:
-+	path_put(&nd->path);
-+	nd->path.dentry = safe.dentry;
-+	nd->path.mnt = safe.mnt;
-+	return res;
-+}
-+
-+/**
-+ * do_union_hash_lookup() - walk down the union stack and lookup_hash()
-+ * @nd: nameidata of parent to lookup from
-+ * @name: pathname component to lookup
-+ * @path: path to store result of lookup in
-+ *
-+ * Walk down the union stack and search for single pathname component name. It
-+ * is assumed that the caller already did a lookup_hash() in the topmost parent
-+ * that gave negative lookup result. Therefore this does call lookup_hash() in
-+ * every lower layer (!) of the union stack. If a directory is found the union
-+ * stack for that is assembled as well.
-+ *
-+ * Note:
-+ * The caller needs to take care of holding a valid reference to the topmost
-+ * parent.
-+ * On error we leave @path untouched as well as when we don't find anything.
-+ */
-+static int do_union_hash_lookup(struct nameidata *nd, struct qstr *name,
-+				struct path *path)
-+{
-+	struct path next;
-+	int err = 0;
-+
-+	while (follow_union_down(&nd->path)) {
-+		/* rehash because of d_op->d_hash() by the previous layer */
-+		name->hash = full_name_hash(name->name, name->len);
-+
-+		mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+		err = lookup_hash(nd, name, &next);
-+		mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
-+
-+		if (err)
-+			break;
-+
-+		if (next.dentry->d_inode) {
-+			mntget(next.mnt);
-+			if (!S_ISDIR(next.dentry->d_inode->i_mode)) {
-+				*path = next;
-+				break;
-+			}
-+			err = __hash_lookup_build_union(nd, name, &next);
-+			if (err)
-+				path_put(&next);
-+			else
-+				*path = next;
-+			break;
-+		}
-+
-+		path_put_conditional(&next, nd);
-+
-+		if ((IS_OPAQUE(nd->path.dentry->d_inode) &&
-+		     !d_is_fallthru(next.dentry)) ||
-+		    d_is_whiteout(next.dentry))
-+			break;
-+	}
-+
-+	return err;
-+}
-+
-+/**
-+ * _hash_lookup_union() - lookup single pathname component
-+ * @nd: nameidata of parent to lookup from
-+ * @name: pathname component to lookup
-+ * @path: path to store result of lookup in
-+ *
-+ * Returns the topmost parent locked and the target dentry found in the union
-+ * or the topmost negative target dentry otherwise.
-+ *
-+ * Note:
-+ * Returns topmost parent locked even on error.
-+ */
-+static int _hash_lookup_union(struct nameidata *nd, struct qstr *name,
-+			      struct path *path)
-+{
-+	struct path parent = nd->path;
-+	struct path topmost;
-+	int err;
-+
-+	mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+	err = lookup_hash(nd, name, path);
-+	if (err)
-+		return err;
-+
-+	/* return if we found something and it isn't a directory we are done */
-+	if (path->dentry->d_inode && !S_ISDIR(path->dentry->d_inode->i_mode))
-+		return 0;
-+
-+	/* stop lookup if the parent directory is marked opaque */
-+	if ((IS_OPAQUE(nd->path.dentry->d_inode) &&
-+	     !d_is_fallthru(path->dentry)) ||
-+	    d_is_whiteout(path->dentry))
-+		return 0;
-+
-+	if (!strcmp(path->mnt->mnt_sb->s_type->name, "proc") ||
-+	    !strcmp(path->mnt->mnt_sb->s_type->name, "sysfs"))
-+		return 0;
-+
-+	mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
-+
-+	/*
-+	 * safe a reference to the topmost parent for walking the union stack
-+	 */
-+	path_get(&parent);
-+	topmost = *path;
-+
-+	if (path->dentry->d_inode && S_ISDIR(path->dentry->d_inode->i_mode)) {
-+		err = __hash_lookup_build_union(nd, name, path);
-+		if (err)
-+			goto err_lock_parent;
-+		goto out_lock_and_revalidate_parent;
-+	}
-+
-+	err = do_union_hash_lookup(nd, name, path);
-+	if (err)
-+		goto err_lock_parent;
-+
-+out_lock_and_revalidate_parent:
-+	/* seems that we haven't found anything, so return the topmost */
-+	path_to_nameidata(&parent, nd);
-+	mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+
-+	if (topmost.dentry == path->dentry) {
-+		spin_lock(&path->dentry->d_lock);
-+		if (nd->path.dentry != path->dentry->d_parent) {
-+			spin_unlock(&path->dentry->d_lock);
-+			dput(path->dentry);
-+			name->hash = full_name_hash(name->name, name->len);
-+			err = lookup_hash(nd, name, path);
-+			if (err)
-+				return err;
-+			/* FIXME: What if we find a directory here ... */
-+			return err;
-+		}
-+		spin_unlock(&path->dentry->d_lock);
-+	} else
-+		dput(topmost.dentry);
-+
-+	return 0;
-+
-+err_lock_parent:
-+	path_to_nameidata(&parent, nd);
-+	path_put_conditional(path, nd);
-+	mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+	return err;
-+}
-+
-+/**
-+ * lookup_rename_source() - lookup the source used by rename
-+ *
-+ * This is a special version of _hash_lookup_union() which becomes necessary
-+ * for finding the source of a rename on union mounts.
-+ *
-+ * See comment for _hash_lookup_union() above.
-+ */
-+static int lookup_rename_source(struct nameidata *oldnd,
-+				struct nameidata *newnd,
-+				struct dentry **trap, struct qstr *name,
-+				struct path *old)
- {
--	struct dentry *dentry;
--	struct inode *inode;
-+	struct path parent = oldnd->path;
-+	struct path topmost;
- 	int err;
- 
--	inode = base->d_inode;
-+	err = lookup_hash(oldnd, name, old);
-+	if (err)
-+		return err;
-+
-+	/* return if we found something and it isn't a directory we are done */
-+	if (old->dentry->d_inode && !S_ISDIR(old->dentry->d_inode->i_mode))
-+		return 0;
-+
-+	/* stop lookup if the parent directory is marked opaque */
-+	if ((IS_OPAQUE(oldnd->path.dentry->d_inode) &&
-+	     !d_is_fallthru(old->dentry)) ||
-+	    d_is_whiteout(old->dentry))
-+		return 0;
-+
-+	if (!strcmp(old->mnt->mnt_sb->s_type->name, "proc") ||
-+	    !strcmp(old->mnt->mnt_sb->s_type->name, "sysfs"))
-+		return 0;
-+
-+	unlock_rename(oldnd->path.dentry, newnd->path.dentry);
- 
- 	/*
--	 * See if the low-level filesystem might want
--	 * to use its own hash..
-+	 * safe a reference to the topmost parent for walking the union stack
- 	 */
--	if (base->d_op && base->d_op->d_hash) {
--		err = base->d_op->d_hash(base, name);
--		dentry = ERR_PTR(err);
--		if (err < 0)
--			goto out;
-+	path_get(&parent);
-+	topmost = *old;
-+
-+	if (old->dentry->d_inode && S_ISDIR(old->dentry->d_inode->i_mode)) {
-+		err = __hash_lookup_build_union(oldnd, name, old);
-+		if (err)
-+			goto err_lock;
-+		goto out_lock_and_revalidate_parent;
- 	}
- 
--	dentry = cached_lookup(base, name, nd);
--	if (!dentry) {
--		struct dentry *new;
-+	err = do_union_hash_lookup(oldnd, name, old);
-+	if (err)
-+		goto err_lock;
- 
--		/* Don't create child dentry for a dead directory. */
--		dentry = ERR_PTR(-ENOENT);
--		if (IS_DEADDIR(inode))
--			goto out;
-+out_lock_and_revalidate_parent:
-+	path_to_nameidata(&parent, oldnd);
-+	*trap = lock_rename(oldnd->path.dentry, newnd->path.dentry);
- 
--		new = d_alloc(base, name);
--		dentry = ERR_PTR(-ENOMEM);
--		if (!new)
--			goto out;
--		dentry = inode->i_op->lookup(inode, new, nd);
--		if (!dentry)
--			dentry = new;
--		else
--			dput(new);
--	}
--out:
--	return dentry;
--}
-+	/*
-+	 * If we return the topmost dentry we have to make sure that it has not
-+	 * been moved away while we gave up the topmost parents i_mutex lock.
-+	 */
-+	if (topmost.dentry == old->dentry) {
-+		spin_lock(&old->dentry->d_lock);
-+		if (oldnd->path.dentry != old->dentry->d_parent) {
-+			spin_unlock(&old->dentry->d_lock);
-+			dput(old->dentry);
-+			name->hash = full_name_hash(name->name, name->len);
-+			err = lookup_hash(oldnd, name, old);
-+			if (err)
-+				return err;
-+			/* FIXME: What if we find a directory here ... */
-+			return err;
-+		}
-+		spin_unlock(&old->dentry->d_lock);
-+	} else
-+		dput(topmost.dentry);
- 
--/*
-- * Restricted form of lookup. Doesn't follow links, single-component only,
-- * needs parent already locked. Doesn't follow mounts.
-- * SMP-safe.
-- */
--static struct dentry *lookup_hash(struct nameidata *nd)
--{
--	int err;
-+	return 0;
- 
--	err = inode_permission(nd->path.dentry->d_inode, MAY_EXEC);
--	if (err)
--		return ERR_PTR(err);
--	return __lookup_hash(&nd->last, nd->path.dentry, nd);
-+err_lock:
-+	path_to_nameidata(&parent, oldnd);
-+	path_put_conditional(old, oldnd);
-+	*trap = lock_rename(oldnd->path.dentry, newnd->path.dentry);
-+	return err;
- }
- 
- static int __lookup_one_len(const char *name, struct qstr *this,
-@@ -1502,8 +2335,9 @@ int vfs_create(struct inode *dir, struct
- 	return error;
- }
- 
--int may_open(struct path *path, int acc_mode, int flag)
-+int may_open(struct nameidata *nd, int acc_mode, int flag)
- {
-+	struct path *path = &nd->path;
- 	struct dentry *dentry = path->dentry;
- 	struct inode *inode = dentry->d_inode;
- 	int error;
-@@ -1529,7 +2363,7 @@ int may_open(struct path *path, int acc_
- 		break;
- 	}
- 
--	error = inode_permission(inode, acc_mode);
-+	error = union_permission(path, acc_mode);
- 	if (error)
- 		return error;
- 
-@@ -1577,6 +2411,9 @@ int may_open(struct path *path, int acc_
- 		if (!error)
- 			error = security_path_truncate(path, 0,
- 					       ATTR_MTIME|ATTR_CTIME|ATTR_OPEN);
-+		/* XXX don't copy up file data */
-+		if (is_unionized(path->dentry, path->mnt))
-+			error = union_copyup(nd, flag /* XXX not used */);
- 		if (!error) {
- 			vfs_dq_init(inode);
- 
-@@ -1623,7 +2460,7 @@ out_unlock:
- 	if (error)
- 		return error;
- 	/* Don't check for write permission, don't truncate */
--	return may_open(&nd->path, 0, flag & ~O_TRUNC);
-+	return may_open(nd, 0, flag & ~O_TRUNC);
- }
- 
- /*
-@@ -1738,12 +2575,10 @@ struct file *do_filp_open(int dfd, const
- 	if (flag & O_EXCL)
- 		nd.flags |= LOOKUP_EXCL;
- 	mutex_lock(&dir->d_inode->i_mutex);
--	path.dentry = lookup_hash(&nd);
--	path.mnt = nd.path.mnt;
-+	error = hash_lookup_union(&nd, &nd.last, &path);
- 
- do_last:
--	error = PTR_ERR(path.dentry);
--	if (IS_ERR(path.dentry)) {
-+	if (error) {
- 		mutex_unlock(&dir->d_inode->i_mutex);
- 		goto exit;
- 	}
-@@ -1803,10 +2638,23 @@ do_last:
- 	if (path.dentry->d_inode->i_op->follow_link)
- 		goto do_link;
- 
--	path_to_nameidata(&path, &nd);
- 	error = -EISDIR;
- 	if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode))
--		goto exit;
-+		goto exit_dput;
-+
-+	/*
-+	 * If this file is on a lower layer of the union stack, copy it to the
-+	 * topmost layer before opening it
-+	 */
-+	if (path.dentry->d_inode &&
-+	    (path.dentry->d_parent != dir) &&
-+	    S_ISREG(path.dentry->d_inode->i_mode)) {
-+		error = __union_copyup(&path, &nd, &path);
-+		if (error)
-+			goto exit_dput;
-+	}
-+
-+	path_to_nameidata(&path, &nd);
- ok:
- 	/*
- 	 * Consider:
-@@ -1824,12 +2672,18 @@ ok:
- 		if (error)
- 			goto exit;
- 	}
--	error = may_open(&nd.path, acc_mode, flag);
-+	error = may_open(&nd, acc_mode, flag);
- 	if (error) {
- 		if (will_write)
- 			mnt_drop_write(nd.path.mnt);
- 		goto exit;
- 	}
-+	/* Okay, all permissions go, now copy up */
-+	if (!(flag & O_CREAT) && (flag & FMODE_WRITE)) {
-+		error = union_copyup(&nd, flag /* XXX not used */);
-+		if (error)
-+			goto exit;
-+	}
- 	filp = nameidata_to_filp(&nd, open_flag);
- 	if (IS_ERR(filp))
- 		ima_counts_put(&nd.path,
-@@ -1904,8 +2758,7 @@ do_link:
- 	}
- 	dir = nd.path.dentry;
- 	mutex_lock(&dir->d_inode->i_mutex);
--	path.dentry = lookup_hash(&nd);
--	path.mnt = nd.path.mnt;
-+	error = hash_lookup_union(&nd, &nd.last, &path);
- 	__putname(nd.last.name);
- 	goto do_last;
- }
-@@ -1939,7 +2792,8 @@ EXPORT_SYMBOL(filp_open);
-  */
- struct dentry *lookup_create(struct nameidata *nd, int is_dir)
- {
--	struct dentry *dentry = ERR_PTR(-EEXIST);
-+	struct path path = { .dentry = ERR_PTR(-EEXIST) } ;
-+	int err;
- 
- 	mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
- 	/*
-@@ -1955,11 +2809,13 @@ struct dentry *lookup_create(struct name
- 	/*
- 	 * Do the final lookup.
- 	 */
--	dentry = lookup_hash(nd);
--	if (IS_ERR(dentry))
-+	err = hash_lookup_union(nd, &nd->last, &path);
-+	if (err) {
-+		path.dentry = ERR_PTR(err);
- 		goto fail;
-+	}
- 
--	if (dentry->d_inode)
-+	if (path.dentry->d_inode)
- 		goto eexist;
- 	/*
- 	 * Special case - lookup gave negative, but... we had foo/bar/
-@@ -1968,15 +2824,17 @@ struct dentry *lookup_create(struct name
- 	 * been asking for (non-existent) directory. -ENOENT for you.
- 	 */
- 	if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
--		dput(dentry);
--		dentry = ERR_PTR(-ENOENT);
-+		path_put_conditional(&path, nd);
-+		path.dentry = ERR_PTR(-ENOENT);
- 	}
--	return dentry;
-+	if (nd->path.mnt != path.mnt)
-+		mntput(path.mnt);
-+	return path.dentry;
- eexist:
--	dput(dentry);
--	dentry = ERR_PTR(-EEXIST);
-+	path_put_conditional(&path, nd);
-+	path.dentry = ERR_PTR(-EEXIST);
- fail:
--	return dentry;
-+	return path.dentry;
- }
- EXPORT_SYMBOL_GPL(lookup_create);
- 
-@@ -2088,6 +2946,7 @@ SYSCALL_DEFINE3(mknod, const char __user
- int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
- {
- 	int error = may_create(dir, dentry);
-+	int opaque = 0;
- 
- 	if (error)
- 		return error;
-@@ -2101,9 +2960,18 @@ int vfs_mkdir(struct inode *dir, struct 
- 		return error;
- 
- 	vfs_dq_init(dir);
-+
-+	if (d_is_whiteout(dentry))
-+		opaque = 1;
-+
- 	error = dir->i_op->mkdir(dir, dentry, mode);
--	if (!error)
-+	if (!error) {
- 		fsnotify_mkdir(dir, dentry);
-+		if (opaque) {
-+			dentry->d_inode->i_flags |= S_OPAQUE;
-+			mark_inode_dirty(dentry->d_inode);
-+		}
-+	}
- 	return error;
- }
- 
-@@ -2149,6 +3017,212 @@ SYSCALL_DEFINE2(mkdir, const char __user
- 	return sys_mkdirat(AT_FDCWD, pathname, mode);
- }
- 
-+
-+/* Checks on the victim for whiteout */
-+static inline int may_whiteout(struct inode *dir, struct dentry *victim,
-+			       int isdir)
-+{
-+	int err;
-+
-+	/* from may_create() */
-+	if (IS_DEADDIR(dir))
-+		return -ENOENT;
-+	err = inode_permission(dir, MAY_WRITE | MAY_EXEC);
-+	if (err)
-+		return err;
-+
-+	/* from may_delete() */
-+	if (IS_APPEND(dir))
-+		return -EPERM;
-+	if (!victim->d_inode)
-+		return 0;
-+	if (check_sticky(dir, victim->d_inode) ||
-+	    IS_APPEND(victim->d_inode) ||
-+	    IS_IMMUTABLE(victim->d_inode))
-+		return -EPERM;
-+	if (isdir) {
-+		if (!S_ISDIR(victim->d_inode->i_mode))
-+			return -ENOTDIR;
-+		if (IS_ROOT(victim))
-+			return -EBUSY;
-+	} else if (S_ISDIR(victim->d_inode->i_mode))
-+		return -EISDIR;
-+	if (victim->d_flags & DCACHE_NFSFS_RENAMED)
-+		return -EBUSY;
-+	return 0;
-+}
-+
-+/**
-+ * vfs_whiteout: creates a white-out for the given directory entry
-+ * @dir: parent inode
-+ * @dentry: directory entry to white-out
-+ *
-+ * Simply white-out a given directory entry. This functionality is usually used
-+ * in the sense of unlink. Therefore the given dentry can still be in-use and
-+ * contains an in-use inode. The filesystem has to do what unlink or rmdir
-+ * would in that case. Since the dentry still might be in-use we have to
-+ * provide a fresh unhashed dentry that whiteout can fill the new inode into.
-+ * In that case the given dentry is dropped and the fresh dentry containing the
-+ * whiteout is rehashed instead. If the given dentry is unused, the whiteout
-+ * inode is instantiated into it instead.
-+ *
-+ * After this returns with success, don't make any assumptions about the inode.
-+ * Just dput() it dentry.
-+ */
-+static int vfs_whiteout(struct inode *dir, struct dentry *dentry, int isdir)
-+{
-+	int err;
-+	struct inode *old_inode = dentry->d_inode;
-+	struct dentry *parent, *whiteout;
-+
-+	err = may_whiteout(dir, dentry, isdir);
-+	if (err)
-+		return err;
-+
-+	BUG_ON(dentry->d_parent->d_inode != dir);
-+
-+	if (!dir->i_op || !dir->i_op->whiteout)
-+		return -EOPNOTSUPP;
-+
-+	if (old_inode) {
-+		vfs_dq_init(dir);
-+
-+		mutex_lock(&old_inode->i_mutex);
-+		if (isdir)
-+			dentry_unhash(dentry);
-+		if (d_mountpoint(dentry))
-+			err = -EBUSY;
-+		else {
-+			if (isdir)
-+				err = security_inode_rmdir(dir, dentry);
-+			else
-+				err = security_inode_unlink(dir, dentry);
-+		}
-+	}
-+
-+	parent = dget_parent(dentry);
-+	whiteout = d_alloc_name(parent, dentry->d_name.name);
-+
-+	if (!err)
-+		err = dir->i_op->whiteout(dir, dentry, whiteout);
-+
-+	if (old_inode) {
-+		mutex_unlock(&old_inode->i_mutex);
-+		if (!err) {
-+			fsnotify_link_count(old_inode);
-+			d_delete(dentry);
-+		}
-+		if (isdir)
-+			dput(dentry);
-+	}
-+
-+	dput(whiteout);
-+	dput(parent);
-+	return err;
-+}
-+
-+int path_whiteout(struct path *dir_path, struct dentry *dentry, int isdir)
-+{
-+	int error = mnt_want_write(dir_path->mnt);
-+
-+	if (!error) {
-+		error = vfs_whiteout(dir_path->dentry->d_inode, dentry, isdir);
-+		mnt_drop_write(dir_path->mnt);
-+	}
-+
-+	return error;
-+}
-+EXPORT_SYMBOL(path_whiteout);
-+
-+/*
-+ * This is abusing readdir to check if a union directory is logically empty.
-+ * Al Viro barfed when he saw this, but Val said: "Well, at this point I'm
-+ * aiming for working, pretty can come later"
-+ */
-+static int filldir_is_empty(void *__buf, const char *name, int namlen,
-+			    loff_t offset, u64 ino, unsigned int d_type)
-+{
-+	int *is_empty = (int *)__buf;
-+
-+	switch (namlen) {
-+	case 2:
-+		if (name[1] != '.')
-+			break;
-+	case 1:
-+		if (name[0] != '.')
-+			break;
-+		return 0;
-+	}
-+
-+	if (d_type == DT_WHT)
-+		return 0;
-+
-+	(*is_empty) = 0;
-+	return 0;
-+}
-+
-+static int directory_is_empty(struct dentry *dentry, struct vfsmount *mnt)
-+{
-+	struct file *file;
-+	int err;
-+	int is_empty = 1;
-+
-+	BUG_ON(!S_ISDIR(dentry->d_inode->i_mode));
-+
-+	/* references for the file pointer */
-+	dget(dentry);
-+	mntget(mnt);
-+
-+	file = dentry_open(dentry, mnt, O_RDONLY, current_cred());
-+	if (IS_ERR(file))
-+		return 0;
-+
-+	err = vfs_readdir(file, filldir_is_empty, &is_empty);
-+
-+	fput(file);
-+	return is_empty;
-+}
-+
-+static int do_whiteout(struct nameidata *nd, struct path *path, int isdir)
-+{
-+	struct path safe = { .dentry = dget(nd->path.dentry),
-+			     .mnt = mntget(nd->path.mnt) };
-+	struct dentry *dentry = path->dentry;
-+	int err;
-+
-+	err = may_whiteout(nd->path.dentry->d_inode, dentry, isdir);
-+	if (err)
-+		goto out;
-+
-+	err = -ENOENT;
-+	if (!dentry->d_inode)
-+		goto out;
-+
-+	err = -ENOTEMPTY;
-+	if (isdir && !directory_is_empty(path->dentry, path->mnt))
-+		goto out;
-+
-+	if (nd->path.dentry != dentry->d_parent) {
-+		dentry = __lookup_hash(&path->dentry->d_name, nd->path.dentry,
-+				       nd);
-+		err = PTR_ERR(dentry);
-+		if (IS_ERR(dentry))
-+			goto out;
-+
-+		dput(path->dentry);
-+		if (path->mnt != safe.mnt)
-+			mntput(path->mnt);
-+		path->mnt = nd->path.mnt;
-+		path->dentry = dentry;
-+	}
-+
-+	err = vfs_whiteout(nd->path.dentry->d_inode, dentry, isdir);
-+
-+out:
-+	path_put(&safe);
-+	return err;
-+}
-+
- /*
-  * We try to drop the dentry early: we should have
-  * a usage count of 2 if we're the only user of this
-@@ -2213,7 +3287,7 @@ static long do_rmdir(int dfd, const char
- {
- 	int error = 0;
- 	char * name;
--	struct dentry *dentry;
-+	struct path path;
- 	struct nameidata nd;
- 
- 	error = user_path_parent(dfd, pathname, &nd, &name);
-@@ -2235,21 +3309,24 @@ static long do_rmdir(int dfd, const char
- 	nd.flags &= ~LOOKUP_PARENT;
- 
- 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
--	dentry = lookup_hash(&nd);
--	error = PTR_ERR(dentry);
--	if (IS_ERR(dentry))
-+	error = hash_lookup_union(&nd, &nd.last, &path);
-+	if (error)
- 		goto exit2;
-+	if (is_unionized(nd.path.dentry, nd.path.mnt)) {
-+		error = do_whiteout(&nd, &path, 1);
-+		goto exit3;
-+	}
- 	error = mnt_want_write(nd.path.mnt);
- 	if (error)
- 		goto exit3;
--	error = security_path_rmdir(&nd.path, dentry);
-+	error = security_path_rmdir(&nd.path, path.dentry);
- 	if (error)
- 		goto exit4;
--	error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
-+	error = vfs_rmdir(nd.path.dentry->d_inode, path.dentry);
- exit4:
- 	mnt_drop_write(nd.path.mnt);
- exit3:
--	dput(dentry);
-+	path_put_conditional(&path, &nd);
- exit2:
- 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
- exit1:
-@@ -2304,7 +3381,7 @@ static long do_unlinkat(int dfd, const c
- {
- 	int error;
- 	char *name;
--	struct dentry *dentry;
-+	struct path path;
- 	struct nameidata nd;
- 	struct inode *inode = NULL;
- 
-@@ -2319,26 +3396,29 @@ static long do_unlinkat(int dfd, const c
- 	nd.flags &= ~LOOKUP_PARENT;
- 
- 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
--	dentry = lookup_hash(&nd);
--	error = PTR_ERR(dentry);
--	if (!IS_ERR(dentry)) {
-+	error = hash_lookup_union(&nd, &nd.last, &path);
-+	if (!error) {
- 		/* Why not before? Because we want correct error value */
- 		if (nd.last.name[nd.last.len])
- 			goto slashes;
--		inode = dentry->d_inode;
-+		inode = path.dentry->d_inode;
- 		if (inode)
- 			atomic_inc(&inode->i_count);
-+		if (is_unionized(nd.path.dentry, nd.path.mnt)) {
-+			error = do_whiteout(&nd, &path, 0);
-+			goto exit2;
-+		}
- 		error = mnt_want_write(nd.path.mnt);
- 		if (error)
- 			goto exit2;
--		error = security_path_unlink(&nd.path, dentry);
-+		error = security_path_unlink(&nd.path, path.dentry);
- 		if (error)
- 			goto exit3;
--		error = vfs_unlink(nd.path.dentry->d_inode, dentry);
-+		error = vfs_unlink(nd.path.dentry->d_inode, path.dentry);
- exit3:
- 		mnt_drop_write(nd.path.mnt);
- 	exit2:
--		dput(dentry);
-+		path_put_conditional(&path, &nd);
- 	}
- 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
- 	if (inode)
-@@ -2349,8 +3429,8 @@ exit1:
- 	return error;
- 
- slashes:
--	error = !dentry->d_inode ? -ENOENT :
--		S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
-+	error = !path.dentry->d_inode ? -ENOENT :
-+		S_ISDIR(path.dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
- 	goto exit2;
- }
- 
-@@ -2686,11 +3766,96 @@ int vfs_rename(struct inode *old_dir, st
- 	return error;
- }
- 
-+static int vfs_rename_union(struct nameidata *oldnd, struct path *old,
-+			    struct nameidata *newnd, struct path *new)
-+{
-+	struct inode *old_dir = oldnd->path.dentry->d_inode;
-+	struct inode *new_dir = newnd->path.dentry->d_inode;
-+	struct qstr old_name;
-+	char *name;
-+	struct dentry *dentry;
-+	int error;
-+
-+	if (old->dentry->d_inode == new->dentry->d_inode)
-+		return 0;
-+	error = may_whiteout(old_dir, old->dentry, 0);
-+	if (error)
-+		return error;
-+	if (!old_dir->i_op || !old_dir->i_op->whiteout)
-+		return -EPERM;
-+
-+	if (!new->dentry->d_inode)
-+		error = may_create(new_dir, new->dentry);
-+	else
-+		error = may_delete(new_dir, new->dentry, 0);
-+	if (error)
-+		return error;
-+
-+	vfs_dq_init(old_dir);
-+	vfs_dq_init(new_dir);
-+
-+	error = -EBUSY;
-+	if (d_mountpoint(old->dentry) || d_mountpoint(new->dentry))
-+		return error;
-+
-+	error = -ENOMEM;
-+	name = kmalloc(old->dentry->d_name.len, GFP_KERNEL);
-+	if (!name)
-+		return error;
-+	strncpy(name, old->dentry->d_name.name, old->dentry->d_name.len);
-+	name[old->dentry->d_name.len] = 0;
-+	old_name.len = old->dentry->d_name.len;
-+	old_name.hash = old->dentry->d_name.hash;
-+	old_name.name = name;
-+
-+	/* possibly delete the existing new file */
-+	if ((newnd->path.dentry == new->dentry->d_parent) &&
-+	    new->dentry->d_inode) {
-+		/* FIXME: inode may be truncated while we hold a lock */
-+		error = vfs_unlink(new_dir, new->dentry);
-+		if (error)
-+			goto freename;
-+
-+		dentry = __lookup_hash(&new->dentry->d_name,
-+				       newnd->path.dentry, newnd);
-+		if (IS_ERR(dentry))
-+			goto freename;
-+
-+		dput(new->dentry);
-+		new->dentry = dentry;
-+	}
-+
-+	/* copyup to the new file */
-+	error = __union_copyup(old, newnd, new);
-+	if (error)
-+		goto freename;
-+
-+	/* whiteout the old file */
-+	dentry = __lookup_hash(&old_name, oldnd->path.dentry, oldnd);
-+	error = PTR_ERR(dentry);
-+	if (IS_ERR(dentry))
-+		goto freename;
-+	error = vfs_whiteout(old_dir, dentry, 0);
-+	dput(dentry);
-+
-+	/* FIXME: This is acutally unlink() && create() ... */
-+/*
-+  if (!error) {
-+  const char *new_name = old_dentry->d_name.name;
-+  fsnotify_move(old_dir, new_dir, old_name.name, new_name, 0,
-+  new_dentry->d_inode, old_dentry->d_inode);
-+  }
-+*/
-+freename:
-+	kfree(old_name.name);
-+	return error;
-+}
-+
- SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
- 		int, newdfd, const char __user *, newname)
- {
- 	struct dentry *old_dir, *new_dir;
--	struct dentry *old_dentry, *new_dentry;
-+	struct path old, new;
- 	struct dentry *trap;
- 	struct nameidata oldnd, newnd;
- 	char *from;
-@@ -2724,16 +3889,28 @@ SYSCALL_DEFINE4(renameat, int, olddfd, c
- 
- 	trap = lock_rename(new_dir, old_dir);
- 
--	old_dentry = lookup_hash(&oldnd);
--	error = PTR_ERR(old_dentry);
--	if (IS_ERR(old_dentry))
-+	/*
-+	 * For union mounts we need to call a giant lookup_rename_source()
-+	 * instead.
-+	 * First lock_rename() and look on the topmost fs like you would do in
-+	 * the normal rename, if you find something which is not a directory,
-+	 * go ahead and lookup target and do normal rename.
-+	 * If you find a negative dentry, unlock_rename() and continue as
-+	 * _hash_lookup_union() would do without locking the topmost parent
-+	 * at the end. After that do lock_rename() of the source parent and the
-+	 * target parent and do a copyup with additional whiteout creation at
-+	 * the end.
-+	 */
-+//	error = hash_lookup_union(&oldnd, &oldnd.last, &old);
-+	error = lookup_rename_source(&oldnd, &newnd, &trap, &oldnd.last, &old);
-+	if (error)
- 		goto exit3;
- 	/* source must exist */
- 	error = -ENOENT;
--	if (!old_dentry->d_inode)
-+	if (!old.dentry->d_inode)
- 		goto exit4;
- 	/* unless the source is a directory trailing slashes give -ENOTDIR */
--	if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
-+	if (!S_ISDIR(old.dentry->d_inode->i_mode)) {
- 		error = -ENOTDIR;
- 		if (oldnd.last.name[oldnd.last.len])
- 			goto exit4;
-@@ -2742,32 +3919,44 @@ SYSCALL_DEFINE4(renameat, int, olddfd, c
- 	}
- 	/* source should not be ancestor of target */
- 	error = -EINVAL;
--	if (old_dentry == trap)
-+	if (old.dentry == trap)
- 		goto exit4;
--	new_dentry = lookup_hash(&newnd);
--	error = PTR_ERR(new_dentry);
--	if (IS_ERR(new_dentry))
-+	/* target is always on topmost fs, even with unions */
-+	error = lookup_hash(&newnd, &newnd.last, &new);
-+	if (error)
- 		goto exit4;
- 	/* target should not be an ancestor of source */
- 	error = -ENOTEMPTY;
--	if (new_dentry == trap)
-+	if (new.dentry == trap)
-+		goto exit5;
-+	/* renaming of directories on unions is done by the user-space */
-+	error = -EXDEV;
-+	if (is_unionized(oldnd.path.dentry, oldnd.path.mnt) &&
-+	    S_ISDIR(old.dentry->d_inode->i_mode))
- 		goto exit5;
-+//	if (is_unionized(newnd.path.dentry, newnd.path.mnt))
-+//		goto exit5;
- 
- 	error = mnt_want_write(oldnd.path.mnt);
- 	if (error)
- 		goto exit5;
--	error = security_path_rename(&oldnd.path, old_dentry,
--				     &newnd.path, new_dentry);
-+	error = security_path_rename(&oldnd.path, old.dentry,
-+				     &newnd.path, new.dentry);
- 	if (error)
- 		goto exit6;
--	error = vfs_rename(old_dir->d_inode, old_dentry,
--				   new_dir->d_inode, new_dentry);
-+	if (is_unionized(oldnd.path.dentry, oldnd.path.mnt) &&
-+	    (old.dentry->d_parent != oldnd.path.dentry)) {
-+		error = vfs_rename_union(&oldnd, &old, &newnd, &new);
-+		goto exit6;
-+	}
-+	error = vfs_rename(old_dir->d_inode, old.dentry,
-+				   new_dir->d_inode, new.dentry);
- exit6:
- 	mnt_drop_write(oldnd.path.mnt);
- exit5:
--	dput(new_dentry);
-+	path_put_conditional(&new, &newnd);
- exit4:
--	dput(old_dentry);
-+	path_put_conditional(&old, &oldnd);
- exit3:
- 	unlock_rename(new_dir, old_dir);
- exit2:
---- a/fs/namespace.c
-+++ b/fs/namespace.c
-@@ -29,6 +29,7 @@
- #include <linux/log2.h>
- #include <linux/idr.h>
- #include <linux/fs_struct.h>
-+#include <linux/union.h>
- #include <asm/uaccess.h>
- #include <asm/unistd.h>
- #include "pnode.h"
-@@ -150,6 +151,9 @@ struct vfsmount *alloc_vfsmnt(const char
- 		INIT_LIST_HEAD(&mnt->mnt_share);
- 		INIT_LIST_HEAD(&mnt->mnt_slave_list);
- 		INIT_LIST_HEAD(&mnt->mnt_slave);
-+#ifdef CONFIG_UNION_MOUNT
-+		INIT_LIST_HEAD(&mnt->mnt_unions);
-+#endif
- #ifdef CONFIG_SMP
- 		mnt->mnt_writers = alloc_percpu(int);
- 		if (!mnt->mnt_writers)
-@@ -469,6 +473,7 @@ static void __touch_mnt_namespace(struct
- 
- static void detach_mnt(struct vfsmount *mnt, struct path *old_path)
- {
-+	detach_mnt_union(mnt);
- 	old_path->dentry = mnt->mnt_mountpoint;
- 	old_path->mnt = mnt->mnt_parent;
- 	mnt->mnt_parent = mnt;
-@@ -492,6 +497,7 @@ static void attach_mnt(struct vfsmount *
- 	list_add_tail(&mnt->mnt_hash, mount_hashtable +
- 			hash(path->mnt, path->dentry));
- 	list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts);
-+	attach_mnt_union(mnt, path->mnt, path->dentry);
- }
- 
- /*
-@@ -514,6 +520,7 @@ static void commit_tree(struct vfsmount 
- 	list_add_tail(&mnt->mnt_hash, mount_hashtable +
- 				hash(parent, mnt->mnt_mountpoint));
- 	list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
-+	attach_mnt_union(mnt, mnt->mnt_parent, mnt->mnt_mountpoint);
- 	touch_mnt_namespace(n);
- }
- 
-@@ -770,6 +777,7 @@ static void show_mnt_opts(struct seq_fil
- 		{ MNT_NODIRATIME, ",nodiratime" },
- 		{ MNT_RELATIME, ",relatime" },
- 		{ MNT_STRICTATIME, ",strictatime" },
-+		{ MNT_UNION, ",union" },
- 		{ 0, NULL }
- 	};
- 	const struct proc_fs_info *fs_infop;
-@@ -984,6 +992,7 @@ void release_mounts(struct list_head *he
- 			struct dentry *dentry;
- 			struct vfsmount *m;
- 			spin_lock(&vfsmount_lock);
-+			detach_mnt_union(mnt);
- 			dentry = mnt->mnt_mountpoint;
- 			m = mnt->mnt_parent;
- 			mnt->mnt_mountpoint = mnt->mnt_root;
-@@ -1102,6 +1111,11 @@ static int do_umount(struct vfsmount *mn
- 	spin_unlock(&vfsmount_lock);
- 	if (retval)
- 		security_sb_umount_busy(mnt);
-+	/* If this was a union mount, we are no longer a read-only
-+	 * user on the underlying mount */
-+	if (mnt->mnt_flags & MNT_UNION)
-+		mnt->mnt_parent->mnt_sb->s_readonly_users--;
-+
- 	up_write(&namespace_sem);
- 	release_mounts(&umount_list);
- 	return retval;
-@@ -1426,6 +1440,10 @@ static int do_change_type(struct path *p
- 	if (path->dentry != path->mnt->mnt_root)
- 		return -EINVAL;
- 
-+	/* Don't change the type of union mounts */
-+	if (IS_MNT_UNION(path->mnt))
-+		return -EINVAL;
-+
- 	down_write(&namespace_sem);
- 	if (type == MS_SHARED) {
- 		err = invent_group_ids(mnt, recurse);
-@@ -1444,10 +1462,65 @@ static int do_change_type(struct path *p
- }
- 
- /*
-+ * Mount-time check of upper and lower layer file systems to see if we
-+ * can union mount one on the other.
-+ *
-+ * Union mounts must follow these rules:
-+ *
-+ * - The lower layer must be read-only.  This avoids lots of nasty
-+ *   unsolvable races where file system structures disappear suddenly.
-+ *   XXX - Checking the vfsmnt for read-only is a temporary hack; the
-+ *   file system could be mounted read-write elsewhere.  We need to
-+ *   enforce read-only at the superblock level (patches coming).
-+ *
-+ * - The upper layer must be writable.  This isn't an absolute
-+ *   requirement; right now we need it to make readdir() work since we
-+ *   copy up directory entries to the top level.  A possible
-+ *   workaround is to mount a tmpfs file system transparently over the
-+ *   top.
-+ *
-+ * - The upper layer must support whiteouts and fallthrus (if it is
-+ *   writeable).
-+ *
-+ * - The lower layer must not also be a union mount.  This is just to
-+ *   make life simpler for now, there is no inherent limitation on the
-+ *   number of layers.
-+ *
-+ * XXX - Check other mount flags for incompatibilities - I'm sure
-+ * there are some.
-+ */
-+
-+static int
-+check_union_mnt(struct path *mntpnt, struct vfsmount *top_mnt, int mnt_flags)
-+{
-+	struct vfsmount *lower_mnt = mntpnt->mnt;
-+
-+	/* Is this even a union mount? */
-+	if (!(mnt_flags & MNT_UNION))
-+		return 0;
-+
-+	/* Lower layer must be read-only and not a union mount */
-+	if (!(lower_mnt->mnt_sb->s_flags & MS_RDONLY) ||
-+	    (lower_mnt->mnt_flags & MNT_UNION))
-+		return -EBUSY;
-+
-+	/* Upper layer must be writable */
-+	if (mnt_flags & MNT_READONLY)
-+		return -EROFS;
-+
-+	/* Upper layer must support whiteouts and fallthrus */
-+	if (!(top_mnt->mnt_sb->s_flags & MS_WHITEOUT))
-+		return -EINVAL;
-+
-+	/* All good! */
-+	return 0;
-+}
-+
-+/*
-  * do loopback mount.
-  */
--static int do_loopback(struct path *path, char *old_name,
--				int recurse)
-+static int do_loopback(struct path *path, char *old_name, int recurse,
-+		       int mnt_flags)
- {
- 	struct path old_path;
- 	struct vfsmount *mnt = NULL;
-@@ -1477,6 +1550,13 @@ static int do_loopback(struct path *path
- 	if (!mnt)
- 		goto out;
- 
-+	err = check_union_mnt(&old_path, mnt, mnt_flags);
-+	if (err)
-+		goto out;
-+
-+	if (mnt_flags & MNT_UNION)
-+		mnt->mnt_flags |= MNT_UNION;
-+
- 	err = graft_tree(mnt, path);
- 	if (err) {
- 		LIST_HEAD(umount_list);
-@@ -1486,6 +1566,10 @@ static int do_loopback(struct path *path
- 		release_mounts(&umount_list);
- 	}
- 
-+	/* If this is a union mount, add ourselves to the readonly users */
-+	if (mnt_flags & MNT_UNION)
-+		mnt->mnt_parent->mnt_sb->s_readonly_users++;
-+
- out:
- 	up_write(&namespace_sem);
- 	path_put(&old_path);
-@@ -1570,6 +1654,13 @@ static int do_move_mount(struct path *pa
- 	if (err)
- 		return err;
- 
-+	/* moving to or from a union mount is not supported */
-+	err = -EINVAL;
-+	if (IS_MNT_UNION(path->mnt))
-+		goto exit;
-+	if (IS_MNT_UNION(old_path.mnt))
-+		goto exit;
-+
- 	down_write(&namespace_sem);
- 	while (d_mountpoint(path->dentry) &&
- 	       follow_down(path))
-@@ -1627,6 +1718,7 @@ out:
- 	up_write(&namespace_sem);
- 	if (!err)
- 		path_put(&parent_path);
-+exit:
- 	path_put(&old_path);
- 	return err;
- }
-@@ -1684,10 +1776,18 @@ int do_add_mount(struct vfsmount *newmnt
- 	if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
- 		goto unlock;
- 
-+	err = check_union_mnt(path, newmnt, mnt_flags);
-+	if (err)
-+		goto unlock;
-+
- 	newmnt->mnt_flags = mnt_flags;
- 	if ((err = graft_tree(newmnt, path)))
- 		goto unlock;
- 
-+	/* If this is a union mount, add ourselves to the readonly users */
-+	if (mnt_flags & MNT_UNION)
-+		newmnt->mnt_parent->mnt_sb->s_readonly_users++;
-+
- 	if (fslist) /* add to the specified expiration list */
- 		list_add_tail(&newmnt->mnt_expire, fslist);
- 
-@@ -1925,10 +2025,12 @@ long do_mount(char *dev_name, char *dir_
- 		mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
- 	if (flags & MS_RDONLY)
- 		mnt_flags |= MNT_READONLY;
-+	if (flags & MS_UNION)
-+		mnt_flags |= MNT_UNION;
- 
- 	flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
- 		   MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
--		   MS_STRICTATIME);
-+		   MS_STRICTATIME | MS_UNION);
- 
- 	/* ... and get the mountpoint */
- 	retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
-@@ -1944,7 +2046,8 @@ long do_mount(char *dev_name, char *dir_
- 		retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
- 				    data_page);
- 	else if (flags & MS_BIND)
--		retval = do_loopback(&path, dev_name, flags & MS_REC);
-+		retval = do_loopback(&path, dev_name, flags & MS_REC,
-+				     mnt_flags);
- 	else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
- 		retval = do_change_type(&path, flags);
- 	else if (flags & MS_MOVE)
-@@ -2179,6 +2282,8 @@ SYSCALL_DEFINE2(pivot_root, const char _
- 	if (d_unlinked(old.dentry))
- 		goto out2;
- 	error = -EBUSY;
-+	follow_union_down(&new);
-+	follow_union_down(&root);
- 	if (new.mnt == root.mnt ||
- 	    old.mnt == root.mnt)
- 		goto out2; /* loop, on the same file system  */
---- a/fs/nfsctl.c
-+++ b/fs/nfsctl.c
-@@ -38,10 +38,10 @@ static struct file *do_open(char *name, 
- 		return ERR_PTR(error);
- 
- 	if (flags == O_RDWR)
--		error = may_open(&nd.path, MAY_READ|MAY_WRITE,
--					   FMODE_READ|FMODE_WRITE);
-+		error = may_open(&nd, MAY_READ|MAY_WRITE,
-+				 FMODE_READ|FMODE_WRITE);
- 	else
--		error = may_open(&nd.path, MAY_WRITE, FMODE_WRITE);
-+		error = may_open(&nd, MAY_WRITE, FMODE_WRITE);
- 
- 	if (!error)
- 		return dentry_open(nd.path.dentry, nd.path.mnt, flags,
---- a/fs/nfsd/nfs3xdr.c
-+++ b/fs/nfsd/nfs3xdr.c
-@@ -884,6 +884,11 @@ encode_entry(struct readdir_cd *ccd, con
- 	int		elen;		/* estimated entry length in words */
- 	int		num_entry_words = 0;	/* actual number of words */
- 
-+	if (d_type == DT_WHT) {
-+		cd->common.err = nfs_ok;
-+		return 0;
-+	}
-+
- 	if (cd->offset) {
- 		u64 offset64 = offset;
- 
---- a/fs/nfsd/nfs4xdr.c
-+++ b/fs/nfsd/nfs4xdr.c
-@@ -2263,7 +2263,7 @@ nfsd4_encode_dirent(void *ccdv, const ch
- 	__be32 nfserr = nfserr_toosmall;
- 
- 	/* In nfsv4, "." and ".." never make it onto the wire.. */
--	if (name && isdotent(name, namlen)) {
-+	if (d_type == DT_WHT || (name && isdotent(name, namlen))) {
- 		cd->common.err = nfs_ok;
- 		return 0;
- 	}
---- a/fs/nfsd/nfsxdr.c
-+++ b/fs/nfsd/nfsxdr.c
-@@ -513,6 +513,10 @@ nfssvc_encode_entry(void *ccdv, const ch
- 			namlen, name, offset, ino);
- 	 */
- 
-+	if (d_type == DT_WHT) {
-+		cd->common.err = nfs_ok;
-+		return 0;
-+	}
- 	if (offset > ~((u32) 0)) {
- 		cd->common.err = nfserr_fbig;
- 		return -EINVAL;
---- a/fs/open.c
-+++ b/fs/open.c
-@@ -30,6 +30,7 @@
- #include <linux/audit.h>
- #include <linux/falloc.h>
- #include <linux/fs_struct.h>
-+#include <linux/union.h>
- 
- int vfs_statfs(struct dentry *dentry, struct kstatfs *buf)
- {
-@@ -222,69 +223,69 @@ int do_truncate(struct dentry *dentry, l
- 	return err;
- }
- 
--static long do_sys_truncate(const char __user *pathname, loff_t length)
-+static int __do_ftruncate(struct file *file, unsigned long length, int small)
- {
--	struct path path;
--	struct inode *inode;
-+	struct inode * inode;
-+	struct dentry *dentry;
- 	int error;
- 
- 	error = -EINVAL;
--	if (length < 0)	/* sorry, but loff_t says... */
-+	if (length < 0)
- 		goto out;
-+	/* explicitly opened as large or we are on 64-bit box */
-+	if (file->f_flags & O_LARGEFILE)
-+		small = 0;
- 
--	error = user_path(pathname, &path);
--	if (error)
-+	dentry = file->f_path.dentry;
-+	inode = dentry->d_inode;
-+	error = -EINVAL;
-+	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
- 		goto out;
--	inode = path.dentry->d_inode;
--
--	/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
--	error = -EISDIR;
--	if (S_ISDIR(inode->i_mode))
--		goto dput_and_out;
- 
- 	error = -EINVAL;
--	if (!S_ISREG(inode->i_mode))
--		goto dput_and_out;
--
--	error = mnt_want_write(path.mnt);
--	if (error)
--		goto dput_and_out;
-+	/* Cannot ftruncate over 2^31 bytes without large file support */
-+	if (small && length > MAX_NON_LFS)
- 
--	error = inode_permission(inode, MAY_WRITE);
--	if (error)
--		goto mnt_drop_write_and_out;
-+		goto out;
- 
- 	error = -EPERM;
- 	if (IS_APPEND(inode))
--		goto mnt_drop_write_and_out;
-+		goto out;
- 
--	error = get_write_access(inode);
--	if (error)
--		goto mnt_drop_write_and_out;
-+	error = locks_verify_truncate(inode, file, length);
-+	if (!error)
-+		error = security_path_truncate(&file->f_path, length,
-+					       ATTR_MTIME|ATTR_CTIME);
-+	if (!error)
-+		/* Already copied up for union, opened with write */
-+		error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
-+out:
-+	return error;
-+}
- 
--	/*
--	 * Make sure that there are no leases.  get_write_access() protects
--	 * against the truncate racing with a lease-granting setlease().
--	 */
--	error = break_lease(inode, FMODE_WRITE);
--	if (error)
--		goto put_write_and_out;
-+static long do_sys_truncate(const char __user *pathname, loff_t length)
-+{
-+	struct file *file;
-+	char *tmp;
-+	int error;
- 
--	error = locks_verify_truncate(inode, NULL, length);
--	if (!error)
--		error = security_path_truncate(&path, length, 0);
--	if (!error) {
--		vfs_dq_init(inode);
--		error = do_truncate(path.dentry, length, 0, NULL);
--	}
-+	error = -EINVAL;
-+	if (length < 0)	/* sorry, but loff_t says... */
-+		return error;
- 
--put_write_and_out:
--	put_write_access(inode);
--mnt_drop_write_and_out:
--	mnt_drop_write(path.mnt);
--dput_and_out:
--	path_put(&path);
--out:
-+	tmp = getname(pathname);
-+	if (IS_ERR(tmp))
-+		return PTR_ERR(tmp);
-+
-+	file = filp_open(tmp, O_RDWR | O_LARGEFILE, 0);
-+	putname(tmp);
-+
-+	if (IS_ERR(file))
-+		return PTR_ERR(file);
-+
-+	error = __do_ftruncate(file, length, 0);
-+
-+	fput(file);
- 	return error;
- }
- 
-@@ -296,45 +297,16 @@ SYSCALL_DEFINE2(truncate, const char __u
- 
- static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
- {
--	struct inode * inode;
--	struct dentry *dentry;
- 	struct file * file;
- 	int error;
- 
--	error = -EINVAL;
--	if (length < 0)
--		goto out;
- 	error = -EBADF;
- 	file = fget(fd);
- 	if (!file)
- 		goto out;
- 
--	/* explicitly opened as large or we are on 64-bit box */
--	if (file->f_flags & O_LARGEFILE)
--		small = 0;
--
--	dentry = file->f_path.dentry;
--	inode = dentry->d_inode;
--	error = -EINVAL;
--	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
--		goto out_putf;
--
--	error = -EINVAL;
--	/* Cannot ftruncate over 2^31 bytes without large file support */
--	if (small && length > MAX_NON_LFS)
--		goto out_putf;
-+	error = __do_ftruncate(file, length, small);
- 
--	error = -EPERM;
--	if (IS_APPEND(inode))
--		goto out_putf;
--
--	error = locks_verify_truncate(inode, file, length);
--	if (!error)
--		error = security_path_truncate(&file->f_path, length,
--					       ATTR_MTIME|ATTR_CTIME);
--	if (!error)
--		error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
--out_putf:
- 	fput(file);
- out:
- 	return error;
-@@ -493,7 +465,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, con
- 			goto out_path_release;
- 	}
- 
--	res = inode_permission(inode, mode | MAY_ACCESS);
-+	res = union_permission(&path, mode | MAY_ACCESS);
-+
- 	/* SuS v2 requires we report a read only fs too */
- 	if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
- 		goto out_path_release;
-@@ -507,7 +480,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, con
- 	 * inherently racy and know that the fs may change
- 	 * state before we even see this result.
- 	 */
--	if (__mnt_is_readonly(path.mnt))
-+	if ((!is_unionized(path.dentry, path.mnt) &&
-+	     (__mnt_is_readonly(path.mnt))))
- 		res = -EROFS;
- 
- out_path_release:
-@@ -553,20 +527,19 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd
- 	error = -EBADF;
- 	file = fget(fd);
- 	if (!file)
--		goto out;
-+		return error;
- 
- 	inode = file->f_path.dentry->d_inode;
- 
- 	error = -ENOTDIR;
- 	if (!S_ISDIR(inode->i_mode))
--		goto out_putf;
-+		goto out;
- 
- 	error = inode_permission(inode, MAY_EXEC | MAY_ACCESS);
- 	if (!error)
- 		set_fs_pwd(current->fs, &file->f_path);
--out_putf:
--	fput(file);
- out:
-+	fput(file);
- 	return error;
- }
- 
---- a/fs/readdir.c
-+++ b/fs/readdir.c
-@@ -16,6 +16,7 @@
- #include <linux/security.h>
- #include <linux/syscalls.h>
- #include <linux/unistd.h>
-+#include <linux/union.h>
- 
- #include <asm/uaccess.h>
- 
-@@ -36,9 +37,24 @@ int vfs_readdir(struct file *file, filld
- 
- 	res = -ENOENT;
- 	if (!IS_DEADDIR(inode)) {
-+		/*
-+		 * XXX Think harder about locking for
-+		 * union_copyup_dir.  Currently we lock the topmost
-+		 * directory and hold that lock while sequentially
-+		 * acquiring and dropping locks for the directories
-+		 * below this one in the union stack.
-+		 */
-+		if (is_unionized(file->f_path.dentry, file->f_path.mnt) &&
-+		    !IS_OPAQUE(inode)) {
-+			res = union_copyup_dir(&file->f_path);
-+			if (res)
-+				goto out_unlock;
-+		}
-+
- 		res = file->f_op->readdir(file, buf, filler);
- 		file_accessed(file);
- 	}
-+out_unlock:
- 	mutex_unlock(&inode->i_mutex);
- out:
- 	return res;
-@@ -77,6 +93,9 @@ static int fillonedir(void * __buf, cons
- 	struct old_linux_dirent __user * dirent;
- 	unsigned long d_ino;
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	if (buf->result)
- 		return -EINVAL;
- 	d_ino = ino;
-@@ -154,6 +173,9 @@ static int filldir(void * __buf, const c
- 	unsigned long d_ino;
- 	int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 2, sizeof(long));
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	buf->error = -EINVAL;	/* only used if we fail.. */
- 	if (reclen > buf->count)
- 		return -EINVAL;
-@@ -239,6 +261,9 @@ static int filldir64(void * __buf, const
- 	struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
- 	int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 1, sizeof(u64));
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	buf->error = -EINVAL;	/* only used if we fail.. */
- 	if (reclen > buf->count)
- 		return -EINVAL;
---- a/fs/super.c
-+++ b/fs/super.c
-@@ -553,6 +553,15 @@ int do_remount_sb(struct super_block *sb
- 	}
- 	remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
- 
-+	/* If we are remounting read/write, make sure that none of the
-+	   users require read-only for correct operation (such as
-+	   union mounts). */
-+	if (remount_rw && sb->s_readonly_users) {
-+		printk(KERN_INFO "%s: In use by %d read-only user(s)\n",
-+		       sb->s_id, sb->s_readonly_users);
-+		return -EROFS;
-+	}
-+
- 	if (sb->s_op->remount_fs) {
- 		retval = sb->s_op->remount_fs(sb, &flags, data);
- 		if (retval)
-@@ -889,6 +898,11 @@ vfs_kern_mount(struct file_system_type *
-  	if (error)
-  		goto out_sb;
- 
-+	error = -EROFS;
-+	if (!(flags & MS_RDONLY) &&
-+	    (mnt->mnt_sb->s_readonly_users))
-+		goto out_sb;
-+
- 	mnt->mnt_mountpoint = mnt->mnt_root;
- 	mnt->mnt_parent = mnt;
- 	up_write(&mnt->mnt_sb->s_umount);
---- /dev/null
-+++ b/fs/union.c
-@@ -0,0 +1,981 @@
-+/*
-+ * VFS based union mount for Linux
-+ *
-+ * Copyright (C) 2004-2007 IBM Corporation, IBM Deutschland Entwicklung GmbH.
-+ * Copyright (C) 2007-2009 Novell Inc.
-+ *
-+ *   Author(s): Jan Blunck ([email protected])
-+ *              Valerie Aurora <[email protected]>
-+ *
-+ * This program is free software; you can redistribute it and/or modify it
-+ * under the terms of the GNU General Public License as published by the Free
-+ * Software Foundation; either version 2 of the License, or (at your option)
-+ * any later version.
-+ */
-+
-+#include <linux/bootmem.h>
-+#include <linux/init.h>
-+#include <linux/module.h>
-+#include <linux/types.h>
-+#include <linux/hash.h>
-+#include <linux/fs.h>
-+#include <linux/mount.h>
-+#include <linux/fs_struct.h>
-+#include <linux/union.h>
-+#include <linux/namei.h>
-+#include <linux/file.h>
-+#include <linux/mm.h>
-+#include <linux/quotaops.h>
-+#include <linux/dnotify.h>
-+#include <linux/security.h>
-+#include <linux/pipe_fs_i.h>
-+#include <linux/splice.h>
-+
-+/*
-+ * This is borrowed from fs/inode.c. The hashtable for lookups. Somebody
-+ * should try to make this good - I've just made it work.
-+ */
-+static unsigned int union_hash_mask __read_mostly;
-+static unsigned int union_hash_shift __read_mostly;
-+static struct hlist_head *union_hashtable __read_mostly;
-+static unsigned int union_rhash_mask __read_mostly;
-+static unsigned int union_rhash_shift __read_mostly;
-+static struct hlist_head *union_rhashtable __read_mostly;
-+
-+/*
-+ * Locking Rules:
-+ * - dcache_lock (for union_rlookup() only)
-+ * - union_lock
-+ */
-+DEFINE_SPINLOCK(union_lock);
-+
-+static struct kmem_cache *union_cache __read_mostly;
-+
-+static unsigned long hash(struct dentry *dentry, struct vfsmount *mnt)
-+{
-+	unsigned long tmp;
-+
-+	tmp = ((unsigned long)mnt * (unsigned long)dentry) ^
-+		(GOLDEN_RATIO_PRIME + (unsigned long)mnt) / L1_CACHE_BYTES;
-+	tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> union_hash_shift);
-+	return tmp & union_hash_mask;
-+}
-+
-+static __initdata unsigned long union_hash_entries;
-+
-+static int __init set_union_hash_entries(char *str)
-+{
-+	if (!str)
-+		return 0;
-+	union_hash_entries = simple_strtoul(str, &str, 0);
-+	return 1;
-+}
-+
-+__setup("union_hash_entries=", set_union_hash_entries);
-+
-+static int __init init_union(void)
-+{
-+	int loop;
-+
-+	union_cache = KMEM_CACHE(union_mount, SLAB_PANIC | SLAB_MEM_SPREAD);
-+	union_hashtable = alloc_large_system_hash("Union-cache",
-+						  sizeof(struct hlist_head),
-+						  union_hash_entries,
-+						  14,
-+						  0,
-+						  &union_hash_shift,
-+						  &union_hash_mask,
-+						  0);
-+
-+	for (loop = 0; loop < (1 << union_hash_shift); loop++)
-+		INIT_HLIST_HEAD(&union_hashtable[loop]);
-+
-+
-+	union_rhashtable = alloc_large_system_hash("rUnion-cache",
-+						  sizeof(struct hlist_head),
-+						  union_hash_entries,
-+						  14,
-+						  0,
-+						  &union_rhash_shift,
-+						  &union_rhash_mask,
-+						  0);
-+
-+	for (loop = 0; loop < (1 << union_rhash_shift); loop++)
-+		INIT_HLIST_HEAD(&union_rhashtable[loop]);
-+
-+	return 0;
-+}
-+
-+fs_initcall(init_union);
-+
-+struct union_mount *union_alloc(struct dentry *this, struct vfsmount *this_mnt,
-+				struct dentry *next, struct vfsmount *next_mnt)
-+{
-+	struct union_mount *um;
-+
-+	BUG_ON(!S_ISDIR(this->d_inode->i_mode));
-+	BUG_ON(!S_ISDIR(next->d_inode->i_mode));
-+
-+	um = kmem_cache_alloc(union_cache, GFP_ATOMIC);
-+	if (!um)
-+		return NULL;
-+
-+	atomic_set(&um->u_count, 1);
-+	INIT_LIST_HEAD(&um->u_unions);
-+	INIT_LIST_HEAD(&um->u_list);
-+	INIT_HLIST_NODE(&um->u_hash);
-+	INIT_HLIST_NODE(&um->u_rhash);
-+
-+	um->u_this.mnt = this_mnt;
-+	um->u_this.dentry = this;
-+	um->u_next.mnt = mntget(next_mnt);
-+	um->u_next.dentry = dget(next);
-+
-+	return um;
-+}
-+
-+struct union_mount *union_get(struct union_mount *um)
-+{
-+	BUG_ON(!atomic_read(&um->u_count));
-+	atomic_inc(&um->u_count);
-+	return um;
-+}
-+
-+static int __union_put(struct union_mount *um)
-+{
-+	if (!atomic_dec_and_test(&um->u_count))
-+		return 0;
-+
-+	BUG_ON(!hlist_unhashed(&um->u_hash));
-+	BUG_ON(!hlist_unhashed(&um->u_rhash));
-+
-+	kmem_cache_free(union_cache, um);
-+	return 1;
-+}
-+
-+void union_put(struct union_mount *um)
-+{
-+	struct path tmp = um->u_next;
-+
-+	if (__union_put(um))
-+		path_put(&tmp);
-+}
-+
-+static void __union_hash(struct union_mount *um)
-+{
-+	hlist_add_head(&um->u_hash, union_hashtable +
-+		       hash(um->u_this.dentry, um->u_this.mnt));
-+	hlist_add_head(&um->u_rhash, union_rhashtable +
-+		       hash(um->u_next.dentry, um->u_next.mnt));
-+}
-+
-+static void __union_unhash(struct union_mount *um)
-+{
-+	hlist_del_init(&um->u_hash);
-+	hlist_del_init(&um->u_rhash);
-+}
-+
-+struct union_mount *union_lookup(struct dentry *dentry, struct vfsmount *mnt)
-+{
-+	struct hlist_head *head = union_hashtable + hash(dentry, mnt);
-+	struct hlist_node *node;
-+	struct union_mount *um;
-+
-+	hlist_for_each_entry(um, node, head, u_hash) {
-+		if ((um->u_this.dentry == dentry) &&
-+		    (um->u_this.mnt == mnt))
-+			return um;
-+	}
-+
-+	return NULL;
-+}
-+
-+struct union_mount *union_rlookup(struct dentry *dentry, struct vfsmount *mnt)
-+{
-+	struct hlist_head *head = union_rhashtable + hash(dentry, mnt);
-+	struct hlist_node *node;
-+	struct union_mount *um;
-+
-+	hlist_for_each_entry(um, node, head, u_rhash) {
-+		if ((um->u_next.dentry == dentry) &&
-+		    (um->u_next.mnt == mnt))
-+			return um;
-+	}
-+
-+	return NULL;
-+}
-+
-+/*
-+ * is_unionized - check if a dentry lives on a union mounted file system
-+ *
-+ * This tests if a dentry is living on an union mounted file system by walking
-+ * the file system hierarchy.
-+ */
-+int is_unionized(struct dentry *dentry, struct vfsmount *mnt)
-+{
-+	struct path this = { .mnt = mntget(mnt),
-+			     .dentry = dget(dentry) };
-+	struct vfsmount *tmp;
-+
-+	do {
-+		/* check if there is an union mounted on top of us */
-+		spin_lock(&vfsmount_lock);
-+		list_for_each_entry(tmp, &this.mnt->mnt_mounts, mnt_child) {
-+			if (!(tmp->mnt_flags & MNT_UNION))
-+				continue;
-+			/* Isn't this a bug? */
-+			if (this.dentry->d_sb != tmp->mnt_mountpoint->d_sb)
-+				continue;
-+			if (is_subdir(this.dentry, tmp->mnt_mountpoint)) {
-+				spin_unlock(&vfsmount_lock);
-+				path_put(&this);
-+				return 1;
-+			}
-+		}
-+		spin_unlock(&vfsmount_lock);
-+
-+		/* check our mountpoint next */
-+		tmp = mntget(this.mnt->mnt_parent);
-+		dput(this.dentry);
-+		this.dentry = dget(this.mnt->mnt_mountpoint);
-+		mntput(this.mnt);
-+		this.mnt = tmp;
-+	} while (this.mnt != this.mnt->mnt_parent);
-+
-+	path_put(&this);
-+	return 0;
-+}
-+
-+int append_to_union(struct vfsmount *mnt, struct dentry *dentry,
-+		    struct vfsmount *dest_mnt, struct dentry *dest_dentry)
-+{
-+	struct union_mount *this, *um;
-+
-+	BUG_ON(!IS_MNT_UNION(mnt));
-+
-+	this = union_alloc(dentry, mnt, dest_dentry, dest_mnt);
-+	if (!this)
-+		return -ENOMEM;
-+
-+	spin_lock(&union_lock);
-+	um = union_lookup(dentry, mnt);
-+	if (um) {
-+		BUG_ON((um->u_next.dentry != dest_dentry) ||
-+		       (um->u_next.mnt != dest_mnt));
-+		spin_unlock(&union_lock);
-+		union_put(this);
-+		return 0;
-+	}
-+	list_add(&this->u_list, &mnt->mnt_unions);
-+	list_add(&this->u_unions, &dentry->d_unions);
-+	dest_dentry->d_unionized++;
-+	__union_hash(this);
-+	spin_unlock(&union_lock);
-+	return 0;
-+}
-+
-+/*
-+ * follow_union_down - follow the union stack one layer down
-+ *
-+ * This is called to traverse the union stack from one layer to the next
-+ * overlayed one. follow_union_down() is called by various lookup functions
-+ * that are aware of union mounts.
-+ *
-+ * Returns non-zero if followed to the next layer, zero otherwise.
-+ */
-+int follow_union_down(struct path *path)
-+{
-+	struct union_mount *um;
-+
-+	if (!IS_MNT_UNION(path->mnt))
-+		return 0;
-+
-+	spin_lock(&union_lock);
-+	um = union_lookup(path->dentry, path->mnt);
-+	spin_unlock(&union_lock);
-+	if (um) {
-+		path_get(&um->u_next);
-+		dput(path->dentry);
-+		path->dentry = um->u_next.dentry;
-+		mntput(path->mnt);
-+		path->mnt = um->u_next.mnt;
-+		return 1;
-+	}
-+	return 0;
-+}
-+
-+/*
-+ * follow_union_mount - follow the union stack to the topmost layer
-+ *
-+ * This is called to traverse the union stack to the topmost layer. This is
-+ * necessary for following parent pointers in an union mount.
-+ *
-+ * Returns none zero if followed to the topmost layer, zero otherwise.
-+ */
-+int follow_union_mount(struct path *path)
-+{
-+	struct union_mount *um;
-+	int res = 0;
-+
-+	while (IS_UNION(path->dentry)) {
-+		spin_lock(&dcache_lock);
-+		spin_lock(&union_lock);
-+		um = union_rlookup(path->dentry, path->mnt);
-+		if (um)
-+			path_get(&um->u_this);
-+		spin_unlock(&union_lock);
-+		spin_unlock(&dcache_lock);
-+
-+		/*
-+		 * Q: Aaargh, how do I validate the topmost dentry pointer?
-+		 * A: Eeeeasy! We took the dcache_lock and union_lock. Since
-+		 *    this protects from any dput'ng going on, we know that the
-+		 *    dentry is valid since the union is unhashed under
-+		 *    dcache_lock too.
-+		 */
-+		if (!um)
-+			break;
-+		dput(path->dentry);
-+		path->dentry = um->u_this.dentry;
-+		mntput(path->mnt);
-+		path->mnt = um->u_this.mnt;
-+		res = 1;
-+	}
-+
-+	return res;
-+}
-+
-+/*
-+ * Union mount copyup support
-+ */
-+
-+extern int hash_lookup_union(struct nameidata *, struct qstr *, struct path *);
-+extern void follow_mount(struct path *);
-+
-+/*
-+ * union_relookup_topmost - lookup and create the topmost path to dentry
-+ * @nd: pointer to nameidata
-+ * @flags: lookup flags
-+ */
-+static int union_relookup_topmost(struct nameidata *nd, int flags)
-+{
-+	int err;
-+	char *kbuf, *name;
-+	struct nameidata this;
-+
-+	kbuf = (char *)__get_free_page(GFP_KERNEL);
-+	if (!kbuf)
-+		return -ENOMEM;
-+
-+	name = d_path(&nd->path, kbuf, PAGE_SIZE);
-+	err = PTR_ERR(name);
-+	if (IS_ERR(name))
-+		goto free_page;
-+
-+	err = path_lookup(name, flags|LOOKUP_CREATE|LOOKUP_TOPMOST, &this);
-+	if (err)
-+		goto free_page;
-+
-+	path_put(&nd->path);
-+	nd->path.dentry = this.path.dentry;
-+	nd->path.mnt = this.path.mnt;
-+
-+	/*
-+	 * the nd->flags should be unchanged
-+	 */
-+	BUG_ON(this.um_flags & LAST_LOWLEVEL);
-+	nd->um_flags &= ~LAST_LOWLEVEL;
-+ free_page:
-+	free_page((unsigned long)kbuf);
-+	return err;
-+}
-+
-+static void __update_fs_pwd(struct path *path, struct dentry *dentry,
-+			    struct vfsmount *mnt)
-+{
-+	struct path old = { NULL, NULL };
-+
-+	write_lock(&current->fs->lock);
-+	if (current->fs->pwd.dentry == path->dentry) {
-+		old = current->fs->pwd;
-+		path_get(&current->fs->pwd);
-+	}
-+	write_unlock(&current->fs->lock);
-+
-+	if (old.dentry)
-+		path_put(&old);
-+
-+	return;
-+}
-+
-+/**
-+ * union_permission  -  check for access rights to a given inode
-+ * @inode:	inode to check permission on
-+ * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
-+ *
-+ * In a union mount, the top layer is always read-write and the bottom
-+ * is always read-only.  Ignore the read-only flag on the lower fs.
-+ *
-+ * Only need for certain activities, like checking to see if write
-+ * access is ok.
-+ */
-+
-+int union_permission(struct path *path, int mask)
-+{
-+	struct inode *inode = path->dentry->d_inode;
-+
-+	if (!is_unionized(path->dentry, path->mnt))
-+		return inode_permission(inode, mask);
-+
-+	/* Tell __inode_permission to ignore MS_RDONLY */
-+	return __inode_permission(inode, mask, 0);
-+}
-+
-+/*
-+ * union_create_topmost - create the topmost path component
-+ * @nd: pointer to nameidata of the base directory
-+ * @name: pointer to file name
-+ * @path: pointer to path of the overlaid file
-+ *
-+ * This is called by __link_path_walk() to create the directories on a path
-+ * when it is called with LOOKUP_TOPMOST.
-+ */
-+struct dentry *union_create_topmost(struct nameidata *nd, struct qstr *name,
-+				    struct path *path)
-+{
-+	struct dentry *dentry, *parent = nd->path.dentry;
-+	int res, mode = path->dentry->d_inode->i_mode;
-+
-+	if (parent->d_sb == path->dentry->d_sb)
-+		return ERR_PTR(-EEXIST);
-+
-+	mutex_lock(&parent->d_inode->i_mutex);
-+	dentry = lookup_one_len(name->name, nd->path.dentry, name->len);
-+	if (IS_ERR(dentry))
-+		goto out_unlock;
-+
-+	switch (mode & S_IFMT) {
-+	case S_IFREG:
-+		/*
-+		 * FIXME: Does this make any sense in this case?
-+		 * Special case - lookup gave negative, but... we had foo/bar/
-+		 * From the vfs_mknod() POV we just have a negative dentry -
-+		 * all is fine. Let's be bastards - you had / on the end,you've
-+		 * been asking for (non-existent) directory. -ENOENT for you.
-+		 */
-+		if (name->name[name->len] && !dentry->d_inode) {
-+			dput(dentry);
-+			dentry = ERR_PTR(-ENOENT);
-+			goto out_unlock;
-+		}
-+
-+		res = vfs_create(parent->d_inode, dentry, mode, nd);
-+		if (res) {
-+			dput(dentry);
-+			dentry = ERR_PTR(res);
-+			goto out_unlock;
-+		}
-+		break;
-+	case S_IFDIR:
-+		res = vfs_mkdir(parent->d_inode, dentry, mode);
-+		if (res) {
-+			dput(dentry);
-+			dentry = ERR_PTR(res);
-+			goto out_unlock;
-+		}
-+
-+		res = append_to_union(nd->path.mnt, dentry, path->mnt,
-+				      path->dentry);
-+		if (res) {
-+			dput(dentry);
-+			dentry = ERR_PTR(res);
-+			goto out_unlock;
-+		}
-+		break;
-+	default:
-+		dput(dentry);
-+		dentry = ERR_PTR(-EINVAL);
-+		goto out_unlock;
-+	}
-+
-+	/* FIXME: Really necessary ??? */
-+/*	__update_fs_pwd(path, dentry, nd->path.mnt); */
-+
-+ out_unlock:
-+	mutex_unlock(&parent->d_inode->i_mutex);
-+	return dentry;
-+}
-+
-+static int union_copy_file(struct dentry *old_dentry, struct vfsmount *old_mnt,
-+			   struct dentry *new_dentry, struct vfsmount *new_mnt)
-+{
-+	int ret;
-+	size_t size;
-+	loff_t offset;
-+	struct file *old_file, *new_file;
-+	const struct cred *cred = current_cred();
-+
-+	dget(old_dentry);
-+	mntget(old_mnt);
-+	old_file = dentry_open(old_dentry, old_mnt, O_RDONLY, cred);
-+	if (IS_ERR(old_file))
-+		return PTR_ERR(old_file);
-+
-+	dget(new_dentry);
-+	mntget(new_mnt);
-+	new_file = dentry_open(new_dentry, new_mnt, O_WRONLY, cred);
-+	ret = PTR_ERR(new_file);
-+	if (IS_ERR(new_file))
-+		goto fput_old;
-+
-+	/* XXX be smart by using a length param, which indicates max
-+	 * data we'll want (e.g., we are about to truncate to 0 or 10
-+	 * bytes or something */
-+	size = i_size_read(old_file->f_path.dentry->d_inode);
-+	if (((size_t)size != size) || ((ssize_t)size != size)) {
-+		ret = -EFBIG;
-+		goto fput_new;
-+	}
-+
-+	offset = 0;
-+	ret = do_splice_direct(old_file, &offset, new_file, size,
-+			       SPLICE_F_MOVE);
-+	if (ret >= 0)
-+		ret = 0;
-+ fput_new:
-+	fput(new_file);
-+ fput_old:
-+	fput(old_file);
-+	return ret;
-+}
-+
-+/**
-+ * __union_copyup - copy a file to the topmost directory
-+ * @old: pointer to path of the old file name
-+ * @new_nd: pointer to nameidata of the topmost directory
-+ * @new: pointer to path of the new file name
-+ *
-+ * The topmost directory @new_nd must already be locked. Creates the topmost
-+ * file if it doesn't exist yet.
-+ */
-+int __union_copyup(struct path *old, struct nameidata *new_nd,
-+		   struct path *new)
-+{
-+	struct dentry *dentry;
-+	int error;
-+
-+	/* Maybe this should be -EINVAL */
-+	if (S_ISDIR(old->dentry->d_inode->i_mode))
-+		return -EISDIR;
-+
-+	if (new_nd->path.dentry != new->dentry->d_parent) {
-+		mutex_lock(&new_nd->path.dentry->d_inode->i_mutex);
-+		dentry = lookup_one_len(new->dentry->d_name.name,
-+					new_nd->path.dentry,
-+					new->dentry->d_name.len);
-+		mutex_unlock(&new_nd->path.dentry->d_inode->i_mutex);
-+		if (IS_ERR(dentry))
-+			return PTR_ERR(dentry);
-+		error = -EEXIST;
-+		if (dentry->d_inode)
-+			goto out_dput;
-+	} else
-+		dentry = dget(new->dentry);
-+
-+	if (!dentry->d_inode) {
-+		error = vfs_create(new_nd->path.dentry->d_inode, dentry,
-+				   old->dentry->d_inode->i_mode, new_nd);
-+		if (error)
-+			goto out_dput;
-+	}
-+
-+	BUG_ON(!S_ISREG(old->dentry->d_inode->i_mode));
-+	error = union_copy_file(old->dentry, old->mnt, dentry,
-+				new_nd->path.mnt);
-+	if (error) {
-+		/* FIXME: are there return value we should not
-+		 * BUG() on ? */
-+		BUG_ON(vfs_unlink(new_nd->path.dentry->d_inode,
-+				  dentry));
-+		goto out_dput;
-+	}
-+
-+	dput(new->dentry);
-+	new->dentry = dentry;
-+	if (new->mnt != new_nd->path.mnt)
-+		mntput(new->mnt);
-+	new->mnt = new_nd->path.mnt;
-+	return error;
-+
-+out_dput:
-+	dput(dentry);
-+	return error;
-+}
-+
-+/*
-+ * union_copyup - copy a file to the topmost layer of the union stack
-+ * @nd: nameidata pointer to the file
-+ * @flags: flags given to open_namei
-+ */
-+int union_copyup(struct nameidata *nd, int flags /* XXX not used */)
-+{
-+	struct qstr this;
-+	char *name;
-+	struct dentry *dir;
-+	struct path path;
-+	int err;
-+
-+	if (!is_unionized(nd->path.dentry, nd->path.mnt))
-+		return 0;
-+	if (!S_ISREG(nd->path.dentry->d_inode->i_mode))
-+		return 0;
-+
-+	/* safe the name for hash_lookup_union() */
-+	this.len = nd->path.dentry->d_name.len;
-+	this.hash = nd->path.dentry->d_name.hash;
-+	name = kmalloc(this.len + 1, GFP_KERNEL);
-+	if (!name)
-+		return -ENOMEM;
-+	this.name = name;
-+	memcpy(name, nd->path.dentry->d_name.name, nd->path.dentry->d_name.len);
-+	name[this.len] = 0;
-+
-+	err = union_relookup_topmost(nd, nd->flags|LOOKUP_PARENT);
-+	if (err) {
-+		kfree(name);
-+		return err;
-+	}
-+	nd->flags &= ~LOOKUP_PARENT;
-+
-+	dir = nd->path.dentry;
-+	mutex_lock(&dir->d_inode->i_mutex);
-+	err = hash_lookup_union(nd, &this, &path);
-+	mutex_unlock(&dir->d_inode->i_mutex);
-+	kfree(name);
-+	if (err)
-+		return err;
-+
-+	err = -ENOENT;
-+	if (!path.dentry->d_inode)
-+		goto exit_dput;
-+
-+	/* Necessary?! I guess not ... */
-+	follow_mount(&path);
-+
-+	err = -ENOENT;
-+	if (!path.dentry->d_inode)
-+		goto exit_dput;
-+
-+	err = -EISDIR;
-+	if (!S_ISREG(path.dentry->d_inode->i_mode))
-+		goto exit_dput;
-+
-+	if (path.dentry->d_parent != nd->path.dentry) {
-+		err = __union_copyup(&path, nd, &path);
-+		if (err)
-+			goto exit_dput;
-+	}
-+
-+	dput(nd->path.dentry);
-+	if (nd->path.mnt != path.mnt)
-+		mntput(nd->path.mnt);
-+	nd->path = path;
-+	return 0;
-+
-+exit_dput:
-+	dput(path.dentry);
-+	if (path.mnt != nd->path.mnt)
-+		mntput(path.mnt);
-+	return err;
-+}
-+
-+/*
-+ * This must be called when unhashing a dentry. This is called with dcache_lock
-+ * and unhashes all unions this dentry is in.
-+ */
-+void __d_drop_unions(struct dentry *dentry)
-+{
-+	struct union_mount *this, *next;
-+
-+	spin_lock(&union_lock);
-+	list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions)
-+		__union_unhash(this);
-+	spin_unlock(&union_lock);
-+}
-+EXPORT_SYMBOL_GPL(__d_drop_unions);
-+
-+/*
-+ * This must be called after __d_drop_unions() without holding any locks.
-+ * Note: The dentry might still be reachable via a lookup but at that time it
-+ * already a negative dentry. Otherwise it would be unhashed. The union_mount
-+ * structure itself is still reachable through mnt->mnt_unions (which we
-+ * protect against with union_lock).
-+ */
-+void shrink_d_unions(struct dentry *dentry)
-+{
-+	struct union_mount *this, *next;
-+
-+repeat:
-+	spin_lock(&union_lock);
-+	list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions) {
-+		BUG_ON(!hlist_unhashed(&this->u_hash));
-+		BUG_ON(!hlist_unhashed(&this->u_rhash));
-+		list_del(&this->u_list);
-+		list_del(&this->u_unions);
-+		this->u_next.dentry->d_unionized--;
-+		spin_unlock(&union_lock);
-+		union_put(this);
-+		goto repeat;
-+	}
-+	spin_unlock(&union_lock);
-+}
-+
-+extern void __dput(struct dentry *, struct list_head *, int);
-+
-+/*
-+ * This is the special variant for use in dput() only.
-+ */
-+void __shrink_d_unions(struct dentry *dentry, struct list_head *list)
-+{
-+	struct union_mount *this, *next;
-+
-+	BUG_ON(!d_unhashed(dentry));
-+
-+repeat:
-+	spin_lock(&union_lock);
-+	list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions) {
-+		struct dentry *n_dentry = this->u_next.dentry;
-+		struct vfsmount *n_mnt = this->u_next.mnt;
-+
-+		BUG_ON(!hlist_unhashed(&this->u_hash));
-+		BUG_ON(!hlist_unhashed(&this->u_rhash));
-+		list_del(&this->u_list);
-+		list_del(&this->u_unions);
-+		this->u_next.dentry->d_unionized--;
-+		spin_unlock(&union_lock);
-+		if (__union_put(this)) {
-+			__dput(n_dentry, list, 0);
-+			mntput(n_mnt);
-+		}
-+		goto repeat;
-+	}
-+	spin_unlock(&union_lock);
-+}
-+
-+/*
-+ * Remove all union_mounts structures belonging to this vfsmount from the
-+ * union lookup hashtable and so on ...
-+ */
-+void shrink_mnt_unions(struct vfsmount *mnt)
-+{
-+	struct union_mount *this, *next;
-+
-+repeat:
-+	spin_lock(&union_lock);
-+	list_for_each_entry_safe(this, next, &mnt->mnt_unions, u_list) {
-+		if (this->u_this.dentry == mnt->mnt_root)
-+			continue;
-+		__union_unhash(this);
-+		list_del(&this->u_list);
-+		list_del(&this->u_unions);
-+		this->u_next.dentry->d_unionized--;
-+		spin_unlock(&union_lock);
-+		union_put(this);
-+		goto repeat;
-+	}
-+	spin_unlock(&union_lock);
-+}
-+
-+int attach_mnt_union(struct vfsmount *mnt, struct vfsmount *dest_mnt,
-+		     struct dentry *dest_dentry)
-+{
-+	if (!IS_MNT_UNION(mnt))
-+		return 0;
-+
-+	return append_to_union(mnt, mnt->mnt_root, dest_mnt, dest_dentry);
-+}
-+
-+void detach_mnt_union(struct vfsmount *mnt)
-+{
-+	struct union_mount *um;
-+
-+	if (!IS_MNT_UNION(mnt))
-+		return;
-+
-+	shrink_mnt_unions(mnt);
-+
-+	spin_lock(&union_lock);
-+	um = union_lookup(mnt->mnt_root, mnt);
-+	__union_unhash(um);
-+	list_del(&um->u_list);
-+	list_del(&um->u_unions);
-+	um->u_next.dentry->d_unionized--;
-+	spin_unlock(&union_lock);
-+	union_put(um);
-+	return;
-+}
-+
-+/**
-+ * union_copyup_dir_one - copy up a single directory entry
-+ *
-+ * Individual directory entry copyup function for union_copyup_dir.
-+ * We get the entries from higher level layers first.
-+ */
-+
-+static int union_copyup_dir_one(void *buf, const char *name, int namlen,
-+				loff_t offset, u64 ino, unsigned int d_type)
-+{
-+	struct dentry *topmost_dentry = (struct dentry *) buf;
-+	struct dentry *dentry;
-+	int err = 0;
-+
-+	switch (namlen) {
-+	case 2:
-+		if (name[1] != '.')
-+			break;
-+	case 1:
-+		if (name[0] != '.')
-+			break;
-+		return 0;
-+	}
-+
-+	/* Lookup this entry in the topmost directory */
-+	dentry = lookup_one_len(name, topmost_dentry, namlen);
-+
-+	if (IS_ERR(dentry)) {
-+		printk(KERN_INFO "error looking up %s\n", dentry->d_name.name);
-+		goto out;
-+	}
-+
-+	/*
-+	 * If the entry already exists, one of the following is true:
-+	 * it was already copied up (due to an earlier lookup), an
-+	 * entry with the same name already exists on the topmost file
-+	 * system, it is a whiteout, or it is a fallthru.  In each
-+	 * case, the top level entry masks any entries from lower file
-+	 * systems, so don't copy up this entry.
-+	 */
-+	if (dentry->d_inode || d_is_whiteout(dentry) ||
-+	    d_is_fallthru(dentry)) {
-+		printk(KERN_INFO "skipping copy of %s\n", dentry->d_name.name);
-+		goto out_dput;
-+	}
-+
-+	/*
-+	 * If the entry doesn't exist, create a fallthru entry in the
-+	 * topmost file system.  All possible directory types are
-+	 * used, so each file system must implement its own way of
-+	 * storing a fallthru entry.
-+	 */
-+	printk(KERN_INFO "creating fallthru for %s\n", dentry->d_name.name);
-+	err = topmost_dentry->d_inode->i_op->fallthru(topmost_dentry->d_inode,
-+						      dentry);
-+	/* FIXME */
-+	BUG_ON(err);
-+	/*
-+	 * At this point, we have a negative dentry marked as fallthru
-+	 * in the cache.  We could potentially lookup the entry lower
-+	 * level file system and turn this into a positive dentry
-+	 * right now, but it is not clear that would be a performance
-+	 * win and adds more opportunities to fail.
-+	 */
-+out_dput:
-+	dput(dentry);
-+out:
-+	return 0;
-+}
-+
-+/**
-+ * union_copyup_dir - copy up low-level directory entries to topmost dir
-+ *
-+ * readdir() is difficult to support on union file systems for two
-+ * reasons: We must eliminate duplicates and apply whiteouts, and we
-+ * must return something in f_pos that lets us restart in the same
-+ * place when we return.  Our solution is to, on first readdir() of
-+ * the directory, copy up all visible entries from the low-level file
-+ * systems and mark the entries that refer to low-level file system
-+ * objects as "fallthru" entries.
-+ */
-+
-+int union_copyup_dir(struct path *topmost_path)
-+{
-+	struct dentry *topmost_dentry = topmost_path->dentry;
-+	struct path path = *topmost_path;
-+	int res = 0;
-+
-+	/*
-+	 * Skip opaque dirs.
-+	 */
-+	if (IS_OPAQUE(topmost_dentry->d_inode))
-+		return 0;
-+
-+	/*
-+	 * Mark this dir opaque to show that we have already copied up
-+	 * the lower entries.  Only fallthru entries pass through to
-+	 * the underlying file system.
-+	 *
-+	 * XXX Deal with the lower file system changing.  This could
-+	 * be through running a tool over the top level file system to
-+	 * make directories transparent again, or we could check the
-+	 * mtime of the underlying directory.
-+	 */
-+
-+	topmost_dentry->d_inode->i_flags |= S_OPAQUE;
-+	mark_inode_dirty(topmost_dentry->d_inode);
-+
-+	/*
-+	 * Loop through each dir on each level copying up the entries
-+	 * to the topmost.
-+	 */
-+
-+	/* Don't drop the caller's reference to the topmost path */
-+	path_get(&path);
-+	while (follow_union_down(&path)) {
-+		struct file * ftmp;
-+		struct inode * inode;
-+
-+		/* XXX Permit fallthrus on lower-level? Would need to
-+		 * pass in opaque flag to union_copyup_dir_one() and
-+		 * only copy up fallthru entries there.  We allow
-+		 * fallthrus in lower level opaque directories on
-+		 * lookup, so for consistency we should do one or the
-+		 * other in both places. */
-+		if (IS_OPAQUE(path.dentry->d_inode))
-+			break;
-+
-+		/* dentry_open() doesn't get a path reference itself */
-+		path_get(&path);
-+		ftmp = dentry_open(path.dentry, path.mnt,
-+				   O_RDONLY | O_DIRECTORY | O_NOATIME,
-+				   current_cred());
-+		if (IS_ERR(ftmp)) {
-+			printk (KERN_ERR "unable to open dir %s for "
-+				"directory copyup: %ld\n",
-+				path.dentry->d_name.name, PTR_ERR(ftmp));
-+			continue;
-+		}
-+
-+		inode = path.dentry->d_inode;
-+		mutex_lock(&inode->i_mutex);
-+
-+		res = -ENOENT;
-+		if (IS_DEADDIR(inode))
-+			goto out_fput;
-+		/*
-+		 * Read the whole directory, calling our directory
-+		 * entry copyup function on each entry.  Pass in the
-+		 * topmost dentry as our private data so we can create
-+		 * new entries in the topmost directory.
-+		 */
-+		res = ftmp->f_op->readdir(ftmp, topmost_dentry,
-+					  union_copyup_dir_one);
-+out_fput:
-+		mutex_unlock(&inode->i_mutex);
-+		fput(ftmp);
-+
-+		if (res)
-+			break;
-+	}
-+	path_put(&path);
-+	return res;
-+}
---- a/include/linux/dcache.h
-+++ b/include/linux/dcache.h
-@@ -101,6 +101,15 @@ struct dentry {
- 	struct dentry *d_parent;	/* parent directory */
- 	struct qstr d_name;
- 
-+#ifdef CONFIG_UNION_MOUNT
-+	/*
-+	 * The following fields are used by the VFS based union mount
-+	 * implementation. Both are protected by union_lock!
-+	 */
-+	struct list_head d_unions;	/* list of union_mount's */
-+	unsigned int d_unionized;	/* unions referencing this dentry */
-+#endif
-+
- 	struct list_head d_lru;		/* LRU list */
- 	/*
- 	 * d_child and d_rcu can share memory
-@@ -186,6 +195,9 @@ d_iput:		no		no		no       yes
- 
- #define DCACHE_FSNOTIFY_PARENT_WATCHED	0x0080 /* Parent inode is watched by some fsnotify listener */
- 
-+#define DCACHE_WHITEOUT		0x0100	/* This negative dentry is a whiteout */
-+#define DCACHE_FALLTHRU		0x0200	/* Keep looking in the file system below */
-+
- extern spinlock_t dcache_lock;
- extern seqlock_t rename_lock;
- 
-@@ -205,12 +217,20 @@ extern seqlock_t rename_lock;
-  * __d_drop requires dentry->d_lock.
-  */
- 
-+#ifdef CONFIG_UNION_MOUNT
-+extern void __d_drop_unions(struct dentry *);
-+#endif
-+
- static inline void __d_drop(struct dentry *dentry)
- {
- 	if (!(dentry->d_flags & DCACHE_UNHASHED)) {
- 		dentry->d_flags |= DCACHE_UNHASHED;
- 		hlist_del_rcu(&dentry->d_hash);
- 	}
-+#ifdef CONFIG_UNION_MOUNT
-+	/* remove dentry from the union hashtable */
-+	__d_drop_unions(dentry);
-+#endif
- }
- 
- static inline void d_drop(struct dentry *dentry)
-@@ -358,6 +378,16 @@ static inline int d_unlinked(struct dent
- 	return d_unhashed(dentry) && !IS_ROOT(dentry);
- }
- 
-+static inline int d_is_whiteout(struct dentry *dentry)
-+{
-+	return (dentry->d_flags & DCACHE_WHITEOUT);
-+}
-+
-+static inline int d_is_fallthru(struct dentry *dentry)
-+{
-+	return (dentry->d_flags & DCACHE_FALLTHRU);
-+}
-+
- static inline struct dentry *dget_parent(struct dentry *dentry)
- {
- 	struct dentry *ret;
---- a/include/linux/ext2_fs.h
-+++ b/include/linux/ext2_fs.h
-@@ -189,6 +189,7 @@ struct ext2_group_desc
- #define EXT2_NOTAIL_FL			FS_NOTAIL_FL	/* file tail should not be merged */
- #define EXT2_DIRSYNC_FL			FS_DIRSYNC_FL	/* dirsync behaviour (directories only) */
- #define EXT2_TOPDIR_FL			FS_TOPDIR_FL	/* Top of directory hierarchies*/
-+#define EXT2_OPAQUE_FL			0x00040000
- #define EXT2_RESERVED_FL		FS_RESERVED_FL	/* reserved for ext2 lib */
- 
- #define EXT2_FL_USER_VISIBLE		FS_FL_USER_VISIBLE	/* User visible flags */
-@@ -503,10 +504,12 @@ struct ext2_super_block {
- #define EXT3_FEATURE_INCOMPAT_RECOVER		0x0004
- #define EXT3_FEATURE_INCOMPAT_JOURNAL_DEV	0x0008
- #define EXT2_FEATURE_INCOMPAT_META_BG		0x0010
-+#define EXT2_FEATURE_INCOMPAT_WHITEOUT		0x0020
- #define EXT2_FEATURE_INCOMPAT_ANY		0xffffffff
- 
- #define EXT2_FEATURE_COMPAT_SUPP	EXT2_FEATURE_COMPAT_EXT_ATTR
- #define EXT2_FEATURE_INCOMPAT_SUPP	(EXT2_FEATURE_INCOMPAT_FILETYPE| \
-+					 EXT2_FEATURE_INCOMPAT_WHITEOUT| \
- 					 EXT2_FEATURE_INCOMPAT_META_BG)
- #define EXT2_FEATURE_RO_COMPAT_SUPP	(EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER| \
- 					 EXT2_FEATURE_RO_COMPAT_LARGE_FILE| \
-@@ -573,6 +576,8 @@ enum {
- 	EXT2_FT_FIFO,
- 	EXT2_FT_SOCK,
- 	EXT2_FT_SYMLINK,
-+	EXT2_FT_WHT,
-+	EXT2_FT_FALLTHRU,
- 	EXT2_FT_MAX
- };
- 
---- a/include/linux/fs.h
-+++ b/include/linux/fs.h
-@@ -188,6 +188,7 @@ struct inodes_stat_t {
- #define MS_REMOUNT	32	/* Alter flags of a mounted FS */
- #define MS_MANDLOCK	64	/* Allow mandatory locks on an FS */
- #define MS_DIRSYNC	128	/* Directory modifications are synchronous */
-+#define MS_UNION	256
- #define MS_NOATIME	1024	/* Do not update access times. */
- #define MS_NODIRATIME	2048	/* Do not update directory access times */
- #define MS_BIND		4096
-@@ -205,6 +206,7 @@ struct inodes_stat_t {
- #define MS_KERNMOUNT	(1<<22) /* this is a kern_mount call */
- #define MS_I_VERSION	(1<<23) /* Update inode I_version field */
- #define MS_STRICTATIME	(1<<24) /* Always perform atime updates */
-+#define MS_WHITEOUT	(1<<26) /* fs does support white-out filetype */
- #define MS_ACTIVE	(1<<30)
- #define MS_NOUSER	(1<<31)
- 
-@@ -231,6 +233,7 @@ struct inodes_stat_t {
- #define S_NOCMTIME	128	/* Do not update file c/mtime */
- #define S_SWAPFILE	256	/* Do not truncate: swapon got its bmaps */
- #define S_PRIVATE	512	/* Inode is fs-internal */
-+#define S_OPAQUE	1024	/* Directory is opaque */
- 
- /*
-  * Note that nosuid etc flags are inode-specific: setting some file-system
-@@ -266,6 +269,8 @@ struct inodes_stat_t {
- #define IS_SWAPFILE(inode)	((inode)->i_flags & S_SWAPFILE)
- #define IS_PRIVATE(inode)	((inode)->i_flags & S_PRIVATE)
- 
-+#define IS_OPAQUE(inode)	((inode)->i_flags & S_OPAQUE)
-+
- /* the read-only stuff doesn't really belong here, but any other place is
-    probably as bad and I don't want to create yet another include file. */
- 
-@@ -1379,6 +1384,11 @@ struct super_block {
- 	 * generic_show_options()
- 	 */
- 	char *s_options;
-+
-+	/*
-+	 * Users who require read-only access - e.g., union mounts
-+	 */
-+	int s_readonly_users;
- };
- 
- extern struct timespec current_fs_time(struct super_block *sb);
-@@ -1521,6 +1531,8 @@ struct inode_operations {
- 	int (*mkdir) (struct inode *,struct dentry *,int);
- 	int (*rmdir) (struct inode *,struct dentry *);
- 	int (*mknod) (struct inode *,struct dentry *,int,dev_t);
-+	int (*whiteout) (struct inode *, struct dentry *, struct dentry *);
-+	int (*fallthru) (struct inode *, struct dentry *);
- 	int (*rename) (struct inode *, struct dentry *,
- 			struct inode *, struct dentry *);
- 	int (*readlink) (struct dentry *, char __user *,int);
-@@ -2094,6 +2106,7 @@ extern void emergency_remount(void);
- extern sector_t bmap(struct inode *, sector_t);
- #endif
- extern int notify_change(struct dentry *, struct iattr *);
-+extern int __inode_permission(struct inode *inode, int mask, int rofs);
- extern int inode_permission(struct inode *, int);
- extern int generic_permission(struct inode *, int,
- 		int (*check_acl)(struct inode *, int));
-@@ -2121,7 +2134,7 @@ extern void free_write_pipe(struct file 
- 
- extern struct file *do_filp_open(int dfd, const char *pathname,
- 		int open_flag, int mode, int acc_mode);
--extern int may_open(struct path *, int, int);
-+extern int may_open(struct nameidata *, int, int);
- 
- extern int kernel_read(struct file *, loff_t, char *, unsigned long);
- extern struct file * open_exec(const char *);
---- a/include/linux/mount.h
-+++ b/include/linux/mount.h
-@@ -35,6 +35,7 @@ struct mnt_namespace;
- #define MNT_SHARED	0x1000	/* if the vfsmount is a shared mount */
- #define MNT_UNBINDABLE	0x2000	/* if the vfsmount is a unbindable mount */
- #define MNT_PNODE_MASK	0x3000	/* propagation flag mask */
-+#define MNT_UNION	0x4000	/* if the vfsmount is a union mount */
- 
- struct vfsmount {
- 	struct list_head mnt_hash;
-@@ -53,6 +54,9 @@ struct vfsmount {
- 	struct list_head mnt_slave_list;/* list of slave mounts */
- 	struct list_head mnt_slave;	/* slave list entry */
- 	struct vfsmount *mnt_master;	/* slave is on master->mnt_slave_list */
-+#ifdef CONFIG_UNION_MOUNT
-+	struct list_head mnt_unions;	/* list of union_mount structures */
-+#endif
- 	struct mnt_namespace *mnt_ns;	/* containing namespace */
- 	int mnt_id;			/* mount identifier */
- 	int mnt_group_id;		/* peer group identifier */
---- a/include/linux/namei.h
-+++ b/include/linux/namei.h
-@@ -20,6 +20,7 @@ struct nameidata {
- 	struct qstr	last;
- 	struct path	root;
- 	unsigned int	flags;
-+	unsigned int	um_flags;
- 	int		last_type;
- 	unsigned	depth;
- 	char *saved_names[MAX_NESTED_LINKS + 1];
-@@ -35,6 +36,9 @@ struct nameidata {
-  */
- enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
- 
-+#define LAST_UNION             0x01
-+#define LAST_LOWLEVEL          0x02
-+
- /*
-  * The bitmask for a lookup event:
-  *  - follow links at the end
-@@ -49,6 +53,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LA
- #define LOOKUP_CONTINUE		 4
- #define LOOKUP_PARENT		16
- #define LOOKUP_REVAL		64
-+#define LOOKUP_TOPMOST	       128
-+
- /*
-  * Intent data
-  */
---- /dev/null
-+++ b/include/linux/union.h
-@@ -0,0 +1,84 @@
-+/*
-+ * VFS based union mount for Linux
-+ *
-+ * Copyright (C) 2004-2007 IBM Corporation, IBM Deutschland Entwicklung GmbH.
-+ * Copyright (C) 2007 Novell Inc.
-+ *   Author(s): Jan Blunck ([email protected])
-+ *
-+ * This program is free software; you can redistribute it and/or modify it
-+ * under the terms of the GNU General Public License as published by the Free
-+ * Software Foundation; either version 2 of the License, or (at your option)
-+ * any later version.
-+ *
-+ */
-+#ifndef __LINUX_UNION_H
-+#define __LINUX_UNION_H
-+#ifdef __KERNEL__
-+
-+#include <linux/list.h>
-+#include <asm/atomic.h>
-+
-+struct dentry;
-+struct vfsmount;
-+
-+#ifdef CONFIG_UNION_MOUNT
-+
-+/*
-+ * The new union mount structure.
-+ */
-+struct union_mount {
-+	atomic_t u_count;		/* reference count */
-+	struct mutex u_mutex;
-+	struct list_head u_unions;	/* list head for d_unions */
-+	struct list_head u_list;	/* list head for mnt_unions */
-+	struct hlist_node u_hash;	/* list head for seaching */
-+	struct hlist_node u_rhash;	/* list head for reverse seaching */
-+
-+	struct path u_this;		/* this is me */
-+	struct path u_next;		/* this is what I overlay */
-+};
-+
-+#define IS_UNION(dentry)	(!list_empty(&(dentry)->d_unions) || \
-+				 (dentry)->d_unionized)
-+#define IS_MNT_UNION(mnt)	((mnt)->mnt_flags & MNT_UNION)
-+
-+extern int is_unionized(struct dentry *, struct vfsmount *);
-+extern int append_to_union(struct vfsmount *, struct dentry *,
-+			   struct vfsmount *, struct dentry *);
-+extern int follow_union_down(struct path *);
-+extern int follow_union_mount(struct path *);
-+extern void __d_drop_unions(struct dentry *);
-+extern void shrink_d_unions(struct dentry *);
-+extern void __shrink_d_unions(struct dentry *, struct list_head *);
-+extern int attach_mnt_union(struct vfsmount *, struct vfsmount *,
-+			    struct dentry *);
-+extern void detach_mnt_union(struct vfsmount *);
-+extern struct dentry *union_create_topmost(struct nameidata *, struct qstr *,
-+					   struct path *);
-+extern int __union_copyup(struct path *, struct nameidata *, struct path *);
-+extern int union_copyup(struct nameidata *, int);
-+extern int union_copyup_dir(struct path *path);
-+extern int union_permission(struct path *, int);
-+
-+#else /* CONFIG_UNION_MOUNT */
-+
-+#define IS_UNION(x)			(0)
-+#define IS_MNT_UNION(x)			(0)
-+#define is_unionized(x, y)		(0)
-+#define append_to_union(x1, y1, x2, y2)	({ BUG(); (0); })
-+#define follow_union_down(x)		({ (0); })
-+#define follow_union_mount(x)	({ (0); })
-+#define __d_drop_unions(x)		do { } while (0)
-+#define shrink_d_unions(x)		do { } while (0)
-+#define __shrink_d_unions(x,y)		do { } while (0)
-+#define attach_mnt_union(x, y, z)	do { } while (0)
-+#define detach_mnt_union(x)		do { } while (0)
-+#define union_create_topmost(x, y, z)	({ BUG(); (NULL); })
-+#define __union_copyup(x, y, z)		({ BUG(); (0); })
-+#define union_copyup(x, y)		({ (0); })
-+#define union_copyup_dir(x)		({ BUG(); (0); })
-+#define union_permission(x, y)		inode_permission(x->dentry->d_inode, y)
-+
-+#endif	/* CONFIG_UNION_MOUNT */
-+#endif	/* __KERNEL__ */
-+#endif	/* __LINUX_UNION_H */
---- a/mm/shmem.c
-+++ b/mm/shmem.c
-@@ -1794,6 +1794,118 @@ static int shmem_statfs(struct dentry *d
- 	return 0;
- }
- 
-+static int shmem_rmdir(struct inode *dir, struct dentry *dentry);
-+static int shmem_unlink(struct inode *dir, struct dentry *dentry);
-+
-+/*
-+ * Create a dentry to signify a whiteout.
-+ */
-+static int shmem_whiteout(struct inode *dir, struct dentry *old_dentry,
-+			  struct dentry *new_dentry)
-+{
-+	struct shmem_sb_info *sbinfo = SHMEM_SB(dir->i_sb);
-+	struct dentry *dentry;
-+
-+	if (!(dir->i_sb->s_flags & MS_WHITEOUT))
-+		return -EPERM;
-+
-+	/* This gives us a proper initialized negative dentry */
-+	dentry = simple_lookup(dir, new_dentry, NULL);
-+	if (dentry && IS_ERR(dentry))
-+		return PTR_ERR(dentry);
-+
-+	/*
-+	 * No ordinary (disk based) filesystem counts whiteouts as inodes;
-+	 * but each new link needs a new dentry, pinning lowmem, and
-+	 * tmpfs dentries cannot be pruned until they are unlinked.
-+	 */
-+	if (sbinfo->max_inodes) {
-+		spin_lock(&sbinfo->stat_lock);
-+		if (!sbinfo->free_inodes) {
-+			spin_unlock(&sbinfo->stat_lock);
-+			return -ENOSPC;
-+		}
-+		sbinfo->free_inodes--;
-+		spin_unlock(&sbinfo->stat_lock);
-+	}
-+
-+	if (old_dentry->d_inode || d_is_fallthru(old_dentry)) {
-+		if (old_dentry->d_inode && S_ISDIR(old_dentry->d_inode->i_mode))
-+			shmem_rmdir(dir, old_dentry);
-+		else
-+			shmem_unlink(dir, old_dentry);
-+	}
-+
-+	dir->i_size += BOGO_DIRENT_SIZE;
-+	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
-+	/* Extra pinning count for the created dentry */
-+	dget(new_dentry);
-+	spin_lock(&new_dentry->d_lock);
-+	new_dentry->d_flags |= DCACHE_WHITEOUT;
-+	spin_unlock(&new_dentry->d_lock);
-+	return 0;
-+}
-+
-+static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry,
-+				struct inode *inode);
-+
-+/*
-+ * Create a dentry to signify a fallthru.  A fallthru lets us read the
-+ * low-level dentries into the dcache once on the first readdir() and
-+ * then
-+ */
-+static int shmem_fallthru(struct inode *dir, struct dentry *dentry)
-+{
-+	struct shmem_sb_info *sbinfo = SHMEM_SB(dir->i_sb);
-+
-+	/* FIXME: this is stupid */
-+	if (!(dir->i_sb->s_flags & MS_WHITEOUT))
-+		return -EPERM;
-+
-+	if (dentry->d_inode || d_is_fallthru(dentry) || d_is_whiteout(dentry))
-+		return -EEXIST;
-+
-+	/*
-+	 * Each new link needs a new dentry, pinning lowmem, and tmpfs
-+	 * dentries cannot be pruned until they are unlinked.
-+	 */
-+	if (sbinfo->max_inodes) {
-+		spin_lock(&sbinfo->stat_lock);
-+		if (!sbinfo->free_inodes) {
-+			spin_unlock(&sbinfo->stat_lock);
-+			return -ENOSPC;
-+		}
-+		sbinfo->free_inodes--;
-+		spin_unlock(&sbinfo->stat_lock);
-+	}
-+
-+	shmem_d_instantiate(dir, dentry, NULL);
-+	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
-+
-+	spin_lock(&dentry->d_lock);
-+	dentry->d_flags |= DCACHE_FALLTHRU;
-+	spin_unlock(&dentry->d_lock);
-+	return 0;
-+}
-+
-+static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry,
-+				struct inode *inode)
-+{
-+	if (d_is_whiteout(dentry)) {
-+		/* Re-using an existing whiteout */
-+		shmem_free_inode(dir->i_sb);
-+		if (S_ISDIR(inode->i_mode))
-+			inode->i_mode |= S_OPAQUE;
-+	} else if (d_is_fallthru(dentry)) {
-+		shmem_free_inode(dir->i_sb);
-+	} else {
-+		/* New dentry */
-+		dir->i_size += BOGO_DIRENT_SIZE;
-+		dget(dentry); /* Extra count - pin the dentry in core */
-+	}
-+	/* Will clear DCACHE_WHITEOUT and DCACHE_FALLTHRU flags */
-+	d_instantiate(dentry, inode);
-+}
- /*
-  * File creation. Allocate an inode, and we're done..
-  */
-@@ -1818,15 +1930,16 @@ shmem_mknod(struct inode *dir, struct de
- 			iput(inode);
- 			return error;
- 		}
-+
- 		if (dir->i_mode & S_ISGID) {
- 			inode->i_gid = dir->i_gid;
- 			if (S_ISDIR(mode))
- 				inode->i_mode |= S_ISGID;
- 		}
--		dir->i_size += BOGO_DIRENT_SIZE;
-+
-+		shmem_d_instantiate(dir, dentry, inode);
-+
- 		dir->i_ctime = dir->i_mtime = CURRENT_TIME;
--		d_instantiate(dentry, inode);
--		dget(dentry); /* Extra count - pin the dentry in core */
- 	}
- 	return error;
- }
-@@ -1864,12 +1977,11 @@ static int shmem_link(struct dentry *old
- 	if (ret)
- 		goto out;
- 
--	dir->i_size += BOGO_DIRENT_SIZE;
-+	shmem_d_instantiate(dir, dentry, inode);
-+
- 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
- 	inc_nlink(inode);
- 	atomic_inc(&inode->i_count);	/* New dentry reference */
--	dget(dentry);		/* Extra pinning count for the created dentry */
--	d_instantiate(dentry, inode);
- out:
- 	return ret;
- }
-@@ -1878,21 +1990,63 @@ static int shmem_unlink(struct inode *di
- {
- 	struct inode *inode = dentry->d_inode;
- 
--	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
--		shmem_free_inode(inode->i_sb);
-+	if (d_is_whiteout(dentry) || d_is_fallthru(dentry) ||
-+	    (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)))
-+		shmem_free_inode(dir->i_sb);
- 
-+	if (inode) {
-+		inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
-+		drop_nlink(inode);
-+	}
- 	dir->i_size -= BOGO_DIRENT_SIZE;
--	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
--	drop_nlink(inode);
- 	dput(dentry);	/* Undo the count from "create" - this does all the work */
- 	return 0;
- }
- 
-+static void shmem_dir_unlink_whiteouts(struct inode *dir, struct dentry *dentry)
-+{
-+	if (!dentry->d_inode)
-+		return;
-+
-+	/* Remove whiteouts from logical empty directory */
-+	if (S_ISDIR(dentry->d_inode->i_mode) &&
-+	    dentry->d_inode->i_sb->s_flags & MS_WHITEOUT) {
-+		struct dentry *child, *next;
-+		LIST_HEAD(list);
-+
-+		spin_lock(&dcache_lock);
-+		list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
-+			spin_lock(&child->d_lock);
-+			/* Unlink fallthrus too */
-+			if (d_is_whiteout(child) || d_is_fallthru(child)) {
-+				__d_drop(child);
-+				if (!list_empty(&child->d_lru)) {
-+					list_del(&child->d_lru);
-+					dentry_stat.nr_unused--;
-+				}
-+				list_add(&child->d_lru, &list);
-+			}
-+			spin_unlock(&child->d_lock);
-+		}
-+		spin_unlock(&dcache_lock);
-+
-+		list_for_each_entry_safe(child, next, &list, d_lru) {
-+			spin_lock(&child->d_lock);
-+			list_del_init(&child->d_lru);
-+			spin_unlock(&child->d_lock);
-+
-+			shmem_unlink(dentry->d_inode, child);
-+		}
-+	}
-+}
-+
- static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
- {
- 	if (!simple_empty(dentry))
- 		return -ENOTEMPTY;
- 
-+	/* Remove whiteouts from logical empty directory */
-+	shmem_dir_unlink_whiteouts(dir, dentry);
- 	drop_nlink(dentry->d_inode);
- 	drop_nlink(dir);
- 	return shmem_unlink(dir, dentry);
-@@ -1901,7 +2055,7 @@ static int shmem_rmdir(struct inode *dir
- /*
-  * The VFS layer already does all the dentry stuff for rename,
-  * we just have to decrement the usage count for the target if
-- * it exists so that the VFS layer correctly free's it when it
-+ * it exists so that the VFS layer correctly frees it when it
-  * gets overwritten.
-  */
- static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
-@@ -1912,7 +2066,12 @@ static int shmem_rename(struct inode *ol
- 	if (!simple_empty(new_dentry))
- 		return -ENOTEMPTY;
- 
-+	if (d_is_whiteout(new_dentry))
-+		shmem_unlink(new_dir, new_dentry);
-+
- 	if (new_dentry->d_inode) {
-+		/* Remove whiteouts from logical empty directory */
-+		shmem_dir_unlink_whiteouts(new_dir, new_dentry);
- 		(void) shmem_unlink(new_dir, new_dentry);
- 		if (they_are_dirs)
- 			drop_nlink(old_dir);
-@@ -1977,12 +2136,12 @@ static int shmem_symlink(struct inode *d
- 		set_page_dirty(page);
- 		page_cache_release(page);
- 	}
-+
-+	shmem_d_instantiate(dir, dentry, inode);
-+
- 	if (dir->i_mode & S_ISGID)
- 		inode->i_gid = dir->i_gid;
--	dir->i_size += BOGO_DIRENT_SIZE;
- 	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
--	d_instantiate(dentry, inode);
--	dget(dentry);
- 	return 0;
- }
- 
-@@ -2363,6 +2522,12 @@ static int shmem_fill_super(struct super
- 	if (!root)
- 		goto failed_iput;
- 	sb->s_root = root;
-+
-+#ifdef CONFIG_TMPFS
-+	if (!(sb->s_flags & MS_NOUSER))
-+		sb->s_flags |= MS_WHITEOUT;
-+#endif
-+
- 	return 0;
- 
- failed_iput:
-@@ -2462,6 +2627,8 @@ static const struct inode_operations shm
- 	.rmdir		= shmem_rmdir,
- 	.mknod		= shmem_mknod,
- 	.rename		= shmem_rename,
-+	.whiteout       = shmem_whiteout,
-+	.fallthru       = shmem_fallthru,
- #endif
- #ifdef CONFIG_TMPFS_POSIX_ACL
- 	.setattr	= shmem_notify_change,

target/linux/generic-2.6/patches-2.6.31/231-union_mounts_bind_fix.patch

@@ -1,11 +0,0 @@
---- a/fs/namespace.c
-+++ b/fs/namespace.c
-@@ -1550,7 +1550,7 @@ static int do_loopback(struct path *path
- 	if (!mnt)
- 		goto out;
- 
--	err = check_union_mnt(&old_path, mnt, mnt_flags);
-+	err = check_union_mnt(path, mnt, mnt_flags);
- 	if (err)
- 		goto out;
- 

target/linux/generic-2.6/patches-2.6.31/232-union_mounts_compile_fix.patch

@@ -1,11 +0,0 @@
---- a/include/linux/union.h
-+++ b/include/linux/union.h
-@@ -77,7 +77,7 @@ extern int union_permission(struct path 
- #define __union_copyup(x, y, z)		({ BUG(); (0); })
- #define union_copyup(x, y)		({ (0); })
- #define union_copyup_dir(x)		({ BUG(); (0); })
--#define union_permission(x, y)		inode_permission(x->dentry->d_inode, y)
-+#define union_permission(x, y)		inode_permission((x)->dentry->d_inode, y)
- 
- #endif	/* CONFIG_UNION_MOUNT */
- #endif	/* __KERNEL__ */

target/linux/generic-2.6/patches-2.6.31/233-jffs2_whiteout_support.patch

@@ -1,186 +0,0 @@
---- a/fs/jffs2/dir.c
-+++ b/fs/jffs2/dir.c
-@@ -34,6 +34,9 @@ static int jffs2_mknod (struct inode *,s
- static int jffs2_rename (struct inode *, struct dentry *,
- 			 struct inode *, struct dentry *);
- 
-+static int jffs2_whiteout (struct inode *, struct dentry *, struct dentry *);
-+static int jffs2_fallthru (struct inode *, struct dentry *);
-+
- const struct file_operations jffs2_dir_operations =
- {
- 	.read =		generic_read_dir,
-@@ -55,6 +58,8 @@ const struct inode_operations jffs2_dir_
- 	.rmdir =	jffs2_rmdir,
- 	.mknod =	jffs2_mknod,
- 	.rename =	jffs2_rename,
-+	.fallthru =     jffs2_fallthru,
-+	.whiteout =     jffs2_whiteout,
- 	.permission =	jffs2_permission,
- 	.setattr =	jffs2_setattr,
- 	.setxattr =	jffs2_setxattr,
-@@ -98,8 +103,21 @@ static struct dentry *jffs2_lookup(struc
- 			fd = fd_list;
- 		}
- 	}
--	if (fd)
--		ino = fd->ino;
-+	if (fd) {
-+		spin_lock(&target->d_lock);
-+		switch(fd->type) {
-+		case DT_WHT:
-+			target->d_flags |= DCACHE_WHITEOUT;
-+			break;
-+		case DT_UNKNOWN:
-+			target->d_flags |= DCACHE_FALLTHRU;
-+			break;
-+		default:
-+			ino = fd->ino;
-+			break;
-+		}
-+		spin_unlock(&target->d_lock);
-+	}
- 	mutex_unlock(&dir_f->sem);
- 	if (ino) {
- 		inode = jffs2_iget(dir_i->i_sb, ino);
-@@ -155,7 +173,9 @@ static int jffs2_readdir(struct file *fi
- 				  fd->name, fd->ino, fd->type, curofs, offset));
- 			continue;
- 		}
--		if (!fd->ino) {
-+		if (fd->type == DT_UNKNOWN)
-+			fd->ino = 100; /* XXX: arbitrary */
-+		else if (!fd->ino && (fd->type != DT_WHT)) {
- 			D2(printk(KERN_DEBUG "Skipping deletion dirent \"%s\"\n", fd->name));
- 			offset++;
- 			continue;
-@@ -498,6 +518,11 @@ static int jffs2_mkdir (struct inode *di
- 		return PTR_ERR(inode);
- 	}
- 
-+	if (dentry->d_flags & DCACHE_WHITEOUT) {
-+		inode->i_flags |= S_OPAQUE;
-+		ri->flags = cpu_to_je16(JFFS2_INO_FLAG_OPAQUE);
-+	}
-+
- 	inode->i_op = &jffs2_dir_inode_operations;
- 	inode->i_fop = &jffs2_dir_operations;
- 
-@@ -779,6 +804,82 @@ static int jffs2_mknod (struct inode *di
- 	return 0;
- }
- 
-+static int jffs2_fallthru (struct inode *dir, struct dentry *dentry)
-+{
-+	struct jffs2_sb_info *c = JFFS2_SB_INFO(dir->i_sb);
-+	uint32_t now;
-+	int ret;
-+
-+	now = get_seconds();
-+	ret = jffs2_do_link(c, JFFS2_INODE_INFO(dir), 0, DT_UNKNOWN,
-+			    dentry->d_name.name, dentry->d_name.len, now);
-+	if (ret)
-+		return ret;
-+
-+	d_instantiate(dentry, NULL);
-+	spin_lock(&dentry->d_lock);
-+	dentry->d_flags |= DCACHE_FALLTHRU;
-+	spin_unlock(&dentry->d_lock);
-+
-+	return 0;
-+}
-+
-+static int jffs2_whiteout (struct inode *dir, struct dentry *old_dentry,
-+			   struct dentry *new_dentry)
-+{
-+	struct jffs2_sb_info *c = JFFS2_SB_INFO(dir->i_sb);
-+	struct jffs2_inode_info *victim_f = NULL;
-+	uint32_t now;
-+	int ret;
-+
-+	/* If it's a directory, then check whether it is really empty
-+	 */
-+	if (new_dentry->d_inode) {
-+		victim_f = JFFS2_INODE_INFO(old_dentry->d_inode);
-+		if (S_ISDIR(old_dentry->d_inode->i_mode)) {
-+			struct jffs2_full_dirent *fd;
-+
-+			mutex_lock(&victim_f->sem);
-+			for (fd = victim_f->dents; fd; fd = fd->next) {
-+				if (fd->ino) {
-+					mutex_unlock(&victim_f->sem);
-+					return -ENOTEMPTY;
-+				}
-+			}
-+			mutex_unlock(&victim_f->sem);
-+		}
-+	}
-+
-+	now = get_seconds();
-+	ret = jffs2_do_link(c, JFFS2_INODE_INFO(dir), 0, DT_WHT,
-+			    new_dentry->d_name.name, new_dentry->d_name.len, now);
-+	if (ret)
-+		return ret;
-+
-+	spin_lock(&new_dentry->d_lock);
-+	new_dentry->d_flags &= ~DCACHE_FALLTHRU;
-+	new_dentry->d_flags |= DCACHE_WHITEOUT;
-+	spin_unlock(&new_dentry->d_lock);
-+	d_add(new_dentry, NULL);
-+
-+	if (victim_f) {
-+		/* There was a victim. Kill it off nicely */
-+		drop_nlink(old_dentry->d_inode);
-+		/* Don't oops if the victim was a dirent pointing to an
-+		   inode which didn't exist. */
-+		if (victim_f->inocache) {
-+			mutex_lock(&victim_f->sem);
-+			if (S_ISDIR(old_dentry->d_inode->i_mode))
-+				victim_f->inocache->pino_nlink = 0;
-+			else
-+				victim_f->inocache->pino_nlink--;
-+			mutex_unlock(&victim_f->sem);
-+		}
-+	}
-+
-+	return 0;
-+}
-+
- static int jffs2_rename (struct inode *old_dir_i, struct dentry *old_dentry,
- 			 struct inode *new_dir_i, struct dentry *new_dentry)
- {
---- a/fs/jffs2/fs.c
-+++ b/fs/jffs2/fs.c
-@@ -301,6 +301,10 @@ struct inode *jffs2_iget(struct super_bl
- 
- 		inode->i_op = &jffs2_dir_inode_operations;
- 		inode->i_fop = &jffs2_dir_operations;
-+
-+		if (je16_to_cpu(latest_node.flags) & JFFS2_INO_FLAG_OPAQUE)
-+			inode->i_flags |= S_OPAQUE;
-+
- 		break;
- 	}
- 	case S_IFREG:
---- a/fs/jffs2/super.c
-+++ b/fs/jffs2/super.c
-@@ -172,7 +172,7 @@ static int jffs2_fill_super(struct super
- 
- 	sb->s_op = &jffs2_super_operations;
- 	sb->s_export_op = &jffs2_export_ops;
--	sb->s_flags = sb->s_flags | MS_NOATIME;
-+	sb->s_flags = sb->s_flags | MS_NOATIME | MS_WHITEOUT;
- 	sb->s_xattr = jffs2_xattr_handlers;
- #ifdef CONFIG_JFFS2_FS_POSIX_ACL
- 	sb->s_flags |= MS_POSIXACL;
---- a/include/linux/jffs2.h
-+++ b/include/linux/jffs2.h
-@@ -87,6 +87,8 @@
- #define JFFS2_INO_FLAG_USERCOMPR  2	/* User has requested a specific
- 					   compression type */
- 
-+#define JFFS2_INO_FLAG_OPAQUE     4	/* Directory is opaque (for union mounts) */
-+
- 
- /* These can go once we've made sure we've caught all uses without
-    byteswapping */

target/linux/generic-2.6/patches-2.6.31/234-union_mounts_no_debug.patch

@@ -1,30 +0,0 @@
---- a/fs/union.c
-+++ b/fs/union.c
-@@ -842,10 +842,8 @@ static int union_copyup_dir_one(void *bu
- 	/* Lookup this entry in the topmost directory */
- 	dentry = lookup_one_len(name, topmost_dentry, namlen);
- 
--	if (IS_ERR(dentry)) {
--		printk(KERN_INFO "error looking up %s\n", dentry->d_name.name);
-+	if (IS_ERR(dentry))
- 		goto out;
--	}
- 
- 	/*
- 	 * If the entry already exists, one of the following is true:
-@@ -857,7 +855,6 @@ static int union_copyup_dir_one(void *bu
- 	 */
- 	if (dentry->d_inode || d_is_whiteout(dentry) ||
- 	    d_is_fallthru(dentry)) {
--		printk(KERN_INFO "skipping copy of %s\n", dentry->d_name.name);
- 		goto out_dput;
- 	}
- 
-@@ -867,7 +864,6 @@ static int union_copyup_dir_one(void *bu
- 	 * used, so each file system must implement its own way of
- 	 * storing a fallthru entry.
- 	 */
--	printk(KERN_INFO "creating fallthru for %s\n", dentry->d_name.name);
- 	err = topmost_dentry->d_inode->i_op->fallthru(topmost_dentry->d_inode,
- 						      dentry);
- 	/* FIXME */

target/linux/generic-2.6/patches-2.6.31/235-union_mount_fixes.patch

@@ -1,117 +0,0 @@
---- a/fs/namespace.c
-+++ b/fs/namespace.c
-@@ -1656,8 +1656,10 @@ static int do_move_mount(struct path *pa
- 
- 	/* moving to or from a union mount is not supported */
- 	err = -EINVAL;
-+#if 0
- 	if (IS_MNT_UNION(path->mnt))
- 		goto exit;
-+#endif
- 	if (IS_MNT_UNION(old_path.mnt))
- 		goto exit;
- 
---- a/fs/union.c
-+++ b/fs/union.c
-@@ -260,8 +260,6 @@ int append_to_union(struct vfsmount *mnt
- 	spin_lock(&union_lock);
- 	um = union_lookup(dentry, mnt);
- 	if (um) {
--		BUG_ON((um->u_next.dentry != dest_dentry) ||
--		       (um->u_next.mnt != dest_mnt));
- 		spin_unlock(&union_lock);
- 		union_put(this);
- 		return 0;
-@@ -274,6 +272,23 @@ int append_to_union(struct vfsmount *mnt
- 	return 0;
- }
- 
-+int follow_union_mountpoint(struct path *path)
-+{
-+	struct path new_path = *path;
-+
-+	path_get(&new_path);
-+	while (follow_union_down(&new_path)) {
-+		if (new_path.dentry != new_path.mnt->mnt_root)
-+			continue;
-+
-+		path_put(path);
-+		*path = new_path;
-+		return 1;
-+	}
-+	path_put(&new_path);
-+	return 0;
-+}
-+
- /*
-  * follow_union_down - follow the union stack one layer down
-  *
---- a/include/linux/union.h
-+++ b/include/linux/union.h
-@@ -47,6 +47,7 @@ extern int append_to_union(struct vfsmou
- 			   struct vfsmount *, struct dentry *);
- extern int follow_union_down(struct path *);
- extern int follow_union_mount(struct path *);
-+extern int follow_union_mountpoint(struct path *path);
- extern void __d_drop_unions(struct dentry *);
- extern void shrink_d_unions(struct dentry *);
- extern void __shrink_d_unions(struct dentry *, struct list_head *);
-@@ -68,6 +69,7 @@ extern int union_permission(struct path 
- #define append_to_union(x1, y1, x2, y2)	({ BUG(); (0); })
- #define follow_union_down(x)		({ (0); })
- #define follow_union_mount(x)	({ (0); })
-+#define follow_union_mountpoint(x)	({ (0); })
- #define __d_drop_unions(x)		do { } while (0)
- #define shrink_d_unions(x)		do { } while (0)
- #define __shrink_d_unions(x,y)		do { } while (0)
---- a/fs/namei.c
-+++ b/fs/namei.c
-@@ -613,6 +613,9 @@ static int cache_lookup_union(struct nam
- 		    !S_ISDIR(path->dentry->d_inode->i_mode))
- 			goto out;
- 
-+		if (follow_union_mountpoint(path))
-+			goto out;
-+
- 		/* Build the union stack for this part */
- 		res = __cache_lookup_build_union(nd, name, path);
- 		if (res) {
-@@ -886,6 +889,9 @@ static int real_lookup_union(struct name
- 	    !S_ISDIR(path->dentry->d_inode->i_mode))
- 		goto out;
- 
-+	if (follow_union_mountpoint(path))
-+		goto out;
-+
- 	/* Build the union stack for this part */
- 	res = __real_lookup_build_union(nd, name, path);
- 	if (res) {
-@@ -1813,6 +1819,9 @@ int hash_lookup_union(struct nameidata *
- 	    !S_ISDIR(path->dentry->d_inode->i_mode))
- 		goto out;
- 
-+	if (follow_union_mountpoint(path))
-+		goto out;
-+
- 	/* Build the union stack for this part */
- 	res = __hash_lookup_build_union(nd, name, path);
- 	if (res) {
---- a/fs/readdir.c
-+++ b/fs/readdir.c
-@@ -17,6 +17,7 @@
- #include <linux/syscalls.h>
- #include <linux/unistd.h>
- #include <linux/union.h>
-+#include <linux/mount.h>
- 
- #include <asm/uaccess.h>
- 
-@@ -45,7 +46,7 @@ int vfs_readdir(struct file *file, filld
- 		 * below this one in the union stack.
- 		 */
- 		if (is_unionized(file->f_path.dentry, file->f_path.mnt) &&
--		    !IS_OPAQUE(inode)) {
-+		    !IS_OPAQUE(inode) && IS_MNT_UNION(file->f_path.mnt)) {
- 			res = union_copyup_dir(&file->f_path);
- 			if (res)
- 				goto out_unlock;

target/linux/generic-2.6/patches-2.6.32/230-union_mounts.patch

@@ -1,5203 +0,0 @@
---- /dev/null
-+++ b/Documentation/filesystems/union-mounts.txt
-@@ -0,0 +1,187 @@
-+VFS based Union Mounts
-+----------------------
-+
-+ 1. What are "Union Mounts"
-+ 2. The Union Stack
-+ 3. Whiteouts, Opaque Directories, and Fallthrus
-+ 4. Copy-up
-+ 5. Directory Reading
-+ 6. Known Problems
-+ 7. References
-+
-+-------------------------------------------------------------------------------
-+
-+1. What are "Union Mounts"
-+==========================
-+
-+Please note: this is NOT about UnionFS and it is NOT derived work!
-+
-+Traditionally the mount operation is opaque, which means that the content of
-+the mount point, the directory where the file system is mounted on, is hidden
-+by the content of the mounted file system's root directory until the file
-+system is unmounted again. Unlike the traditional UNIX mount mechanism, that
-+hides the contents of the mount point, a union mount presents a view as if
-+both filesystems are merged together. Although only the topmost layer of the
-+mount stack can be altered, it appears as if transparent file system mounts
-+allow any file to be created, modified or deleted.
-+
-+Most people know the concepts and features of union mounts from other
-+operating systems like Sun's Translucent Filesystem, Plan9 or BSD. For an
-+in-depth review of union mounts and other unioning file systems, see:
-+
-+http://lwn.net/Articles/324291/
-+http://lwn.net/Articles/325369/
-+http://lwn.net/Articles/327738/
-+
-+Here are the key features of this implementation:
-+- completely VFS based
-+- does not change the namespace stacking
-+- directory listings have duplicate entries removed in the kernel
-+- writable unions: only the topmost file system layer may be writable
-+- writable unions: new whiteout filetype handled inside the kernel
-+
-+-------------------------------------------------------------------------------
-+
-+2. The Union Stack
-+==================
-+
-+The mounted file systems are organized in the "file system hierarchy" (tree of
-+vfsmount structures), which keeps track about the stacking of file systems
-+upon each other. The per-directory view on the file system hierarchy is called
-+"mount stack" and reflects the order of file systems, which are mounted on a
-+specific directory.
-+
-+Union mounts present a single unified view of the contents of two or more file
-+systems as if they are merged together. Since the information which file
-+system objects are part of a unified view is not directly available from the
-+file system hierarchy there is a need for a new structure. The file system
-+objects, which are part of a unified view are ordered in a so-called "union
-+stack". Only directories can be part of a unified view.
-+
-+The link between two layers of the union stack is maintained using the
-+union_mount structure (#include <linux/union.h>):
-+
-+struct union_mount {
-+       atomic_t u_count;               /* reference count */
-+       struct mutex u_mutex;
-+       struct list_head u_unions;      /* list head for d_unions */
-+       struct hlist_node u_hash;       /* list head for searching */
-+       struct hlist_node u_rhash;      /* list head for reverse searching */
-+
-+       struct path u_this;             /* this is me */
-+       struct path u_next;             /* this is what I overlay */
-+};
-+
-+The union_mount structure holds a reference (dget,mntget) to the next lower
-+layer of the union stack. Since a dentry can be part of multiple unions
-+(e.g. with bind mounts) they are tied together via the d_unions field of the
-+dentry structure.
-+
-+All union_mount structures are cached in two hash tables, one for lookups of
-+the next lower layer of the union stack and one for reverse lookups of the
-+next upper layer of the union stack. The reverse lookup is necessary to
-+resolve CWD relative path lookups. For calculation of the hash value, the
-+(dentry,vfsmount) pair is used. The u_this field is used for the hash table
-+which is used in forward lookups and the u_next field for the reverse lookups.
-+
-+During every new mount (or mount propagation), a new union_mount structure is
-+allocated. A reference to the mountpoint's vfsmount and dentry is taken and
-+stored in the u_next field.  In almost the same manner an union_mount
-+structure is created during the first time lookup of a directory within a
-+union mount point. In this case the lookup proceeds to all lower layers of the
-+union. Therefore the complete union stack is constructed during lookups.
-+
-+The union_mount structures of a dentry are destroyed when the dentry itself is
-+destroyed. Therefore the dentry cache is indirectly driving the union_mount
-+cache like this is done for inodes too. Please note that lower layer
-+union_mount structures are kept in memory until the topmost dentry is
-+destroyed.
-+
-+-------------------------------------------------------------------------------
-+
-+3. Whiteouts, Opaque Directories, and Fallthrus
-+===========================================================
-+
-+The whiteout filetype isn't new. It has been there for quite some time now
-+but Linux's VFS hasn't used it yet. With the availability of union mount code
-+inside the VFS the whiteout filetype is getting important to support writable
-+union mounts. For read-only union mounts, support for whiteouts or
-+copy-on-open is not necessary.
-+
-+The whiteout filetype has the same function as negative dentries: they
-+describe a filename which isn't there. The creation of whiteouts needs
-+lowlevel filesystem support. At the time of writing this, there is whiteout
-+support for tmpfs, ext2 and ext3 available. The VFS is extended to make the
-+whiteout handling transparent to all its users. The whiteouts are not
-+visible to user-space.
-+
-+What happens when we create a directory that was previously whited-out? We
-+don't want the directory entries from underlying filesystems to suddenly appear
-+in the newly created directory.  So we mark the directory opaque (the file
-+system must support storage of the opaque flag).
-+
-+Fallthrus are directory entries that override the opaque flag on a directory
-+for that specific directory entry name (the lookup "falls through" to the next
-+layer of the union mount).  Fallthrus are mainly useful for implementing
-+readdir().
-+
-+-------------------------------------------------------------------------------
-+
-+4. Copy-up
-+===========
-+
-+Any write to an object on any layer other than the topmost triggers a copy-up
-+of the object to the topmost file system. For regular files, the copy-up
-+happens when it is opened in writable mode.
-+
-+Directories are copied up on open, regardless of intent to write, to simplify
-+copy-up of any object located below it in the namespace. Otherwise we have to
-+walk the entire pathname to create intermediate directories whenever we do a
-+copy-up. This is the same approach as BSD union mounts and uses a negigible
-+amount of disk space.  Note that the actual directory entries themselves are
-+not copied-up from the lower levels until (a) the directory is written to, or
-+(b) the first readdir() of the directory (more on that later).
-+
-+Rename across different levels of the union is implemented as a copy-up
-+operation for regular files. Rename of directories simply returns EXDEV, the
-+same as if we tried to rename across different mounts. Most applications have
-+to handle this case anyway. Some applications do not expect EXDEV on
-+rename operations within the same directory, but these applications will also
-+be broken with bind mounts.
-+
-+-------------------------------------------------------------------------------
-+
-+5. Directory Reading
-+====================
-+
-+readdir() is somewhat difficult to implement in a unioning file system. We must
-+eliminate duplicates, apply whiteouts, and start up readdir() where we left
-+off, given a single f_pos value. Our solution is to copy up all the directory
-+entries to the topmost directory the first time readdir() is called on a
-+directory. During this copy-up, we skip duplicates and entries covered by
-+whiteouts, and then create fallthru entries for each remaining visible dentry.
-+Then we mark the whole directory opaque. From then on, we just use the topmost
-+file system's normal readdir() operation.
-+
-+-------------------------------------------------------------------------------
-+
-+6. Known Problems
-+=================
-+
-+- copyup() for other filetypes that reg and dir (e.g. for chown() on devices)
-+- symlinks are untested
-+
-+-------------------------------------------------------------------------------
-+
-+7. References
-+=============
-+
-+[1] http://marc.info/?l=linux-fsdevel&m=96035682927821&w=2
-+[2] http://marc.info/?l=linux-fsdevel&m=117681527820133&w=2
-+[3] http://marc.info/?l=linux-fsdevel&m=117913503200362&w=2
-+[4] http://marc.info/?l=linux-fsdevel&m=118231827024394&w=2
-+
-+Authors:
-+Jan Blunck <[email protected]>
-+Bharata B Rao <[email protected]>
-+Valerie Aurora <[email protected]>
---- a/fs/autofs4/autofs_i.h
-+++ b/fs/autofs4/autofs_i.h
-@@ -130,6 +130,7 @@ struct autofs_sb_info {
- 	int reghost_enabled;
- 	int needs_reghost;
- 	struct super_block *sb;
-+	struct vfsmount *mnt;
- 	struct mutex wq_mutex;
- 	spinlock_t fs_lock;
- 	struct autofs_wait_queue *queues; /* Wait queue pointer */
---- a/fs/autofs4/init.c
-+++ b/fs/autofs4/init.c
-@@ -17,7 +17,16 @@
- static int autofs_get_sb(struct file_system_type *fs_type,
- 	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
- {
--	return get_sb_nodev(fs_type, flags, data, autofs4_fill_super, mnt);
-+	struct autofs_sb_info *sbi;
-+	int ret;
-+
-+	ret = get_sb_nodev(fs_type, flags, data, autofs4_fill_super, mnt);
-+	if (ret)
-+		return ret;
-+
-+	sbi = autofs4_sbi(mnt->mnt_sb);
-+	sbi->mnt = mnt;
-+	return 0;
- }
- 
- static struct file_system_type autofs_fs_type = {
---- a/fs/autofs4/root.c
-+++ b/fs/autofs4/root.c
-@@ -179,6 +179,12 @@ static void *autofs4_follow_link(struct 
- 	DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d",
- 		dentry, dentry->d_name.len, dentry->d_name.name, oz_mode,
- 		nd->flags);
-+
-+	dput(nd->path.dentry);
-+	mntput(nd->path.mnt);
-+	nd->path.mnt = mntget(sbi->mnt);
-+	nd->path.dentry = dget(dentry);
-+
- 	/*
- 	 * For an expire of a covered direct or offset mount we need
- 	 * to break out of follow_down() at the autofs mount trigger
---- a/fs/compat.c
-+++ b/fs/compat.c
-@@ -840,6 +840,9 @@ static int compat_fillonedir(void *__buf
- 	struct compat_old_linux_dirent __user *dirent;
- 	compat_ulong_t d_ino;
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	if (buf->result)
- 		return -EINVAL;
- 	d_ino = ino;
-@@ -911,6 +914,9 @@ static int compat_filldir(void *__buf, c
- 	compat_ulong_t d_ino;
- 	int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 2, sizeof(compat_long_t));
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	buf->error = -EINVAL;	/* only used if we fail.. */
- 	if (reclen > buf->count)
- 		return -EINVAL;
-@@ -1000,6 +1006,9 @@ static int compat_filldir64(void * __buf
- 	int reclen = ALIGN(jj + namlen + 1, sizeof(u64));
- 	u64 off;
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	buf->error = -EINVAL;	/* only used if we fail.. */
- 	if (reclen > buf->count)
- 		return -EINVAL;
---- a/fs/dcache.c
-+++ b/fs/dcache.c
-@@ -18,6 +18,7 @@
- #include <linux/string.h>
- #include <linux/mm.h>
- #include <linux/fs.h>
-+#include <linux/union.h>
- #include <linux/fsnotify.h>
- #include <linux/slab.h>
- #include <linux/init.h>
-@@ -158,14 +159,19 @@ static void dentry_lru_del_init(struct d
- }
- 
- /**
-- * d_kill - kill dentry and return parent
-+ * __d_kill - kill dentry and return parent
-  * @dentry: dentry to kill
-+ * @list: kill list
-+ * @greedy: return parent instead of putting it on the kill list
-  *
-  * The dentry must already be unhashed and removed from the LRU.
-  *
-- * If this is the root of the dentry tree, return NULL.
-+ * If this is the root of the dentry tree, return NULL. If greedy is zero, we
-+ * put the parent of this dentry on the kill list instead. The callers must
-+ * make sure that __d_kill_final() is called on all dentries on the kill list.
-  */
--static struct dentry *d_kill(struct dentry *dentry)
-+static struct dentry *__d_kill(struct dentry *dentry, struct list_head *list,
-+			       int greedy)
- 	__releases(dentry->d_lock)
- 	__releases(dcache_lock)
- {
-@@ -173,13 +179,78 @@ static struct dentry *d_kill(struct dent
- 
- 	list_del(&dentry->d_u.d_child);
- 	dentry_stat.nr_dentry--;	/* For d_free, below */
--	/*drops the locks, at that point nobody can reach this dentry */
-+
-+	/*
-+	 * If we are not greedy we just put this on a list for later processing
-+	 * (follow up to parent, releasing of inode and freeing dentry memory).
-+	 */
-+	if (!greedy) {
-+		list_del_init(&dentry->d_alias);
-+		/* at this point nobody can reach this dentry */
-+		list_add(&dentry->d_lru, list);
-+		spin_unlock(&dentry->d_lock);
-+		spin_unlock(&dcache_lock);
-+		__shrink_d_unions(dentry, list);
-+		return NULL;
-+	}
-+
-+	/* drops the locks, at that point nobody can reach this dentry */
- 	dentry_iput(dentry);
-+	/* If the dentry was in an union delete them */
-+	__shrink_d_unions(dentry, list);
-+	if (IS_ROOT(dentry))
-+		parent = NULL;
-+	else
-+		parent = dentry->d_parent;
-+	d_free(dentry);
-+	return parent;
-+}
-+
-+void __dput(struct dentry *, struct list_head *, int);
-+
-+static void __d_kill_final(struct dentry *dentry, struct list_head *list)
-+{
-+	struct dentry *parent;
-+	struct inode *inode = dentry->d_inode;
-+
-+	if (inode) {
-+		dentry->d_inode = NULL;
-+		if (!inode->i_nlink)
-+			fsnotify_inoderemove(inode);
-+		if (dentry->d_op && dentry->d_op->d_iput)
-+			dentry->d_op->d_iput(dentry, inode);
-+		else
-+			iput(inode);
-+	}
-+
- 	if (IS_ROOT(dentry))
- 		parent = NULL;
- 	else
- 		parent = dentry->d_parent;
- 	d_free(dentry);
-+	__dput(parent, list, 1);
-+}
-+
-+/**
-+ * d_kill - kill dentry and return parent
-+ * @dentry: dentry to kill
-+ *
-+ * The dentry must already be unhashed and removed from the LRU.
-+ *
-+ * If this is the root of the dentry tree, return NULL.
-+ */
-+static struct dentry *d_kill(struct dentry *dentry)
-+{
-+	LIST_HEAD(mortuary);
-+	struct dentry *parent;
-+
-+	parent = __d_kill(dentry, &mortuary, 1);
-+	while (!list_empty(&mortuary)) {
-+		dentry = list_entry(mortuary.next, struct dentry, d_lru);
-+		list_del(&dentry->d_lru);
-+		__d_kill_final(dentry, &mortuary);
-+	}
-+
- 	return parent;
- }
- 
-@@ -200,19 +271,24 @@ static struct dentry *d_kill(struct dent
-  * Real recursion would eat up our stack space.
-  */
- 
--/*
-- * dput - release a dentry
-- * @dentry: dentry to release 
-+/**
-+ * __dput - release a dentry
-+ * @dentry: dentry to release
-+ * @list: kill list argument for __d_kill()
-+ * @greedy: greedy argument for __d_kill()
-  *
-  * Release a dentry. This will drop the usage count and if appropriate
-  * call the dentry unlink method as well as removing it from the queues and
-  * releasing its resources. If the parent dentries were scheduled for release
-- * they too may now get deleted.
-+ * they too may now get deleted if @greedy is not zero. Otherwise parent is
-+ * added to the kill list. The callers must make sure that __d_kill_final() is
-+ * called on all dentries on the kill list.
-+ *
-+ * You probably want to use dput() instead.
-  *
-  * no dcache lock, please.
-  */
--
--void dput(struct dentry *dentry)
-+void __dput(struct dentry *dentry, struct list_head *list, int greedy)
- {
- 	if (!dentry)
- 		return;
-@@ -253,12 +329,35 @@ unhash_it:
- kill_it:
- 	/* if dentry was on the d_lru list delete it from there */
- 	dentry_lru_del(dentry);
--	dentry = d_kill(dentry);
-+	dentry = __d_kill(dentry, list, greedy);
- 	if (dentry)
- 		goto repeat;
- }
- 
- /**
-+ * dput - release a dentry
-+ * @dentry: dentry to release
-+ *
-+ * Release a dentry. This will drop the usage count and if appropriate
-+ * call the dentry unlink method as well as removing it from the queues and
-+ * releasing its resources. If the parent dentries were scheduled for release
-+ * they too may now get deleted.
-+ *
-+ * no dcache lock, please.
-+ */
-+void dput(struct dentry *dentry)
-+{
-+	LIST_HEAD(mortuary);
-+
-+	__dput(dentry, &mortuary, 1);
-+	while (!list_empty(&mortuary)) {
-+		dentry = list_entry(mortuary.next, struct dentry, d_lru);
-+		list_del(&dentry->d_lru);
-+		__d_kill_final(dentry, &mortuary);
-+	}
-+}
-+
-+/**
-  * d_invalidate - invalidate a dentry
-  * @dentry: dentry to invalidate
-  *
-@@ -690,6 +789,7 @@ static void shrink_dcache_for_umount_sub
- 					iput(inode);
- 			}
- 
-+			shrink_d_unions(dentry);
- 			d_free(dentry);
- 
- 			/* finished when we fall off the top of the tree,
-@@ -952,6 +1052,10 @@ struct dentry *d_alloc(struct dentry * p
- 	INIT_LIST_HEAD(&dentry->d_lru);
- 	INIT_LIST_HEAD(&dentry->d_subdirs);
- 	INIT_LIST_HEAD(&dentry->d_alias);
-+#ifdef CONFIG_UNION_MOUNT
-+	INIT_LIST_HEAD(&dentry->d_unions);
-+	dentry->d_unionized = 0;
-+#endif
- 
- 	if (parent) {
- 		dentry->d_parent = dget(parent);
-@@ -982,8 +1086,10 @@ struct dentry *d_alloc_name(struct dentr
- /* the caller must hold dcache_lock */
- static void __d_instantiate(struct dentry *dentry, struct inode *inode)
- {
--	if (inode)
-+	if (inode) {
-+		dentry->d_flags &= ~(DCACHE_WHITEOUT|DCACHE_FALLTHRU);
- 		list_add(&dentry->d_alias, &inode->i_dentry);
-+	}
- 	dentry->d_inode = inode;
- 	fsnotify_d_instantiate(dentry, inode);
- }
-@@ -1514,7 +1620,9 @@ void d_delete(struct dentry * dentry)
- 	spin_lock(&dentry->d_lock);
- 	isdir = S_ISDIR(dentry->d_inode->i_mode);
- 	if (atomic_read(&dentry->d_count) == 1) {
-+		__d_drop_unions(dentry);
- 		dentry_iput(dentry);
-+		shrink_d_unions(dentry);
- 		fsnotify_nameremove(dentry, isdir);
- 		return;
- 	}
-@@ -1525,14 +1633,14 @@ void d_delete(struct dentry * dentry)
- 	spin_unlock(&dentry->d_lock);
- 	spin_unlock(&dcache_lock);
- 
-+	shrink_d_unions(dentry);
- 	fsnotify_nameremove(dentry, isdir);
- }
- 
- static void __d_rehash(struct dentry * entry, struct hlist_head *list)
- {
--
-- 	entry->d_flags &= ~DCACHE_UNHASHED;
-- 	hlist_add_head_rcu(&entry->d_hash, list);
-+	entry->d_flags &= ~DCACHE_UNHASHED;
-+	hlist_add_head_rcu(&entry->d_hash, list);
- }
- 
- static void _d_rehash(struct dentry * entry)
-@@ -1551,6 +1659,7 @@ void d_rehash(struct dentry * entry)
- {
- 	spin_lock(&dcache_lock);
- 	spin_lock(&entry->d_lock);
-+	BUG_ON(!d_unhashed(entry));
- 	_d_rehash(entry);
- 	spin_unlock(&entry->d_lock);
- 	spin_unlock(&dcache_lock);
-@@ -2183,7 +2292,9 @@ resume:
- 		struct list_head *tmp = next;
- 		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
- 		next = tmp->next;
--		if (d_unhashed(dentry)||!dentry->d_inode)
-+		if (d_unhashed(dentry)||(!dentry->d_inode &&
-+					 !d_is_whiteout(dentry) &&
-+					 !d_is_fallthru(dentry)))
- 			continue;
- 		if (!list_empty(&dentry->d_subdirs)) {
- 			this_parent = dentry;
---- a/fs/ext2/dir.c
-+++ b/fs/ext2/dir.c
-@@ -219,7 +219,8 @@ static inline int ext2_match (int len, c
- {
- 	if (len != de->name_len)
- 		return 0;
--	if (!de->inode)
-+	if (!de->inode && ((de->file_type != EXT2_FT_WHT) &&
-+			   (de->file_type != EXT2_FT_FALLTHRU)))
- 		return 0;
- 	return !memcmp(name, de->name, len);
- }
-@@ -255,6 +256,8 @@ static unsigned char ext2_filetype_table
- 	[EXT2_FT_FIFO]		= DT_FIFO,
- 	[EXT2_FT_SOCK]		= DT_SOCK,
- 	[EXT2_FT_SYMLINK]	= DT_LNK,
-+	[EXT2_FT_WHT]		= DT_WHT,
-+	[EXT2_FT_FALLTHRU]	= DT_UNKNOWN,
- };
- 
- #define S_SHIFT 12
-@@ -341,6 +344,18 @@ ext2_readdir (struct file * filp, void *
- 					ext2_put_page(page);
- 					return 0;
- 				}
-+			} else if (de->file_type == EXT2_FT_FALLTHRU) {
-+				int over;
-+				unsigned char d_type = DT_UNKNOWN;
-+
-+				offset = (char *)de - kaddr;
-+				over = filldir(dirent, de->name, de->name_len,
-+						(n<<PAGE_CACHE_SHIFT) | offset,
-+						123, d_type);
-+				if (over) {
-+					ext2_put_page(page);
-+					return 0;
-+				}
- 			}
- 			filp->f_pos += ext2_rec_len_from_disk(de->rec_len);
- 		}
-@@ -448,6 +463,30 @@ ino_t ext2_inode_by_name(struct inode *d
- 	return res;
- }
- 
-+/* Special version for filetype based whiteout support */
-+ino_t ext2_inode_by_dentry(struct inode *dir, struct dentry *dentry)
-+{
-+	ino_t res = 0;
-+	struct ext2_dir_entry_2 *de;
-+	struct page *page;
-+
-+	de = ext2_find_entry (dir, &dentry->d_name, &page);
-+	if (de) {
-+		res = le32_to_cpu(de->inode);
-+		if (!res && de->file_type == EXT2_FT_WHT) {
-+			spin_lock(&dentry->d_lock);
-+			dentry->d_flags |= DCACHE_WHITEOUT;
-+			spin_unlock(&dentry->d_lock);
-+		} else if(!res && de->file_type == EXT2_FT_FALLTHRU) {
-+			spin_lock(&dentry->d_lock);
-+			dentry->d_flags |= DCACHE_FALLTHRU;
-+			spin_unlock(&dentry->d_lock);
-+		}
-+		ext2_put_page(page);
-+	}
-+	return res;
-+}
-+
- /* Releases the page */
- void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
- 		   struct page *page, struct inode *inode, int update_times)
-@@ -472,9 +511,10 @@ void ext2_set_link(struct inode *dir, st
- }
- 
- /*
-- *	Parent is locked.
-+ * Find or append a given dentry to the parent directory
-  */
--int ext2_add_link (struct dentry *dentry, struct inode *inode)
-+static ext2_dirent * ext2_append_entry(struct dentry * dentry,
-+				       struct page ** page)
- {
- 	struct inode *dir = dentry->d_parent->d_inode;
- 	const char *name = dentry->d_name.name;
-@@ -482,13 +522,10 @@ int ext2_add_link (struct dentry *dentry
- 	unsigned chunk_size = ext2_chunk_size(dir);
- 	unsigned reclen = EXT2_DIR_REC_LEN(namelen);
- 	unsigned short rec_len, name_len;
--	struct page *page = NULL;
--	ext2_dirent * de;
-+	ext2_dirent * de = NULL;
- 	unsigned long npages = dir_pages(dir);
- 	unsigned long n;
- 	char *kaddr;
--	loff_t pos;
--	int err;
- 
- 	/*
- 	 * We take care of directory expansion in the same loop.
-@@ -498,55 +535,97 @@ int ext2_add_link (struct dentry *dentry
- 	for (n = 0; n <= npages; n++) {
- 		char *dir_end;
- 
--		page = ext2_get_page(dir, n, 0);
--		err = PTR_ERR(page);
--		if (IS_ERR(page))
-+		*page = ext2_get_page(dir, n, 0);
-+		de = ERR_PTR(PTR_ERR(*page));
-+		if (IS_ERR(*page))
- 			goto out;
--		lock_page(page);
--		kaddr = page_address(page);
-+		lock_page(*page);
-+		kaddr = page_address(*page);
- 		dir_end = kaddr + ext2_last_byte(dir, n);
- 		de = (ext2_dirent *)kaddr;
- 		kaddr += PAGE_CACHE_SIZE - reclen;
- 		while ((char *)de <= kaddr) {
- 			if ((char *)de == dir_end) {
- 				/* We hit i_size */
--				name_len = 0;
--				rec_len = chunk_size;
-+				de->name_len = 0;
- 				de->rec_len = ext2_rec_len_to_disk(chunk_size);
- 				de->inode = 0;
-+				de->file_type = 0;
- 				goto got_it;
- 			}
- 			if (de->rec_len == 0) {
- 				ext2_error(dir->i_sb, __func__,
- 					"zero-length directory entry");
--				err = -EIO;
-+				de = ERR_PTR(-EIO);
- 				goto out_unlock;
- 			}
--			err = -EEXIST;
- 			if (ext2_match (namelen, name, de))
--				goto out_unlock;
-+				goto got_it;
- 			name_len = EXT2_DIR_REC_LEN(de->name_len);
- 			rec_len = ext2_rec_len_from_disk(de->rec_len);
--			if (!de->inode && rec_len >= reclen)
-+			if (!de->inode && (de->file_type != EXT2_FT_WHT) &&
-+			    (de->file_type != EXT2_FT_FALLTHRU) &&
-+			    (rec_len >= reclen))
- 				goto got_it;
- 			if (rec_len >= name_len + reclen)
- 				goto got_it;
- 			de = (ext2_dirent *) ((char *) de + rec_len);
- 		}
--		unlock_page(page);
--		ext2_put_page(page);
-+		unlock_page(*page);
-+		ext2_put_page(*page);
- 	}
-+
- 	BUG();
--	return -EINVAL;
- 
- got_it:
-+	return de;
-+	/* OFFSET_CACHE */
-+out_unlock:
-+	unlock_page(*page);
-+	ext2_put_page(*page);
-+out:
-+	return de;
-+}
-+
-+/*
-+ *	Parent is locked.
-+ */
-+int ext2_add_link (struct dentry *dentry, struct inode *inode)
-+{
-+	struct inode *dir = dentry->d_parent->d_inode;
-+	const char *name = dentry->d_name.name;
-+	int namelen = dentry->d_name.len;
-+	unsigned short rec_len, name_len;
-+	ext2_dirent * de;
-+	struct page *page;
-+	loff_t pos;
-+	int err;
-+
-+	de = ext2_append_entry(dentry, &page);
-+	if (IS_ERR(de))
-+		return PTR_ERR(de);
-+
-+	err = -EEXIST;
-+	if (ext2_match (namelen, name, de)) {
-+		if ((de->file_type == EXT2_FT_WHT) ||
-+		    (de->file_type == EXT2_FT_FALLTHRU))
-+			goto got_it;
-+		goto out_unlock;
-+	}
-+
-+got_it:
-+	name_len = EXT2_DIR_REC_LEN(de->name_len);
-+	rec_len = ext2_rec_len_from_disk(de->rec_len);
-+
- 	pos = page_offset(page) +
- 		(char*)de - (char*)page_address(page);
- 	err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
- 							&page, NULL);
- 	if (err)
- 		goto out_unlock;
--	if (de->inode) {
-+	if (de->inode || (((de->file_type == EXT2_FT_WHT) ||
-+			   (de->file_type == EXT2_FT_FALLTHRU)) &&
-+			  !ext2_match (namelen, name, de))) {
- 		ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
- 		de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
- 		de->rec_len = ext2_rec_len_to_disk(name_len);
-@@ -563,7 +642,60 @@ got_it:
- 	/* OFFSET_CACHE */
- out_put:
- 	ext2_put_page(page);
--out:
-+	return err;
-+out_unlock:
-+	unlock_page(page);
-+	goto out_put;
-+}
-+
-+/*
-+ * Create a fallthru entry.
-+ */
-+int ext2_fallthru_entry (struct inode *dir, struct dentry *dentry)
-+{
-+	const char *name = dentry->d_name.name;
-+	int namelen = dentry->d_name.len;
-+	unsigned short rec_len, name_len;
-+	ext2_dirent * de;
-+	struct page *page;
-+	loff_t pos;
-+	int err;
-+
-+	de = ext2_append_entry(dentry, &page);
-+	if (IS_ERR(de))
-+		return PTR_ERR(de);
-+
-+	err = -EEXIST;
-+	if (ext2_match (namelen, name, de))
-+		goto out_unlock;
-+
-+	name_len = EXT2_DIR_REC_LEN(de->name_len);
-+	rec_len = ext2_rec_len_from_disk(de->rec_len);
-+
-+	pos = page_offset(page) +
-+		(char*)de - (char*)page_address(page);
-+	err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
-+							&page, NULL);
-+	if (err)
-+		goto out_unlock;
-+	if (de->inode || (de->file_type == EXT2_FT_WHT) ||
-+	    (de->file_type == EXT2_FT_FALLTHRU)) {
-+		ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
-+		de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
-+		de->rec_len = ext2_rec_len_to_disk(name_len);
-+		de = de1;
-+	}
-+	de->name_len = namelen;
-+	memcpy(de->name, name, namelen);
-+	de->inode = 0;
-+	de->file_type = EXT2_FT_FALLTHRU;
-+	err = ext2_commit_chunk(page, pos, rec_len);
-+	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
-+	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
-+	mark_inode_dirty(dir);
-+	/* OFFSET_CACHE */
-+out_put:
-+	ext2_put_page(page);
- 	return err;
- out_unlock:
- 	unlock_page(page);
-@@ -616,6 +748,70 @@ out:
- 	return err;
- }
- 
-+int ext2_whiteout_entry (struct inode * dir, struct dentry * dentry,
-+			 struct ext2_dir_entry_2 * de, struct page * page)
-+{
-+	const char *name = dentry->d_name.name;
-+	int namelen = dentry->d_name.len;
-+	unsigned short rec_len, name_len;
-+	loff_t pos;
-+	int err;
-+
-+	if (!de) {
-+		de = ext2_append_entry(dentry, &page);
-+		BUG_ON(!de);
-+	}
-+
-+	err = -EEXIST;
-+	if (ext2_match (namelen, name, de) &&
-+	    (de->file_type == EXT2_FT_WHT)) {
-+		ext2_error(dir->i_sb, __func__,
-+			   "entry is already a whiteout in directory #%lu",
-+			   dir->i_ino);
-+		goto out_unlock;
-+	}
-+
-+	name_len = EXT2_DIR_REC_LEN(de->name_len);
-+	rec_len = ext2_rec_len_from_disk(de->rec_len);
-+
-+	pos = page_offset(page) +
-+		(char*)de - (char*)page_address(page);
-+	err = __ext2_write_begin(NULL, page->mapping, pos, rec_len, 0,
-+							&page, NULL);
-+	if (err)
-+		goto out_unlock;
-+	/*
-+	 * We whiteout an existing entry. Do what ext2_delete_entry() would do,
-+	 * except that we don't need to merge with the previous entry since
-+	 * we are going to reuse it.
-+	 */
-+	if (ext2_match (namelen, name, de))
-+		de->inode = 0;
-+	if (de->inode || (((de->file_type == EXT2_FT_WHT) ||
-+			   (de->file_type == EXT2_FT_FALLTHRU)) &&
-+			  !ext2_match (namelen, name, de))) {
-+		ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
-+		de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
-+		de->rec_len = ext2_rec_len_to_disk(name_len);
-+		de = de1;
-+	}
-+	de->name_len = namelen;
-+	memcpy(de->name, name, namelen);
-+	de->inode = 0;
-+	de->file_type = EXT2_FT_WHT;
-+	err = ext2_commit_chunk(page, pos, rec_len);
-+	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
-+	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
-+	mark_inode_dirty(dir);
-+	/* OFFSET_CACHE */
-+out_put:
-+	ext2_put_page(page);
-+	return err;
-+out_unlock:
-+	unlock_page(page);
-+	goto out_put;
-+}
-+
- /*
-  * Set the first fragment of directory.
-  */
---- a/fs/ext2/ext2.h
-+++ b/fs/ext2/ext2.h
-@@ -102,9 +102,13 @@ extern void ext2_rsv_window_add(struct s
- /* dir.c */
- extern int ext2_add_link (struct dentry *, struct inode *);
- extern ino_t ext2_inode_by_name(struct inode *, struct qstr *);
-+extern ino_t ext2_inode_by_dentry(struct inode *, struct dentry *);
- extern int ext2_make_empty(struct inode *, struct inode *);
- extern struct ext2_dir_entry_2 * ext2_find_entry (struct inode *,struct qstr *, struct page **);
- extern int ext2_delete_entry (struct ext2_dir_entry_2 *, struct page *);
-+extern int ext2_whiteout_entry (struct inode *, struct dentry *,
-+				struct ext2_dir_entry_2 *, struct page *);
-+extern int ext2_fallthru_entry (struct inode *, struct dentry *);
- extern int ext2_empty_dir (struct inode *);
- extern struct ext2_dir_entry_2 * ext2_dotdot (struct inode *, struct page **);
- extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, struct inode *, int);
---- a/fs/ext2/inode.c
-+++ b/fs/ext2/inode.c
-@@ -1178,7 +1178,8 @@ void ext2_set_inode_flags(struct inode *
- {
- 	unsigned int flags = EXT2_I(inode)->i_flags;
- 
--	inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
-+	inode->i_flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|
-+			    S_OPAQUE);
- 	if (flags & EXT2_SYNC_FL)
- 		inode->i_flags |= S_SYNC;
- 	if (flags & EXT2_APPEND_FL)
-@@ -1189,6 +1190,8 @@ void ext2_set_inode_flags(struct inode *
- 		inode->i_flags |= S_NOATIME;
- 	if (flags & EXT2_DIRSYNC_FL)
- 		inode->i_flags |= S_DIRSYNC;
-+	if (flags & EXT2_OPAQUE_FL)
-+		inode->i_flags |= S_OPAQUE;
- }
- 
- /* Propagate flags from i_flags to EXT2_I(inode)->i_flags */
-@@ -1196,8 +1199,8 @@ void ext2_get_inode_flags(struct ext2_in
- {
- 	unsigned int flags = ei->vfs_inode.i_flags;
- 
--	ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|
--			EXT2_IMMUTABLE_FL|EXT2_NOATIME_FL|EXT2_DIRSYNC_FL);
-+	ei->i_flags &= ~(EXT2_SYNC_FL|EXT2_APPEND_FL|EXT2_IMMUTABLE_FL|
-+			 EXT2_NOATIME_FL|EXT2_DIRSYNC_FL|EXT2_OPAQUE_FL);
- 	if (flags & S_SYNC)
- 		ei->i_flags |= EXT2_SYNC_FL;
- 	if (flags & S_APPEND)
-@@ -1208,6 +1211,8 @@ void ext2_get_inode_flags(struct ext2_in
- 		ei->i_flags |= EXT2_NOATIME_FL;
- 	if (flags & S_DIRSYNC)
- 		ei->i_flags |= EXT2_DIRSYNC_FL;
-+	if (flags & S_OPAQUE)
-+		ei->i_flags |= EXT2_OPAQUE_FL;
- }
- 
- struct inode *ext2_iget (struct super_block *sb, unsigned long ino)
---- a/fs/ext2/namei.c
-+++ b/fs/ext2/namei.c
-@@ -54,15 +54,16 @@ static inline int ext2_add_nondir(struct
-  * Methods themselves.
-  */
- 
--static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, struct nameidata *nd)
-+static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry,
-+				  struct nameidata *nd)
- {
- 	struct inode * inode;
- 	ino_t ino;
--	
-+
- 	if (dentry->d_name.len > EXT2_NAME_LEN)
- 		return ERR_PTR(-ENAMETOOLONG);
- 
--	ino = ext2_inode_by_name(dir, &dentry->d_name);
-+	ino = ext2_inode_by_dentry(dir, dentry);
- 	inode = NULL;
- 	if (ino) {
- 		inode = ext2_iget(dir->i_sb, ino);
-@@ -230,6 +231,10 @@ static int ext2_mkdir(struct inode * dir
- 	else
- 		inode->i_mapping->a_ops = &ext2_aops;
- 
-+	/* if we call mkdir on a whiteout create an opaque directory */
-+	if (dentry->d_flags & DCACHE_WHITEOUT)
-+		inode->i_flags |= S_OPAQUE;
-+
- 	inode_inc_link_count(inode);
- 
- 	err = ext2_make_empty(inode, dir);
-@@ -293,6 +298,78 @@ static int ext2_rmdir (struct inode * di
- 	return err;
- }
- 
-+/*
-+ * Create a whiteout for the dentry
-+ */
-+static int ext2_whiteout(struct inode *dir, struct dentry *dentry,
-+			 struct dentry *new_dentry)
-+{
-+	struct inode * inode = dentry->d_inode;
-+	struct ext2_dir_entry_2 * de = NULL;
-+	struct page * page;
-+	int err = -ENOTEMPTY;
-+
-+	if (!EXT2_HAS_INCOMPAT_FEATURE(dir->i_sb,
-+				       EXT2_FEATURE_INCOMPAT_FILETYPE)) {
-+		ext2_error (dir->i_sb, "ext2_whiteout",
-+			    "can't set whiteout filetype");
-+		err = -EPERM;
-+		goto out;
-+	}
-+
-+	if (inode) {
-+		if (S_ISDIR(inode->i_mode) && !ext2_empty_dir(inode))
-+			goto out;
-+
-+		err = -ENOENT;
-+		de = ext2_find_entry (dir, &dentry->d_name, &page);
-+		if (!de)
-+			goto out;
-+		lock_page(page);
-+	}
-+
-+	err = ext2_whiteout_entry (dir, dentry, de, page);
-+	if (err)
-+		goto out;
-+
-+	spin_lock(&new_dentry->d_lock);
-+	new_dentry->d_flags &= ~DCACHE_FALLTHRU;
-+	new_dentry->d_flags |= DCACHE_WHITEOUT;
-+	spin_unlock(&new_dentry->d_lock);
-+	d_add(new_dentry, NULL);
-+
-+	if (inode) {
-+		inode->i_ctime = dir->i_ctime;
-+		inode_dec_link_count(inode);
-+		if (S_ISDIR(inode->i_mode)) {
-+			inode->i_size = 0;
-+			inode_dec_link_count(inode);
-+			inode_dec_link_count(dir);
-+		}
-+	}
-+	err = 0;
-+out:
-+	return err;
-+}
-+
-+/*
-+ * Create a fallthru entry.
-+ */
-+static int ext2_fallthru (struct inode *dir, struct dentry *dentry)
-+{
-+	int err;
-+
-+	err = ext2_fallthru_entry(dir, dentry);
-+	if (err)
-+		return err;
-+
-+	d_instantiate(dentry, NULL);
-+	spin_lock(&dentry->d_lock);
-+	dentry->d_flags |= DCACHE_FALLTHRU;
-+	spin_unlock(&dentry->d_lock);
-+	return 0;
-+}
-+
- static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
- 	struct inode * new_dir,	struct dentry * new_dentry )
- {
-@@ -392,6 +469,8 @@ const struct inode_operations ext2_dir_i
- 	.mkdir		= ext2_mkdir,
- 	.rmdir		= ext2_rmdir,
- 	.mknod		= ext2_mknod,
-+	.whiteout	= ext2_whiteout,
-+	.fallthru	= ext2_fallthru,
- 	.rename		= ext2_rename,
- #ifdef CONFIG_EXT2_FS_XATTR
- 	.setxattr	= generic_setxattr,
---- a/fs/ext2/super.c
-+++ b/fs/ext2/super.c
-@@ -1062,6 +1062,13 @@ static int ext2_fill_super(struct super_
- 	if (EXT2_HAS_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_HAS_JOURNAL))
- 		ext2_warning(sb, __func__,
- 			"mounting ext3 filesystem as ext2");
-+
-+	/*
-+	 * Whiteouts (and fallthrus) require explicit whiteout support.
-+	 */
-+	if (EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_WHITEOUT))
-+		sb->s_flags |= MS_WHITEOUT;
-+
- 	ext2_setup_super (sb, es, sb->s_flags & MS_RDONLY);
- 	return 0;
- 
---- a/fs/Kconfig
-+++ b/fs/Kconfig
-@@ -59,6 +59,14 @@ source "fs/notify/Kconfig"
- 
- source "fs/quota/Kconfig"
- 
-+config UNION_MOUNT
-+       bool "Union mount support (EXPERIMENTAL)"
-+       depends on EXPERIMENTAL
-+       ---help---
-+         If you say Y here, you will be able to mount file systems as
-+         union mount stacks. This is a VFS based implementation and
-+         should work with all file systems. If unsure, say N.
-+
- source "fs/autofs/Kconfig"
- source "fs/autofs4/Kconfig"
- source "fs/fuse/Kconfig"
---- a/fs/libfs.c
-+++ b/fs/libfs.c
-@@ -133,6 +133,7 @@ int dcache_readdir(struct file * filp, v
- 	struct dentry *cursor = filp->private_data;
- 	struct list_head *p, *q = &cursor->d_u.d_child;
- 	ino_t ino;
-+	int d_type;
- 	int i = filp->f_pos;
- 
- 	switch (i) {
-@@ -158,14 +159,25 @@ int dcache_readdir(struct file * filp, v
- 			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
- 				struct dentry *next;
- 				next = list_entry(p, struct dentry, d_u.d_child);
--				if (d_unhashed(next) || !next->d_inode)
-+				if (d_unhashed(next) || (!next->d_inode && !d_is_fallthru(next)))
- 					continue;
- 
-+				if (d_is_fallthru(next)) {
-+					/* XXX Make up things we can
-+					 * only get out of the inode.
-+					 * Should probably really do a
-+					 * lookup instead. */
-+					ino = 100; /* XXX Made up number of no significance */
-+					d_type = DT_UNKNOWN;
-+				} else {
-+					ino = next->d_inode->i_ino;
-+					d_type = dt_type(next->d_inode);
-+				}
-+
- 				spin_unlock(&dcache_lock);
- 				if (filldir(dirent, next->d_name.name, 
- 					    next->d_name.len, filp->f_pos, 
--					    next->d_inode->i_ino, 
--					    dt_type(next->d_inode)) < 0)
-+					    ino, d_type) < 0)
- 					return 0;
- 				spin_lock(&dcache_lock);
- 				/* next is still alive */
---- a/fs/Makefile
-+++ b/fs/Makefile
-@@ -52,6 +52,7 @@ obj-$(CONFIG_NFS_COMMON)	+= nfs_common/
- obj-$(CONFIG_GENERIC_ACL)	+= generic_acl.o
- 
- obj-y				+= quota/
-+obj-$(CONFIG_UNION_MOUNT)	+= union.o
- 
- obj-$(CONFIG_PROC_FS)		+= proc/
- obj-y				+= partitions/
---- a/fs/namei.c
-+++ b/fs/namei.c
-@@ -33,6 +33,7 @@
- #include <linux/fcntl.h>
- #include <linux/device_cgroup.h>
- #include <linux/fs_struct.h>
-+#include <linux/union.h>
- #include <asm/uaccess.h>
- 
- #define ACC_MODE(x) ("\000\004\002\006"[(x)&O_ACCMODE])
-@@ -242,16 +243,17 @@ int generic_permission(struct inode *ino
- }
- 
- /**
-- * inode_permission  -  check for access rights to a given inode
-+ * __inode_permission  -  check for access rights to a given inode
-  * @inode:	inode to check permission on
-  * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
-+ * @rofs:	check for read-only fs
-  *
-  * Used to check for read/write/execute permissions on an inode.
-  * We use "fsuid" for this, letting us set arbitrary permissions
-  * for filesystem access without changing the "normal" uids which
-  * are used for other things.
-  */
--int inode_permission(struct inode *inode, int mask)
-+int __inode_permission(struct inode *inode, int mask, int rofs)
- {
- 	int retval;
- 
-@@ -261,7 +263,7 @@ int inode_permission(struct inode *inode
- 		/*
- 		 * Nobody gets write access to a read-only fs.
- 		 */
--		if (IS_RDONLY(inode) &&
-+		if ((rofs & IS_RDONLY(inode)) &&
- 		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
- 			return -EROFS;
- 
-@@ -289,6 +291,18 @@ int inode_permission(struct inode *inode
- }
- 
- /**
-+ * inode_permission  -  check for access rights to a given inode
-+ * @inode:	inode to check permission on
-+ * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
-+ *
-+ * This version pays attention to the MS_RDONLY flag on the fs.
-+ */
-+int inode_permission(struct inode *inode, int mask)
-+{
-+	return __inode_permission(inode, mask, 1);
-+}
-+
-+/**
-  * file_permission  -  check for additional access rights to a given file
-  * @file:	file to check access rights for
-  * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
-@@ -417,15 +431,10 @@ do_revalidate(struct dentry *dentry, str
-  * Internal lookup() using the new generic dcache.
-  * SMP-safe
-  */
--static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
-+static struct dentry *cache_lookup(struct dentry *parent, struct qstr *name,
-+				   struct nameidata *nd)
- {
--	struct dentry * dentry = __d_lookup(parent, name);
--
--	/* lockess __d_lookup may fail due to concurrent d_move() 
--	 * in some unrelated directory, so try with d_lookup
--	 */
--	if (!dentry)
--		dentry = d_lookup(parent, name);
-+	struct dentry *dentry = d_lookup(parent, name);
- 
- 	if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
- 		dentry = do_revalidate(dentry, nd);
-@@ -434,6 +443,208 @@ static struct dentry * cached_lookup(str
- }
- 
- /*
-+ * Theory of operation for opaque, whiteout, and fallthru:
-+ *
-+ * whiteout: Unconditionally stop lookup here - ENOENT
-+ *
-+ * opaque: Don't lookup in directories lower in the union stack
-+ *
-+ * fallthru: While looking up an entry, ignore the opaque flag for the
-+ * current directory only.
-+ *
-+ * A union stack is a linked list of directory dentries which appear
-+ * in the same place in the namespace.  When constructing the union
-+ * stack, we include directories below opaque directories so that we
-+ * can properly handle fallthrus.  All non-fallthru lookups have to
-+ * check for the opaque flag on the parent directory and obey it.
-+ *
-+ * In general, the code pattern is to lookup the the topmost entry
-+ * first (either the first visible non-negative dentry or a negative
-+ * dentry in the topmost layer of the union), then build the union
-+ * stack for the newly looked-up entry (if it is a directory).
-+ */
-+
-+/**
-+ * __cache_lookup_topmost - lookup the topmost (non-)negative dentry
-+ *
-+ * @nd - parent's nameidata
-+ * @name - pathname part to lookup
-+ * @path - found dentry for pathname part
-+ *
-+ * This is used for union mount lookups from dcache. The first non-negative
-+ * dentry is searched on all layers of the union stack. Otherwise the topmost
-+ * negative dentry is returned.
-+ */
-+static int __cache_lookup_topmost(struct nameidata *nd, struct qstr *name,
-+				  struct path *path)
-+{
-+	struct dentry *dentry;
-+
-+	dentry = d_lookup(nd->path.dentry, name);
-+	if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
-+		dentry = do_revalidate(dentry, nd);
-+
-+	/*
-+	 * Remember the topmost negative dentry in case we don't find anything
-+	 */
-+	path->dentry = dentry;
-+	path->mnt = dentry ? nd->path.mnt : NULL;
-+
-+	if (!dentry || (dentry->d_inode || d_is_whiteout(dentry)))
-+		return !dentry;
-+
-+	/* Keep going through opaque directories if we found a fallthru */
-+	if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry))
-+		return !dentry;
-+
-+	/* look for the first non-negative or whiteout dentry */
-+
-+	while (follow_union_down(&nd->path)) {
-+		dentry = d_hash_and_lookup(nd->path.dentry, name);
-+
-+		/*
-+		 * If parts of the union stack are not in the dcache we need
-+		 * to do a real lookup
-+		 */
-+		if (!dentry)
-+			goto out_dput;
-+
-+		/*
-+		 * If parts of the union don't survive the revalidation we
-+		 * need to do a real lookup
-+		 */
-+		if (dentry->d_op && dentry->d_op->d_revalidate) {
-+			dentry = do_revalidate(dentry, nd);
-+			if (!dentry)
-+				goto out_dput;
-+		}
-+
-+		if (dentry->d_inode || d_is_whiteout(dentry))
-+			goto out_dput;
-+
-+		/* Stop the lookup on opaque parent and non-fallthru child */
-+		if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(dentry))
-+			goto out_dput;
-+
-+		dput(dentry);
-+	}
-+
-+	return !dentry;
-+
-+out_dput:
-+	dput(path->dentry);
-+	path->dentry = dentry;
-+	path->mnt = dentry ? mntget(nd->path.mnt) : NULL;
-+	return !dentry;
-+}
-+
-+/**
-+ * __cache_lookup_build_union - build the union stack for this part,
-+ * cached version
-+ *
-+ * This is called after you have the topmost dentry in @path.
-+ */
-+static int __cache_lookup_build_union(struct nameidata *nd, struct qstr *name,
-+				      struct path *path)
-+{
-+	struct path last = *path;
-+	struct dentry *dentry;
-+
-+	while (follow_union_down(&nd->path)) {
-+		dentry = d_hash_and_lookup(nd->path.dentry, name);
-+		if (!dentry)
-+			return 1;
-+
-+		if (dentry->d_op && dentry->d_op->d_revalidate) {
-+			dentry = do_revalidate(dentry, nd);
-+			if (!dentry)
-+				return 1;
-+		}
-+
-+		if (d_is_whiteout(dentry)) {
-+			dput(dentry);
-+			break;
-+		}
-+
-+		if (!dentry->d_inode) {
-+			dput(dentry);
-+			continue;
-+		}
-+
-+		/* only directories can be part of a union stack */
-+		if (!S_ISDIR(dentry->d_inode->i_mode)) {
-+			dput(dentry);
-+			break;
-+		}
-+
-+		/* Add the newly discovered dir to the union stack */
-+		append_to_union(last.mnt, last.dentry, nd->path.mnt, dentry);
-+
-+		if (last.dentry != path->dentry)
-+			path_put(&last);
-+		last.dentry = dentry;
-+		last.mnt = mntget(nd->path.mnt);
-+	}
-+
-+	if (last.dentry != path->dentry)
-+		path_put(&last);
-+
-+	return 0;
-+}
-+
-+/**
-+ * cache_lookup_union - lookup a single pathname part from dcache
-+ *
-+ * This is a union mount capable version of what d_lookup() & revalidate()
-+ * would do. This function returns a valid (union) dentry on success.
-+ *
-+ * Remember: On failure it means that parts of the union aren't cached. You
-+ * should call real_lookup() afterwards to find the proper (union) dentry.
-+ */
-+static int cache_lookup_union(struct nameidata *nd, struct qstr *name,
-+			      struct path *path)
-+{
-+	int res ;
-+
-+	if (!IS_MNT_UNION(nd->path.mnt)) {
-+		path->dentry = cache_lookup(nd->path.dentry, name, nd);
-+		path->mnt = path->dentry ? nd->path.mnt : NULL;
-+		res = path->dentry ? 0 : 1;
-+	} else {
-+		struct path safe = {
-+			.dentry = nd->path.dentry,
-+			.mnt = nd->path.mnt
-+		};
-+
-+		path_get(&safe);
-+		res = __cache_lookup_topmost(nd, name, path);
-+		if (res)
-+			goto out;
-+
-+		/* only directories can be part of a union stack */
-+		if (!path->dentry->d_inode ||
-+		    !S_ISDIR(path->dentry->d_inode->i_mode))
-+			goto out;
-+
-+		/* Build the union stack for this part */
-+		res = __cache_lookup_build_union(nd, name, path);
-+		if (res) {
-+			dput(path->dentry);
-+			if (path->mnt != safe.mnt)
-+				mntput(path->mnt);
-+			goto out;
-+		}
-+
-+out:
-+		path_put(&nd->path);
-+		nd->path.dentry = safe.dentry;
-+		nd->path.mnt = safe.mnt;
-+	}
-+
-+	return res;
-+}
-+
-+/*
-  * Short-cut version of permission(), for calling by
-  * path_walk(), when dcache lock is held.  Combines parts
-  * of permission() and generic_permission(), and tests ONLY for
-@@ -473,10 +684,11 @@ ok:
-  * make sure that nobody added the entry to the dcache in the meantime..
-  * SMP-safe
-  */
--static struct dentry * real_lookup(struct dentry * parent, struct qstr * name, struct nameidata *nd)
-+static int real_lookup(struct nameidata *nd, struct qstr *name,
-+		       struct path *path)
- {
--	struct dentry * result;
--	struct inode *dir = parent->d_inode;
-+	struct inode *dir = nd->path.dentry->d_inode;
-+	int res = 0;
- 
- 	mutex_lock(&dir->i_mutex);
- 	/*
-@@ -493,27 +705,36 @@ static struct dentry * real_lookup(struc
- 	 *
- 	 * so doing d_lookup() (with seqlock), instead of lockfree __d_lookup
- 	 */
--	result = d_lookup(parent, name);
--	if (!result) {
-+	path->dentry = d_lookup(nd->path.dentry, name);
-+	path->mnt = nd->path.mnt;
-+	if (!path->dentry) {
- 		struct dentry *dentry;
- 
- 		/* Don't create child dentry for a dead directory. */
--		result = ERR_PTR(-ENOENT);
--		if (IS_DEADDIR(dir))
-+		if (IS_DEADDIR(dir)) {
-+			res = -ENOENT;
- 			goto out_unlock;
-+		}
- 
--		dentry = d_alloc(parent, name);
--		result = ERR_PTR(-ENOMEM);
-+		dentry = d_alloc(nd->path.dentry, name);
- 		if (dentry) {
--			result = dir->i_op->lookup(dir, dentry, nd);
--			if (result)
-+			path->dentry = dir->i_op->lookup(dir, dentry, nd);
-+			if (path->dentry) {
- 				dput(dentry);
--			else
--				result = dentry;
-+				if (IS_ERR(path->dentry)) {
-+					res = PTR_ERR(path->dentry);
-+					path->dentry = NULL;
-+					path->mnt = NULL;
-+				}
-+			} else
-+				path->dentry = dentry;
-+		} else {
-+			res = -ENOMEM;
-+			path->mnt = NULL;
- 		}
- out_unlock:
- 		mutex_unlock(&dir->i_mutex);
--		return result;
-+		return res;
- 	}
- 
- 	/*
-@@ -521,12 +742,170 @@ out_unlock:
- 	 * we waited on the semaphore. Need to revalidate.
- 	 */
- 	mutex_unlock(&dir->i_mutex);
--	if (result->d_op && result->d_op->d_revalidate) {
--		result = do_revalidate(result, nd);
--		if (!result)
--			result = ERR_PTR(-ENOENT);
-+	if (path->dentry->d_op && path->dentry->d_op->d_revalidate) {
-+		path->dentry = do_revalidate(path->dentry, nd);
-+		if (!path->dentry) {
-+			res = -ENOENT;
-+			path->mnt = NULL;
-+		}
-+		if (IS_ERR(path->dentry)) {
-+			res = PTR_ERR(path->dentry);
-+			path->dentry = NULL;
-+			path->mnt = NULL;
-+		}
- 	}
--	return result;
-+
-+	return res;
-+}
-+
-+/**
-+ * __real_lookup_topmost - lookup topmost dentry, non-cached version
-+ *
-+ * If we reach a dentry with restricted access, we just stop the lookup
-+ * because we shouldn't see through that dentry. Same thing for dentry
-+ * type mismatch and whiteouts.
-+ *
-+ * FIXME:
-+ * - handle union stacks in use
-+ * - handle union stacks mounted upon union stacks
-+ * - avoid unnecessary allocations of union locks
-+ */
-+static int __real_lookup_topmost(struct nameidata *nd, struct qstr *name,
-+				 struct path *path)
-+{
-+	struct path next;
-+	int err;
-+
-+	err = real_lookup(nd, name, path);
-+	if (err)
-+		return err;
-+
-+	if (path->dentry->d_inode || d_is_whiteout(path->dentry))
-+		return 0;
-+
-+	if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry))
-+		return 0;
-+
-+	while (follow_union_down(&nd->path)) {
-+		name->hash = full_name_hash(name->name, name->len);
-+		if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
-+			err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
-+							    name);
-+			if (err < 0)
-+				goto out;
-+		}
-+
-+		err = real_lookup(nd, name, &next);
-+		if (err)
-+			goto out;
-+
-+		if (next.dentry->d_inode || d_is_whiteout(next.dentry)) {
-+			dput(path->dentry);
-+			mntget(next.mnt);
-+			*path = next;
-+			goto out;
-+		}
-+
-+		if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry))
-+			goto out;
-+
-+		dput(next.dentry);
-+	}
-+out:
-+	if (err)
-+		dput(path->dentry);
-+	return err;
-+}
-+
-+/**
-+ * __real_lookup_build_union: build the union stack for this pathname
-+ * part, non-cached version
-+ *
-+ * Called when not all parts of the union stack are in cache
-+ */
-+
-+static int __real_lookup_build_union(struct nameidata *nd, struct qstr *name,
-+				     struct path *path)
-+{
-+	struct path last = *path;
-+	struct path next;
-+	int err = 0;
-+
-+	while (follow_union_down(&nd->path)) {
-+		/* We need to recompute the hash for lower layer lookups */
-+		name->hash = full_name_hash(name->name, name->len);
-+		if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
-+			err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
-+							    name);
-+			if (err < 0)
-+				goto out;
-+		}
-+
-+		err = real_lookup(nd, name, &next);
-+		if (err)
-+			goto out;
-+
-+		if (d_is_whiteout(next.dentry)) {
-+			dput(next.dentry);
-+			break;
-+		}
-+
-+		if (!next.dentry->d_inode) {
-+			dput(next.dentry);
-+			continue;
-+		}
-+
-+		/* only directories can be part of a union stack */
-+		if (!S_ISDIR(next.dentry->d_inode->i_mode)) {
-+			dput(next.dentry);
-+			break;
-+		}
-+
-+		/* now we know we found something "real" */
-+		append_to_union(last.mnt, last.dentry, next.mnt, next.dentry);
-+
-+		if (last.dentry != path->dentry)
-+			path_put(&last);
-+		last.dentry = next.dentry;
-+		last.mnt = mntget(next.mnt);
-+	}
-+
-+	if (last.dentry != path->dentry)
-+		path_put(&last);
-+out:
-+	return err;
-+}
-+
-+static int real_lookup_union(struct nameidata *nd, struct qstr *name,
-+			     struct path *path)
-+{
-+	struct path safe = { .dentry = nd->path.dentry, .mnt = nd->path.mnt };
-+	int res ;
-+
-+	path_get(&safe);
-+	res = __real_lookup_topmost(nd, name, path);
-+	if (res)
-+		goto out;
-+
-+	/* only directories can be part of a union stack */
-+	if (!path->dentry->d_inode ||
-+	    !S_ISDIR(path->dentry->d_inode->i_mode))
-+		goto out;
-+
-+	/* Build the union stack for this part */
-+	res = __real_lookup_build_union(nd, name, path);
-+	if (res) {
-+		dput(path->dentry);
-+		if (path->mnt != safe.mnt)
-+			mntput(path->mnt);
-+		goto out;
-+	}
-+
-+out:
-+	path_put(&nd->path);
-+	nd->path.dentry = safe.dentry;
-+	nd->path.mnt = safe.mnt;
-+	return res;
- }
- 
- /*
-@@ -629,11 +1008,8 @@ static __always_inline int __do_follow_l
- 	touch_atime(path->mnt, dentry);
- 	nd_set_link(nd, NULL);
- 
--	if (path->mnt != nd->path.mnt) {
--		path_to_nameidata(path, nd);
--		dget(dentry);
--	}
--	mntget(path->mnt);
-+	if (path->mnt == nd->path.mnt)
-+		mntget(nd->path.mnt);
- 	cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
- 	error = PTR_ERR(cookie);
- 	if (!IS_ERR(cookie)) {
-@@ -721,7 +1097,7 @@ static int __follow_mount(struct path *p
- 	return res;
- }
- 
--static void follow_mount(struct path *path)
-+void follow_mount(struct path *path)
- {
- 	while (d_mountpoint(path->dentry)) {
- 		struct vfsmount *mounted = lookup_mnt(path);
-@@ -786,6 +1162,7 @@ static __always_inline void follow_dotdo
- 		nd->path.mnt = parent;
- 	}
- 	follow_mount(&nd->path);
-+	follow_union_mount(&nd->path);
- }
- 
- /*
-@@ -796,35 +1173,55 @@ static __always_inline void follow_dotdo
- static int do_lookup(struct nameidata *nd, struct qstr *name,
- 		     struct path *path)
- {
--	struct vfsmount *mnt = nd->path.mnt;
--	struct dentry *dentry = __d_lookup(nd->path.dentry, name);
-+	int err;
-+
-+	if (IS_MNT_UNION(nd->path.mnt))
-+		goto need_union_lookup;
- 
--	if (!dentry)
-+	path->dentry = __d_lookup(nd->path.dentry, name);
-+	path->mnt = nd->path.mnt;
-+	if (!path->dentry)
- 		goto need_lookup;
--	if (dentry->d_op && dentry->d_op->d_revalidate)
-+	if (path->dentry->d_op && path->dentry->d_op->d_revalidate)
- 		goto need_revalidate;
-+
- done:
--	path->mnt = mnt;
--	path->dentry = dentry;
--	__follow_mount(path);
-+	if (nd->path.mnt != path->mnt) {
-+		nd->um_flags |= LAST_LOWLEVEL;
-+		follow_mount(path);
-+	} else
-+		__follow_mount(path);
-+	follow_union_mount(path);
- 	return 0;
- 
- need_lookup:
--	dentry = real_lookup(nd->path.dentry, name, nd);
--	if (IS_ERR(dentry))
-+	err = real_lookup(nd, name, path);
-+	if (err)
-+		goto fail;
-+	goto done;
-+
-+need_union_lookup:
-+	err = cache_lookup_union(nd, name, path);
-+	if (!err && path->dentry)
-+		goto done;
-+
-+	err = real_lookup_union(nd, name, path);
-+	if (err)
- 		goto fail;
- 	goto done;
- 
- need_revalidate:
--	dentry = do_revalidate(dentry, nd);
--	if (!dentry)
-+	path->dentry = do_revalidate(path->dentry, nd);
-+	if (!path->dentry)
- 		goto need_lookup;
--	if (IS_ERR(dentry))
-+	if (IS_ERR(path->dentry)) {
-+		err = PTR_ERR(path->dentry);
- 		goto fail;
-+	}
- 	goto done;
- 
- fail:
--	return PTR_ERR(dentry);
-+	return err;
- }
- 
- /*
-@@ -851,6 +1248,8 @@ static int __link_path_walk(const char *
- 	if (nd->depth)
- 		lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
- 
-+	follow_union_mount(&nd->path);
-+
- 	/* At this point we know we have a real path component. */
- 	for(;;) {
- 		unsigned long hash;
-@@ -913,6 +1312,44 @@ static int __link_path_walk(const char *
- 		if (err)
- 			break;
- 
-+		/*
-+		 * We want to create this element on the top level
-+		 * file system in two cases:
-+		 *
-+		 * - We are specifically told to - LOOKUP_TOPMOST.
-+		 * - This is a directory, and it does not yet exist on
-+		 *   the top level.  Various tricks only work if
-+		 *   directories always exist on the top level.
-+		 *
-+		 * In either case, only create this element on the top
-+		 * level if the last element is located on the lower
-+		 * level.  If the last element is located on the top
-+		 * level, then every single element in the path
-+		 * already exists on the top level.
-+		 *
-+		 * Note that we can assume that the parent is on the
-+		 * top level since we always create the directory on
-+		 * the top level.
-+		 */
-+
-+		if ((nd->um_flags & LAST_LOWLEVEL) &&
-+		    ((next.dentry->d_inode &&
-+		      S_ISDIR(next.dentry->d_inode->i_mode) &&
-+		      (nd->path.mnt != next.mnt)) ||
-+		     (nd->flags & LOOKUP_TOPMOST))) {
-+			struct dentry *dentry;
-+
-+			dentry = union_create_topmost(nd, &this, &next);
-+			if (IS_ERR(dentry)) {
-+				err = PTR_ERR(dentry);
-+				goto out_dput;
-+			}
-+			path_put_conditional(&next, nd);
-+			next.mnt = nd->path.mnt;
-+			next.dentry = dentry;
-+			nd->um_flags &= ~LAST_LOWLEVEL;
-+		}
-+
- 		err = -ENOENT;
- 		inode = next.dentry->d_inode;
- 		if (!inode)
-@@ -962,6 +1399,25 @@ last_component:
- 		err = do_lookup(nd, &this, &next);
- 		if (err)
- 			break;
-+
-+		if ((nd->um_flags & LAST_LOWLEVEL) &&
-+		    ((next.dentry->d_inode &&
-+		      S_ISDIR(next.dentry->d_inode->i_mode) &&
-+		      (nd->path.mnt != next.mnt)) ||
-+		     (nd->flags & LOOKUP_TOPMOST))) {
-+			struct dentry *dentry;
-+
-+			dentry = union_create_topmost(nd, &this, &next);
-+			if (IS_ERR(dentry)) {
-+				err = PTR_ERR(dentry);
-+				goto out_dput;
-+			}
-+			path_put_conditional(&next, nd);
-+			next.mnt = nd->path.mnt;
-+			next.dentry = dentry;
-+			nd->um_flags &= ~LAST_LOWLEVEL;
-+		}
-+
- 		inode = next.dentry->d_inode;
- 		if ((lookup_flags & LOOKUP_FOLLOW)
- 		    && inode && inode->i_op->follow_link) {
-@@ -1029,6 +1485,7 @@ static int path_init(int dfd, const char
- 
- 	nd->last_type = LAST_ROOT; /* if there are only slashes... */
- 	nd->flags = flags;
-+	nd->um_flags = 0;
- 	nd->depth = 0;
- 	nd->root.mnt = NULL;
- 
-@@ -1172,61 +1629,437 @@ static int path_lookup_open(int dfd, con
- }
- 
- static struct dentry *__lookup_hash(struct qstr *name,
--		struct dentry *base, struct nameidata *nd)
-+				    struct dentry *base, struct nameidata *nd)
-+{
-+	struct dentry *dentry;
-+	struct inode *inode;
-+	int err;
-+
-+	inode = base->d_inode;
-+
-+	/*
-+	 * See if the low-level filesystem might want
-+	 * to use its own hash..
-+	 */
-+	if (base->d_op && base->d_op->d_hash) {
-+		err = base->d_op->d_hash(base, name);
-+		dentry = ERR_PTR(err);
-+		if (err < 0)
-+			goto out;
-+	}
-+
-+	dentry = cache_lookup(base, name, nd);
-+	if (!dentry) {
-+		struct dentry *new;
-+
-+		/* Don't create child dentry for a dead directory. */
-+		dentry = ERR_PTR(-ENOENT);
-+		if (IS_DEADDIR(inode))
-+			goto out;
-+
-+		new = d_alloc(base, name);
-+		dentry = ERR_PTR(-ENOMEM);
-+		if (!new)
-+			goto out;
-+		dentry = inode->i_op->lookup(inode, new, nd);
-+		if (!dentry)
-+			dentry = new;
-+		else
-+			dput(new);
-+	}
-+out:
-+	return dentry;
-+}
-+
-+/*
-+ * Restricted form of lookup. Doesn't follow links, single-component only,
-+ * needs parent already locked. Doesn't follow mounts.
-+ * SMP-safe.
-+ */
-+static int lookup_hash(struct nameidata *nd, struct qstr *name,
-+		       struct path *path)
-+{
-+	int err;
-+
-+	err = inode_permission(nd->path.dentry->d_inode, MAY_EXEC);
-+	if (err)
-+		return err;
-+	path->mnt = nd->path.mnt;
-+	path->dentry =  __lookup_hash(name, nd->path.dentry, nd);
-+	if (IS_ERR(path->dentry)) {
-+		err = PTR_ERR(path->dentry);
-+		path->dentry = NULL;
-+		path->mnt = NULL;
-+	}
-+	return err;
-+}
-+
-+static int __hash_lookup_topmost(struct nameidata *nd, struct qstr *name,
-+				 struct path *path)
-+{
-+	struct path next;
-+	int err;
-+
-+	err = lookup_hash(nd, name, path);
-+	if (err)
-+		return err;
-+
-+	if (path->dentry->d_inode || d_is_whiteout(path->dentry))
-+		return 0;
-+
-+	if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(path->dentry))
-+		return 0;
-+
-+	while (follow_union_down(&nd->path)) {
-+		name->hash = full_name_hash(name->name, name->len);
-+		if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
-+			err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
-+							    name);
-+			if (err < 0)
-+				goto out;
-+		}
-+
-+		mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+		err = lookup_hash(nd, name, &next);
-+		mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
-+		if (err)
-+			goto out;
-+
-+		if (next.dentry->d_inode || d_is_whiteout(next.dentry)) {
-+			dput(path->dentry);
-+			mntget(next.mnt);
-+			*path = next;
-+			goto out;
-+		}
-+
-+		if (IS_OPAQUE(nd->path.dentry->d_inode) && !d_is_fallthru(next.dentry))
-+			goto out;
-+
-+		dput(next.dentry);
-+	}
-+out:
-+	if (err)
-+		dput(path->dentry);
-+	return err;
-+}
-+
-+static int __hash_lookup_build_union(struct nameidata *nd, struct qstr *name,
-+				     struct path *path)
-+{
-+	struct path last = *path;
-+	struct path next;
-+	int err = 0;
-+
-+	while (follow_union_down(&nd->path)) {
-+		/* We need to recompute the hash for lower layer lookups */
-+		name->hash = full_name_hash(name->name, name->len);
-+		if (nd->path.dentry->d_op && nd->path.dentry->d_op->d_hash) {
-+			err = nd->path.dentry->d_op->d_hash(nd->path.dentry,
-+							    name);
-+			if (err < 0)
-+				goto out;
-+		}
-+
-+		mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+		err = lookup_hash(nd, name, &next);
-+		mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
-+		if (err)
-+			goto out;
-+
-+		if (d_is_whiteout(next.dentry)) {
-+			dput(next.dentry);
-+			break;
-+		}
-+
-+		if (!next.dentry->d_inode) {
-+			dput(next.dentry);
-+			continue;
-+		}
-+
-+		/* only directories can be part of a union stack */
-+		if (!S_ISDIR(next.dentry->d_inode->i_mode)) {
-+			dput(next.dentry);
-+			break;
-+		}
-+
-+		/* now we know we found something "real" */
-+		append_to_union(last.mnt, last.dentry, next.mnt, next.dentry);
-+
-+		if (last.dentry != path->dentry)
-+			path_put(&last);
-+		last.dentry = next.dentry;
-+		last.mnt = mntget(next.mnt);
-+	}
-+
-+	if (last.dentry != path->dentry)
-+		path_put(&last);
-+out:
-+	return err;
-+}
-+
-+int hash_lookup_union(struct nameidata *nd, struct qstr *name,
-+			     struct path *path)
-+{
-+	struct path safe = { .dentry = nd->path.dentry, .mnt = nd->path.mnt };
-+	int res ;
-+
-+	path_get(&safe);
-+	res = __hash_lookup_topmost(nd, name, path);
-+	if (res)
-+		goto out;
-+
-+	/* only directories can be part of a union stack */
-+	if (!path->dentry->d_inode ||
-+	    !S_ISDIR(path->dentry->d_inode->i_mode))
-+		goto out;
-+
-+	/* Build the union stack for this part */
-+	res = __hash_lookup_build_union(nd, name, path);
-+	if (res) {
-+		dput(path->dentry);
-+		if (path->mnt != safe.mnt)
-+			mntput(path->mnt);
-+		goto out;
-+	}
-+
-+out:
-+	path_put(&nd->path);
-+	nd->path.dentry = safe.dentry;
-+	nd->path.mnt = safe.mnt;
-+	return res;
-+}
-+
-+/**
-+ * do_union_hash_lookup() - walk down the union stack and lookup_hash()
-+ * @nd: nameidata of parent to lookup from
-+ * @name: pathname component to lookup
-+ * @path: path to store result of lookup in
-+ *
-+ * Walk down the union stack and search for single pathname component name. It
-+ * is assumed that the caller already did a lookup_hash() in the topmost parent
-+ * that gave negative lookup result. Therefore this does call lookup_hash() in
-+ * every lower layer (!) of the union stack. If a directory is found the union
-+ * stack for that is assembled as well.
-+ *
-+ * Note:
-+ * The caller needs to take care of holding a valid reference to the topmost
-+ * parent.
-+ * On error we leave @path untouched as well as when we don't find anything.
-+ */
-+static int do_union_hash_lookup(struct nameidata *nd, struct qstr *name,
-+				struct path *path)
-+{
-+	struct path next;
-+	int err = 0;
-+
-+	while (follow_union_down(&nd->path)) {
-+		/* rehash because of d_op->d_hash() by the previous layer */
-+		name->hash = full_name_hash(name->name, name->len);
-+
-+		mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+		err = lookup_hash(nd, name, &next);
-+		mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
-+
-+		if (err)
-+			break;
-+
-+		if (next.dentry->d_inode) {
-+			mntget(next.mnt);
-+			if (!S_ISDIR(next.dentry->d_inode->i_mode)) {
-+				*path = next;
-+				break;
-+			}
-+			err = __hash_lookup_build_union(nd, name, &next);
-+			if (err)
-+				path_put(&next);
-+			else
-+				*path = next;
-+			break;
-+		}
-+
-+		path_put_conditional(&next, nd);
-+
-+		if ((IS_OPAQUE(nd->path.dentry->d_inode) &&
-+		     !d_is_fallthru(next.dentry)) ||
-+		    d_is_whiteout(next.dentry))
-+			break;
-+	}
-+
-+	return err;
-+}
-+
-+/**
-+ * _hash_lookup_union() - lookup single pathname component
-+ * @nd: nameidata of parent to lookup from
-+ * @name: pathname component to lookup
-+ * @path: path to store result of lookup in
-+ *
-+ * Returns the topmost parent locked and the target dentry found in the union
-+ * or the topmost negative target dentry otherwise.
-+ *
-+ * Note:
-+ * Returns topmost parent locked even on error.
-+ */
-+static int _hash_lookup_union(struct nameidata *nd, struct qstr *name,
-+			      struct path *path)
-+{
-+	struct path parent = nd->path;
-+	struct path topmost;
-+	int err;
-+
-+	mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+	err = lookup_hash(nd, name, path);
-+	if (err)
-+		return err;
-+
-+	/* return if we found something and it isn't a directory we are done */
-+	if (path->dentry->d_inode && !S_ISDIR(path->dentry->d_inode->i_mode))
-+		return 0;
-+
-+	/* stop lookup if the parent directory is marked opaque */
-+	if ((IS_OPAQUE(nd->path.dentry->d_inode) &&
-+	     !d_is_fallthru(path->dentry)) ||
-+	    d_is_whiteout(path->dentry))
-+		return 0;
-+
-+	if (!strcmp(path->mnt->mnt_sb->s_type->name, "proc") ||
-+	    !strcmp(path->mnt->mnt_sb->s_type->name, "sysfs"))
-+		return 0;
-+
-+	mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
-+
-+	/*
-+	 * safe a reference to the topmost parent for walking the union stack
-+	 */
-+	path_get(&parent);
-+	topmost = *path;
-+
-+	if (path->dentry->d_inode && S_ISDIR(path->dentry->d_inode->i_mode)) {
-+		err = __hash_lookup_build_union(nd, name, path);
-+		if (err)
-+			goto err_lock_parent;
-+		goto out_lock_and_revalidate_parent;
-+	}
-+
-+	err = do_union_hash_lookup(nd, name, path);
-+	if (err)
-+		goto err_lock_parent;
-+
-+out_lock_and_revalidate_parent:
-+	/* seems that we haven't found anything, so return the topmost */
-+	path_to_nameidata(&parent, nd);
-+	mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+
-+	if (topmost.dentry == path->dentry) {
-+		spin_lock(&path->dentry->d_lock);
-+		if (nd->path.dentry != path->dentry->d_parent) {
-+			spin_unlock(&path->dentry->d_lock);
-+			dput(path->dentry);
-+			name->hash = full_name_hash(name->name, name->len);
-+			err = lookup_hash(nd, name, path);
-+			if (err)
-+				return err;
-+			/* FIXME: What if we find a directory here ... */
-+			return err;
-+		}
-+		spin_unlock(&path->dentry->d_lock);
-+	} else
-+		dput(topmost.dentry);
-+
-+	return 0;
-+
-+err_lock_parent:
-+	path_to_nameidata(&parent, nd);
-+	path_put_conditional(path, nd);
-+	mutex_lock(&nd->path.dentry->d_inode->i_mutex);
-+	return err;
-+}
-+
-+/**
-+ * lookup_rename_source() - lookup the source used by rename
-+ *
-+ * This is a special version of _hash_lookup_union() which becomes necessary
-+ * for finding the source of a rename on union mounts.
-+ *
-+ * See comment for _hash_lookup_union() above.
-+ */
-+static int lookup_rename_source(struct nameidata *oldnd,
-+				struct nameidata *newnd,
-+				struct dentry **trap, struct qstr *name,
-+				struct path *old)
- {
--	struct dentry *dentry;
--	struct inode *inode;
-+	struct path parent = oldnd->path;
-+	struct path topmost;
- 	int err;
- 
--	inode = base->d_inode;
-+	err = lookup_hash(oldnd, name, old);
-+	if (err)
-+		return err;
-+
-+	/* return if we found something and it isn't a directory we are done */
-+	if (old->dentry->d_inode && !S_ISDIR(old->dentry->d_inode->i_mode))
-+		return 0;
-+
-+	/* stop lookup if the parent directory is marked opaque */
-+	if ((IS_OPAQUE(oldnd->path.dentry->d_inode) &&
-+	     !d_is_fallthru(old->dentry)) ||
-+	    d_is_whiteout(old->dentry))
-+		return 0;
-+
-+	if (!strcmp(old->mnt->mnt_sb->s_type->name, "proc") ||
-+	    !strcmp(old->mnt->mnt_sb->s_type->name, "sysfs"))
-+		return 0;
-+
-+	unlock_rename(oldnd->path.dentry, newnd->path.dentry);
- 
- 	/*
--	 * See if the low-level filesystem might want
--	 * to use its own hash..
-+	 * safe a reference to the topmost parent for walking the union stack
- 	 */
--	if (base->d_op && base->d_op->d_hash) {
--		err = base->d_op->d_hash(base, name);
--		dentry = ERR_PTR(err);
--		if (err < 0)
--			goto out;
-+	path_get(&parent);
-+	topmost = *old;
-+
-+	if (old->dentry->d_inode && S_ISDIR(old->dentry->d_inode->i_mode)) {
-+		err = __hash_lookup_build_union(oldnd, name, old);
-+		if (err)
-+			goto err_lock;
-+		goto out_lock_and_revalidate_parent;
- 	}
- 
--	dentry = cached_lookup(base, name, nd);
--	if (!dentry) {
--		struct dentry *new;
-+	err = do_union_hash_lookup(oldnd, name, old);
-+	if (err)
-+		goto err_lock;
- 
--		/* Don't create child dentry for a dead directory. */
--		dentry = ERR_PTR(-ENOENT);
--		if (IS_DEADDIR(inode))
--			goto out;
-+out_lock_and_revalidate_parent:
-+	path_to_nameidata(&parent, oldnd);
-+	*trap = lock_rename(oldnd->path.dentry, newnd->path.dentry);
- 
--		new = d_alloc(base, name);
--		dentry = ERR_PTR(-ENOMEM);
--		if (!new)
--			goto out;
--		dentry = inode->i_op->lookup(inode, new, nd);
--		if (!dentry)
--			dentry = new;
--		else
--			dput(new);
--	}
--out:
--	return dentry;
--}
-+	/*
-+	 * If we return the topmost dentry we have to make sure that it has not
-+	 * been moved away while we gave up the topmost parents i_mutex lock.
-+	 */
-+	if (topmost.dentry == old->dentry) {
-+		spin_lock(&old->dentry->d_lock);
-+		if (oldnd->path.dentry != old->dentry->d_parent) {
-+			spin_unlock(&old->dentry->d_lock);
-+			dput(old->dentry);
-+			name->hash = full_name_hash(name->name, name->len);
-+			err = lookup_hash(oldnd, name, old);
-+			if (err)
-+				return err;
-+			/* FIXME: What if we find a directory here ... */
-+			return err;
-+		}
-+		spin_unlock(&old->dentry->d_lock);
-+	} else
-+		dput(topmost.dentry);
- 
--/*
-- * Restricted form of lookup. Doesn't follow links, single-component only,
-- * needs parent already locked. Doesn't follow mounts.
-- * SMP-safe.
-- */
--static struct dentry *lookup_hash(struct nameidata *nd)
--{
--	int err;
-+	return 0;
- 
--	err = inode_permission(nd->path.dentry->d_inode, MAY_EXEC);
--	if (err)
--		return ERR_PTR(err);
--	return __lookup_hash(&nd->last, nd->path.dentry, nd);
-+err_lock:
-+	path_to_nameidata(&parent, oldnd);
-+	path_put_conditional(old, oldnd);
-+	*trap = lock_rename(oldnd->path.dentry, newnd->path.dentry);
-+	return err;
- }
- 
- static int __lookup_one_len(const char *name, struct qstr *this,
-@@ -1502,8 +2335,9 @@ int vfs_create(struct inode *dir, struct
- 	return error;
- }
- 
--int may_open(struct path *path, int acc_mode, int flag)
-+int may_open(struct nameidata *nd, int acc_mode, int flag)
- {
-+	struct path *path = &nd->path;
- 	struct dentry *dentry = path->dentry;
- 	struct inode *inode = dentry->d_inode;
- 	int error;
-@@ -1529,7 +2363,7 @@ int may_open(struct path *path, int acc_
- 		break;
- 	}
- 
--	error = inode_permission(inode, acc_mode);
-+	error = union_permission(path, acc_mode);
- 	if (error)
- 		return error;
- 
-@@ -1577,6 +2411,9 @@ int may_open(struct path *path, int acc_
- 		if (!error)
- 			error = security_path_truncate(path, 0,
- 					       ATTR_MTIME|ATTR_CTIME|ATTR_OPEN);
-+		/* XXX don't copy up file data */
-+		if (is_unionized(path->dentry, path->mnt))
-+			error = union_copyup(nd, flag /* XXX not used */);
- 		if (!error) {
- 			vfs_dq_init(inode);
- 
-@@ -1623,7 +2460,7 @@ out_unlock:
- 	if (error)
- 		return error;
- 	/* Don't check for write permission, don't truncate */
--	return may_open(&nd->path, 0, flag & ~O_TRUNC);
-+	return may_open(nd, 0, flag & ~O_TRUNC);
- }
- 
- /*
-@@ -1738,12 +2575,10 @@ struct file *do_filp_open(int dfd, const
- 	if (flag & O_EXCL)
- 		nd.flags |= LOOKUP_EXCL;
- 	mutex_lock(&dir->d_inode->i_mutex);
--	path.dentry = lookup_hash(&nd);
--	path.mnt = nd.path.mnt;
-+	error = hash_lookup_union(&nd, &nd.last, &path);
- 
- do_last:
--	error = PTR_ERR(path.dentry);
--	if (IS_ERR(path.dentry)) {
-+	if (error) {
- 		mutex_unlock(&dir->d_inode->i_mutex);
- 		goto exit;
- 	}
-@@ -1803,10 +2638,23 @@ do_last:
- 	if (path.dentry->d_inode->i_op->follow_link)
- 		goto do_link;
- 
--	path_to_nameidata(&path, &nd);
- 	error = -EISDIR;
- 	if (path.dentry->d_inode && S_ISDIR(path.dentry->d_inode->i_mode))
--		goto exit;
-+		goto exit_dput;
-+
-+	/*
-+	 * If this file is on a lower layer of the union stack, copy it to the
-+	 * topmost layer before opening it
-+	 */
-+	if (path.dentry->d_inode &&
-+	    (path.dentry->d_parent != dir) &&
-+	    S_ISREG(path.dentry->d_inode->i_mode)) {
-+		error = __union_copyup(&path, &nd, &path);
-+		if (error)
-+			goto exit_dput;
-+	}
-+
-+	path_to_nameidata(&path, &nd);
- ok:
- 	/*
- 	 * Consider:
-@@ -1824,12 +2672,18 @@ ok:
- 		if (error)
- 			goto exit;
- 	}
--	error = may_open(&nd.path, acc_mode, flag);
-+	error = may_open(&nd, acc_mode, flag);
- 	if (error) {
- 		if (will_write)
- 			mnt_drop_write(nd.path.mnt);
- 		goto exit;
- 	}
-+	/* Okay, all permissions go, now copy up */
-+	if (!(flag & O_CREAT) && (flag & FMODE_WRITE)) {
-+		error = union_copyup(&nd, flag /* XXX not used */);
-+		if (error)
-+			goto exit;
-+	}
- 	filp = nameidata_to_filp(&nd, open_flag);
- 	if (IS_ERR(filp))
- 		ima_counts_put(&nd.path,
-@@ -1904,8 +2758,7 @@ do_link:
- 	}
- 	dir = nd.path.dentry;
- 	mutex_lock(&dir->d_inode->i_mutex);
--	path.dentry = lookup_hash(&nd);
--	path.mnt = nd.path.mnt;
-+	error = hash_lookup_union(&nd, &nd.last, &path);
- 	__putname(nd.last.name);
- 	goto do_last;
- }
-@@ -1939,7 +2792,8 @@ EXPORT_SYMBOL(filp_open);
-  */
- struct dentry *lookup_create(struct nameidata *nd, int is_dir)
- {
--	struct dentry *dentry = ERR_PTR(-EEXIST);
-+	struct path path = { .dentry = ERR_PTR(-EEXIST) } ;
-+	int err;
- 
- 	mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
- 	/*
-@@ -1955,11 +2809,13 @@ struct dentry *lookup_create(struct name
- 	/*
- 	 * Do the final lookup.
- 	 */
--	dentry = lookup_hash(nd);
--	if (IS_ERR(dentry))
-+	err = hash_lookup_union(nd, &nd->last, &path);
-+	if (err) {
-+		path.dentry = ERR_PTR(err);
- 		goto fail;
-+	}
- 
--	if (dentry->d_inode)
-+	if (path.dentry->d_inode)
- 		goto eexist;
- 	/*
- 	 * Special case - lookup gave negative, but... we had foo/bar/
-@@ -1968,15 +2824,17 @@ struct dentry *lookup_create(struct name
- 	 * been asking for (non-existent) directory. -ENOENT for you.
- 	 */
- 	if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
--		dput(dentry);
--		dentry = ERR_PTR(-ENOENT);
-+		path_put_conditional(&path, nd);
-+		path.dentry = ERR_PTR(-ENOENT);
- 	}
--	return dentry;
-+	if (nd->path.mnt != path.mnt)
-+		mntput(path.mnt);
-+	return path.dentry;
- eexist:
--	dput(dentry);
--	dentry = ERR_PTR(-EEXIST);
-+	path_put_conditional(&path, nd);
-+	path.dentry = ERR_PTR(-EEXIST);
- fail:
--	return dentry;
-+	return path.dentry;
- }
- EXPORT_SYMBOL_GPL(lookup_create);
- 
-@@ -2088,6 +2946,7 @@ SYSCALL_DEFINE3(mknod, const char __user
- int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
- {
- 	int error = may_create(dir, dentry);
-+	int opaque = 0;
- 
- 	if (error)
- 		return error;
-@@ -2101,9 +2960,18 @@ int vfs_mkdir(struct inode *dir, struct 
- 		return error;
- 
- 	vfs_dq_init(dir);
-+
-+	if (d_is_whiteout(dentry))
-+		opaque = 1;
-+
- 	error = dir->i_op->mkdir(dir, dentry, mode);
--	if (!error)
-+	if (!error) {
- 		fsnotify_mkdir(dir, dentry);
-+		if (opaque) {
-+			dentry->d_inode->i_flags |= S_OPAQUE;
-+			mark_inode_dirty(dentry->d_inode);
-+		}
-+	}
- 	return error;
- }
- 
-@@ -2149,6 +3017,212 @@ SYSCALL_DEFINE2(mkdir, const char __user
- 	return sys_mkdirat(AT_FDCWD, pathname, mode);
- }
- 
-+
-+/* Checks on the victim for whiteout */
-+static inline int may_whiteout(struct inode *dir, struct dentry *victim,
-+			       int isdir)
-+{
-+	int err;
-+
-+	/* from may_create() */
-+	if (IS_DEADDIR(dir))
-+		return -ENOENT;
-+	err = inode_permission(dir, MAY_WRITE | MAY_EXEC);
-+	if (err)
-+		return err;
-+
-+	/* from may_delete() */
-+	if (IS_APPEND(dir))
-+		return -EPERM;
-+	if (!victim->d_inode)
-+		return 0;
-+	if (check_sticky(dir, victim->d_inode) ||
-+	    IS_APPEND(victim->d_inode) ||
-+	    IS_IMMUTABLE(victim->d_inode))
-+		return -EPERM;
-+	if (isdir) {
-+		if (!S_ISDIR(victim->d_inode->i_mode))
-+			return -ENOTDIR;
-+		if (IS_ROOT(victim))
-+			return -EBUSY;
-+	} else if (S_ISDIR(victim->d_inode->i_mode))
-+		return -EISDIR;
-+	if (victim->d_flags & DCACHE_NFSFS_RENAMED)
-+		return -EBUSY;
-+	return 0;
-+}
-+
-+/**
-+ * vfs_whiteout: creates a white-out for the given directory entry
-+ * @dir: parent inode
-+ * @dentry: directory entry to white-out
-+ *
-+ * Simply white-out a given directory entry. This functionality is usually used
-+ * in the sense of unlink. Therefore the given dentry can still be in-use and
-+ * contains an in-use inode. The filesystem has to do what unlink or rmdir
-+ * would in that case. Since the dentry still might be in-use we have to
-+ * provide a fresh unhashed dentry that whiteout can fill the new inode into.
-+ * In that case the given dentry is dropped and the fresh dentry containing the
-+ * whiteout is rehashed instead. If the given dentry is unused, the whiteout
-+ * inode is instantiated into it instead.
-+ *
-+ * After this returns with success, don't make any assumptions about the inode.
-+ * Just dput() it dentry.
-+ */
-+static int vfs_whiteout(struct inode *dir, struct dentry *dentry, int isdir)
-+{
-+	int err;
-+	struct inode *old_inode = dentry->d_inode;
-+	struct dentry *parent, *whiteout;
-+
-+	err = may_whiteout(dir, dentry, isdir);
-+	if (err)
-+		return err;
-+
-+	BUG_ON(dentry->d_parent->d_inode != dir);
-+
-+	if (!dir->i_op || !dir->i_op->whiteout)
-+		return -EOPNOTSUPP;
-+
-+	if (old_inode) {
-+		vfs_dq_init(dir);
-+
-+		mutex_lock(&old_inode->i_mutex);
-+		if (isdir)
-+			dentry_unhash(dentry);
-+		if (d_mountpoint(dentry))
-+			err = -EBUSY;
-+		else {
-+			if (isdir)
-+				err = security_inode_rmdir(dir, dentry);
-+			else
-+				err = security_inode_unlink(dir, dentry);
-+		}
-+	}
-+
-+	parent = dget_parent(dentry);
-+	whiteout = d_alloc_name(parent, dentry->d_name.name);
-+
-+	if (!err)
-+		err = dir->i_op->whiteout(dir, dentry, whiteout);
-+
-+	if (old_inode) {
-+		mutex_unlock(&old_inode->i_mutex);
-+		if (!err) {
-+			fsnotify_link_count(old_inode);
-+			d_delete(dentry);
-+		}
-+		if (isdir)
-+			dput(dentry);
-+	}
-+
-+	dput(whiteout);
-+	dput(parent);
-+	return err;
-+}
-+
-+int path_whiteout(struct path *dir_path, struct dentry *dentry, int isdir)
-+{
-+	int error = mnt_want_write(dir_path->mnt);
-+
-+	if (!error) {
-+		error = vfs_whiteout(dir_path->dentry->d_inode, dentry, isdir);
-+		mnt_drop_write(dir_path->mnt);
-+	}
-+
-+	return error;
-+}
-+EXPORT_SYMBOL(path_whiteout);
-+
-+/*
-+ * This is abusing readdir to check if a union directory is logically empty.
-+ * Al Viro barfed when he saw this, but Val said: "Well, at this point I'm
-+ * aiming for working, pretty can come later"
-+ */
-+static int filldir_is_empty(void *__buf, const char *name, int namlen,
-+			    loff_t offset, u64 ino, unsigned int d_type)
-+{
-+	int *is_empty = (int *)__buf;
-+
-+	switch (namlen) {
-+	case 2:
-+		if (name[1] != '.')
-+			break;
-+	case 1:
-+		if (name[0] != '.')
-+			break;
-+		return 0;
-+	}
-+
-+	if (d_type == DT_WHT)
-+		return 0;
-+
-+	(*is_empty) = 0;
-+	return 0;
-+}
-+
-+static int directory_is_empty(struct dentry *dentry, struct vfsmount *mnt)
-+{
-+	struct file *file;
-+	int err;
-+	int is_empty = 1;
-+
-+	BUG_ON(!S_ISDIR(dentry->d_inode->i_mode));
-+
-+	/* references for the file pointer */
-+	dget(dentry);
-+	mntget(mnt);
-+
-+	file = dentry_open(dentry, mnt, O_RDONLY, current_cred());
-+	if (IS_ERR(file))
-+		return 0;
-+
-+	err = vfs_readdir(file, filldir_is_empty, &is_empty);
-+
-+	fput(file);
-+	return is_empty;
-+}
-+
-+static int do_whiteout(struct nameidata *nd, struct path *path, int isdir)
-+{
-+	struct path safe = { .dentry = dget(nd->path.dentry),
-+			     .mnt = mntget(nd->path.mnt) };
-+	struct dentry *dentry = path->dentry;
-+	int err;
-+
-+	err = may_whiteout(nd->path.dentry->d_inode, dentry, isdir);
-+	if (err)
-+		goto out;
-+
-+	err = -ENOENT;
-+	if (!dentry->d_inode)
-+		goto out;
-+
-+	err = -ENOTEMPTY;
-+	if (isdir && !directory_is_empty(path->dentry, path->mnt))
-+		goto out;
-+
-+	if (nd->path.dentry != dentry->d_parent) {
-+		dentry = __lookup_hash(&path->dentry->d_name, nd->path.dentry,
-+				       nd);
-+		err = PTR_ERR(dentry);
-+		if (IS_ERR(dentry))
-+			goto out;
-+
-+		dput(path->dentry);
-+		if (path->mnt != safe.mnt)
-+			mntput(path->mnt);
-+		path->mnt = nd->path.mnt;
-+		path->dentry = dentry;
-+	}
-+
-+	err = vfs_whiteout(nd->path.dentry->d_inode, dentry, isdir);
-+
-+out:
-+	path_put(&safe);
-+	return err;
-+}
-+
- /*
-  * We try to drop the dentry early: we should have
-  * a usage count of 2 if we're the only user of this
-@@ -2213,7 +3287,7 @@ static long do_rmdir(int dfd, const char
- {
- 	int error = 0;
- 	char * name;
--	struct dentry *dentry;
-+	struct path path;
- 	struct nameidata nd;
- 
- 	error = user_path_parent(dfd, pathname, &nd, &name);
-@@ -2235,21 +3309,24 @@ static long do_rmdir(int dfd, const char
- 	nd.flags &= ~LOOKUP_PARENT;
- 
- 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
--	dentry = lookup_hash(&nd);
--	error = PTR_ERR(dentry);
--	if (IS_ERR(dentry))
-+	error = hash_lookup_union(&nd, &nd.last, &path);
-+	if (error)
- 		goto exit2;
-+	if (is_unionized(nd.path.dentry, nd.path.mnt)) {
-+		error = do_whiteout(&nd, &path, 1);
-+		goto exit3;
-+	}
- 	error = mnt_want_write(nd.path.mnt);
- 	if (error)
- 		goto exit3;
--	error = security_path_rmdir(&nd.path, dentry);
-+	error = security_path_rmdir(&nd.path, path.dentry);
- 	if (error)
- 		goto exit4;
--	error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
-+	error = vfs_rmdir(nd.path.dentry->d_inode, path.dentry);
- exit4:
- 	mnt_drop_write(nd.path.mnt);
- exit3:
--	dput(dentry);
-+	path_put_conditional(&path, &nd);
- exit2:
- 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
- exit1:
-@@ -2304,7 +3381,7 @@ static long do_unlinkat(int dfd, const c
- {
- 	int error;
- 	char *name;
--	struct dentry *dentry;
-+	struct path path;
- 	struct nameidata nd;
- 	struct inode *inode = NULL;
- 
-@@ -2319,26 +3396,29 @@ static long do_unlinkat(int dfd, const c
- 	nd.flags &= ~LOOKUP_PARENT;
- 
- 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
--	dentry = lookup_hash(&nd);
--	error = PTR_ERR(dentry);
--	if (!IS_ERR(dentry)) {
-+	error = hash_lookup_union(&nd, &nd.last, &path);
-+	if (!error) {
- 		/* Why not before? Because we want correct error value */
- 		if (nd.last.name[nd.last.len])
- 			goto slashes;
--		inode = dentry->d_inode;
-+		inode = path.dentry->d_inode;
- 		if (inode)
- 			atomic_inc(&inode->i_count);
-+		if (is_unionized(nd.path.dentry, nd.path.mnt)) {
-+			error = do_whiteout(&nd, &path, 0);
-+			goto exit2;
-+		}
- 		error = mnt_want_write(nd.path.mnt);
- 		if (error)
- 			goto exit2;
--		error = security_path_unlink(&nd.path, dentry);
-+		error = security_path_unlink(&nd.path, path.dentry);
- 		if (error)
- 			goto exit3;
--		error = vfs_unlink(nd.path.dentry->d_inode, dentry);
-+		error = vfs_unlink(nd.path.dentry->d_inode, path.dentry);
- exit3:
- 		mnt_drop_write(nd.path.mnt);
- 	exit2:
--		dput(dentry);
-+		path_put_conditional(&path, &nd);
- 	}
- 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
- 	if (inode)
-@@ -2349,8 +3429,8 @@ exit1:
- 	return error;
- 
- slashes:
--	error = !dentry->d_inode ? -ENOENT :
--		S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
-+	error = !path.dentry->d_inode ? -ENOENT :
-+		S_ISDIR(path.dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
- 	goto exit2;
- }
- 
-@@ -2686,11 +3766,96 @@ int vfs_rename(struct inode *old_dir, st
- 	return error;
- }
- 
-+static int vfs_rename_union(struct nameidata *oldnd, struct path *old,
-+			    struct nameidata *newnd, struct path *new)
-+{
-+	struct inode *old_dir = oldnd->path.dentry->d_inode;
-+	struct inode *new_dir = newnd->path.dentry->d_inode;
-+	struct qstr old_name;
-+	char *name;
-+	struct dentry *dentry;
-+	int error;
-+
-+	if (old->dentry->d_inode == new->dentry->d_inode)
-+		return 0;
-+	error = may_whiteout(old_dir, old->dentry, 0);
-+	if (error)
-+		return error;
-+	if (!old_dir->i_op || !old_dir->i_op->whiteout)
-+		return -EPERM;
-+
-+	if (!new->dentry->d_inode)
-+		error = may_create(new_dir, new->dentry);
-+	else
-+		error = may_delete(new_dir, new->dentry, 0);
-+	if (error)
-+		return error;
-+
-+	vfs_dq_init(old_dir);
-+	vfs_dq_init(new_dir);
-+
-+	error = -EBUSY;
-+	if (d_mountpoint(old->dentry) || d_mountpoint(new->dentry))
-+		return error;
-+
-+	error = -ENOMEM;
-+	name = kmalloc(old->dentry->d_name.len, GFP_KERNEL);
-+	if (!name)
-+		return error;
-+	strncpy(name, old->dentry->d_name.name, old->dentry->d_name.len);
-+	name[old->dentry->d_name.len] = 0;
-+	old_name.len = old->dentry->d_name.len;
-+	old_name.hash = old->dentry->d_name.hash;
-+	old_name.name = name;
-+
-+	/* possibly delete the existing new file */
-+	if ((newnd->path.dentry == new->dentry->d_parent) &&
-+	    new->dentry->d_inode) {
-+		/* FIXME: inode may be truncated while we hold a lock */
-+		error = vfs_unlink(new_dir, new->dentry);
-+		if (error)
-+			goto freename;
-+
-+		dentry = __lookup_hash(&new->dentry->d_name,
-+				       newnd->path.dentry, newnd);
-+		if (IS_ERR(dentry))
-+			goto freename;
-+
-+		dput(new->dentry);
-+		new->dentry = dentry;
-+	}
-+
-+	/* copyup to the new file */
-+	error = __union_copyup(old, newnd, new);
-+	if (error)
-+		goto freename;
-+
-+	/* whiteout the old file */
-+	dentry = __lookup_hash(&old_name, oldnd->path.dentry, oldnd);
-+	error = PTR_ERR(dentry);
-+	if (IS_ERR(dentry))
-+		goto freename;
-+	error = vfs_whiteout(old_dir, dentry, 0);
-+	dput(dentry);
-+
-+	/* FIXME: This is acutally unlink() && create() ... */
-+/*
-+  if (!error) {
-+  const char *new_name = old_dentry->d_name.name;
-+  fsnotify_move(old_dir, new_dir, old_name.name, new_name, 0,
-+  new_dentry->d_inode, old_dentry->d_inode);
-+  }
-+*/
-+freename:
-+	kfree(old_name.name);
-+	return error;
-+}
-+
- SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
- 		int, newdfd, const char __user *, newname)
- {
- 	struct dentry *old_dir, *new_dir;
--	struct dentry *old_dentry, *new_dentry;
-+	struct path old, new;
- 	struct dentry *trap;
- 	struct nameidata oldnd, newnd;
- 	char *from;
-@@ -2724,16 +3889,28 @@ SYSCALL_DEFINE4(renameat, int, olddfd, c
- 
- 	trap = lock_rename(new_dir, old_dir);
- 
--	old_dentry = lookup_hash(&oldnd);
--	error = PTR_ERR(old_dentry);
--	if (IS_ERR(old_dentry))
-+	/*
-+	 * For union mounts we need to call a giant lookup_rename_source()
-+	 * instead.
-+	 * First lock_rename() and look on the topmost fs like you would do in
-+	 * the normal rename, if you find something which is not a directory,
-+	 * go ahead and lookup target and do normal rename.
-+	 * If you find a negative dentry, unlock_rename() and continue as
-+	 * _hash_lookup_union() would do without locking the topmost parent
-+	 * at the end. After that do lock_rename() of the source parent and the
-+	 * target parent and do a copyup with additional whiteout creation at
-+	 * the end.
-+	 */
-+//	error = hash_lookup_union(&oldnd, &oldnd.last, &old);
-+	error = lookup_rename_source(&oldnd, &newnd, &trap, &oldnd.last, &old);
-+	if (error)
- 		goto exit3;
- 	/* source must exist */
- 	error = -ENOENT;
--	if (!old_dentry->d_inode)
-+	if (!old.dentry->d_inode)
- 		goto exit4;
- 	/* unless the source is a directory trailing slashes give -ENOTDIR */
--	if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
-+	if (!S_ISDIR(old.dentry->d_inode->i_mode)) {
- 		error = -ENOTDIR;
- 		if (oldnd.last.name[oldnd.last.len])
- 			goto exit4;
-@@ -2742,32 +3919,44 @@ SYSCALL_DEFINE4(renameat, int, olddfd, c
- 	}
- 	/* source should not be ancestor of target */
- 	error = -EINVAL;
--	if (old_dentry == trap)
-+	if (old.dentry == trap)
- 		goto exit4;
--	new_dentry = lookup_hash(&newnd);
--	error = PTR_ERR(new_dentry);
--	if (IS_ERR(new_dentry))
-+	/* target is always on topmost fs, even with unions */
-+	error = lookup_hash(&newnd, &newnd.last, &new);
-+	if (error)
- 		goto exit4;
- 	/* target should not be an ancestor of source */
- 	error = -ENOTEMPTY;
--	if (new_dentry == trap)
-+	if (new.dentry == trap)
-+		goto exit5;
-+	/* renaming of directories on unions is done by the user-space */
-+	error = -EXDEV;
-+	if (is_unionized(oldnd.path.dentry, oldnd.path.mnt) &&
-+	    S_ISDIR(old.dentry->d_inode->i_mode))
- 		goto exit5;
-+//	if (is_unionized(newnd.path.dentry, newnd.path.mnt))
-+//		goto exit5;
- 
- 	error = mnt_want_write(oldnd.path.mnt);
- 	if (error)
- 		goto exit5;
--	error = security_path_rename(&oldnd.path, old_dentry,
--				     &newnd.path, new_dentry);
-+	error = security_path_rename(&oldnd.path, old.dentry,
-+				     &newnd.path, new.dentry);
- 	if (error)
- 		goto exit6;
--	error = vfs_rename(old_dir->d_inode, old_dentry,
--				   new_dir->d_inode, new_dentry);
-+	if (is_unionized(oldnd.path.dentry, oldnd.path.mnt) &&
-+	    (old.dentry->d_parent != oldnd.path.dentry)) {
-+		error = vfs_rename_union(&oldnd, &old, &newnd, &new);
-+		goto exit6;
-+	}
-+	error = vfs_rename(old_dir->d_inode, old.dentry,
-+				   new_dir->d_inode, new.dentry);
- exit6:
- 	mnt_drop_write(oldnd.path.mnt);
- exit5:
--	dput(new_dentry);
-+	path_put_conditional(&new, &newnd);
- exit4:
--	dput(old_dentry);
-+	path_put_conditional(&old, &oldnd);
- exit3:
- 	unlock_rename(new_dir, old_dir);
- exit2:
---- a/fs/namespace.c
-+++ b/fs/namespace.c
-@@ -29,6 +29,7 @@
- #include <linux/log2.h>
- #include <linux/idr.h>
- #include <linux/fs_struct.h>
-+#include <linux/union.h>
- #include <asm/uaccess.h>
- #include <asm/unistd.h>
- #include "pnode.h"
-@@ -150,6 +151,9 @@ struct vfsmount *alloc_vfsmnt(const char
- 		INIT_LIST_HEAD(&mnt->mnt_share);
- 		INIT_LIST_HEAD(&mnt->mnt_slave_list);
- 		INIT_LIST_HEAD(&mnt->mnt_slave);
-+#ifdef CONFIG_UNION_MOUNT
-+		INIT_LIST_HEAD(&mnt->mnt_unions);
-+#endif
- #ifdef CONFIG_SMP
- 		mnt->mnt_writers = alloc_percpu(int);
- 		if (!mnt->mnt_writers)
-@@ -469,6 +473,7 @@ static void __touch_mnt_namespace(struct
- 
- static void detach_mnt(struct vfsmount *mnt, struct path *old_path)
- {
-+	detach_mnt_union(mnt);
- 	old_path->dentry = mnt->mnt_mountpoint;
- 	old_path->mnt = mnt->mnt_parent;
- 	mnt->mnt_parent = mnt;
-@@ -492,6 +497,7 @@ static void attach_mnt(struct vfsmount *
- 	list_add_tail(&mnt->mnt_hash, mount_hashtable +
- 			hash(path->mnt, path->dentry));
- 	list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts);
-+	attach_mnt_union(mnt, path->mnt, path->dentry);
- }
- 
- /*
-@@ -514,6 +520,7 @@ static void commit_tree(struct vfsmount 
- 	list_add_tail(&mnt->mnt_hash, mount_hashtable +
- 				hash(parent, mnt->mnt_mountpoint));
- 	list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
-+	attach_mnt_union(mnt, mnt->mnt_parent, mnt->mnt_mountpoint);
- 	touch_mnt_namespace(n);
- }
- 
-@@ -770,6 +777,7 @@ static void show_mnt_opts(struct seq_fil
- 		{ MNT_NODIRATIME, ",nodiratime" },
- 		{ MNT_RELATIME, ",relatime" },
- 		{ MNT_STRICTATIME, ",strictatime" },
-+		{ MNT_UNION, ",union" },
- 		{ 0, NULL }
- 	};
- 	const struct proc_fs_info *fs_infop;
-@@ -984,6 +992,7 @@ void release_mounts(struct list_head *he
- 			struct dentry *dentry;
- 			struct vfsmount *m;
- 			spin_lock(&vfsmount_lock);
-+			detach_mnt_union(mnt);
- 			dentry = mnt->mnt_mountpoint;
- 			m = mnt->mnt_parent;
- 			mnt->mnt_mountpoint = mnt->mnt_root;
-@@ -1102,6 +1111,11 @@ static int do_umount(struct vfsmount *mn
- 	spin_unlock(&vfsmount_lock);
- 	if (retval)
- 		security_sb_umount_busy(mnt);
-+	/* If this was a union mount, we are no longer a read-only
-+	 * user on the underlying mount */
-+	if (mnt->mnt_flags & MNT_UNION)
-+		mnt->mnt_parent->mnt_sb->s_readonly_users--;
-+
- 	up_write(&namespace_sem);
- 	release_mounts(&umount_list);
- 	return retval;
-@@ -1426,6 +1440,10 @@ static int do_change_type(struct path *p
- 	if (path->dentry != path->mnt->mnt_root)
- 		return -EINVAL;
- 
-+	/* Don't change the type of union mounts */
-+	if (IS_MNT_UNION(path->mnt))
-+		return -EINVAL;
-+
- 	down_write(&namespace_sem);
- 	if (type == MS_SHARED) {
- 		err = invent_group_ids(mnt, recurse);
-@@ -1444,10 +1462,65 @@ static int do_change_type(struct path *p
- }
- 
- /*
-+ * Mount-time check of upper and lower layer file systems to see if we
-+ * can union mount one on the other.
-+ *
-+ * Union mounts must follow these rules:
-+ *
-+ * - The lower layer must be read-only.  This avoids lots of nasty
-+ *   unsolvable races where file system structures disappear suddenly.
-+ *   XXX - Checking the vfsmnt for read-only is a temporary hack; the
-+ *   file system could be mounted read-write elsewhere.  We need to
-+ *   enforce read-only at the superblock level (patches coming).
-+ *
-+ * - The upper layer must be writable.  This isn't an absolute
-+ *   requirement; right now we need it to make readdir() work since we
-+ *   copy up directory entries to the top level.  A possible
-+ *   workaround is to mount a tmpfs file system transparently over the
-+ *   top.
-+ *
-+ * - The upper layer must support whiteouts and fallthrus (if it is
-+ *   writeable).
-+ *
-+ * - The lower layer must not also be a union mount.  This is just to
-+ *   make life simpler for now, there is no inherent limitation on the
-+ *   number of layers.
-+ *
-+ * XXX - Check other mount flags for incompatibilities - I'm sure
-+ * there are some.
-+ */
-+
-+static int
-+check_union_mnt(struct path *mntpnt, struct vfsmount *top_mnt, int mnt_flags)
-+{
-+	struct vfsmount *lower_mnt = mntpnt->mnt;
-+
-+	/* Is this even a union mount? */
-+	if (!(mnt_flags & MNT_UNION))
-+		return 0;
-+
-+	/* Lower layer must be read-only and not a union mount */
-+	if (!(lower_mnt->mnt_sb->s_flags & MS_RDONLY) ||
-+	    (lower_mnt->mnt_flags & MNT_UNION))
-+		return -EBUSY;
-+
-+	/* Upper layer must be writable */
-+	if (mnt_flags & MNT_READONLY)
-+		return -EROFS;
-+
-+	/* Upper layer must support whiteouts and fallthrus */
-+	if (!(top_mnt->mnt_sb->s_flags & MS_WHITEOUT))
-+		return -EINVAL;
-+
-+	/* All good! */
-+	return 0;
-+}
-+
-+/*
-  * do loopback mount.
-  */
--static int do_loopback(struct path *path, char *old_name,
--				int recurse)
-+static int do_loopback(struct path *path, char *old_name, int recurse,
-+		       int mnt_flags)
- {
- 	struct path old_path;
- 	struct vfsmount *mnt = NULL;
-@@ -1477,6 +1550,13 @@ static int do_loopback(struct path *path
- 	if (!mnt)
- 		goto out;
- 
-+	err = check_union_mnt(&old_path, mnt, mnt_flags);
-+	if (err)
-+		goto out;
-+
-+	if (mnt_flags & MNT_UNION)
-+		mnt->mnt_flags |= MNT_UNION;
-+
- 	err = graft_tree(mnt, path);
- 	if (err) {
- 		LIST_HEAD(umount_list);
-@@ -1486,6 +1566,10 @@ static int do_loopback(struct path *path
- 		release_mounts(&umount_list);
- 	}
- 
-+	/* If this is a union mount, add ourselves to the readonly users */
-+	if (mnt_flags & MNT_UNION)
-+		mnt->mnt_parent->mnt_sb->s_readonly_users++;
-+
- out:
- 	up_write(&namespace_sem);
- 	path_put(&old_path);
-@@ -1570,6 +1654,13 @@ static int do_move_mount(struct path *pa
- 	if (err)
- 		return err;
- 
-+	/* moving to or from a union mount is not supported */
-+	err = -EINVAL;
-+	if (IS_MNT_UNION(path->mnt))
-+		goto exit;
-+	if (IS_MNT_UNION(old_path.mnt))
-+		goto exit;
-+
- 	down_write(&namespace_sem);
- 	while (d_mountpoint(path->dentry) &&
- 	       follow_down(path))
-@@ -1627,6 +1718,7 @@ out:
- 	up_write(&namespace_sem);
- 	if (!err)
- 		path_put(&parent_path);
-+exit:
- 	path_put(&old_path);
- 	return err;
- }
-@@ -1684,10 +1776,18 @@ int do_add_mount(struct vfsmount *newmnt
- 	if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
- 		goto unlock;
- 
-+	err = check_union_mnt(path, newmnt, mnt_flags);
-+	if (err)
-+		goto unlock;
-+
- 	newmnt->mnt_flags = mnt_flags;
- 	if ((err = graft_tree(newmnt, path)))
- 		goto unlock;
- 
-+	/* If this is a union mount, add ourselves to the readonly users */
-+	if (mnt_flags & MNT_UNION)
-+		newmnt->mnt_parent->mnt_sb->s_readonly_users++;
-+
- 	if (fslist) /* add to the specified expiration list */
- 		list_add_tail(&newmnt->mnt_expire, fslist);
- 
-@@ -1940,10 +2040,12 @@ long do_mount(char *dev_name, char *dir_
- 		mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
- 	if (flags & MS_RDONLY)
- 		mnt_flags |= MNT_READONLY;
-+	if (flags & MS_UNION)
-+		mnt_flags |= MNT_UNION;
- 
- 	flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
- 		   MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
--		   MS_STRICTATIME);
-+		   MS_STRICTATIME | MS_UNION);
- 
- 	/* ... and get the mountpoint */
- 	retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
-@@ -1959,7 +2061,8 @@ long do_mount(char *dev_name, char *dir_
- 		retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
- 				    data_page);
- 	else if (flags & MS_BIND)
--		retval = do_loopback(&path, dev_name, flags & MS_REC);
-+		retval = do_loopback(&path, dev_name, flags & MS_REC,
-+				     mnt_flags);
- 	else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
- 		retval = do_change_type(&path, flags);
- 	else if (flags & MS_MOVE)
-@@ -2196,6 +2299,8 @@ SYSCALL_DEFINE2(pivot_root, const char _
- 	if (d_unlinked(old.dentry))
- 		goto out2;
- 	error = -EBUSY;
-+	follow_union_down(&new);
-+	follow_union_down(&root);
- 	if (new.mnt == root.mnt ||
- 	    old.mnt == root.mnt)
- 		goto out2; /* loop, on the same file system  */
---- a/fs/nfsctl.c
-+++ b/fs/nfsctl.c
-@@ -38,10 +38,10 @@ static struct file *do_open(char *name, 
- 		return ERR_PTR(error);
- 
- 	if (flags == O_RDWR)
--		error = may_open(&nd.path, MAY_READ|MAY_WRITE,
--					   FMODE_READ|FMODE_WRITE);
-+		error = may_open(&nd, MAY_READ|MAY_WRITE,
-+				 FMODE_READ|FMODE_WRITE);
- 	else
--		error = may_open(&nd.path, MAY_WRITE, FMODE_WRITE);
-+		error = may_open(&nd, MAY_WRITE, FMODE_WRITE);
- 
- 	if (!error)
- 		return dentry_open(nd.path.dentry, nd.path.mnt, flags,
---- a/fs/nfsd/nfs3xdr.c
-+++ b/fs/nfsd/nfs3xdr.c
-@@ -898,6 +898,11 @@ encode_entry(struct readdir_cd *ccd, con
- 	int		elen;		/* estimated entry length in words */
- 	int		num_entry_words = 0;	/* actual number of words */
- 
-+	if (d_type == DT_WHT) {
-+		cd->common.err = nfs_ok;
-+		return 0;
-+	}
-+
- 	if (cd->offset) {
- 		u64 offset64 = offset;
- 
---- a/fs/nfsd/nfs4xdr.c
-+++ b/fs/nfsd/nfs4xdr.c
-@@ -2261,7 +2261,7 @@ nfsd4_encode_dirent(void *ccdv, const ch
- 	__be32 nfserr = nfserr_toosmall;
- 
- 	/* In nfsv4, "." and ".." never make it onto the wire.. */
--	if (name && isdotent(name, namlen)) {
-+	if (d_type == DT_WHT || (name && isdotent(name, namlen))) {
- 		cd->common.err = nfs_ok;
- 		return 0;
- 	}
---- a/fs/nfsd/nfsxdr.c
-+++ b/fs/nfsd/nfsxdr.c
-@@ -513,6 +513,10 @@ nfssvc_encode_entry(void *ccdv, const ch
- 			namlen, name, offset, ino);
- 	 */
- 
-+	if (d_type == DT_WHT) {
-+		cd->common.err = nfs_ok;
-+		return 0;
-+	}
- 	if (offset > ~((u32) 0)) {
- 		cd->common.err = nfserr_fbig;
- 		return -EINVAL;
---- a/fs/open.c
-+++ b/fs/open.c
-@@ -30,6 +30,7 @@
- #include <linux/audit.h>
- #include <linux/falloc.h>
- #include <linux/fs_struct.h>
-+#include <linux/union.h>
- 
- int vfs_statfs(struct dentry *dentry, struct kstatfs *buf)
- {
-@@ -224,69 +225,69 @@ int do_truncate(struct dentry *dentry, l
- 	return ret;
- }
- 
--static long do_sys_truncate(const char __user *pathname, loff_t length)
-+static int __do_ftruncate(struct file *file, unsigned long length, int small)
- {
--	struct path path;
--	struct inode *inode;
-+	struct inode * inode;
-+	struct dentry *dentry;
- 	int error;
- 
- 	error = -EINVAL;
--	if (length < 0)	/* sorry, but loff_t says... */
-+	if (length < 0)
- 		goto out;
-+	/* explicitly opened as large or we are on 64-bit box */
-+	if (file->f_flags & O_LARGEFILE)
-+		small = 0;
- 
--	error = user_path(pathname, &path);
--	if (error)
-+	dentry = file->f_path.dentry;
-+	inode = dentry->d_inode;
-+	error = -EINVAL;
-+	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
- 		goto out;
--	inode = path.dentry->d_inode;
--
--	/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
--	error = -EISDIR;
--	if (S_ISDIR(inode->i_mode))
--		goto dput_and_out;
- 
- 	error = -EINVAL;
--	if (!S_ISREG(inode->i_mode))
--		goto dput_and_out;
--
--	error = mnt_want_write(path.mnt);
--	if (error)
--		goto dput_and_out;
-+	/* Cannot ftruncate over 2^31 bytes without large file support */
-+	if (small && length > MAX_NON_LFS)
- 
--	error = inode_permission(inode, MAY_WRITE);
--	if (error)
--		goto mnt_drop_write_and_out;
-+		goto out;
- 
- 	error = -EPERM;
- 	if (IS_APPEND(inode))
--		goto mnt_drop_write_and_out;
-+		goto out;
- 
--	error = get_write_access(inode);
--	if (error)
--		goto mnt_drop_write_and_out;
-+	error = locks_verify_truncate(inode, file, length);
-+	if (!error)
-+		error = security_path_truncate(&file->f_path, length,
-+					       ATTR_MTIME|ATTR_CTIME);
-+	if (!error)
-+		/* Already copied up for union, opened with write */
-+		error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
-+out:
-+	return error;
-+}
- 
--	/*
--	 * Make sure that there are no leases.  get_write_access() protects
--	 * against the truncate racing with a lease-granting setlease().
--	 */
--	error = break_lease(inode, FMODE_WRITE);
--	if (error)
--		goto put_write_and_out;
-+static long do_sys_truncate(const char __user *pathname, loff_t length)
-+{
-+	struct file *file;
-+	char *tmp;
-+	int error;
- 
--	error = locks_verify_truncate(inode, NULL, length);
--	if (!error)
--		error = security_path_truncate(&path, length, 0);
--	if (!error) {
--		vfs_dq_init(inode);
--		error = do_truncate(path.dentry, length, 0, NULL);
--	}
-+	error = -EINVAL;
-+	if (length < 0)	/* sorry, but loff_t says... */
-+		return error;
- 
--put_write_and_out:
--	put_write_access(inode);
--mnt_drop_write_and_out:
--	mnt_drop_write(path.mnt);
--dput_and_out:
--	path_put(&path);
--out:
-+	tmp = getname(pathname);
-+	if (IS_ERR(tmp))
-+		return PTR_ERR(tmp);
-+
-+	file = filp_open(tmp, O_RDWR | O_LARGEFILE, 0);
-+	putname(tmp);
-+
-+	if (IS_ERR(file))
-+		return PTR_ERR(file);
-+
-+	error = __do_ftruncate(file, length, 0);
-+
-+	fput(file);
- 	return error;
- }
- 
-@@ -297,45 +298,16 @@ SYSCALL_DEFINE2(truncate, const char __u
- 
- static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
- {
--	struct inode * inode;
--	struct dentry *dentry;
- 	struct file * file;
- 	int error;
- 
--	error = -EINVAL;
--	if (length < 0)
--		goto out;
- 	error = -EBADF;
- 	file = fget(fd);
- 	if (!file)
- 		goto out;
- 
--	/* explicitly opened as large or we are on 64-bit box */
--	if (file->f_flags & O_LARGEFILE)
--		small = 0;
--
--	dentry = file->f_path.dentry;
--	inode = dentry->d_inode;
--	error = -EINVAL;
--	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
--		goto out_putf;
--
--	error = -EINVAL;
--	/* Cannot ftruncate over 2^31 bytes without large file support */
--	if (small && length > MAX_NON_LFS)
--		goto out_putf;
-+	error = __do_ftruncate(file, length, small);
- 
--	error = -EPERM;
--	if (IS_APPEND(inode))
--		goto out_putf;
--
--	error = locks_verify_truncate(inode, file, length);
--	if (!error)
--		error = security_path_truncate(&file->f_path, length,
--					       ATTR_MTIME|ATTR_CTIME);
--	if (!error)
--		error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
--out_putf:
- 	fput(file);
- out:
- 	return error;
-@@ -494,7 +466,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, con
- 			goto out_path_release;
- 	}
- 
--	res = inode_permission(inode, mode | MAY_ACCESS);
-+	res = union_permission(&path, mode | MAY_ACCESS);
-+
- 	/* SuS v2 requires we report a read only fs too */
- 	if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
- 		goto out_path_release;
-@@ -508,7 +481,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, con
- 	 * inherently racy and know that the fs may change
- 	 * state before we even see this result.
- 	 */
--	if (__mnt_is_readonly(path.mnt))
-+	if ((!is_unionized(path.dentry, path.mnt) &&
-+	     (__mnt_is_readonly(path.mnt))))
- 		res = -EROFS;
- 
- out_path_release:
-@@ -554,20 +528,19 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd
- 	error = -EBADF;
- 	file = fget(fd);
- 	if (!file)
--		goto out;
-+		return error;
- 
- 	inode = file->f_path.dentry->d_inode;
- 
- 	error = -ENOTDIR;
- 	if (!S_ISDIR(inode->i_mode))
--		goto out_putf;
-+		goto out;
- 
- 	error = inode_permission(inode, MAY_EXEC | MAY_ACCESS);
- 	if (!error)
- 		set_fs_pwd(current->fs, &file->f_path);
--out_putf:
--	fput(file);
- out:
-+	fput(file);
- 	return error;
- }
- 
---- a/fs/readdir.c
-+++ b/fs/readdir.c
-@@ -16,6 +16,7 @@
- #include <linux/security.h>
- #include <linux/syscalls.h>
- #include <linux/unistd.h>
-+#include <linux/union.h>
- 
- #include <asm/uaccess.h>
- 
-@@ -36,9 +37,24 @@ int vfs_readdir(struct file *file, filld
- 
- 	res = -ENOENT;
- 	if (!IS_DEADDIR(inode)) {
-+		/*
-+		 * XXX Think harder about locking for
-+		 * union_copyup_dir.  Currently we lock the topmost
-+		 * directory and hold that lock while sequentially
-+		 * acquiring and dropping locks for the directories
-+		 * below this one in the union stack.
-+		 */
-+		if (is_unionized(file->f_path.dentry, file->f_path.mnt) &&
-+		    !IS_OPAQUE(inode)) {
-+			res = union_copyup_dir(&file->f_path);
-+			if (res)
-+				goto out_unlock;
-+		}
-+
- 		res = file->f_op->readdir(file, buf, filler);
- 		file_accessed(file);
- 	}
-+out_unlock:
- 	mutex_unlock(&inode->i_mutex);
- out:
- 	return res;
-@@ -77,6 +93,9 @@ static int fillonedir(void * __buf, cons
- 	struct old_linux_dirent __user * dirent;
- 	unsigned long d_ino;
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	if (buf->result)
- 		return -EINVAL;
- 	d_ino = ino;
-@@ -154,6 +173,9 @@ static int filldir(void * __buf, const c
- 	unsigned long d_ino;
- 	int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 2, sizeof(long));
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	buf->error = -EINVAL;	/* only used if we fail.. */
- 	if (reclen > buf->count)
- 		return -EINVAL;
-@@ -239,6 +261,9 @@ static int filldir64(void * __buf, const
- 	struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
- 	int reclen = ALIGN(NAME_OFFSET(dirent) + namlen + 1, sizeof(u64));
- 
-+	if (d_type == DT_WHT)
-+		return 0;
-+
- 	buf->error = -EINVAL;	/* only used if we fail.. */
- 	if (reclen > buf->count)
- 		return -EINVAL;
---- a/fs/super.c
-+++ b/fs/super.c
-@@ -596,6 +596,15 @@ int do_remount_sb(struct super_block *sb
- 	}
- 	remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
- 
-+	/* If we are remounting read/write, make sure that none of the
-+	   users require read-only for correct operation (such as
-+	   union mounts). */
-+	if (remount_rw && sb->s_readonly_users) {
-+		printk(KERN_INFO "%s: In use by %d read-only user(s)\n",
-+		       sb->s_id, sb->s_readonly_users);
-+		return -EROFS;
-+	}
-+
- 	if (sb->s_op->remount_fs) {
- 		retval = sb->s_op->remount_fs(sb, &flags, data);
- 		if (retval)
-@@ -953,6 +962,11 @@ vfs_kern_mount(struct file_system_type *
- 	WARN((mnt->mnt_sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
- 		"negative value (%lld)\n", type->name, mnt->mnt_sb->s_maxbytes);
- 
-+	error = -EROFS;
-+	if (!(flags & MS_RDONLY) &&
-+	    (mnt->mnt_sb->s_readonly_users))
-+		goto out_sb;
-+
- 	mnt->mnt_mountpoint = mnt->mnt_root;
- 	mnt->mnt_parent = mnt;
- 	up_write(&mnt->mnt_sb->s_umount);
---- /dev/null
-+++ b/fs/union.c
-@@ -0,0 +1,981 @@
-+/*
-+ * VFS based union mount for Linux
-+ *
-+ * Copyright (C) 2004-2007 IBM Corporation, IBM Deutschland Entwicklung GmbH.
-+ * Copyright (C) 2007-2009 Novell Inc.
-+ *
-+ *   Author(s): Jan Blunck ([email protected])
-+ *              Valerie Aurora <[email protected]>
-+ *
-+ * This program is free software; you can redistribute it and/or modify it
-+ * under the terms of the GNU General Public License as published by the Free
-+ * Software Foundation; either version 2 of the License, or (at your option)
-+ * any later version.
-+ */
-+
-+#include <linux/bootmem.h>
-+#include <linux/init.h>
-+#include <linux/module.h>
-+#include <linux/types.h>
-+#include <linux/hash.h>
-+#include <linux/fs.h>
-+#include <linux/mount.h>
-+#include <linux/fs_struct.h>
-+#include <linux/union.h>
-+#include <linux/namei.h>
-+#include <linux/file.h>
-+#include <linux/mm.h>
-+#include <linux/quotaops.h>
-+#include <linux/dnotify.h>
-+#include <linux/security.h>
-+#include <linux/pipe_fs_i.h>
-+#include <linux/splice.h>
-+
-+/*
-+ * This is borrowed from fs/inode.c. The hashtable for lookups. Somebody
-+ * should try to make this good - I've just made it work.
-+ */
-+static unsigned int union_hash_mask __read_mostly;
-+static unsigned int union_hash_shift __read_mostly;
-+static struct hlist_head *union_hashtable __read_mostly;
-+static unsigned int union_rhash_mask __read_mostly;
-+static unsigned int union_rhash_shift __read_mostly;
-+static struct hlist_head *union_rhashtable __read_mostly;
-+
-+/*
-+ * Locking Rules:
-+ * - dcache_lock (for union_rlookup() only)
-+ * - union_lock
-+ */
-+DEFINE_SPINLOCK(union_lock);
-+
-+static struct kmem_cache *union_cache __read_mostly;
-+
-+static unsigned long hash(struct dentry *dentry, struct vfsmount *mnt)
-+{
-+	unsigned long tmp;
-+
-+	tmp = ((unsigned long)mnt * (unsigned long)dentry) ^
-+		(GOLDEN_RATIO_PRIME + (unsigned long)mnt) / L1_CACHE_BYTES;
-+	tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> union_hash_shift);
-+	return tmp & union_hash_mask;
-+}
-+
-+static __initdata unsigned long union_hash_entries;
-+
-+static int __init set_union_hash_entries(char *str)
-+{
-+	if (!str)
-+		return 0;
-+	union_hash_entries = simple_strtoul(str, &str, 0);
-+	return 1;
-+}
-+
-+__setup("union_hash_entries=", set_union_hash_entries);
-+
-+static int __init init_union(void)
-+{
-+	int loop;
-+
-+	union_cache = KMEM_CACHE(union_mount, SLAB_PANIC | SLAB_MEM_SPREAD);
-+	union_hashtable = alloc_large_system_hash("Union-cache",
-+						  sizeof(struct hlist_head),
-+						  union_hash_entries,
-+						  14,
-+						  0,
-+						  &union_hash_shift,
-+						  &union_hash_mask,
-+						  0);
-+
-+	for (loop = 0; loop < (1 << union_hash_shift); loop++)
-+		INIT_HLIST_HEAD(&union_hashtable[loop]);
-+
-+
-+	union_rhashtable = alloc_large_system_hash("rUnion-cache",
-+						  sizeof(struct hlist_head),
-+						  union_hash_entries,
-+						  14,
-+						  0,
-+						  &union_rhash_shift,
-+						  &union_rhash_mask,
-+						  0);
-+
-+	for (loop = 0; loop < (1 << union_rhash_shift); loop++)
-+		INIT_HLIST_HEAD(&union_rhashtable[loop]);
-+
-+	return 0;
-+}
-+
-+fs_initcall(init_union);
-+
-+struct union_mount *union_alloc(struct dentry *this, struct vfsmount *this_mnt,
-+				struct dentry *next, struct vfsmount *next_mnt)
-+{
-+	struct union_mount *um;
-+
-+	BUG_ON(!S_ISDIR(this->d_inode->i_mode));
-+	BUG_ON(!S_ISDIR(next->d_inode->i_mode));
-+
-+	um = kmem_cache_alloc(union_cache, GFP_ATOMIC);
-+	if (!um)
-+		return NULL;
-+
-+	atomic_set(&um->u_count, 1);
-+	INIT_LIST_HEAD(&um->u_unions);
-+	INIT_LIST_HEAD(&um->u_list);
-+	INIT_HLIST_NODE(&um->u_hash);
-+	INIT_HLIST_NODE(&um->u_rhash);
-+
-+	um->u_this.mnt = this_mnt;
-+	um->u_this.dentry = this;
-+	um->u_next.mnt = mntget(next_mnt);
-+	um->u_next.dentry = dget(next);
-+
-+	return um;
-+}
-+
-+struct union_mount *union_get(struct union_mount *um)
-+{
-+	BUG_ON(!atomic_read(&um->u_count));
-+	atomic_inc(&um->u_count);
-+	return um;
-+}
-+
-+static int __union_put(struct union_mount *um)
-+{
-+	if (!atomic_dec_and_test(&um->u_count))
-+		return 0;
-+
-+	BUG_ON(!hlist_unhashed(&um->u_hash));
-+	BUG_ON(!hlist_unhashed(&um->u_rhash));
-+
-+	kmem_cache_free(union_cache, um);
-+	return 1;
-+}
-+
-+void union_put(struct union_mount *um)
-+{
-+	struct path tmp = um->u_next;
-+
-+	if (__union_put(um))
-+		path_put(&tmp);
-+}
-+
-+static void __union_hash(struct union_mount *um)
-+{
-+	hlist_add_head(&um->u_hash, union_hashtable +
-+		       hash(um->u_this.dentry, um->u_this.mnt));
-+	hlist_add_head(&um->u_rhash, union_rhashtable +
-+		       hash(um->u_next.dentry, um->u_next.mnt));
-+}
-+
-+static void __union_unhash(struct union_mount *um)
-+{
-+	hlist_del_init(&um->u_hash);
-+	hlist_del_init(&um->u_rhash);
-+}
-+
-+struct union_mount *union_lookup(struct dentry *dentry, struct vfsmount *mnt)
-+{
-+	struct hlist_head *head = union_hashtable + hash(dentry, mnt);
-+	struct hlist_node *node;
-+	struct union_mount *um;
-+
-+	hlist_for_each_entry(um, node, head, u_hash) {
-+		if ((um->u_this.dentry == dentry) &&
-+		    (um->u_this.mnt == mnt))
-+			return um;
-+	}
-+
-+	return NULL;
-+}
-+
-+struct union_mount *union_rlookup(struct dentry *dentry, struct vfsmount *mnt)
-+{
-+	struct hlist_head *head = union_rhashtable + hash(dentry, mnt);
-+	struct hlist_node *node;
-+	struct union_mount *um;
-+
-+	hlist_for_each_entry(um, node, head, u_rhash) {
-+		if ((um->u_next.dentry == dentry) &&
-+		    (um->u_next.mnt == mnt))
-+			return um;
-+	}
-+
-+	return NULL;
-+}
-+
-+/*
-+ * is_unionized - check if a dentry lives on a union mounted file system
-+ *
-+ * This tests if a dentry is living on an union mounted file system by walking
-+ * the file system hierarchy.
-+ */
-+int is_unionized(struct dentry *dentry, struct vfsmount *mnt)
-+{
-+	struct path this = { .mnt = mntget(mnt),
-+			     .dentry = dget(dentry) };
-+	struct vfsmount *tmp;
-+
-+	do {
-+		/* check if there is an union mounted on top of us */
-+		spin_lock(&vfsmount_lock);
-+		list_for_each_entry(tmp, &this.mnt->mnt_mounts, mnt_child) {
-+			if (!(tmp->mnt_flags & MNT_UNION))
-+				continue;
-+			/* Isn't this a bug? */
-+			if (this.dentry->d_sb != tmp->mnt_mountpoint->d_sb)
-+				continue;
-+			if (is_subdir(this.dentry, tmp->mnt_mountpoint)) {
-+				spin_unlock(&vfsmount_lock);
-+				path_put(&this);
-+				return 1;
-+			}
-+		}
-+		spin_unlock(&vfsmount_lock);
-+
-+		/* check our mountpoint next */
-+		tmp = mntget(this.mnt->mnt_parent);
-+		dput(this.dentry);
-+		this.dentry = dget(this.mnt->mnt_mountpoint);
-+		mntput(this.mnt);
-+		this.mnt = tmp;
-+	} while (this.mnt != this.mnt->mnt_parent);
-+
-+	path_put(&this);
-+	return 0;
-+}
-+
-+int append_to_union(struct vfsmount *mnt, struct dentry *dentry,
-+		    struct vfsmount *dest_mnt, struct dentry *dest_dentry)
-+{
-+	struct union_mount *this, *um;
-+
-+	BUG_ON(!IS_MNT_UNION(mnt));
-+
-+	this = union_alloc(dentry, mnt, dest_dentry, dest_mnt);
-+	if (!this)
-+		return -ENOMEM;
-+
-+	spin_lock(&union_lock);
-+	um = union_lookup(dentry, mnt);
-+	if (um) {
-+		BUG_ON((um->u_next.dentry != dest_dentry) ||
-+		       (um->u_next.mnt != dest_mnt));
-+		spin_unlock(&union_lock);
-+		union_put(this);
-+		return 0;
-+	}
-+	list_add(&this->u_list, &mnt->mnt_unions);
-+	list_add(&this->u_unions, &dentry->d_unions);
-+	dest_dentry->d_unionized++;
-+	__union_hash(this);
-+	spin_unlock(&union_lock);
-+	return 0;
-+}
-+
-+/*
-+ * follow_union_down - follow the union stack one layer down
-+ *
-+ * This is called to traverse the union stack from one layer to the next
-+ * overlayed one. follow_union_down() is called by various lookup functions
-+ * that are aware of union mounts.
-+ *
-+ * Returns non-zero if followed to the next layer, zero otherwise.
-+ */
-+int follow_union_down(struct path *path)
-+{
-+	struct union_mount *um;
-+
-+	if (!IS_MNT_UNION(path->mnt))
-+		return 0;
-+
-+	spin_lock(&union_lock);
-+	um = union_lookup(path->dentry, path->mnt);
-+	spin_unlock(&union_lock);
-+	if (um) {
-+		path_get(&um->u_next);
-+		dput(path->dentry);
-+		path->dentry = um->u_next.dentry;
-+		mntput(path->mnt);
-+		path->mnt = um->u_next.mnt;
-+		return 1;
-+	}
-+	return 0;
-+}
-+
-+/*
-+ * follow_union_mount - follow the union stack to the topmost layer
-+ *
-+ * This is called to traverse the union stack to the topmost layer. This is
-+ * necessary for following parent pointers in an union mount.
-+ *
-+ * Returns none zero if followed to the topmost layer, zero otherwise.
-+ */
-+int follow_union_mount(struct path *path)
-+{
-+	struct union_mount *um;
-+	int res = 0;
-+
-+	while (IS_UNION(path->dentry)) {
-+		spin_lock(&dcache_lock);
-+		spin_lock(&union_lock);
-+		um = union_rlookup(path->dentry, path->mnt);
-+		if (um)
-+			path_get(&um->u_this);
-+		spin_unlock(&union_lock);
-+		spin_unlock(&dcache_lock);
-+
-+		/*
-+		 * Q: Aaargh, how do I validate the topmost dentry pointer?
-+		 * A: Eeeeasy! We took the dcache_lock and union_lock. Since
-+		 *    this protects from any dput'ng going on, we know that the
-+		 *    dentry is valid since the union is unhashed under
-+		 *    dcache_lock too.
-+		 */
-+		if (!um)
-+			break;
-+		dput(path->dentry);
-+		path->dentry = um->u_this.dentry;
-+		mntput(path->mnt);
-+		path->mnt = um->u_this.mnt;
-+		res = 1;
-+	}
-+
-+	return res;
-+}
-+
-+/*
-+ * Union mount copyup support
-+ */
-+
-+extern int hash_lookup_union(struct nameidata *, struct qstr *, struct path *);
-+extern void follow_mount(struct path *);
-+
-+/*
-+ * union_relookup_topmost - lookup and create the topmost path to dentry
-+ * @nd: pointer to nameidata
-+ * @flags: lookup flags
-+ */
-+static int union_relookup_topmost(struct nameidata *nd, int flags)
-+{
-+	int err;
-+	char *kbuf, *name;
-+	struct nameidata this;
-+
-+	kbuf = (char *)__get_free_page(GFP_KERNEL);
-+	if (!kbuf)
-+		return -ENOMEM;
-+
-+	name = d_path(&nd->path, kbuf, PAGE_SIZE);
-+	err = PTR_ERR(name);
-+	if (IS_ERR(name))
-+		goto free_page;
-+
-+	err = path_lookup(name, flags|LOOKUP_CREATE|LOOKUP_TOPMOST, &this);
-+	if (err)
-+		goto free_page;
-+
-+	path_put(&nd->path);
-+	nd->path.dentry = this.path.dentry;
-+	nd->path.mnt = this.path.mnt;
-+
-+	/*
-+	 * the nd->flags should be unchanged
-+	 */
-+	BUG_ON(this.um_flags & LAST_LOWLEVEL);
-+	nd->um_flags &= ~LAST_LOWLEVEL;
-+ free_page:
-+	free_page((unsigned long)kbuf);
-+	return err;
-+}
-+
-+static void __update_fs_pwd(struct path *path, struct dentry *dentry,
-+			    struct vfsmount *mnt)
-+{
-+	struct path old = { NULL, NULL };
-+
-+	write_lock(&current->fs->lock);
-+	if (current->fs->pwd.dentry == path->dentry) {
-+		old = current->fs->pwd;
-+		path_get(&current->fs->pwd);
-+	}
-+	write_unlock(&current->fs->lock);
-+
-+	if (old.dentry)
-+		path_put(&old);
-+
-+	return;
-+}
-+
-+/**
-+ * union_permission  -  check for access rights to a given inode
-+ * @inode:	inode to check permission on
-+ * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
-+ *
-+ * In a union mount, the top layer is always read-write and the bottom
-+ * is always read-only.  Ignore the read-only flag on the lower fs.
-+ *
-+ * Only need for certain activities, like checking to see if write
-+ * access is ok.
-+ */
-+
-+int union_permission(struct path *path, int mask)
-+{
-+	struct inode *inode = path->dentry->d_inode;
-+
-+	if (!is_unionized(path->dentry, path->mnt))
-+		return inode_permission(inode, mask);
-+
-+	/* Tell __inode_permission to ignore MS_RDONLY */
-+	return __inode_permission(inode, mask, 0);
-+}
-+
-+/*
-+ * union_create_topmost - create the topmost path component
-+ * @nd: pointer to nameidata of the base directory
-+ * @name: pointer to file name
-+ * @path: pointer to path of the overlaid file
-+ *
-+ * This is called by __link_path_walk() to create the directories on a path
-+ * when it is called with LOOKUP_TOPMOST.
-+ */
-+struct dentry *union_create_topmost(struct nameidata *nd, struct qstr *name,
-+				    struct path *path)
-+{
-+	struct dentry *dentry, *parent = nd->path.dentry;
-+	int res, mode = path->dentry->d_inode->i_mode;
-+
-+	if (parent->d_sb == path->dentry->d_sb)
-+		return ERR_PTR(-EEXIST);
-+
-+	mutex_lock(&parent->d_inode->i_mutex);
-+	dentry = lookup_one_len(name->name, nd->path.dentry, name->len);
-+	if (IS_ERR(dentry))
-+		goto out_unlock;
-+
-+	switch (mode & S_IFMT) {
-+	case S_IFREG:
-+		/*
-+		 * FIXME: Does this make any sense in this case?
-+		 * Special case - lookup gave negative, but... we had foo/bar/
-+		 * From the vfs_mknod() POV we just have a negative dentry -
-+		 * all is fine. Let's be bastards - you had / on the end,you've
-+		 * been asking for (non-existent) directory. -ENOENT for you.
-+		 */
-+		if (name->name[name->len] && !dentry->d_inode) {
-+			dput(dentry);
-+			dentry = ERR_PTR(-ENOENT);
-+			goto out_unlock;
-+		}
-+
-+		res = vfs_create(parent->d_inode, dentry, mode, nd);
-+		if (res) {
-+			dput(dentry);
-+			dentry = ERR_PTR(res);
-+			goto out_unlock;
-+		}
-+		break;
-+	case S_IFDIR:
-+		res = vfs_mkdir(parent->d_inode, dentry, mode);
-+		if (res) {
-+			dput(dentry);
-+			dentry = ERR_PTR(res);
-+			goto out_unlock;
-+		}
-+
-+		res = append_to_union(nd->path.mnt, dentry, path->mnt,
-+				      path->dentry);
-+		if (res) {
-+			dput(dentry);
-+			dentry = ERR_PTR(res);
-+			goto out_unlock;
-+		}
-+		break;
-+	default:
-+		dput(dentry);
-+		dentry = ERR_PTR(-EINVAL);
-+		goto out_unlock;
-+	}
-+
-+	/* FIXME: Really necessary ??? */
-+/*	__update_fs_pwd(path, dentry, nd->path.mnt); */
-+
-+ out_unlock:
-+	mutex_unlock(&parent->d_inode->i_mutex);
-+	return dentry;
-+}
-+
-+static int union_copy_file(struct dentry *old_dentry, struct vfsmount *old_mnt,
-+			   struct dentry *new_dentry, struct vfsmount *new_mnt)
-+{
-+	int ret;
-+	size_t size;
-+	loff_t offset;
-+	struct file *old_file, *new_file;
-+	const struct cred *cred = current_cred();
-+
-+	dget(old_dentry);
-+	mntget(old_mnt);
-+	old_file = dentry_open(old_dentry, old_mnt, O_RDONLY, cred);
-+	if (IS_ERR(old_file))
-+		return PTR_ERR(old_file);
-+
-+	dget(new_dentry);
-+	mntget(new_mnt);
-+	new_file = dentry_open(new_dentry, new_mnt, O_WRONLY, cred);
-+	ret = PTR_ERR(new_file);
-+	if (IS_ERR(new_file))
-+		goto fput_old;
-+
-+	/* XXX be smart by using a length param, which indicates max
-+	 * data we'll want (e.g., we are about to truncate to 0 or 10
-+	 * bytes or something */
-+	size = i_size_read(old_file->f_path.dentry->d_inode);
-+	if (((size_t)size != size) || ((ssize_t)size != size)) {
-+		ret = -EFBIG;
-+		goto fput_new;
-+	}
-+
-+	offset = 0;
-+	ret = do_splice_direct(old_file, &offset, new_file, size,
-+			       SPLICE_F_MOVE);
-+	if (ret >= 0)
-+		ret = 0;
-+ fput_new:
-+	fput(new_file);
-+ fput_old:
-+	fput(old_file);
-+	return ret;
-+}
-+
-+/**
-+ * __union_copyup - copy a file to the topmost directory
-+ * @old: pointer to path of the old file name
-+ * @new_nd: pointer to nameidata of the topmost directory
-+ * @new: pointer to path of the new file name
-+ *
-+ * The topmost directory @new_nd must already be locked. Creates the topmost
-+ * file if it doesn't exist yet.
-+ */
-+int __union_copyup(struct path *old, struct nameidata *new_nd,
-+		   struct path *new)
-+{
-+	struct dentry *dentry;
-+	int error;
-+
-+	/* Maybe this should be -EINVAL */
-+	if (S_ISDIR(old->dentry->d_inode->i_mode))
-+		return -EISDIR;
-+
-+	if (new_nd->path.dentry != new->dentry->d_parent) {
-+		mutex_lock(&new_nd->path.dentry->d_inode->i_mutex);
-+		dentry = lookup_one_len(new->dentry->d_name.name,
-+					new_nd->path.dentry,
-+					new->dentry->d_name.len);
-+		mutex_unlock(&new_nd->path.dentry->d_inode->i_mutex);
-+		if (IS_ERR(dentry))
-+			return PTR_ERR(dentry);
-+		error = -EEXIST;
-+		if (dentry->d_inode)
-+			goto out_dput;
-+	} else
-+		dentry = dget(new->dentry);
-+
-+	if (!dentry->d_inode) {
-+		error = vfs_create(new_nd->path.dentry->d_inode, dentry,
-+				   old->dentry->d_inode->i_mode, new_nd);
-+		if (error)
-+			goto out_dput;
-+	}
-+
-+	BUG_ON(!S_ISREG(old->dentry->d_inode->i_mode));
-+	error = union_copy_file(old->dentry, old->mnt, dentry,
-+				new_nd->path.mnt);
-+	if (error) {
-+		/* FIXME: are there return value we should not
-+		 * BUG() on ? */
-+		BUG_ON(vfs_unlink(new_nd->path.dentry->d_inode,
-+				  dentry));
-+		goto out_dput;
-+	}
-+
-+	dput(new->dentry);
-+	new->dentry = dentry;
-+	if (new->mnt != new_nd->path.mnt)
-+		mntput(new->mnt);
-+	new->mnt = new_nd->path.mnt;
-+	return error;
-+
-+out_dput:
-+	dput(dentry);
-+	return error;
-+}
-+
-+/*
-+ * union_copyup - copy a file to the topmost layer of the union stack
-+ * @nd: nameidata pointer to the file
-+ * @flags: flags given to open_namei
-+ */
-+int union_copyup(struct nameidata *nd, int flags /* XXX not used */)
-+{
-+	struct qstr this;
-+	char *name;
-+	struct dentry *dir;
-+	struct path path;
-+	int err;
-+
-+	if (!is_unionized(nd->path.dentry, nd->path.mnt))
-+		return 0;
-+	if (!S_ISREG(nd->path.dentry->d_inode->i_mode))
-+		return 0;
-+
-+	/* safe the name for hash_lookup_union() */
-+	this.len = nd->path.dentry->d_name.len;
-+	this.hash = nd->path.dentry->d_name.hash;
-+	name = kmalloc(this.len + 1, GFP_KERNEL);
-+	if (!name)
-+		return -ENOMEM;
-+	this.name = name;
-+	memcpy(name, nd->path.dentry->d_name.name, nd->path.dentry->d_name.len);
-+	name[this.len] = 0;
-+
-+	err = union_relookup_topmost(nd, nd->flags|LOOKUP_PARENT);
-+	if (err) {
-+		kfree(name);
-+		return err;
-+	}
-+	nd->flags &= ~LOOKUP_PARENT;
-+
-+	dir = nd->path.dentry;
-+	mutex_lock(&dir->d_inode->i_mutex);
-+	err = hash_lookup_union(nd, &this, &path);
-+	mutex_unlock(&dir->d_inode->i_mutex);
-+	kfree(name);
-+	if (err)
-+		return err;
-+
-+	err = -ENOENT;
-+	if (!path.dentry->d_inode)
-+		goto exit_dput;
-+
-+	/* Necessary?! I guess not ... */
-+	follow_mount(&path);
-+
-+	err = -ENOENT;
-+	if (!path.dentry->d_inode)
-+		goto exit_dput;
-+
-+	err = -EISDIR;
-+	if (!S_ISREG(path.dentry->d_inode->i_mode))
-+		goto exit_dput;
-+
-+	if (path.dentry->d_parent != nd->path.dentry) {
-+		err = __union_copyup(&path, nd, &path);
-+		if (err)
-+			goto exit_dput;
-+	}
-+
-+	dput(nd->path.dentry);
-+	if (nd->path.mnt != path.mnt)
-+		mntput(nd->path.mnt);
-+	nd->path = path;
-+	return 0;
-+
-+exit_dput:
-+	dput(path.dentry);
-+	if (path.mnt != nd->path.mnt)
-+		mntput(path.mnt);
-+	return err;
-+}
-+
-+/*
-+ * This must be called when unhashing a dentry. This is called with dcache_lock
-+ * and unhashes all unions this dentry is in.
-+ */
-+void __d_drop_unions(struct dentry *dentry)
-+{
-+	struct union_mount *this, *next;
-+
-+	spin_lock(&union_lock);
-+	list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions)
-+		__union_unhash(this);
-+	spin_unlock(&union_lock);
-+}
-+EXPORT_SYMBOL_GPL(__d_drop_unions);
-+
-+/*
-+ * This must be called after __d_drop_unions() without holding any locks.
-+ * Note: The dentry might still be reachable via a lookup but at that time it
-+ * already a negative dentry. Otherwise it would be unhashed. The union_mount
-+ * structure itself is still reachable through mnt->mnt_unions (which we
-+ * protect against with union_lock).
-+ */
-+void shrink_d_unions(struct dentry *dentry)
-+{
-+	struct union_mount *this, *next;
-+
-+repeat:
-+	spin_lock(&union_lock);
-+	list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions) {
-+		BUG_ON(!hlist_unhashed(&this->u_hash));
-+		BUG_ON(!hlist_unhashed(&this->u_rhash));
-+		list_del(&this->u_list);
-+		list_del(&this->u_unions);
-+		this->u_next.dentry->d_unionized--;
-+		spin_unlock(&union_lock);
-+		union_put(this);
-+		goto repeat;
-+	}
-+	spin_unlock(&union_lock);
-+}
-+
-+extern void __dput(struct dentry *, struct list_head *, int);
-+
-+/*
-+ * This is the special variant for use in dput() only.
-+ */
-+void __shrink_d_unions(struct dentry *dentry, struct list_head *list)
-+{
-+	struct union_mount *this, *next;
-+
-+	BUG_ON(!d_unhashed(dentry));
-+
-+repeat:
-+	spin_lock(&union_lock);
-+	list_for_each_entry_safe(this, next, &dentry->d_unions, u_unions) {
-+		struct dentry *n_dentry = this->u_next.dentry;
-+		struct vfsmount *n_mnt = this->u_next.mnt;
-+
-+		BUG_ON(!hlist_unhashed(&this->u_hash));
-+		BUG_ON(!hlist_unhashed(&this->u_rhash));
-+		list_del(&this->u_list);
-+		list_del(&this->u_unions);
-+		this->u_next.dentry->d_unionized--;
-+		spin_unlock(&union_lock);
-+		if (__union_put(this)) {
-+			__dput(n_dentry, list, 0);
-+			mntput(n_mnt);
-+		}
-+		goto repeat;
-+	}
-+	spin_unlock(&union_lock);
-+}
-+
-+/*
-+ * Remove all union_mounts structures belonging to this vfsmount from the
-+ * union lookup hashtable and so on ...
-+ */
-+void shrink_mnt_unions(struct vfsmount *mnt)
-+{
-+	struct union_mount *this, *next;
-+
-+repeat:
-+	spin_lock(&union_lock);
-+	list_for_each_entry_safe(this, next, &mnt->mnt_unions, u_list) {
-+		if (this->u_this.dentry == mnt->mnt_root)
-+			continue;
-+		__union_unhash(this);
-+		list_del(&this->u_list);
-+		list_del(&this->u_unions);
-+		this->u_next.dentry->d_unionized--;
-+		spin_unlock(&union_lock);
-+		union_put(this);
-+		goto repeat;
-+	}
-+	spin_unlock(&union_lock);
-+}
-+
-+int attach_mnt_union(struct vfsmount *mnt, struct vfsmount *dest_mnt,
-+		     struct dentry *dest_dentry)
-+{
-+	if (!IS_MNT_UNION(mnt))
-+		return 0;
-+
-+	return append_to_union(mnt, mnt->mnt_root, dest_mnt, dest_dentry);
-+}
-+
-+void detach_mnt_union(struct vfsmount *mnt)
-+{
-+	struct union_mount *um;
-+
-+	if (!IS_MNT_UNION(mnt))
-+		return;
-+
-+	shrink_mnt_unions(mnt);
-+
-+	spin_lock(&union_lock);
-+	um = union_lookup(mnt->mnt_root, mnt);
-+	__union_unhash(um);
-+	list_del(&um->u_list);
-+	list_del(&um->u_unions);
-+	um->u_next.dentry->d_unionized--;
-+	spin_unlock(&union_lock);
-+	union_put(um);
-+	return;
-+}
-+
-+/**
-+ * union_copyup_dir_one - copy up a single directory entry
-+ *
-+ * Individual directory entry copyup function for union_copyup_dir.
-+ * We get the entries from higher level layers first.
-+ */
-+
-+static int union_copyup_dir_one(void *buf, const char *name, int namlen,
-+				loff_t offset, u64 ino, unsigned int d_type)
-+{
-+	struct dentry *topmost_dentry = (struct dentry *) buf;
-+	struct dentry *dentry;
-+	int err = 0;
-+
-+	switch (namlen) {
-+	case 2:
-+		if (name[1] != '.')
-+			break;
-+	case 1:
-+		if (name[0] != '.')
-+			break;
-+		return 0;
-+	}
-+
-+	/* Lookup this entry in the topmost directory */
-+	dentry = lookup_one_len(name, topmost_dentry, namlen);
-+
-+	if (IS_ERR(dentry)) {
-+		printk(KERN_INFO "error looking up %s\n", dentry->d_name.name);
-+		goto out;
-+	}
-+
-+	/*
-+	 * If the entry already exists, one of the following is true:
-+	 * it was already copied up (due to an earlier lookup), an
-+	 * entry with the same name already exists on the topmost file
-+	 * system, it is a whiteout, or it is a fallthru.  In each
-+	 * case, the top level entry masks any entries from lower file
-+	 * systems, so don't copy up this entry.
-+	 */
-+	if (dentry->d_inode || d_is_whiteout(dentry) ||
-+	    d_is_fallthru(dentry)) {
-+		printk(KERN_INFO "skipping copy of %s\n", dentry->d_name.name);
-+		goto out_dput;
-+	}
-+
-+	/*
-+	 * If the entry doesn't exist, create a fallthru entry in the
-+	 * topmost file system.  All possible directory types are
-+	 * used, so each file system must implement its own way of
-+	 * storing a fallthru entry.
-+	 */
-+	printk(KERN_INFO "creating fallthru for %s\n", dentry->d_name.name);
-+	err = topmost_dentry->d_inode->i_op->fallthru(topmost_dentry->d_inode,
-+						      dentry);
-+	/* FIXME */
-+	BUG_ON(err);
-+	/*
-+	 * At this point, we have a negative dentry marked as fallthru
-+	 * in the cache.  We could potentially lookup the entry lower
-+	 * level file system and turn this into a positive dentry
-+	 * right now, but it is not clear that would be a performance
-+	 * win and adds more opportunities to fail.
-+	 */
-+out_dput:
-+	dput(dentry);
-+out:
-+	return 0;
-+}
-+
-+/**
-+ * union_copyup_dir - copy up low-level directory entries to topmost dir
-+ *
-+ * readdir() is difficult to support on union file systems for two
-+ * reasons: We must eliminate duplicates and apply whiteouts, and we
-+ * must return something in f_pos that lets us restart in the same
-+ * place when we return.  Our solution is to, on first readdir() of
-+ * the directory, copy up all visible entries from the low-level file
-+ * systems and mark the entries that refer to low-level file system
-+ * objects as "fallthru" entries.
-+ */
-+
-+int union_copyup_dir(struct path *topmost_path)
-+{
-+	struct dentry *topmost_dentry = topmost_path->dentry;
-+	struct path path = *topmost_path;
-+	int res = 0;
-+
-+	/*
-+	 * Skip opaque dirs.
-+	 */
-+	if (IS_OPAQUE(topmost_dentry->d_inode))
-+		return 0;
-+
-+	/*
-+	 * Mark this dir opaque to show that we have already copied up
-+	 * the lower entries.  Only fallthru entries pass through to
-+	 * the underlying file system.
-+	 *
-+	 * XXX Deal with the lower file system changing.  This could
-+	 * be through running a tool over the top level file system to
-+	 * make directories transparent again, or we could check the
-+	 * mtime of the underlying directory.
-+	 */
-+
-+	topmost_dentry->d_inode->i_flags |= S_OPAQUE;
-+	mark_inode_dirty(topmost_dentry->d_inode);
-+
-+	/*
-+	 * Loop through each dir on each level copying up the entries
-+	 * to the topmost.
-+	 */
-+
-+	/* Don't drop the caller's reference to the topmost path */
-+	path_get(&path);
-+	while (follow_union_down(&path)) {
-+		struct file * ftmp;
-+		struct inode * inode;
-+
-+		/* XXX Permit fallthrus on lower-level? Would need to
-+		 * pass in opaque flag to union_copyup_dir_one() and
-+		 * only copy up fallthru entries there.  We allow
-+		 * fallthrus in lower level opaque directories on
-+		 * lookup, so for consistency we should do one or the
-+		 * other in both places. */
-+		if (IS_OPAQUE(path.dentry->d_inode))
-+			break;
-+
-+		/* dentry_open() doesn't get a path reference itself */
-+		path_get(&path);
-+		ftmp = dentry_open(path.dentry, path.mnt,
-+				   O_RDONLY | O_DIRECTORY | O_NOATIME,
-+				   current_cred());
-+		if (IS_ERR(ftmp)) {
-+			printk (KERN_ERR "unable to open dir %s for "
-+				"directory copyup: %ld\n",
-+				path.dentry->d_name.name, PTR_ERR(ftmp));
-+			continue;
-+		}
-+
-+		inode = path.dentry->d_inode;
-+		mutex_lock(&inode->i_mutex);
-+
-+		res = -ENOENT;
-+		if (IS_DEADDIR(inode))
-+			goto out_fput;
-+		/*
-+		 * Read the whole directory, calling our directory
-+		 * entry copyup function on each entry.  Pass in the
-+		 * topmost dentry as our private data so we can create
-+		 * new entries in the topmost directory.
-+		 */
-+		res = ftmp->f_op->readdir(ftmp, topmost_dentry,
-+					  union_copyup_dir_one);
-+out_fput:
-+		mutex_unlock(&inode->i_mutex);
-+		fput(ftmp);
-+
-+		if (res)
-+			break;
-+	}
-+	path_put(&path);
-+	return res;
-+}
---- a/include/linux/dcache.h
-+++ b/include/linux/dcache.h
-@@ -101,6 +101,15 @@ struct dentry {
- 	struct dentry *d_parent;	/* parent directory */
- 	struct qstr d_name;
- 
-+#ifdef CONFIG_UNION_MOUNT
-+	/*
-+	 * The following fields are used by the VFS based union mount
-+	 * implementation. Both are protected by union_lock!
-+	 */
-+	struct list_head d_unions;	/* list of union_mount's */
-+	unsigned int d_unionized;	/* unions referencing this dentry */
-+#endif
-+
- 	struct list_head d_lru;		/* LRU list */
- 	/*
- 	 * d_child and d_rcu can share memory
-@@ -186,6 +195,9 @@ d_iput:		no		no		no       yes
- 
- #define DCACHE_FSNOTIFY_PARENT_WATCHED	0x0080 /* Parent inode is watched by some fsnotify listener */
- 
-+#define DCACHE_WHITEOUT		0x0100	/* This negative dentry is a whiteout */
-+#define DCACHE_FALLTHRU		0x0200	/* Keep looking in the file system below */
-+
- extern spinlock_t dcache_lock;
- extern seqlock_t rename_lock;
- 
-@@ -205,12 +217,20 @@ extern seqlock_t rename_lock;
-  * __d_drop requires dentry->d_lock.
-  */
- 
-+#ifdef CONFIG_UNION_MOUNT
-+extern void __d_drop_unions(struct dentry *);
-+#endif
-+
- static inline void __d_drop(struct dentry *dentry)
- {
- 	if (!(dentry->d_flags & DCACHE_UNHASHED)) {
- 		dentry->d_flags |= DCACHE_UNHASHED;
- 		hlist_del_rcu(&dentry->d_hash);
- 	}
-+#ifdef CONFIG_UNION_MOUNT
-+	/* remove dentry from the union hashtable */
-+	__d_drop_unions(dentry);
-+#endif
- }
- 
- static inline void d_drop(struct dentry *dentry)
-@@ -358,6 +378,16 @@ static inline int d_unlinked(struct dent
- 	return d_unhashed(dentry) && !IS_ROOT(dentry);
- }
- 
-+static inline int d_is_whiteout(struct dentry *dentry)
-+{
-+	return (dentry->d_flags & DCACHE_WHITEOUT);
-+}
-+
-+static inline int d_is_fallthru(struct dentry *dentry)
-+{
-+	return (dentry->d_flags & DCACHE_FALLTHRU);
-+}
-+
- static inline struct dentry *dget_parent(struct dentry *dentry)
- {
- 	struct dentry *ret;
---- a/include/linux/ext2_fs.h
-+++ b/include/linux/ext2_fs.h
-@@ -189,6 +189,7 @@ struct ext2_group_desc
- #define EXT2_NOTAIL_FL			FS_NOTAIL_FL	/* file tail should not be merged */
- #define EXT2_DIRSYNC_FL			FS_DIRSYNC_FL	/* dirsync behaviour (directories only) */
- #define EXT2_TOPDIR_FL			FS_TOPDIR_FL	/* Top of directory hierarchies*/
-+#define EXT2_OPAQUE_FL			0x00040000
- #define EXT2_RESERVED_FL		FS_RESERVED_FL	/* reserved for ext2 lib */
- 
- #define EXT2_FL_USER_VISIBLE		FS_FL_USER_VISIBLE	/* User visible flags */
-@@ -503,10 +504,12 @@ struct ext2_super_block {
- #define EXT3_FEATURE_INCOMPAT_RECOVER		0x0004
- #define EXT3_FEATURE_INCOMPAT_JOURNAL_DEV	0x0008
- #define EXT2_FEATURE_INCOMPAT_META_BG		0x0010
-+#define EXT2_FEATURE_INCOMPAT_WHITEOUT		0x0020
- #define EXT2_FEATURE_INCOMPAT_ANY		0xffffffff
- 
- #define EXT2_FEATURE_COMPAT_SUPP	EXT2_FEATURE_COMPAT_EXT_ATTR
- #define EXT2_FEATURE_INCOMPAT_SUPP	(EXT2_FEATURE_INCOMPAT_FILETYPE| \
-+					 EXT2_FEATURE_INCOMPAT_WHITEOUT| \
- 					 EXT2_FEATURE_INCOMPAT_META_BG)
- #define EXT2_FEATURE_RO_COMPAT_SUPP	(EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER| \
- 					 EXT2_FEATURE_RO_COMPAT_LARGE_FILE| \
-@@ -573,6 +576,8 @@ enum {
- 	EXT2_FT_FIFO,
- 	EXT2_FT_SOCK,
- 	EXT2_FT_SYMLINK,
-+	EXT2_FT_WHT,
-+	EXT2_FT_FALLTHRU,
- 	EXT2_FT_MAX
- };
- 
---- a/include/linux/fs.h
-+++ b/include/linux/fs.h
-@@ -188,6 +188,7 @@ struct inodes_stat_t {
- #define MS_REMOUNT	32	/* Alter flags of a mounted FS */
- #define MS_MANDLOCK	64	/* Allow mandatory locks on an FS */
- #define MS_DIRSYNC	128	/* Directory modifications are synchronous */
-+#define MS_UNION	256
- #define MS_NOATIME	1024	/* Do not update access times. */
- #define MS_NODIRATIME	2048	/* Do not update directory access times */
- #define MS_BIND		4096
-@@ -205,6 +206,7 @@ struct inodes_stat_t {
- #define MS_KERNMOUNT	(1<<22) /* this is a kern_mount call */
- #define MS_I_VERSION	(1<<23) /* Update inode I_version field */
- #define MS_STRICTATIME	(1<<24) /* Always perform atime updates */
-+#define MS_WHITEOUT	(1<<26) /* fs does support white-out filetype */
- #define MS_ACTIVE	(1<<30)
- #define MS_NOUSER	(1<<31)
- 
-@@ -231,6 +233,7 @@ struct inodes_stat_t {
- #define S_NOCMTIME	128	/* Do not update file c/mtime */
- #define S_SWAPFILE	256	/* Do not truncate: swapon got its bmaps */
- #define S_PRIVATE	512	/* Inode is fs-internal */
-+#define S_OPAQUE	1024	/* Directory is opaque */
- 
- /*
-  * Note that nosuid etc flags are inode-specific: setting some file-system
-@@ -266,6 +269,8 @@ struct inodes_stat_t {
- #define IS_SWAPFILE(inode)	((inode)->i_flags & S_SWAPFILE)
- #define IS_PRIVATE(inode)	((inode)->i_flags & S_PRIVATE)
- 
-+#define IS_OPAQUE(inode)	((inode)->i_flags & S_OPAQUE)
-+
- /* the read-only stuff doesn't really belong here, but any other place is
-    probably as bad and I don't want to create yet another include file. */
- 
-@@ -1380,6 +1385,11 @@ struct super_block {
- 	 * generic_show_options()
- 	 */
- 	char *s_options;
-+
-+	/*
-+	 * Users who require read-only access - e.g., union mounts
-+	 */
-+	int s_readonly_users;
- };
- 
- extern struct timespec current_fs_time(struct super_block *sb);
-@@ -1517,6 +1527,8 @@ struct inode_operations {
- 	int (*mkdir) (struct inode *,struct dentry *,int);
- 	int (*rmdir) (struct inode *,struct dentry *);
- 	int (*mknod) (struct inode *,struct dentry *,int,dev_t);
-+	int (*whiteout) (struct inode *, struct dentry *, struct dentry *);
-+	int (*fallthru) (struct inode *, struct dentry *);
- 	int (*rename) (struct inode *, struct dentry *,
- 			struct inode *, struct dentry *);
- 	int (*readlink) (struct dentry *, char __user *,int);
-@@ -2108,6 +2120,7 @@ extern void emergency_remount(void);
- extern sector_t bmap(struct inode *, sector_t);
- #endif
- extern int notify_change(struct dentry *, struct iattr *);
-+extern int __inode_permission(struct inode *inode, int mask, int rofs);
- extern int inode_permission(struct inode *, int);
- extern int generic_permission(struct inode *, int,
- 		int (*check_acl)(struct inode *, int));
-@@ -2135,7 +2148,7 @@ extern void free_write_pipe(struct file 
- 
- extern struct file *do_filp_open(int dfd, const char *pathname,
- 		int open_flag, int mode, int acc_mode);
--extern int may_open(struct path *, int, int);
-+extern int may_open(struct nameidata *, int, int);
- 
- extern int kernel_read(struct file *, loff_t, char *, unsigned long);
- extern struct file * open_exec(const char *);
---- a/include/linux/mount.h
-+++ b/include/linux/mount.h
-@@ -35,6 +35,7 @@ struct mnt_namespace;
- #define MNT_SHARED	0x1000	/* if the vfsmount is a shared mount */
- #define MNT_UNBINDABLE	0x2000	/* if the vfsmount is a unbindable mount */
- #define MNT_PNODE_MASK	0x3000	/* propagation flag mask */
-+#define MNT_UNION	0x4000	/* if the vfsmount is a union mount */
- 
- struct vfsmount {
- 	struct list_head mnt_hash;
-@@ -53,6 +54,9 @@ struct vfsmount {
- 	struct list_head mnt_slave_list;/* list of slave mounts */
- 	struct list_head mnt_slave;	/* slave list entry */
- 	struct vfsmount *mnt_master;	/* slave is on master->mnt_slave_list */
-+#ifdef CONFIG_UNION_MOUNT
-+	struct list_head mnt_unions;	/* list of union_mount structures */
-+#endif
- 	struct mnt_namespace *mnt_ns;	/* containing namespace */
- 	int mnt_id;			/* mount identifier */
- 	int mnt_group_id;		/* peer group identifier */
---- a/include/linux/namei.h
-+++ b/include/linux/namei.h
-@@ -20,6 +20,7 @@ struct nameidata {
- 	struct qstr	last;
- 	struct path	root;
- 	unsigned int	flags;
-+	unsigned int	um_flags;
- 	int		last_type;
- 	unsigned	depth;
- 	char *saved_names[MAX_NESTED_LINKS + 1];
-@@ -35,6 +36,9 @@ struct nameidata {
-  */
- enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
- 
-+#define LAST_UNION             0x01
-+#define LAST_LOWLEVEL          0x02
-+
- /*
-  * The bitmask for a lookup event:
-  *  - follow links at the end
-@@ -49,6 +53,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LA
- #define LOOKUP_CONTINUE		 4
- #define LOOKUP_PARENT		16
- #define LOOKUP_REVAL		64
-+#define LOOKUP_TOPMOST	       128
-+
- /*
-  * Intent data
-  */
---- /dev/null
-+++ b/include/linux/union.h
-@@ -0,0 +1,84 @@
-+/*
-+ * VFS based union mount for Linux
-+ *
-+ * Copyright (C) 2004-2007 IBM Corporation, IBM Deutschland Entwicklung GmbH.
-+ * Copyright (C) 2007 Novell Inc.
-+ *   Author(s): Jan Blunck ([email protected])
-+ *
-+ * This program is free software; you can redistribute it and/or modify it
-+ * under the terms of the GNU General Public License as published by the Free
-+ * Software Foundation; either version 2 of the License, or (at your option)
-+ * any later version.
-+ *
-+ */
-+#ifndef __LINUX_UNION_H
-+#define __LINUX_UNION_H
-+#ifdef __KERNEL__
-+
-+#include <linux/list.h>
-+#include <asm/atomic.h>
-+
-+struct dentry;
-+struct vfsmount;
-+
-+#ifdef CONFIG_UNION_MOUNT
-+
-+/*
-+ * The new union mount structure.
-+ */
-+struct union_mount {
-+	atomic_t u_count;		/* reference count */
-+	struct mutex u_mutex;
-+	struct list_head u_unions;	/* list head for d_unions */
-+	struct list_head u_list;	/* list head for mnt_unions */
-+	struct hlist_node u_hash;	/* list head for seaching */
-+	struct hlist_node u_rhash;	/* list head for reverse seaching */
-+
-+	struct path u_this;		/* this is me */
-+	struct path u_next;		/* this is what I overlay */
-+};
-+
-+#define IS_UNION(dentry)	(!list_empty(&(dentry)->d_unions) || \
-+				 (dentry)->d_unionized)
-+#define IS_MNT_UNION(mnt)	((mnt)->mnt_flags & MNT_UNION)
-+
-+extern int is_unionized(struct dentry *, struct vfsmount *);
-+extern int append_to_union(struct vfsmount *, struct dentry *,
-+			   struct vfsmount *, struct dentry *);
-+extern int follow_union_down(struct path *);
-+extern int follow_union_mount(struct path *);
-+extern void __d_drop_unions(struct dentry *);
-+extern void shrink_d_unions(struct dentry *);
-+extern void __shrink_d_unions(struct dentry *, struct list_head *);
-+extern int attach_mnt_union(struct vfsmount *, struct vfsmount *,
-+			    struct dentry *);
-+extern void detach_mnt_union(struct vfsmount *);
-+extern struct dentry *union_create_topmost(struct nameidata *, struct qstr *,
-+					   struct path *);
-+extern int __union_copyup(struct path *, struct nameidata *, struct path *);
-+extern int union_copyup(struct nameidata *, int);
-+extern int union_copyup_dir(struct path *path);
-+extern int union_permission(struct path *, int);
-+
-+#else /* CONFIG_UNION_MOUNT */
-+
-+#define IS_UNION(x)			(0)
-+#define IS_MNT_UNION(x)			(0)
-+#define is_unionized(x, y)		(0)
-+#define append_to_union(x1, y1, x2, y2)	({ BUG(); (0); })
-+#define follow_union_down(x)		({ (0); })
-+#define follow_union_mount(x)	({ (0); })
-+#define __d_drop_unions(x)		do { } while (0)
-+#define shrink_d_unions(x)		do { } while (0)
-+#define __shrink_d_unions(x,y)		do { } while (0)
-+#define attach_mnt_union(x, y, z)	do { } while (0)
-+#define detach_mnt_union(x)		do { } while (0)
-+#define union_create_topmost(x, y, z)	({ BUG(); (NULL); })
-+#define __union_copyup(x, y, z)		({ BUG(); (0); })
-+#define union_copyup(x, y)		({ (0); })
-+#define union_copyup_dir(x)		({ BUG(); (0); })
-+#define union_permission(x, y)		inode_permission(x->dentry->d_inode, y)
-+
-+#endif	/* CONFIG_UNION_MOUNT */
-+#endif	/* __KERNEL__ */
-+#endif	/* __LINUX_UNION_H */
---- a/mm/shmem.c
-+++ b/mm/shmem.c
-@@ -1798,6 +1798,118 @@ static int shmem_statfs(struct dentry *d
- 	return 0;
- }
- 
-+static int shmem_rmdir(struct inode *dir, struct dentry *dentry);
-+static int shmem_unlink(struct inode *dir, struct dentry *dentry);
-+
-+/*
-+ * Create a dentry to signify a whiteout.
-+ */
-+static int shmem_whiteout(struct inode *dir, struct dentry *old_dentry,
-+			  struct dentry *new_dentry)
-+{
-+	struct shmem_sb_info *sbinfo = SHMEM_SB(dir->i_sb);
-+	struct dentry *dentry;
-+
-+	if (!(dir->i_sb->s_flags & MS_WHITEOUT))
-+		return -EPERM;
-+
-+	/* This gives us a proper initialized negative dentry */
-+	dentry = simple_lookup(dir, new_dentry, NULL);
-+	if (dentry && IS_ERR(dentry))
-+		return PTR_ERR(dentry);
-+
-+	/*
-+	 * No ordinary (disk based) filesystem counts whiteouts as inodes;
-+	 * but each new link needs a new dentry, pinning lowmem, and
-+	 * tmpfs dentries cannot be pruned until they are unlinked.
-+	 */
-+	if (sbinfo->max_inodes) {
-+		spin_lock(&sbinfo->stat_lock);
-+		if (!sbinfo->free_inodes) {
-+			spin_unlock(&sbinfo->stat_lock);
-+			return -ENOSPC;
-+		}
-+		sbinfo->free_inodes--;
-+		spin_unlock(&sbinfo->stat_lock);
-+	}
-+
-+	if (old_dentry->d_inode || d_is_fallthru(old_dentry)) {
-+		if (old_dentry->d_inode && S_ISDIR(old_dentry->d_inode->i_mode))
-+			shmem_rmdir(dir, old_dentry);
-+		else
-+			shmem_unlink(dir, old_dentry);
-+	}
-+
-+	dir->i_size += BOGO_DIRENT_SIZE;
-+	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
-+	/* Extra pinning count for the created dentry */
-+	dget(new_dentry);
-+	spin_lock(&new_dentry->d_lock);
-+	new_dentry->d_flags |= DCACHE_WHITEOUT;
-+	spin_unlock(&new_dentry->d_lock);
-+	return 0;
-+}
-+
-+static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry,
-+				struct inode *inode);
-+
-+/*
-+ * Create a dentry to signify a fallthru.  A fallthru lets us read the
-+ * low-level dentries into the dcache once on the first readdir() and
-+ * then
-+ */
-+static int shmem_fallthru(struct inode *dir, struct dentry *dentry)
-+{
-+	struct shmem_sb_info *sbinfo = SHMEM_SB(dir->i_sb);
-+
-+	/* FIXME: this is stupid */
-+	if (!(dir->i_sb->s_flags & MS_WHITEOUT))
-+		return -EPERM;
-+
-+	if (dentry->d_inode || d_is_fallthru(dentry) || d_is_whiteout(dentry))
-+		return -EEXIST;
-+
-+	/*
-+	 * Each new link needs a new dentry, pinning lowmem, and tmpfs
-+	 * dentries cannot be pruned until they are unlinked.
-+	 */
-+	if (sbinfo->max_inodes) {
-+		spin_lock(&sbinfo->stat_lock);
-+		if (!sbinfo->free_inodes) {
-+			spin_unlock(&sbinfo->stat_lock);
-+			return -ENOSPC;
-+		}
-+		sbinfo->free_inodes--;
-+		spin_unlock(&sbinfo->stat_lock);
-+	}
-+
-+	shmem_d_instantiate(dir, dentry, NULL);
-+	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
-+
-+	spin_lock(&dentry->d_lock);
-+	dentry->d_flags |= DCACHE_FALLTHRU;
-+	spin_unlock(&dentry->d_lock);
-+	return 0;
-+}
-+
-+static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry,
-+				struct inode *inode)
-+{
-+	if (d_is_whiteout(dentry)) {
-+		/* Re-using an existing whiteout */
-+		shmem_free_inode(dir->i_sb);
-+		if (S_ISDIR(inode->i_mode))
-+			inode->i_mode |= S_OPAQUE;
-+	} else if (d_is_fallthru(dentry)) {
-+		shmem_free_inode(dir->i_sb);
-+	} else {
-+		/* New dentry */
-+		dir->i_size += BOGO_DIRENT_SIZE;
-+		dget(dentry); /* Extra count - pin the dentry in core */
-+	}
-+	/* Will clear DCACHE_WHITEOUT and DCACHE_FALLTHRU flags */
-+	d_instantiate(dentry, inode);
-+}
- /*
-  * File creation. Allocate an inode, and we're done..
-  */
-@@ -1822,15 +1934,16 @@ shmem_mknod(struct inode *dir, struct de
- 			iput(inode);
- 			return error;
- 		}
-+
- 		if (dir->i_mode & S_ISGID) {
- 			inode->i_gid = dir->i_gid;
- 			if (S_ISDIR(mode))
- 				inode->i_mode |= S_ISGID;
- 		}
--		dir->i_size += BOGO_DIRENT_SIZE;
-+
-+		shmem_d_instantiate(dir, dentry, inode);
-+
- 		dir->i_ctime = dir->i_mtime = CURRENT_TIME;
--		d_instantiate(dentry, inode);
--		dget(dentry); /* Extra count - pin the dentry in core */
- 	}
- 	return error;
- }
-@@ -1868,12 +1981,11 @@ static int shmem_link(struct dentry *old
- 	if (ret)
- 		goto out;
- 
--	dir->i_size += BOGO_DIRENT_SIZE;
-+	shmem_d_instantiate(dir, dentry, inode);
-+
- 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
- 	inc_nlink(inode);
- 	atomic_inc(&inode->i_count);	/* New dentry reference */
--	dget(dentry);		/* Extra pinning count for the created dentry */
--	d_instantiate(dentry, inode);
- out:
- 	return ret;
- }
-@@ -1882,21 +1994,63 @@ static int shmem_unlink(struct inode *di
- {
- 	struct inode *inode = dentry->d_inode;
- 
--	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
--		shmem_free_inode(inode->i_sb);
-+	if (d_is_whiteout(dentry) || d_is_fallthru(dentry) ||
-+	    (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)))
-+		shmem_free_inode(dir->i_sb);
- 
-+	if (inode) {
-+		inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
-+		drop_nlink(inode);
-+	}
- 	dir->i_size -= BOGO_DIRENT_SIZE;
--	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
--	drop_nlink(inode);
- 	dput(dentry);	/* Undo the count from "create" - this does all the work */
- 	return 0;
- }
- 
-+static void shmem_dir_unlink_whiteouts(struct inode *dir, struct dentry *dentry)
-+{
-+	if (!dentry->d_inode)
-+		return;
-+
-+	/* Remove whiteouts from logical empty directory */
-+	if (S_ISDIR(dentry->d_inode->i_mode) &&
-+	    dentry->d_inode->i_sb->s_flags & MS_WHITEOUT) {
-+		struct dentry *child, *next;
-+		LIST_HEAD(list);
-+
-+		spin_lock(&dcache_lock);
-+		list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
-+			spin_lock(&child->d_lock);
-+			/* Unlink fallthrus too */
-+			if (d_is_whiteout(child) || d_is_fallthru(child)) {
-+				__d_drop(child);
-+				if (!list_empty(&child->d_lru)) {
-+					list_del(&child->d_lru);
-+					dentry_stat.nr_unused--;
-+				}
-+				list_add(&child->d_lru, &list);
-+			}
-+			spin_unlock(&child->d_lock);
-+		}
-+		spin_unlock(&dcache_lock);
-+
-+		list_for_each_entry_safe(child, next, &list, d_lru) {
-+			spin_lock(&child->d_lock);
-+			list_del_init(&child->d_lru);
-+			spin_unlock(&child->d_lock);
-+
-+			shmem_unlink(dentry->d_inode, child);
-+		}
-+	}
-+}
-+
- static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
- {
- 	if (!simple_empty(dentry))
- 		return -ENOTEMPTY;
- 
-+	/* Remove whiteouts from logical empty directory */
-+	shmem_dir_unlink_whiteouts(dir, dentry);
- 	drop_nlink(dentry->d_inode);
- 	drop_nlink(dir);
- 	return shmem_unlink(dir, dentry);
-@@ -1905,7 +2059,7 @@ static int shmem_rmdir(struct inode *dir
- /*
-  * The VFS layer already does all the dentry stuff for rename,
-  * we just have to decrement the usage count for the target if
-- * it exists so that the VFS layer correctly free's it when it
-+ * it exists so that the VFS layer correctly frees it when it
-  * gets overwritten.
-  */
- static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
-@@ -1916,7 +2070,12 @@ static int shmem_rename(struct inode *ol
- 	if (!simple_empty(new_dentry))
- 		return -ENOTEMPTY;
- 
-+	if (d_is_whiteout(new_dentry))
-+		shmem_unlink(new_dir, new_dentry);
-+
- 	if (new_dentry->d_inode) {
-+		/* Remove whiteouts from logical empty directory */
-+		shmem_dir_unlink_whiteouts(new_dir, new_dentry);
- 		(void) shmem_unlink(new_dir, new_dentry);
- 		if (they_are_dirs)
- 			drop_nlink(old_dir);
-@@ -1981,12 +2140,12 @@ static int shmem_symlink(struct inode *d
- 		unlock_page(page);
- 		page_cache_release(page);
- 	}
-+
-+	shmem_d_instantiate(dir, dentry, inode);
-+
- 	if (dir->i_mode & S_ISGID)
- 		inode->i_gid = dir->i_gid;
--	dir->i_size += BOGO_DIRENT_SIZE;
- 	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
--	d_instantiate(dentry, inode);
--	dget(dentry);
- 	return 0;
- }
- 
-@@ -2363,6 +2522,12 @@ int shmem_fill_super(struct super_block 
- 	if (!root)
- 		goto failed_iput;
- 	sb->s_root = root;
-+
-+#ifdef CONFIG_TMPFS
-+	if (!(sb->s_flags & MS_NOUSER))
-+		sb->s_flags |= MS_WHITEOUT;
-+#endif
-+
- 	return 0;
- 
- failed_iput:
-@@ -2463,6 +2628,8 @@ static const struct inode_operations shm
- 	.rmdir		= shmem_rmdir,
- 	.mknod		= shmem_mknod,
- 	.rename		= shmem_rename,
-+	.whiteout       = shmem_whiteout,
-+	.fallthru       = shmem_fallthru,
- #endif
- #ifdef CONFIG_TMPFS_POSIX_ACL
- 	.setattr	= shmem_notify_change,

target/linux/generic-2.6/patches-2.6.32/231-union_mounts_bind_fix.patch

@@ -1,11 +0,0 @@
---- a/fs/namespace.c
-+++ b/fs/namespace.c
-@@ -1550,7 +1550,7 @@ static int do_loopback(struct path *path
- 	if (!mnt)
- 		goto out;
- 
--	err = check_union_mnt(&old_path, mnt, mnt_flags);
-+	err = check_union_mnt(path, mnt, mnt_flags);
- 	if (err)
- 		goto out;
- 

target/linux/generic-2.6/patches-2.6.32/232-union_mounts_compile_fix.patch

@@ -1,11 +0,0 @@
---- a/include/linux/union.h
-+++ b/include/linux/union.h
-@@ -77,7 +77,7 @@ extern int union_permission(struct path 
- #define __union_copyup(x, y, z)		({ BUG(); (0); })
- #define union_copyup(x, y)		({ (0); })
- #define union_copyup_dir(x)		({ BUG(); (0); })
--#define union_permission(x, y)		inode_permission(x->dentry->d_inode, y)
-+#define union_permission(x, y)		inode_permission((x)->dentry->d_inode, y)
- 
- #endif	/* CONFIG_UNION_MOUNT */
- #endif	/* __KERNEL__ */

target/linux/generic-2.6/patches-2.6.32/233-jffs2_whiteout_support.patch

@@ -1,186 +0,0 @@
---- a/fs/jffs2/dir.c
-+++ b/fs/jffs2/dir.c
-@@ -34,6 +34,9 @@ static int jffs2_mknod (struct inode *,s
- static int jffs2_rename (struct inode *, struct dentry *,
- 			 struct inode *, struct dentry *);
- 
-+static int jffs2_whiteout (struct inode *, struct dentry *, struct dentry *);
-+static int jffs2_fallthru (struct inode *, struct dentry *);
-+
- const struct file_operations jffs2_dir_operations =
- {
- 	.read =		generic_read_dir,
-@@ -55,6 +58,8 @@ const struct inode_operations jffs2_dir_
- 	.rmdir =	jffs2_rmdir,
- 	.mknod =	jffs2_mknod,
- 	.rename =	jffs2_rename,
-+	.fallthru =     jffs2_fallthru,
-+	.whiteout =     jffs2_whiteout,
- 	.check_acl =	jffs2_check_acl,
- 	.setattr =	jffs2_setattr,
- 	.setxattr =	jffs2_setxattr,
-@@ -98,8 +103,21 @@ static struct dentry *jffs2_lookup(struc
- 			fd = fd_list;
- 		}
- 	}
--	if (fd)
--		ino = fd->ino;
-+	if (fd) {
-+		spin_lock(&target->d_lock);
-+		switch(fd->type) {
-+		case DT_WHT:
-+			target->d_flags |= DCACHE_WHITEOUT;
-+			break;
-+		case DT_UNKNOWN:
-+			target->d_flags |= DCACHE_FALLTHRU;
-+			break;
-+		default:
-+			ino = fd->ino;
-+			break;
-+		}
-+		spin_unlock(&target->d_lock);
-+	}
- 	mutex_unlock(&dir_f->sem);
- 	if (ino) {
- 		inode = jffs2_iget(dir_i->i_sb, ino);
-@@ -155,7 +173,9 @@ static int jffs2_readdir(struct file *fi
- 				  fd->name, fd->ino, fd->type, curofs, offset));
- 			continue;
- 		}
--		if (!fd->ino) {
-+		if (fd->type == DT_UNKNOWN)
-+			fd->ino = 100; /* XXX: arbitrary */
-+		else if (!fd->ino && (fd->type != DT_WHT)) {
- 			D2(printk(KERN_DEBUG "Skipping deletion dirent \"%s\"\n", fd->name));
- 			offset++;
- 			continue;
-@@ -498,6 +518,11 @@ static int jffs2_mkdir (struct inode *di
- 		return PTR_ERR(inode);
- 	}
- 
-+	if (dentry->d_flags & DCACHE_WHITEOUT) {
-+		inode->i_flags |= S_OPAQUE;
-+		ri->flags = cpu_to_je16(JFFS2_INO_FLAG_OPAQUE);
-+	}
-+
- 	inode->i_op = &jffs2_dir_inode_operations;
- 	inode->i_fop = &jffs2_dir_operations;
- 
-@@ -779,6 +804,82 @@ static int jffs2_mknod (struct inode *di
- 	return 0;
- }
- 
-+static int jffs2_fallthru (struct inode *dir, struct dentry *dentry)
-+{
-+	struct jffs2_sb_info *c = JFFS2_SB_INFO(dir->i_sb);
-+	uint32_t now;
-+	int ret;
-+
-+	now = get_seconds();
-+	ret = jffs2_do_link(c, JFFS2_INODE_INFO(dir), 0, DT_UNKNOWN,
-+			    dentry->d_name.name, dentry->d_name.len, now);
-+	if (ret)
-+		return ret;
-+
-+	d_instantiate(dentry, NULL);
-+	spin_lock(&dentry->d_lock);
-+	dentry->d_flags |= DCACHE_FALLTHRU;
-+	spin_unlock(&dentry->d_lock);
-+
-+	return 0;
-+}
-+
-+static int jffs2_whiteout (struct inode *dir, struct dentry *old_dentry,
-+			   struct dentry *new_dentry)
-+{
-+	struct jffs2_sb_info *c = JFFS2_SB_INFO(dir->i_sb);
-+	struct jffs2_inode_info *victim_f = NULL;
-+	uint32_t now;
-+	int ret;
-+
-+	/* If it's a directory, then check whether it is really empty
-+	 */
-+	if (new_dentry->d_inode) {
-+		victim_f = JFFS2_INODE_INFO(old_dentry->d_inode);
-+		if (S_ISDIR(old_dentry->d_inode->i_mode)) {
-+			struct jffs2_full_dirent *fd;
-+
-+			mutex_lock(&victim_f->sem);
-+			for (fd = victim_f->dents; fd; fd = fd->next) {
-+				if (fd->ino) {
-+					mutex_unlock(&victim_f->sem);
-+					return -ENOTEMPTY;
-+				}
-+			}
-+			mutex_unlock(&victim_f->sem);
-+		}
-+	}
-+
-+	now = get_seconds();
-+	ret = jffs2_do_link(c, JFFS2_INODE_INFO(dir), 0, DT_WHT,
-+			    new_dentry->d_name.name, new_dentry->d_name.len, now);
-+	if (ret)
-+		return ret;
-+
-+	spin_lock(&new_dentry->d_lock);
-+	new_dentry->d_flags &= ~DCACHE_FALLTHRU;
-+	new_dentry->d_flags |= DCACHE_WHITEOUT;
-+	spin_unlock(&new_dentry->d_lock);
-+	d_add(new_dentry, NULL);
-+
-+	if (victim_f) {
-+		/* There was a victim. Kill it off nicely */
-+		drop_nlink(old_dentry->d_inode);
-+		/* Don't oops if the victim was a dirent pointing to an
-+		   inode which didn't exist. */
-+		if (victim_f->inocache) {
-+			mutex_lock(&victim_f->sem);
-+			if (S_ISDIR(old_dentry->d_inode->i_mode))
-+				victim_f->inocache->pino_nlink = 0;
-+			else
-+				victim_f->inocache->pino_nlink--;
-+			mutex_unlock(&victim_f->sem);
-+		}
-+	}
-+
-+	return 0;
-+}
-+
- static int jffs2_rename (struct inode *old_dir_i, struct dentry *old_dentry,
- 			 struct inode *new_dir_i, struct dentry *new_dentry)
- {
---- a/fs/jffs2/fs.c
-+++ b/fs/jffs2/fs.c
-@@ -301,6 +301,10 @@ struct inode *jffs2_iget(struct super_bl
- 
- 		inode->i_op = &jffs2_dir_inode_operations;
- 		inode->i_fop = &jffs2_dir_operations;
-+
-+		if (je16_to_cpu(latest_node.flags) & JFFS2_INO_FLAG_OPAQUE)
-+			inode->i_flags |= S_OPAQUE;
-+
- 		break;
- 	}
- 	case S_IFREG:
---- a/fs/jffs2/super.c
-+++ b/fs/jffs2/super.c
-@@ -172,7 +172,7 @@ static int jffs2_fill_super(struct super
- 
- 	sb->s_op = &jffs2_super_operations;
- 	sb->s_export_op = &jffs2_export_ops;
--	sb->s_flags = sb->s_flags | MS_NOATIME;
-+	sb->s_flags = sb->s_flags | MS_NOATIME | MS_WHITEOUT;
- 	sb->s_xattr = jffs2_xattr_handlers;
- #ifdef CONFIG_JFFS2_FS_POSIX_ACL
- 	sb->s_flags |= MS_POSIXACL;
---- a/include/linux/jffs2.h
-+++ b/include/linux/jffs2.h
-@@ -87,6 +87,8 @@
- #define JFFS2_INO_FLAG_USERCOMPR  2	/* User has requested a specific
- 					   compression type */
- 
-+#define JFFS2_INO_FLAG_OPAQUE     4	/* Directory is opaque (for union mounts) */
-+
- 
- /* These can go once we've made sure we've caught all uses without
-    byteswapping */

target/linux/generic-2.6/patches-2.6.32/234-union_mounts_no_debug.patch

@@ -1,30 +0,0 @@
---- a/fs/union.c
-+++ b/fs/union.c
-@@ -842,10 +842,8 @@ static int union_copyup_dir_one(void *bu
- 	/* Lookup this entry in the topmost directory */
- 	dentry = lookup_one_len(name, topmost_dentry, namlen);
- 
--	if (IS_ERR(dentry)) {
--		printk(KERN_INFO "error looking up %s\n", dentry->d_name.name);
-+	if (IS_ERR(dentry))
- 		goto out;
--	}
- 
- 	/*
- 	 * If the entry already exists, one of the following is true:
-@@ -857,7 +855,6 @@ static int union_copyup_dir_one(void *bu
- 	 */
- 	if (dentry->d_inode || d_is_whiteout(dentry) ||
- 	    d_is_fallthru(dentry)) {
--		printk(KERN_INFO "skipping copy of %s\n", dentry->d_name.name);
- 		goto out_dput;
- 	}
- 
-@@ -867,7 +864,6 @@ static int union_copyup_dir_one(void *bu
- 	 * used, so each file system must implement its own way of
- 	 * storing a fallthru entry.
- 	 */
--	printk(KERN_INFO "creating fallthru for %s\n", dentry->d_name.name);
- 	err = topmost_dentry->d_inode->i_op->fallthru(topmost_dentry->d_inode,
- 						      dentry);
- 	/* FIXME */

target/linux/generic-2.6/patches-2.6.32/235-union_mount_fixes.patch

@@ -1,117 +0,0 @@
---- a/fs/namespace.c
-+++ b/fs/namespace.c
-@@ -1656,8 +1656,10 @@ static int do_move_mount(struct path *pa
- 
- 	/* moving to or from a union mount is not supported */
- 	err = -EINVAL;
-+#if 0
- 	if (IS_MNT_UNION(path->mnt))
- 		goto exit;
-+#endif
- 	if (IS_MNT_UNION(old_path.mnt))
- 		goto exit;
- 
---- a/fs/union.c
-+++ b/fs/union.c
-@@ -260,8 +260,6 @@ int append_to_union(struct vfsmount *mnt
- 	spin_lock(&union_lock);
- 	um = union_lookup(dentry, mnt);
- 	if (um) {
--		BUG_ON((um->u_next.dentry != dest_dentry) ||
--		       (um->u_next.mnt != dest_mnt));
- 		spin_unlock(&union_lock);
- 		union_put(this);
- 		return 0;
-@@ -274,6 +272,23 @@ int append_to_union(struct vfsmount *mnt
- 	return 0;
- }
- 
-+int follow_union_mountpoint(struct path *path)
-+{
-+	struct path new_path = *path;
-+
-+	path_get(&new_path);
-+	while (follow_union_down(&new_path)) {
-+		if (new_path.dentry != new_path.mnt->mnt_root)
-+			continue;
-+
-+		path_put(path);
-+		*path = new_path;
-+		return 1;
-+	}
-+	path_put(&new_path);
-+	return 0;
-+}
-+
- /*
-  * follow_union_down - follow the union stack one layer down
-  *
---- a/include/linux/union.h
-+++ b/include/linux/union.h
-@@ -47,6 +47,7 @@ extern int append_to_union(struct vfsmou
- 			   struct vfsmount *, struct dentry *);
- extern int follow_union_down(struct path *);
- extern int follow_union_mount(struct path *);
-+extern int follow_union_mountpoint(struct path *path);
- extern void __d_drop_unions(struct dentry *);
- extern void shrink_d_unions(struct dentry *);
- extern void __shrink_d_unions(struct dentry *, struct list_head *);
-@@ -68,6 +69,7 @@ extern int union_permission(struct path 
- #define append_to_union(x1, y1, x2, y2)	({ BUG(); (0); })
- #define follow_union_down(x)		({ (0); })
- #define follow_union_mount(x)	({ (0); })
-+#define follow_union_mountpoint(x)	({ (0); })
- #define __d_drop_unions(x)		do { } while (0)
- #define shrink_d_unions(x)		do { } while (0)
- #define __shrink_d_unions(x,y)		do { } while (0)
---- a/fs/namei.c
-+++ b/fs/namei.c
-@@ -626,6 +626,9 @@ static int cache_lookup_union(struct nam
- 		    !S_ISDIR(path->dentry->d_inode->i_mode))
- 			goto out;
- 
-+		if (follow_union_mountpoint(path))
-+			goto out;
-+
- 		/* Build the union stack for this part */
- 		res = __cache_lookup_build_union(nd, name, path);
- 		if (res) {
-@@ -892,6 +895,9 @@ static int real_lookup_union(struct name
- 	    !S_ISDIR(path->dentry->d_inode->i_mode))
- 		goto out;
- 
-+	if (follow_union_mountpoint(path))
-+		goto out;
-+
- 	/* Build the union stack for this part */
- 	res = __real_lookup_build_union(nd, name, path);
- 	if (res) {
-@@ -1813,6 +1819,9 @@ int hash_lookup_union(struct nameidata *
- 	    !S_ISDIR(path->dentry->d_inode->i_mode))
- 		goto out;
- 
-+	if (follow_union_mountpoint(path))
-+		goto out;
-+
- 	/* Build the union stack for this part */
- 	res = __hash_lookup_build_union(nd, name, path);
- 	if (res) {
---- a/fs/readdir.c
-+++ b/fs/readdir.c
-@@ -17,6 +17,7 @@
- #include <linux/syscalls.h>
- #include <linux/unistd.h>
- #include <linux/union.h>
-+#include <linux/mount.h>
- 
- #include <asm/uaccess.h>
- 
-@@ -45,7 +46,7 @@ int vfs_readdir(struct file *file, filld
- 		 * below this one in the union stack.
- 		 */
- 		if (is_unionized(file->f_path.dentry, file->f_path.mnt) &&
--		    !IS_OPAQUE(inode)) {
-+		    !IS_OPAQUE(inode) && IS_MNT_UNION(file->f_path.mnt)) {
- 			res = union_copyup_dir(&file->f_path);
- 			if (res)
- 				goto out_unlock;