md: Make flush bios explicitely sync
authorJan Kara <jack@suse.cz>
Wed, 31 May 2017 07:44:33 +0000 (09:44 +0200)
committerShaohua Li <shli@fb.com>
Wed, 31 May 2017 16:25:53 +0000 (09:25 -0700)
commit5a8948f8a32ba56c17b3fb75d318ac98157f3ba5
tree7e44dac2d01cddccb74415a51d3df9a45d913502
parente153903686deac9ea8c499b49516126f1a844fdb
md: Make flush bios explicitely sync

Commit b685d3d65ac7 "block: treat REQ_FUA and REQ_PREFLUSH as
synchronous" removed REQ_SYNC flag from WRITE_{FUA|PREFLUSH|...}
definitions.  generic_make_request_checks() however strips REQ_FUA and
REQ_PREFLUSH flags from a bio when the storage doesn't report volatile
write cache and thus write effectively becomes asynchronous which can
lead to performance regressions

Fix the problem by making sure all bios which are synchronous are
properly marked with REQ_SYNC.

CC: linux-raid@vger.kernel.org
CC: Shaohua Li <shli@kernel.org>
Fixes: b685d3d65ac791406e0dfd8779cc9b3707fea5a3
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Shaohua Li <shli@fb.com>
drivers/md/md.c
drivers/md/raid5-cache.c
drivers/md/raid5-ppl.c