From: Omar Sandoval osandov@fb.com
[ Upstream commit 1b9e619c5bc8235cfba3dc4ced2fb0e3554a05d4 ]
I was seeing disk flushes still happening when I mounted a Btrfs filesystem with nobarrier for testing. This is because we use FUA to write out the first super block, and on devices without FUA support, the block layer translates FUA to a flush. Even on devices supporting true FUA, using FUA when we asked for no barriers is surprising.
Fixes: 387125fc722a8ed ("Btrfs: fix barrier flushes") Signed-off-by: Omar Sandoval osandov@fb.com Reviewed-by: Qu Wenruo wqu@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- fs/btrfs/disk-io.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index dfdab849037b..167ce43cabe8 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -3391,6 +3391,7 @@ static int write_dev_supers(struct btrfs_device *device, int errors = 0; u32 crc; u64 bytenr; + int op_flags;
if (max_mirrors == 0) max_mirrors = BTRFS_SUPER_MIRROR_MAX; @@ -3433,13 +3434,10 @@ 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_SYNC | REQ_FUA | REQ_META | REQ_PRIO, bh); - } else { - ret = btrfsic_submit_bh(REQ_OP_WRITE, - REQ_SYNC | REQ_META | REQ_PRIO, bh); - } + op_flags = REQ_SYNC | REQ_META | REQ_PRIO; + if (i == 0 && !btrfs_test_opt(device->fs_info, NOBARRIER)) + op_flags |= REQ_FUA; + ret = btrfsic_submit_bh(REQ_OP_WRITE, op_flags, bh); if (ret) errors++; }