dm: disable barriers

This patch causes device-mapper to reject any barrier requests.  This is done
since most of the targets won't handle this correctly anyway.  So until the
situation improves it is better to reject these requests at the first place.
Since barrier requests won't get to the targets, the checks there can be
removed.

Cc: stable@kernel.org
Signed-off-by: Stefan Bader <shbader@de.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 6 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 854891d07b59..83ddbfe6b8a4 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -889,9 +889,6 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
         if (!s->valid)
                 return -EIO;
 
-        if (unlikely(bio_barrier(bio)))
-                return -EOPNOTSUPP;
-
         /* FIXME: should only take write lock if we need
          * to copy an exception */
         down_write(&s->lock);
@@ -1162,9 +1159,6 @@ static int origin_map(struct dm_target *ti, struct bio *bio,
         struct dm_dev *dev = ti->private;
         bio->bi_bdev = dev->bdev;
 
-        if (unlikely(bio_barrier(bio)))
-                return -EOPNOTSUPP;
-
         /* Only tell snapshots if this is a write */
         return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
 }