Re: [PATCH v2 6/6] ata: libata-scsi: Check ATA_QCFLAG_RTF_FILLED before using result_tf

[Igor Pylypiv <ipylypiv@google.com>]

On Wed, Jun 26, 2024 at 03:21:58PM +0900, Damien Le Moal wrote:
> On 6/26/24 09:30, Igor Pylypiv wrote:
> > On Tue, Jun 25, 2024 at 08:26:59AM +0200, Hannes Reinecke wrote:
> >> On 6/25/24 00:12, Igor Pylypiv wrote:
> >>> qc->result_tf contents are only valid when the ATA_QCFLAG_RTF_FILLED flag
> >>> is set. The ATA_QCFLAG_RTF_FILLED flag should be always set for commands
> >>> that failed or for commands that have the ATA_QCFLAG_RESULT_TF flag set.
> >>>
> >>> For ATA errors and ATA PASS-THROUGH commands the ATA_QCFLAG_RTF_FILLED
> >>> flag should be always set. Added WARN_ON_ONCE() checks to generate
> >>> a warning when ATA_QCFLAG_RTF_FILLED is not set and libata needs to
> >>> generate sense data.
> >>>
> >>> Signed-off-by: Igor Pylypiv <ipylypiv@google.com>
> >>> ---
> >>>   drivers/ata/libata-scsi.c | 10 ++++++++++
> >>>   1 file changed, 10 insertions(+)
> >>>
> >>> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> >>> index e5669a296d81..7a8a08692ce9 100644
> >>> --- a/drivers/ata/libata-scsi.c
> >>> +++ b/drivers/ata/libata-scsi.c
> >>> @@ -246,6 +246,9 @@ static void ata_scsi_set_passthru_sense_fields(struct ata_queued_cmd *qc)
> >>>   	struct ata_taskfile *tf = &qc->result_tf;
> >>>   	unsigned char *sb = cmd->sense_buffer;
> >>>
> >>> +	if (WARN_ON_ONCE(!(qc->flags & ATA_QCFLAG_RTF_FILLED)))
> >>> +		return;
> >>> +
> >>>   	if ((sb[0] & 0x7f) >= 0x72) {
> >>>   		unsigned char *desc;
> >>>   		u8 len;
> >>> @@ -928,6 +931,9 @@ static void ata_gen_passthru_sense(struct ata_queued_cmd *qc)
> >>>   	unsigned char *sb = cmd->sense_buffer;
> >>>   	u8 sense_key, asc, ascq;
> >>> +	if (WARN_ON_ONCE(!(qc->flags & ATA_QCFLAG_RTF_FILLED)))
> >>> +		return;
> >>> +
> >>>   	/*
> >>>   	 * Use ata_to_sense_error() to map status register bits
> >>>   	 * onto sense key, asc & ascq.
> >>> @@ -971,6 +977,10 @@ static void ata_gen_ata_sense(struct ata_queued_cmd *qc)
> >>>   		ata_scsi_set_sense(dev, cmd, NOT_READY, 0x04, 0x21);
> >>>   		return;
> >>>   	}
> >>> +
> >>> +	if (WARN_ON_ONCE(!(qc->flags & ATA_QCFLAG_RTF_FILLED)))
> >>> +		return;
> >>> +
> >>>   	/* Use ata_to_sense_error() to map status register bits
> >>>   	 * onto sense key, asc & ascq.
> >>>   	 */
> >>
> >> Hmm. Not sure if we really need the WARN_ON() here or whether a simple
> >> logging message wouldn't be sufficient; after all, we continue fine here.
> >>
> > 
> > My worry about adding a simple log statement is that it might cause a log
> > spam if things go wrong for some reason.
> > 
> > This code is more like a "this should never happen" comment and we always
> > expect ATA_QCFLAG_RTF_FILLED to be present when generating sense data
> > based on ATA registers.
> > 
> > If WARN_ON_ONCE() is too much for this case I guess we can just remove it
> > and silently return?
> 
> what about ata_dev_dbg() or ata_port_dbg() ?
> No message spamming by default and if problems are detected, they can be turned
> on to figure out what is going on.

ata_dev_dbg() should work. Updated the patch in v3.

Thank you!
Igor
> 
> > 
> > Damien, Niklas, what are your thoughts on this?
> > 
> > Thanks,
> > Igor
> > 
> >> Cheers,
> >>
> >> Hannes
> >> -- 
> >> Dr. Hannes Reinecke                  Kernel Storage Architect
> >> hare@suse.de                                +49 911 74053 688
> >> SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
> >> HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
> >>
> 
> -- 
> Damien Le Moal
> Western Digital Research
>