From: Bart Van Assche <bvanassche@acm.org>
To: Gabriel Krisman Bertazi <krisman@collabora.com>
Cc: "André Almeida" <andrealmeid@collabora.com>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
axboe@kernel.dk, kernel@collabora.com
Subject: Re: [PATCH v2 1/1] blk-mq: fill header with kernel-doc
Date: Tue, 8 Oct 2019 13:01:38 -0700 [thread overview]
Message-ID: <86de2c88-5812-4a87-b5d8-1b7b1808d013@acm.org> (raw)
In-Reply-To: <85zhibyt14.fsf@collabora.com>
On 10/8/19 11:46 AM, Gabriel Krisman Bertazi wrote:
> Hmm, sorry, but I'm confused. I'm sure I'm missing something simple,
> since I haven't touched this in a while, so maybe you can quickly point
> me in the right direction?
>
> I see blk_mq_requeue_request() being used by device drivers to retry
> requests that failed, but if I read the code correctly, the flushed
> queue seems to be moved to hctx->dispatch when the device
> driver returned BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE to
> blk_mq_dispatch_rq_list(). I thought BLK_STS_RESOURCE was returned by
> the driver on .queue_rq() to signal there was no more resources on the
> hardware to service further requests.
Hi Gabriel,
The simplified version of how requests are requeued as follows:
* A block driver calls blk_mq_requeue_request().
* blk_mq_requeue_request() calls blk_mq_add_to_requeue_list()
* blk_mq_add_to_requeue_list() executes the following code:
list_add_tail(&rq->queuelist, &q->requeue_list)
* A block driver or the block layer core calls
blk_mq_kick_requeue_list() or blk_mq_delay_kick_requeue_list(). Both
functions trigger a call of blk_mq_requeue_work().
* blk_mq_requeue_work() processes q->requeue_list.
Bart.
next prev parent reply other threads:[~2019-10-08 20:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 0:14 [PATCH v2 1/1] blk-mq: fill header with kernel-doc André Almeida
2019-10-08 16:35 ` Gabriel Krisman Bertazi
2019-10-08 17:30 ` Bart Van Assche
2019-10-08 18:46 ` Gabriel Krisman Bertazi
2019-10-08 20:01 ` Bart Van Assche [this message]
2019-10-10 20:38 ` André Almeida
2019-10-11 17:00 ` Bart Van Assche
2019-10-08 18:12 ` Bart Van Assche
2019-10-10 20:41 ` André Almeida
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