Re: [PATCH 6/7] btrfs: Make flush bios explicitely sync
From: Liu Bo <hidden>
Date: 2017-05-09 19:11:12
Also in:
linux-fsdevel
On Tue, May 02, 2017 at 05:03:50PM +0200, Jan Kara wrote:
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.Reviewed-by: Liu Bo <redacted> Thanks, -liubo
quoted hunk ↗ jump to hunk
CC: David Sterba <dsterba@suse.com> CC: linux-btrfs@vger.kernel.org Fixes: b685d3d65ac791406e0dfd8779cc9b3707fea5a3 Signed-off-by: Jan Kara <jack@suse.cz> --- fs/btrfs/disk-io.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index eb1ee7b6f532..af75a9aab81e 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c@@ -3488,10 +3488,12 @@ static int write_dev_supers(struct btrfs_device *device, * we fua the first super. The others we allow * to go down lazy. */ - if (i == 0) - ret = btrfsic_submit_bh(REQ_OP_WRITE, REQ_FUA, bh); - else + if (i == 0) { + ret = btrfsic_submit_bh(REQ_OP_WRITE, + REQ_SYNC | REQ_FUA, bh); + } else { ret = btrfsic_submit_bh(REQ_OP_WRITE, REQ_SYNC, bh); + } if (ret) errors++; }@@ -3555,7 +3557,7 @@ static int write_dev_flush(struct btrfs_device *device, int wait) bio->bi_end_io = btrfs_end_empty_barrier; bio->bi_bdev = device->bdev; - bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH; + bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH; init_completion(&device->flush_wait); bio->bi_private = &device->flush_wait; device->flush_bio = bio;-- 2.12.0