block: check bio_mergeable() early before merging

After bio splitting is introduced, one bio can be splitted
and it is marked as NOMERGE because it is too fat to be merged,
so check bio_mergeable() earlier to avoid to try to merge it
unnecessarily.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/block/elevator.c b/block/elevator.c
index 84d63943f2de..c3555c9c672f 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -420,7 +420,7 @@ int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
          *      noxmerges: Only simple one-hit cache try
          *      merges:    All merge tries attempted
          */
-        if (blk_queue_nomerges(q))
+        if (blk_queue_nomerges(q) || !bio_mergeable(bio))
                 return ELEVATOR_NO_MERGE;
 
         /*