2013-10-11 04:11:27

by Shaohua Li

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

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 <[email protected]>
---
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)

2013-10-11 14:26:43

by Jens Axboe

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

On 10/10/2013 10:11 PM, Shaohua Li wrote:
>
> If a tag is freed, the request might be used very soon. There is a short window
> rq->q is null, so cache it.

Thanks, good catch! Applied.

--
Jens Axboe