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

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Message-ID: <4dfcddff-7736-e01e-7fcf-804de77ac623@huawei.com>
Date:   Wed, 16 Mar 2022 10:46:57 +0000
From:   John Garry <john.garry@...wei.com>
To:     Christoph Hellwig <hch@....de>
CC:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        <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 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.

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