linux-kernel - Re: [PATCH 1/2] blk-mq: don't complete un-started request in timeout handler

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Date:   Wed, 15 Mar 2017 20:40:25 +0800
From:   Ming Lei <tom.leiming@...il.com>
To:     Bart Van Assche <Bart.VanAssche@...disk.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hch@...radead.org" <hch@...radead.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "axboe@...com" <axboe@...com>,
        "yizhan@...hat.com" <yizhan@...hat.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH 1/2] blk-mq: don't complete un-started request in timeout
 handler

On Wed, Mar 15, 2017 at 08:18:53PM +0800, Ming Lei wrote:
> On Wed, Mar 15, 2017 at 12:07:37AM +0000, Bart Van Assche wrote:
> 
> > or __blk_mq_requeue_request(). Another issue with this function is that the
> 
> __blk_mq_requeue_request() can be run from two pathes:
> 
> 	- dispatch failure, in which case the req/tag isn't released to tag set
> 	
> 	- IO completion path, in which COMPLETE flag is cleared before requeue.
> 	
> so I can't see races with timeout in case of start rq vs. requeue rq. 

Actually rq/tag won't be released to tag set if it will be requeued, so
the timeout race is nothing to do with requeue.

Thanks,
Ming