Btrfs: disable FUA if mounted with nobarrier

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>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 10a2a579cc7f6a3569212444fb37dd5ddcf0c0c7..a8ecccfc36ded1d9470deb0d78f77bcdacb6d0cf 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3231,6 +3231,7 @@ 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;
@@ -3273,13 +3274,10 @@ 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++;
        }