[PATCH] block: Do not merge if merging is disabled

[Bart Van Assche <bvanassche@acm.org>]

While testing the performance impact of zoned write pipelining, I
noticed that merging happens even if merging has been disabled via
sysfs. Fix this.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 block/blk-mq-sched.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 67c95f31b15b..8883721f419a 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -375,7 +375,8 @@ bool blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
 bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq,
 				   struct list_head *free)
 {
-	return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq, free);
+	return !blk_queue_nomerges(q) && rq_mergeable(rq) &&
+		elv_attempt_insert_merge(q, rq, free);
 }
 EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);