linux-kernel - Re: [PATCH v3 4/9] scsi: ufs: Complete the cmd before returning in queuecommand

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Date:   Sat, 12 Jun 2021 08:50:12 -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 v3 4/9] scsi: ufs: Complete the cmd before returning in
 queuecommand

On 6/12/21 12:38 AM, Can Guo wrote:
> On 2021-06-12 04:52, Bart Van Assche wrote:
>> On 6/9/21 9:43 PM, Can Guo wrote:
>>> @@ -2768,15 +2778,6 @@ static int ufshcd_queuecommand(struct
>>> Scsi_Host *host, struct scsi_cmnd *cmd)
>>>      WARN_ON(ufshcd_is_clkgating_allowed(hba) &&
>>>          (hba->clk_gating.state != CLKS_ON));
>>>
>>> -    if (unlikely(test_bit(tag, &hba->outstanding_reqs))) {
>>> -        if (hba->wl_pm_op_in_progress)
>>> -            set_host_byte(cmd, DID_BAD_TARGET);
>>> -        else
>>> -            err = SCSI_MLQUEUE_HOST_BUSY;
>>> -        ufshcd_release(hba);
>>> -        goto out;
>>> -    }
>>> -
>>>      lrbp = &hba->lrb[tag];
>>>      WARN_ON(lrbp->cmd);
>>>      lrbp->cmd = cmd;
>>
>> Can the code under "if (unlikely(test_bit(tag,
>> &hba->outstanding_reqs)))" be deleted instead of moving it? I don't
>> think that it is useful to verify whether the block layer tag allocator
>> works correctly. Additionally, I'm not aware of any similar code in any
>> other SCSI LLD.
> 
> ufshcd_abort() aborts PM requests differently from other requests -
> it simply evicts the cmd from lrbp [1], schedules error handler and
> returns SUCCESS (the reason why I am doing it this way is in patch #8).
> 
> After ufshcd_abort() returns, the tag shall be released, the logic
> here is to prevent subsequent cmds re-use the lrbp [1] before error
> handler recovers the device and host.

Thanks for the background information. However, this approach sounds
cumbersome to me. For PM requests, please change the UFS driver such
that calling scsi_done() for aborted requests is postponed until error
handling has finished and delete the code shown above from
ufshcd_queuecommand().

Thanks,

Bart.