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Subject: Re: [PATCH v4 09/10] scsi: ufs: Update the fast abort path in
 ufshcd_abort() for PM requests
To:     Can Guo <cang@codeaurora.org>
Cc:     asutoshd@codeaurora.org, nguyenb@codeaurora.org,
        hongwus@codeaurora.org, ziqichen@codeaurora.org,
        linux-scsi@vger.kernel.org, kernel-team@android.com,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Bean Huo <beanhuo@micron.com>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        open list <linux-kernel@vger.kernel.org>
References: <1624433711-9339-1-git-send-email-cang@codeaurora.org>
 <1624433711-9339-11-git-send-email-cang@codeaurora.org>
 <b28d71a7-3839-2c07-2630-6196ea10951f@acm.org>
 <5ff72cfab707b571ef395d52931edd0f@codeaurora.org>
From:   Bart Van Assche <bvanassche@acm.org>
Message-ID: <da7f134c-3a2a-e3b9-72a1-56a19f720c70@acm.org>
Date:   Thu, 24 Jun 2021 09:57:39 -0700
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On 6/23/21 9:16 PM, Can Guo wrote:
> On 2021-06-24 05:33, Bart Van Assche wrote:
>> On 6/23/21 12:35 AM, Can Guo wrote:
>>> @@ -2737,7 +2737,7 @@ static int ufshcd_queuecommand(struct Scsi_Host
>>> *host, struct scsi_cmnd *cmd)
>>>           * err handler blocked for too long. So, just fail the scsi cmd
>>>           * sent from PM ops, err handler can recover PM error anyways.
>>>           */
>>> -        if (hba->wlu_pm_op_in_progress) {
>>> +        if (cmd->request->rq_flags & RQF_PM) {
>>>              hba->force_reset = true;
>>>              set_host_byte(cmd, DID_BAD_TARGET);
>>>              cmd->scsi_done(cmd);
>>
>> I'm still concerned that the above code may trigger data corruption. I
>> prefer that the above code is removed instead of being modified.
> 
> Removing the change will lead to deadlock when error handling prepare
> calls pm_runtime_get_sync().
> 
> RQF_PM is only given to requests sent from power management operations,
> during which the specific device/LU is suspending/resuming, meaning no
> data transaction is ongoing. How can fast failing a PM request trigger
> data corruption?

Right, the above code only affects power management requests so there is
no risk for data corruption.

Thanks,

Bart.