[PATCH] device-mapper snapshot: barriers not supported

The snapshot and origin targets are incapable of handling barriers and need to
indicate this.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index ad9b61f16c5e..f3759dd7828e 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -792,6 +792,9 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
         if (!s->valid)
                 return -EIO;
 
+        if (unlikely(bio_barrier(bio)))
+                return -EOPNOTSUPP;
+
         /*
          * Write to snapshot - higher level takes care of RW/RO
          * flags so we should only get this if we are
@@ -1058,6 +1061,9 @@ static int origin_map(struct dm_target *ti, struct bio *bio,
         struct dm_dev *dev = (struct dm_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) : 1;
 }