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....@canonical.com>
---
 block/elevator.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/elevator.c b/block/elevator.c
index 84d6394..c3555c9 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;
 
        /*
-- 
1.9.1

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