linux-kernel - Re: [PATCH v4 09/10] scsi: ufs: Update the fast abort path in ufshcd

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Message-ID: <da7f134c-3a2a-e3b9-72a1-56a19f720c70@acm.org>
Date:   Thu, 24 Jun 2021 09:57:39 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Can Guo <cang@...eaurora.org>
Cc:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, ziqichen@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 09/10] scsi: ufs: Update the fast abort path in
 ufshcd_abort() for PM requests

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.