[PATCH v2 5/7] block: check bio_mergeable() early before merging

From: Ming Lei
Date: Tue Oct 20 2015 - 11:14:37 EST


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@xxxxxxxxxxxxx>
---
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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