From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <jianchao.w.wang@oracle.com>
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>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        linux-block <linux-block@vger.kernel.org>,
        Linux SCSI List <linux-scsi@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <1529027847-29085-1-git-send-email-jianchao.w.wang@oracle.com>
 <CACVXFVMe4zSvfXfuSn0NFayeQqbmDwBBy1kcso=5iznT6EfpSA@mail.gmail.com>
 <3dd3f82a-5b68-f039-3a8a-7c5fe4e24c3e@oracle.com>
 <e5344293-b0b7-d2e0-f2e7-c0700efdfbe4@oracle.com>
 <CACVXFVMRCM6AvNJjAESbwOeJ_P5AZ+1C-7RfhE9L4u0T=_5h4Q@mail.gmail.com>
From: "jianchao.wang" <jianchao.w.wang@oracle.com>
Message-ID: <3970fdc7-52d9-d05b-4118-059d48bf4f2d@oracle.com>
Date: Fri, 15 Jun 2018 11:04:02 +0800
MIME-Version: 1.0
In-Reply-To: <CACVXFVMRCM6AvNJjAESbwOeJ_P5AZ+1C-7RfhE9L4u0T=_5h4Q@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
List-ID: <linux-block@vger.kernel.org>

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