linux-kernel - Re: [PATCH 1/6] scsi: libsas: Add sas_task_find

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Date:   Thu, 29 Sep 2022 16:56:28 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     John Garry <john.garry@...wei.com>, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, jinpu.wang@...ud.ionos.com,
        damien.lemoal@....com
Cc:     hare@...e.de, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linuxarm@...wei.com,
        ipylypiv@...gle.com, changyuanl@...gle.com, hch@....de
Subject: Re: [PATCH 1/6] scsi: libsas: Add sas_task_find_rq()

On 9/29/22 16:33, John Garry wrote:
> On 29/09/2022 03:09, Damien Le Moal wrote:
>> On 9/28/22 21:27, John Garry wrote:
>>> blk-mq already provides a unique tag per request. Some libsas LLDDs - like
>>> hisi_sas - already use this tag as the unique per-IO HW tag.
>>>
>>> Add a common function to provide the request associated with a sas_task
>>> for all libsas LLDDs.
>>>
>>> Signed-off-by: John Garry <john.garry@...wei.com>
>>> ---
>>>   include/scsi/libsas.h | 22 ++++++++++++++++++++++
>>>   1 file changed, 22 insertions(+)
>>>
>>> diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
>>> index f86b56bf7833..bc51756a3317 100644
>>> --- a/include/scsi/libsas.h
>>> +++ b/include/scsi/libsas.h
>>> @@ -644,6 +644,28 @@ static inline bool sas_is_internal_abort(struct sas_task *task)
>>>   	return task->task_proto == SAS_PROTOCOL_INTERNAL_ABORT;
>>>   }
>>>   
>>> +static inline struct request *sas_task_find_rq(struct sas_task *task)
>>> +{
>>> +	struct scsi_cmnd *scmd;
>>> +
>>> +	if (!task || !task->uldd_task)
>>> +		return NULL;
>>> +
>>> +	if (task->task_proto & SAS_PROTOCOL_STP_ALL) {
>>> +		struct ata_queued_cmd *qc;
>>> +
>>> +		qc = task->uldd_task;
>>
>> I would change these 2 lines into a single line:
>>
>> 		struct ata_queued_cmd *qc = task->uldd_task;
>>
>> And no cast as suggested.
>>
>>> +		scmd = qc->scsicmd;
> 
> So do you prefer:
> 
>   scmd = ((struct ata_queued_cmd *)task->uldd_task)->scsicmd

Not a fan of the cast approach suggested by Jason. I prefer my above
suggestion, but no strong feeling about it. Either way will be OK.

> 
> As Jason suggested?
> 
> Thanks,
> John

-- 
Damien Le Moal
Western Digital Research