linux-kernel - [PATCH v1 4/6] block: check bio_mergeable() early before merging

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Message-Id: <1445097154-18229-5-git-send-email-ming.lei@canonical.com>
Date:	Sat, 17 Oct 2015 23:52:32 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Cc:	Ming Lin <ming.l@....samsung.com>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	Jeff Moyer <jmoyer@...hat.com>,
	Ming Lei <ming.lei@...onical.com>
Subject: [PATCH v1 4/6] 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@...onical.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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