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ext4: mark superblock writes synchronous for nobarrier mounts

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Commit b685d3d65a "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: b685d3d65a
CC: linux-ext4@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jan Kara
2017-05-04 10:58:03 -04:00
committed by Theodore Ts'o
parent aa1dca3bd9
commit 00473374b7
1 changed files with 1 additions and 1 deletions
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fs/ext4/super.c
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@@ -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;