From 00473374b72a6e5aba01af083f0d5100f3151210 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Thu, 4 May 2017 10:58:03 -0400 Subject: [PATCH] ext4: mark superblock writes synchronous for nobarrier mounts Commit b685d3d65ac7 "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: b685d3d65ac791406e0dfd8779cc9b3707fea5a3 CC: linux-ext4@vger.kernel.org Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o --- fs/ext4/super.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 9a40e0c16dcc..931053cf20d6 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -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; -- 2.30.2