linux-kernel - Re: [PATCH] blk-mq: auto-start hw queue in requeue

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Message-ID: <541C6D7B.5000005@kernel.dk>
Date:	Fri, 19 Sep 2014 11:52:59 -0600
From:	Jens Axboe <axboe@...nel.dk>
To:	Christoph Hellwig <hch@....de>, Ming Lei <ming.lei@...onical.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] blk-mq: auto-start hw queue in requeue

On 09/19/2014 11:48 AM, Christoph Hellwig wrote:
> On Fri, Sep 19, 2014 at 10:22:50PM +0800, Ming Lei wrote:
>> Requests often need to be retried because of timeout, hardware
>> busy or sort of reasons via blk_mq_requeue_request(), but at
>> that time dispatch queue may have been stopped.
>>
>> This patch starts the dispatch queue automatically in requeue's
>> work handler, and fixes scsi-mq's timeout issue, which can be
>> triggered if there are two or more requests timedout.
> 
> Sounds like blk_mq_requeue_work should simply call void
> blk_mq_start_hw_queues where it calls blk_mq_run_queues currently.

I agree. I think Ming wanted to avoid an unnecessary bitflip if
possible, but the fix is more convoluted than I would like.


-- 
Jens Axboe

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