On Mon, Jun 17, 2024 at 08:13:51AM +0900, Damien Le Moal wrote:
> On 6/15/24 04:18, Igor Pylypiv wrote:
> > scsi_queue_rq() memsets sense_buffer before a command is dispatched.
> >
> > Libata is not memsetting sense_buffer before setting sense data that
> > was obtained from a disk so there should be no reason to do a memset
> > for ATA PASS-THROUGH / ATAPI.
>
> This sentence is not very clear at all... I assume that the first part of the
> sentence is for non passthrough commands. In this case, libata does not clear
> the sense buffer because the scsi layer did that already, in scsi_queue_rq() as
> noted above.
>
> For passthrough commands, the same should be happening as well since passthrough
> commands are also executed through blk_execute_rq() -> scsi_queue_rq(). So I do
> not really understand (but I do agree that the memset() in libata seem useless).
Thanks! I'll update the commit message to make it more clear.
>
> > Memsetting the sense_buffer in ata_gen_passthru_sense() is erasing valid
> > sense data that was previously obtained from a disk. A follow-up patch
> > will modify ata_gen_passthru_sense() to stop generating sense data based
> > on ATA status register bits if a valid sense data is already present.
>
> This fix should come first in the series, since that commit will likely need to
> go into current rc and cc-stable. And that will simplify this patch as well.
>
Ack. I'll reorder the commits.
> >
> > Signed-off-by: Igor Pylypiv <ipylypiv@xxxxxxxxxx>
> > ---
> > drivers/ata/libata-eh.c | 2 --
> > drivers/ata/libata-scsi.c | 4 ----
> > 2 files changed, 6 deletions(-)
> >
> > diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
> > index 214b935c2ced..b5e05efe73f6 100644
> > --- a/drivers/ata/libata-eh.c
> > +++ b/drivers/ata/libata-eh.c
> > @@ -1479,8 +1479,6 @@ unsigned int atapi_eh_request_sense(struct ata_device *dev,
> > struct ata_port *ap = dev->link->ap;
> > struct ata_taskfile tf;
> >
> > - memset(sense_buf, 0, SCSI_SENSE_BUFFERSIZE);
> > -
> > /* initialize sense_buf with the error register,
> > * for the case where they are -not- overwritten
> > */
> > diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> > index cdf29b178ddc..032cf11d0bcc 100644
> > --- a/drivers/ata/libata-scsi.c
> > +++ b/drivers/ata/libata-scsi.c
> > @@ -858,8 +858,6 @@ static void ata_gen_passthru_sense(struct ata_queued_cmd *qc)
> > unsigned char *desc = sb + 8;
> > u8 sense_key, asc, ascq;
> >
> > - memset(sb, 0, SCSI_SENSE_BUFFERSIZE);
> > -
> > /*
> > * Use ata_to_sense_error() to map status register bits
> > * onto sense key, asc & ascq.
> > @@ -953,8 +951,6 @@ static void ata_gen_ata_sense(struct ata_queued_cmd *qc)
> > u64 block;
> > u8 sense_key, asc, ascq;
> >
> > - memset(sb, 0, SCSI_SENSE_BUFFERSIZE);
> > -
> > if (ata_dev_disabled(dev)) {
> > /* Device disabled after error recovery */
> > /* LOGICAL UNIT NOT READY, HARD RESET REQUIRED */
>
> --
> Damien Le Moal
> Western Digital Research
>
Thank you,
Igor
