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

[Damien Le Moal <dlemoal@kernel.org>]

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.

> 
> 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