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Subject: Re: [PATCH 1/2] block: export __blk_complete_request
To:     Ming Lei <tom.leiming@gmail.com>
Cc:     Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
        James Bottomley <jejb@linux.vnet.ibm.com>,
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From:   "jianchao.wang" <jianchao.w.wang@oracle.com>
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Date:   Fri, 15 Jun 2018 11:04:02 +0800
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Hi Ming

Thanks for your kindly response.

On 06/15/2018 10:56 AM, Ming Lei wrote:
>>> IMO, ref-counter is just to fix the blk-mq req life recycle issue.
>>> It cannot replace the blk_mark_rq_complete which could avoid the race between
>>> timeout and io completion path.
>> The .timeout return BLK_EH_DONE doesn't always mean the request has been completed.
>> Such as scsi-mid layer, its .timeout callback return BLK_EH_DONE but the timed out
>> request is still in abort or eh process. What if a completion irq come during that ?
> For blk-mq, it is avoided by the atomic state change in
> __blk_mq_complete_request(),
> that is why I mentioned the question in my last reply.
> 

but blk_mq_check_expired doesn't do that.
do I miss anything ?

> But what if the timed-out request has been freed by EH? Then seems
> req's ref_counter

Thanks
Jianchao