linux-kernel - Re: [PATCH 0/5]stop normal completion path entering a timeout req

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Message-ID: <df1633e8-7df4-976b-a7d5-77679c92843a@oracle.com>
Date:   Thu, 21 Jun 2018 21:13:30 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Keith Busch <keith.busch@...el.com>, axboe@...nel.dk,
        martin.petersen@...cle.com, josef@...icpanda.com,
        ulf.hansson@...aro.org, linux-block@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5]stop normal completion path entering a timeout req

Hi Christoph

On 06/21/2018 04:19 PM, Christoph Hellwig wrote:
> On Thu, Jun 21, 2018 at 09:43:26AM +0800, jianchao.wang wrote:
>> So we have to preserve the ability of block layer that it could prevent
>> IO completion path from entering a timeout request.
>>
>> With scsi-debug module, I tried to simulate a scenario where timeout and IO
>> completion path could occur concurrently, the system ran into crash easily.
> 
> Trace, please.  With the latest kernel.  I'm not saying that there
> is nothing to fix, but the mode of never completing once timeout
> requests as currently done is SCSI is clearly broken.
> 

Sorry, I don't quite get your point.
Do you mean we should do the modification in the scsi layer ?
Actually, I used to look at the code to try to stop io completion on timeout request
in scsi-mid layer, but it looks like difficult, especially, scsi eh would try
to borrow the command to issue admin command such as get sense, test unit,etc.

Thanks
Jianchao