union mounts: fix various bugs related to handling of mountpoints and copyups

SVN-Revision: 17777

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

@@ -0,0 +1,117 @@
+--- 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;