Patch "jbd2: fix dbench4 performance regression for 'nobarrier' mounts" has been added to the 4.10-stable tree

Patch "jbd2: fix dbench4 performance regression for 'nobarrier' mounts" has been added to the 4.10-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    jbd2: fix dbench4 performance regression for 'nobarrier' mounts

to the 4.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     jbd2-fix-dbench4-performance-regression-for-nobarrier-mounts.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 5052b069acf73866d00077d8bc49983c3ee903e5 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Sat, 29 Apr 2017 21:07:30 -0400
Subject: jbd2: fix dbench4 performance regression for 'nobarrier' mounts

From: Jan Kara <jack@suse.cz>

commit 5052b069acf73866d00077d8bc49983c3ee903e5 upstream.

Commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as
synchronous" removed REQ_SYNC flag from WRITE_FUA implementation. Since
JBD2 strips REQ_FUA and REQ_FLUSH flags from submitted IO when the
filesystem is mounted with nobarrier mount option, journal superblock
writes ended up being async writes after this patch and that caused
heavy performance regression for dbench4 benchmark with high number of
processes. In my test setup with HP RAID array with non-volatile write
cache and 32 GB ram, dbench4 runs with 8 processes regressed by ~25%.

Fix the problem by making sure journal superblock writes are always
treated as synchronous since they generally block progress of the
journalling machinery and thus the whole filesystem.

Fixes: b685d3d65ac791406e0dfd8779cc9b3707fea5a3
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/jbd2/journal.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1348,7 +1348,7 @@ static int jbd2_write_superblock(journal
 	jbd2_superblock_csum_set(journal, sb);
 	get_bh(bh);
 	bh->b_end_io = end_buffer_write_sync;
-	ret = submit_bh(REQ_OP_WRITE, write_flags, bh);
+	ret = submit_bh(REQ_OP_WRITE, write_flags | REQ_SYNC, bh);
 	wait_on_buffer(bh);
 	if (buffer_write_io_error(bh)) {
 		clear_buffer_write_io_error(bh);


Patches currently in stable-queue which might be from jack@suse.cz are

queue-4.10/fs-block_dev-always-invalidate-cleancache-in-invalidate_bdev.patch
queue-4.10/jbd2-fix-dbench4-performance-regression-for-nobarrier-mounts.patch