linux-kernel - [PATCH 3/4] blk-mq: check bio_mergeable() early before merging

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Message-Id: <1444793448-9994-4-git-send-email-ming.lei@canonical.com>
Date:	Wed, 14 Oct 2015 11:30:47 +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>,
	Ming Lei <ming.lei@...onical.com>
Subject: [PATCH 3/4] blk-mq: check bio_mergeable() early before merging

It isn't necessary to try to merge the bio which is marked
as NOMERGE.

Signed-off-by: Ming Lei <ming.lei@...onical.com>
---
 block/blk-mq.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 546b3b8..deb5f4c 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -671,6 +671,9 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
 	struct request *rq;
 	int checked = 8;
 
+	if (!bio_mergeable(bio))
+		return false;
+
 	list_for_each_entry_reverse(rq, &ctx->rq_list, queuelist) {
 		int el_ret;
 
@@ -1140,7 +1143,7 @@ static inline bool blk_mq_merge_queue_io(struct blk_mq_hw_ctx *hctx,
 					 struct blk_mq_ctx *ctx,
 					 struct request *rq, struct bio *bio)
 {
-	if (!hctx_allow_merges(hctx)) {
+	if (!hctx_allow_merges(hctx) || !bio_mergeable(bio)) {
 		blk_mq_bio_to_request(rq, bio);
 		spin_lock(&ctx->lock);
 insert_rq:
-- 
1.9.1

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