On Fri, Jun 14, 2024 at 07:18:32PM +0000, 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.
>
> 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.
>
> 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);
> -
Are you sure that this is safe?
atapi_eh_request_sense() is called both by:
ata_eh_analyze_tf():
tmp = atapi_eh_request_sense(.., qc->scsicmd->sense_buffer, ..)
and by:
atapi_eh_clear_ua():
atapi_eh_request_sense(.., sense_buffer, ..);
where sense_buffer is dev->link->ap->sector_buf.
Wouldn't a better fix be for ata_gen_* functions to return early if
ATA_QCFLAG_SENSE_VALID is set?
> /* 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 */
> --
> 2.45.2.627.g7a2c4fd464-goog
>
