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From: Jens Axboe <axboe@kernel.dk>
To: Omar Sandoval <osandov@osandov.com>, linux-block@vger.kernel.org
Cc: kernel-team@fb.com, Yang Yang <yang.yang@vivo.com>,
	Paolo Valente <paolo.valente@linaro.org>
Subject: Re: [PATCH] block: only call sched requeue_request() for scheduled requests
Date: Tue, 8 Sep 2020 17:42:04 -0600	[thread overview]
Message-ID: <3ec128e1-2f0c-205d-a700-e215f5f7c451@kernel.dk> (raw)
In-Reply-To: <80b64d8a0408e7c8c30b363aaf6d39e735521c1d.1599597940.git.osandov@osandov.com>

On 9/8/20 2:46 PM, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> Yang Yang reported the following crash caused by requeueing a flush
> request in Kyber:
> 
>   [    2.517297] Unable to handle kernel paging request at virtual address ffffffd8071c0b00
>   ...
>   [    2.517468] pc : clear_bit+0x18/0x2c
>   [    2.517502] lr : sbitmap_queue_clear+0x40/0x228
>   [    2.517503] sp : ffffff800832bc60 pstate : 00c00145
>   ...
>   [    2.517599] Process ksoftirqd/5 (pid: 51, stack limit = 0xffffff8008328000)
>   [    2.517602] Call trace:
>   [    2.517606]  clear_bit+0x18/0x2c
>   [    2.517619]  kyber_finish_request+0x74/0x80
>   [    2.517627]  blk_mq_requeue_request+0x3c/0xc0
>   [    2.517637]  __scsi_queue_insert+0x11c/0x148
>   [    2.517640]  scsi_softirq_done+0x114/0x130
>   [    2.517643]  blk_done_softirq+0x7c/0xb0
>   [    2.517651]  __do_softirq+0x208/0x3bc
>   [    2.517657]  run_ksoftirqd+0x34/0x60
>   [    2.517663]  smpboot_thread_fn+0x1c4/0x2c0
>   [    2.517667]  kthread+0x110/0x120
>   [    2.517669]  ret_from_fork+0x10/0x18
> 
> This happens because Kyber doesn't track flush requests, so
> kyber_finish_request() reads a garbage domain token. Only call the
> scheduler's requeue_request() hook if RQF_ELVPRIV is set (like we do for
> the finish_request() hook in blk_mq_free_request()). Now that we're
> handling it in blk-mq, also remove the check from BFQ.

Thanks, applied.

-- 
Jens Axboe


      reply	other threads:[~2020-09-08 23:42 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-08 20:46 [PATCH] block: only call sched requeue_request() for scheduled requests Omar Sandoval
2020-09-08 23:42 ` Jens Axboe [this message]

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