From: Ming Lei <ming.lei@canonical.com>
Date: Tue, 20 Oct 2015 15:13:55 +0000 (+0800)
Subject: block: check bio_mergeable() early before merging
X-Git-Tag: v4.4-rc1~134^2~4
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=7460d389c01741f0dfff733af93d3b3abd9b974e;p=linux.git

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>
---

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;
 
 	/*