linux-kernel - Re: [PATCH v1 3/4] ata: libata-scsi: Report valid sense data for ATA PT if present

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Message-ID: <ZnDOfqq9Jo-38LBl@google.com>
Date: Tue, 18 Jun 2024 00:02:06 +0000
From: Igor Pylypiv <ipylypiv@...gle.com>
To: Damien Le Moal <dlemoal@...nel.org>
Cc: Niklas Cassel <cassel@...nel.org>, Tejun Heo <tj@...nel.org>,
	Hannes Reinecke <hare@...e.de>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/4] ata: libata-scsi: Report valid sense data for ATA
 PT if present

On Mon, Jun 17, 2024 at 08:25:54AM +0900, Damien Le Moal wrote:
> On 6/15/24 04:18, Igor Pylypiv wrote:
> > Do not generate sense data from ATA status/error registers
> > if valid sense data is already present.
> 
> This kind of contradicts what you said in patch 2... So I am really confused now.

Sorry about the confustion. I think the problem is that I was using "sense data"
to describe two different things:
#1. SK/ASC/ASCQ
#2. ATA Status Return sense data descriptor

Both #1 and #2 need to be populated into sense buffer. The problem with
the current code is that we can only have either valid #1 or valid #2 but
not both at the same time.

> Though this patch actually looks good to me, modulo the comment below.
> But shouldn't this be squashed with patch 2 ?

Yes, that's a good point. Let me factor out the sense data descriptor
population code into a separate function and then squash this patch with
the patch 2.

>
> > 
> > Signed-off-by: Igor Pylypiv <ipylypiv@...gle.com>
> > ---
> >  drivers/ata/libata-scsi.c | 17 +++++++++++------
> >  1 file changed, 11 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> > index 79e8103ef3a9..4bfe47e7d266 100644
> > --- a/drivers/ata/libata-scsi.c
> > +++ b/drivers/ata/libata-scsi.c
> > @@ -858,12 +858,17 @@ static void ata_gen_passthru_sense(struct ata_queued_cmd *qc)
> >  	unsigned char *desc = sb + 8;
> >  	u8 sense_key, asc, ascq;
> >  
> > -	/*
> > -	 * Use ata_to_sense_error() to map status register bits
> > -	 * onto sense key, asc & ascq.
> > -	 */
> > -	if (qc->err_mask ||
> > -	    tf->status & (ATA_BUSY | ATA_DF | ATA_ERR | ATA_DRQ)) {
> > +	if (qc->flags & ATA_QCFLAG_SENSE_VALID) {
> > +		/*
> > +		 * Do not generate sense data from ATA status/error
> > +		 * registers if valid sense data is already present.
> > +		 */
> 
> The empty "if" here is really horrible. Please revert the condition and add it
> as a "&&" in the below if.
>
Adding the condition to the below if will change the code flow and we'll end
up executing scsi_build_sense(cmd, 1, RECOVERED_ERROR, 0, 0x1D) when
ATA_QCFLAG_SENSE_VALID is set, which is not what we want.

I agree about horrible :)

Perhaps I should have factored out the descriptor population code into
a separate function to make the code correct and not so horrible. Let me
do that in v2.

> > +	} else if (qc->err_mask ||
> > +		   tf->status & (ATA_BUSY | ATA_DF | ATA_ERR | ATA_DRQ)) {
> > +		/*
> > +		 * Use ata_to_sense_error() to map status register bits
> > +		 * onto sense key, asc & ascq.
> > +		 */
> >  		ata_to_sense_error(qc->ap->print_id, tf->status, tf->error,
> >  				   &sense_key, &asc, &ascq);
> >  		ata_scsi_set_sense(qc->dev, cmd, sense_key, asc, ascq);
> 
> -- 
> Damien Le Moal
> Western Digital Research
>
Thank you,
Igor