linux-mainline 3.8: backport sync(2) fix from 3.11

Signed-off-by: Koen Kooi <[email protected]>

common-bsp/recipes-kernel/linux/linux-mainline-3.8/fixes/0001-sync-don-t-block-the-flusher-thread-waiting-on-IO.patch

@@ -0,0 +1,114 @@
+From 4e3f4e9a8f2076743265cb4e76e3d26827325d5a Mon Sep 17 00:00:00 2001
+From: Dave Chinner <[email protected]>
+Date: Tue, 2 Jul 2013 22:38:35 +1000
+Subject: [PATCH] sync: don't block the flusher thread waiting on IO
+
+When sync does it's WB_SYNC_ALL writeback, it issues data Io and
+then immediately waits for IO completion. This is done in the
+context of the flusher thread, and hence completely ties up the
+flusher thread for the backing device until all the dirty inodes
+have been synced. On filesystems that are dirtying inodes constantly
+and quickly, this means the flusher thread can be tied up for
+minutes per sync call and hence badly affect system level write IO
+performance as the page cache cannot be cleaned quickly.
+
+We already have a wait loop for IO completion for sync(2), so cut
+this out of the flusher thread and delegate it to wait_sb_inodes().
+Hence we can do rapid IO submission, and then wait for it all to
+complete.
+
+Effect of sync on fsmark before the patch:
+
+FSUse%        Count         Size    Files/sec     App Overhead
+.....
+     0       640000         4096      35154.6          1026984
+     0       720000         4096      36740.3          1023844
+     0       800000         4096      36184.6           916599
+     0       880000         4096       1282.7          1054367
+     0       960000         4096       3951.3           918773
+     0      1040000         4096      40646.2           996448
+     0      1120000         4096      43610.1           895647
+     0      1200000         4096      40333.1           921048
+
+And a single sync pass took:
+
+  real    0m52.407s
+  user    0m0.000s
+  sys     0m0.090s
+
+After the patch, there is no impact on fsmark results, and each
+individual sync(2) operation run concurrently with the same fsmark
+workload takes roughly 7s:
+
+  real    0m6.930s
+  user    0m0.000s
+  sys     0m0.039s
+
+IOWs, sync is 7-8x faster on a busy filesystem and does not have an
+adverse impact on ongoing async data write operations.
+
+Signed-off-by: Dave Chinner <[email protected]>
+Reviewed-by: Jan Kara <[email protected]>
+Signed-off-by: Linus Torvalds <[email protected]>
+---
+ fs/fs-writeback.c         | 9 +++++++--
+ include/linux/writeback.h | 1 +
+ 2 files changed, 8 insertions(+), 2 deletions(-)
+
+diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
+index 310972b..c5862a9 100644
+--- a/fs/fs-writeback.c
++++ b/fs/fs-writeback.c
+@@ -46,6 +46,7 @@ struct wb_writeback_work {
+ 	unsigned int for_kupdate:1;
+ 	unsigned int range_cyclic:1;
+ 	unsigned int for_background:1;
++	unsigned int for_sync:1;	/* sync(2) WB_SYNC_ALL writeback */
+ 	enum wb_reason reason;		/* why was writeback initiated? */
+
+ 	struct list_head list;		/* pending work list */
+@@ -455,9 +456,11 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
+ 	/*
+ 	 * Make sure to wait on the data before writing out the metadata.
+ 	 * This is important for filesystems that modify metadata on data
+-	 * I/O completion.
++	 * I/O completion. We don't do it for sync(2) writeback because it has a
++	 * separate, external IO completion path and ->sync_fs for guaranteeing
++	 * inode metadata is written back correctly.
+ 	 */
+-	if (wbc->sync_mode == WB_SYNC_ALL) {
++	if (wbc->sync_mode == WB_SYNC_ALL && !wbc->for_sync) {
+ 		int err = filemap_fdatawait(mapping);
+ 		if (ret == 0)
+ 			ret = err;
+@@ -590,6 +593,7 @@ static long writeback_sb_inodes(struct super_block *sb,
+ 		.tagged_writepages	= work->tagged_writepages,
+ 		.for_kupdate		= work->for_kupdate,
+ 		.for_background		= work->for_background,
++		.for_sync		= work->for_sync,
+ 		.range_cyclic		= work->range_cyclic,
+ 		.range_start		= 0,
+ 		.range_end		= LLONG_MAX,
+@@ -1391,6 +1395,7 @@ void sync_inodes_sb(struct super_block *sb)
+ 		.range_cyclic	= 0,
+ 		.done		= &done,
+ 		.reason		= WB_REASON_SYNC,
++		.for_sync	= 1,
+ 	};
+
+ 	/* Nothing to do? */
+diff --git a/include/linux/writeback.h b/include/linux/writeback.h
+index b82a83a..7aa94e5 100644
+--- a/include/linux/writeback.h
++++ b/include/linux/writeback.h
+@@ -77,6 +77,7 @@ struct writeback_control {
+ 	unsigned tagged_writepages:1;	/* tag-and-write to avoid livelock */
+ 	unsigned for_reclaim:1;		/* Invoked from the page allocator */
+ 	unsigned range_cyclic:1;	/* range_start is cyclic */
++	unsigned for_sync:1;		/* sync(2) WB_SYNC_ALL writeback */
+ };
+
+ /*
+-- 
+1.8.2.1
+

common-bsp/recipes-kernel/linux/linux-mainline_3.8.bb

@@ -700,6 +700,7 @@ SRC_URI += " \
 	file://capes/0015-DT-overlay-for-BeBoPr-with-enable-patch-and-BeagleBo.patch \
 	file://capes/0016-DT-overlay-for-BeBoPr-Bridge-and-BeagleBone-any-colo.patch \
 	file://capes/0017-Removed-Whitelist-and-Blacklist-Modes-From-HDMI-Devi.patch \
+	file://fixes/0001-sync-don-t-block-the-flusher-thread-waiting-on-IO.patch \
 	file://defconfig \
   file://am335x-pm-firmware.bin \
   file://logo_linux_clut224.ppm \