kernel: backport ubifs support for dirty_writeback_interval

These patches were queued for 4.10. For possible use cases see added:
[PATCH] ubifs: Use dirty_writeback_interval value for wbuf timer

Signed-off-by: Rafał Miłecki <[email protected]>

target/linux/generic/patches-4.4/053-0001-ubifs-Drop-softlimit-and-delta-fields-from-struct-ub.patch

@@ -0,0 +1,82 @@
+From 854826c9d526fd81077742c3b000e3f7fcaef3ce Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <[email protected]>
+Date: Tue, 20 Sep 2016 10:36:14 +0200
+Subject: [PATCH] ubifs: Drop softlimit and delta fields from struct ubifs_wbuf
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Values of these fields are set during init and never modified. They are
+used (read) in a single function only. There isn't really any reason to
+keep them in a struct. It only makes struct just a bit bigger without
+any visible gain.
+
+Signed-off-by: Rafał Miłecki <[email protected]>
+Reviewed-by: Boris Brezillon <[email protected]>
+Signed-off-by: Richard Weinberger <[email protected]>
+---
+ fs/ubifs/io.c    | 18 ++++++++++--------
+ fs/ubifs/ubifs.h |  5 -----
+ 2 files changed, 10 insertions(+), 13 deletions(-)
+
+--- a/fs/ubifs/io.c
++++ b/fs/ubifs/io.c
+@@ -452,16 +452,22 @@ static enum hrtimer_restart wbuf_timer_c
+  */
+ static void new_wbuf_timer_nolock(struct ubifs_wbuf *wbuf)
+ {
++	ktime_t softlimit = ktime_set(WBUF_TIMEOUT_SOFTLIMIT, 0);
++	unsigned long long delta;
++
++	delta = WBUF_TIMEOUT_HARDLIMIT - WBUF_TIMEOUT_SOFTLIMIT;
++	delta *= 1000000000ULL;
++
+ 	ubifs_assert(!hrtimer_active(&wbuf->timer));
++	ubifs_assert(delta <= ULONG_MAX);
+ 
+ 	if (wbuf->no_timer)
+ 		return;
+ 	dbg_io("set timer for jhead %s, %llu-%llu millisecs",
+ 	       dbg_jhead(wbuf->jhead),
+-	       div_u64(ktime_to_ns(wbuf->softlimit), USEC_PER_SEC),
+-	       div_u64(ktime_to_ns(wbuf->softlimit) + wbuf->delta,
+-		       USEC_PER_SEC));
+-	hrtimer_start_range_ns(&wbuf->timer, wbuf->softlimit, wbuf->delta,
++	       div_u64(ktime_to_ns(softlimit), USEC_PER_SEC),
++	       div_u64(ktime_to_ns(softlimit) + delta, USEC_PER_SEC));
++	hrtimer_start_range_ns(&wbuf->timer, softlimit, delta,
+ 			       HRTIMER_MODE_REL);
+ }
+ 
+@@ -1059,10 +1065,6 @@ int ubifs_wbuf_init(struct ubifs_info *c
+ 
+ 	hrtimer_init(&wbuf->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ 	wbuf->timer.function = wbuf_timer_callback_nolock;
+-	wbuf->softlimit = ktime_set(WBUF_TIMEOUT_SOFTLIMIT, 0);
+-	wbuf->delta = WBUF_TIMEOUT_HARDLIMIT - WBUF_TIMEOUT_SOFTLIMIT;
+-	wbuf->delta *= 1000000000ULL;
+-	ubifs_assert(wbuf->delta <= ULONG_MAX);
+ 	return 0;
+ }
+ 
+--- a/fs/ubifs/ubifs.h
++++ b/fs/ubifs/ubifs.h
+@@ -668,9 +668,6 @@ typedef int (*ubifs_lpt_scan_callback)(s
+  * @io_mutex: serializes write-buffer I/O
+  * @lock: serializes @buf, @lnum, @offs, @avail, @used, @next_ino and @inodes
+  *        fields
+- * @softlimit: soft write-buffer timeout interval
+- * @delta: hard and soft timeouts delta (the timer expire interval is @softlimit
+- *         and @softlimit + @delta)
+  * @timer: write-buffer timer
+  * @no_timer: non-zero if this write-buffer does not have a timer
+  * @need_sync: non-zero if the timer expired and the wbuf needs sync'ing
+@@ -699,8 +696,6 @@ struct ubifs_wbuf {
+ 	int (*sync_callback)(struct ubifs_info *c, int lnum, int free, int pad);
+ 	struct mutex io_mutex;
+ 	spinlock_t lock;
+-	ktime_t softlimit;
+-	unsigned long long delta;
+ 	struct hrtimer timer;
+ 	unsigned int no_timer:1;
+ 	unsigned int need_sync:1;

target/linux/generic/patches-4.4/053-0002-ubifs-Use-dirty_writeback_interval-value-for-wbuf-ti.patch

@@ -0,0 +1,66 @@
+From 1b7fc2c0069f3864a3dda15430b7aded31c0bfcc Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <[email protected]>
+Date: Tue, 20 Sep 2016 10:36:15 +0200
+Subject: [PATCH] ubifs: Use dirty_writeback_interval value for wbuf timer
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Right now wbuf timer has hardcoded timeouts and there is no place for
+manual adjustments. Some projects / cases many need that though. Few
+file systems allow doing that by respecting dirty_writeback_interval
+that can be set using sysctl (dirty_writeback_centisecs).
+
+Lowering dirty_writeback_interval could be some way of dealing with user
+space apps lacking proper fsyncs. This is definitely *not* a perfect
+solution but we don't have ideal (user space) world. There were already
+advanced discussions on this matter, mostly when ext4 was introduced and
+it wasn't behaving as ext3. Anyway, the final decision was to add some
+hacks to the ext4, as trying to fix whole user space or adding new API
+was pointless.
+
+We can't (and shouldn't?) just follow ext4. We can't e.g. sync on close
+as this would cause too many commits and flash wearing. On the other
+hand we still should allow some trade-off between -o sync and default
+wbuf timeout. Respecting dirty_writeback_interval should allow some sane
+cutomizations if used warily.
+
+Signed-off-by: Rafał Miłecki <[email protected]>
+Reviewed-by: Boris Brezillon <[email protected]>
+Signed-off-by: Richard Weinberger <[email protected]>
+---
+ fs/ubifs/io.c    | 8 ++++----
+ fs/ubifs/ubifs.h | 4 ----
+ 2 files changed, 4 insertions(+), 8 deletions(-)
+
+--- a/fs/ubifs/io.c
++++ b/fs/ubifs/io.c
+@@ -452,11 +452,11 @@ static enum hrtimer_restart wbuf_timer_c
+  */
+ static void new_wbuf_timer_nolock(struct ubifs_wbuf *wbuf)
+ {
+-	ktime_t softlimit = ktime_set(WBUF_TIMEOUT_SOFTLIMIT, 0);
+-	unsigned long long delta;
++	ktime_t softlimit = ms_to_ktime(dirty_writeback_interval * 10);
++	unsigned long long delta = dirty_writeback_interval;
+ 
+-	delta = WBUF_TIMEOUT_HARDLIMIT - WBUF_TIMEOUT_SOFTLIMIT;
+-	delta *= 1000000000ULL;
++	/* centi to milli, milli to nano, then 10% */
++	delta *= 10ULL * NSEC_PER_MSEC / 10ULL;
+ 
+ 	ubifs_assert(!hrtimer_active(&wbuf->timer));
+ 	ubifs_assert(delta <= ULONG_MAX);
+--- a/fs/ubifs/ubifs.h
++++ b/fs/ubifs/ubifs.h
+@@ -106,10 +106,6 @@
+  */
+ #define BGT_NAME_PATTERN "ubifs_bgt%d_%d"
+ 
+-/* Write-buffer synchronization timeout interval in seconds */
+-#define WBUF_TIMEOUT_SOFTLIMIT 3
+-#define WBUF_TIMEOUT_HARDLIMIT 5
+-
+ /* Maximum possible inode number (only 32-bit inodes are supported now) */
+ #define MAX_INUM 0xFFFFFFFF
+