linux-kernel - Re: [PATCH RFC 2/2] libata: Use scsi cmnd budget token for qc tag for SAS host

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Date:   Thu, 17 Mar 2022 08:23:03 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     John Garry <john.garry@...wei.com>, Christoph Hellwig <hch@....de>
Cc:     jejb@...ux.ibm.com, martin.petersen@...cle.com, bvanassche@....org,
        ming.lei@...hat.com, hare@...e.de, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        martin.wilck@...e.com
Subject: Re: [PATCH RFC 2/2] libata: Use scsi cmnd budget token for qc tag for
 SAS host

On 3/16/22 19:46, John Garry wrote:
> On 16/03/2022 08:34, Christoph Hellwig wrote:
>> In addition to the comments from Damien:  I think we should kill
>> ata_qc_new_init as well.  It is a bit pointless and having it in
>> libata-core.c when it pokes into scsi internals also doesn't make sense.
>>
>> So maybe something like:
> 
> Seems reasonable to me at least.

Yep, that will be a nice cleanup.

> 
> But I'd send these as 2x separate patches.
> 
>>    *	sata_async_notification - SATA async notification handler
>>    *	@ap: ATA port where async notification is received
>> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
>> index ed8be585a98f7c..5e0bc7b05a107e 100644
>> --- a/drivers/ata/libata-scsi.c
>> +++ b/drivers/ata/libata-scsi.c
>> @@ -638,24 +638,44 @@ EXPORT_SYMBOL_GPL(ata_scsi_ioctl);
>>   static struct ata_queued_cmd *ata_scsi_qc_new(struct ata_device *dev,
>>   					      struct scsi_cmnd *cmd)
>>   {
> ...
> 
>>   
>> -		if (scsi_cmd_to_rq(cmd)->rq_flags & RQF_QUIET)
>> -			qc->flags |= ATA_QCFLAG_QUIET;
>> +	if (ap->flags & ATA_FLAG_SAS_HOST) {
>> +		/* XXX: add a comment here why SAS is different */
> 
> I think this is simply because SAS hosts have shost.can_queue > 32
> 
>> +		if (WARN_ON_ONCE(cmd->budget_token >= ATA_MAX_QUEUE))
>> +			goto fail;
>> +		tag = cmd->budget_token;
> 
> thanks,
> John


-- 
Damien Le Moal
Western Digital Research