From: Ming Lei <ming.lei@redhat.com>
To: "jianchao.wang" <jianchao.w.wang@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued
Date: Wed, 13 Sep 2017 09:24:53 +0800 [thread overview]
Message-ID: <20170913012452.GA24642@ming.t460p> (raw)
In-Reply-To: <23b700aa-ed37-1081-d980-4073804f293b@oracle.com>
On Wed, Sep 13, 2017 at 09:01:25AM +0800, jianchao.wang wrote:
> Hi ming
>
> On 09/12/2017 06:23 PM, Ming Lei wrote:
> >> @@ -1029,14 +1029,20 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list)
> >> if (list_empty(list))
> >> bd.last = true;
> >> else {
> >> - struct request *nxt;
> >> -
> >> nxt = list_first_entry(list, struct request, queuelist);
> >> bd.last = !blk_mq_get_driver_tag(nxt, NULL, false);
> >> }
> >>
> >> ret = q->mq_ops->queue_rq(hctx, &bd);
> >> if (ret == BLK_STS_RESOURCE) {
> >> + /*
> >> + * If an I/O scheduler has been configured and we got a
> >> + * driver tag for the next request already, free it again.
> >> + */
> >> + if (!list_empty(list)) {
> >> + nxt = list_first_entry(list, struct request, queuelist);
> >> + blk_mq_put_driver_tag(nxt);
> >> + }
> > The following way might be more simple and clean:
> >
> > if (nxt)
> > blk_mq_put_driver_tag(nxt);
> >
> > meantime 'nxt' need to be cleared inside the 'if (list_empty(list))'
> > before .queue_rq().
>
> I had ever thought about that, but to avoid add extra command in the
> fast path, I made the patch above.
Got it, so how about changing to the following way simply:
if (nxt && !list_empty(list))
blk_mq_put_driver_tag(nxt);
--
Ming
next prev parent reply other threads:[~2017-09-13 1:24 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-12 17:14 [PATCH] blk-mq: put the driver tag of nxt rq before first one is requeued Jianchao Wang
2017-09-12 10:23 ` Ming Lei
2017-09-13 1:01 ` jianchao.wang
2017-09-13 1:24 ` Ming Lei [this message]
2017-09-13 1:39 ` jianchao.wang
2017-09-13 1:52 ` Ming Lei
2017-09-13 2:23 ` Jens Axboe
2017-09-13 2:42 ` jianchao.wang
2017-09-13 2:45 ` Jens Axboe
2017-09-13 3:39 ` jianchao.wang
2017-09-13 3:54 ` Jens Axboe
2017-09-13 3:59 ` jianchao.wang
2017-09-13 3:50 ` Ming Lei
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