linux-kernel - Re: [PATCH v4 1/2] scsi: ufs: Fix task management request completion timeout

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Message-ID: <3206bafd-6a5a-1e9b-7939-a1360b5c55fc@acm.org>
Date:   Wed, 31 Mar 2021 20:39:27 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Avri Altman <Avri.Altman@....com>, Can Guo <cang@...eaurora.org>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "nguyenb@...eaurora.org" <nguyenb@...eaurora.org>,
        "hongwus@...eaurora.org" <hongwus@...eaurora.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "kernel-team@...roid.com" <kernel-team@...roid.com>
Cc:     Alim Akhtar <alim.akhtar@...sung.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 1/2] scsi: ufs: Fix task management request completion
 timeout

On 3/31/21 9:45 AM, Avri Altman wrote:
>> ufshcd_tmc_handler() calls blk_mq_tagset_busy_iter(fn =
>> ufshcd_compl_tm()),
>> but since blk_mq_tagset_busy_iter() only iterates over all reserved tags
>> and requests which are not in IDLE state, ufshcd_compl_tm() never gets a
>> chance to run. Thus, TMR always ends up with completion timeout. Fix it by
>> calling blk_mq_start_request() in  __ufshcd_issue_tm_cmd().
>>
>> Fixes: 69a6c269c097 ("scsi: ufs: Use blk_{get,put}_request() to allocate and
>> free TMFs")
>>
>> Signed-off-by: Can Guo <cang@...eaurora.org>
>> ---
>>  drivers/scsi/ufs/ufshcd.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index b49555fa..d4f8cb2 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -6464,6 +6464,7 @@ static int __ufshcd_issue_tm_cmd(struct ufs_hba
>> *hba,
>>
>>         spin_lock_irqsave(host->host_lock, flags);
>>         task_tag = hba->nutrs + free_slot;
>> +       blk_mq_start_request(req);
> Maybe just set req->state to MQ_RQ_IN_FLIGHT
> Without all other irrelevant initializations such as add timeout etc.

Hmm ... I'm not sure that any of the actions performed by
blk_mq_start_request() are irrelevant in this context. Additionally, no
other block or SCSI driver sets MQ_RQ_IN_FLIGHT directly.

Thanks,

Bart.