[PATCH] blk-mq: cache rq->q

[Shaohua Li <shli@kernel.org>]

If a tag is freed, the request might be used very soon. There is a short window
rq->q is null, so cache it.

Signed-off-by: Shaohua Li <shli@fusionio.com>
---
 block/blk-mq.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: master/block/blk-mq.c
===================================================================
--- master.orig/block/blk-mq.c	2013-10-11 12:07:32.282133638 +0800
+++ master/block/blk-mq.c	2013-10-11 12:07:32.282133638 +0800
@@ -250,11 +250,12 @@ static void __blk_mq_free_request(struct
 				  struct blk_mq_ctx *ctx, struct request *rq)
 {
 	const int tag = rq->tag;
+	struct request_queue *q = rq->q;
 
 	blk_mq_rq_init(hctx, rq);
 	blk_mq_put_tag(hctx->tags, tag);
 
-	blk_mq_queue_exit(rq->q);
+	blk_mq_queue_exit(q);
 }
 
 void blk_mq_free_request(struct request *rq)