Commit 00473374 authored May 04, 2017 by Jan Kara Committed by Theodore Ts'o May 04, 2017

ext4: mark superblock writes synchronous for nobarrier mounts



Commit b685d3d6 "block: treat REQ_FUA and REQ_PREFLUSH as
synchronous" removed REQ_SYNC flag from WRITE_FUA implementation.
generic_make_request_checks() however strips REQ_FUA flag from a bio
when the storage doesn't report volatile write cache and thus write
effectively becomes asynchronous which can lead to performance
regressions. This affects superblock writes for ext4. Fix the problem
by marking superblock writes always as synchronous.

Fixes: b685d3d6
CC: linux-ext4@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

parent aa1dca3b

fs/ext4/super.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -4637,7 +4637,7 @@ static int ext4_commit_super(struct super_block *sb, int sync)
		if (sync) {
		unlock_buffer(sbh);
		error = __sync_dirty_buffer(sbh,
		test_opt(sb, BARRIER) ? REQ_FUA : REQ_SYNC);
		REQ_SYNC \| (test_opt(sb, BARRIER) ? REQ_FUA : 0));
		if (error)
		return error;

Admin message