dm: Use kzalloc for all structs with embedded biosets/mempools

mempool_init()/bioset_init() require that the mempools/biosets be zeroed
first; they probably should not _require_ this, but not allocating those
structs with kzalloc is a fairly nonsensical thing to do (calling
mempool_exit()/bioset_exit() on an uninitialized mempool/bioset is legal
and safe, but only works if said memory was zeroed.)

Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index b11ddc5..f745404 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1120,7 +1120,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		origin_mode = FMODE_WRITE;
 	}
 
-	s = kmalloc(sizeof(*s), GFP_KERNEL);
+	s = kzalloc(sizeof(*s), GFP_KERNEL);
 	if (!s) {
 		ti->error = "Cannot allocate private snapshot structure";
 		r = -ENOMEM;