From 3124668ab255a53e5c612b52e8c329bc614733af Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 2 May 2017 17:03:50 +0200 Subject: [PATCH] btrfs: Make flush bios explicitely sync Commit 8eecb540590c "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: David Sterba CC: linux-btrfs@vger.kernel.org Fixes: 8eecb540590c70d97c0366ea02a6a436c87fa8ef Signed-off-by: Jan Kara Reviewed-by: Liu Bo Signed-off-by: David Sterba --- 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 683194242deb1..b3579d11fb26d 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++; } @@ -3556,7 +3558,7 @@ 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; -- 2.39.5