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.

Signed-off-by: Stefan Bader <shbader@de.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

4 files changed, 9 insertions, 12 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index be3ad7ce86d2..45e1c314369e 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -943,9 +943,6 @@ static int crypt_map(struct dm_target *ti, struct bio *bio,
 	struct crypt_config *cc = ti->private;
 	struct crypt_io *io;
 
-	if (bio_barrier(bio))
-		return -EOPNOTSUPP;
-
 	io = mempool_alloc(cc->io_pool, GFP_NOIO);
 	io->target = ti;
 	io->base_bio = bio;
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index de54b39e6ffe..bfb2ea3037b6 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -798,9 +798,6 @@ static int multipath_map(struct dm_target *ti, struct bio *bio,
 	struct mpath_io *mpio;
 	struct multipath *m = (struct multipath *) ti->private;
 
-	if (bio_barrier(bio))
-		return -EOPNOTSUPP;
-
 	mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
 	dm_bio_record(&mpio->details, bio);
 
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 9227ba4f19db..39556210db55 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -887,9 +887,6 @@ 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);
@@ -1160,9 +1157,6 @@ 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) : DM_MAPIO_REMAPPED;
 }
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 2717a355dc5b..75bd2fd8575e 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -802,6 +802,15 @@ static int dm_request(request_queue_t *q, struct bio *bio)
 	int rw = bio_data_dir(bio);
 	struct mapped_device *md = q->queuedata;
 
+	/*
+	 * There is no use in forwarding any barrier request since we can't
+	 * guarantee it is (or can be) handled by the targets correctly.
+	 */
+	if (unlikely(bio_barrier(bio))) {
+		bio_endio(bio, bio->bi_size, -EOPNOTSUPP);
+		return 0;
+	}
+
 	down_read(&md->io_lock);
 
 	disk_stat_inc(dm_disk(md), ios[rw]);