Re: [PATCH v3 2/6] ata: libata-scsi: Do not overwrite valid sense data when CK_COND=1

[Damien Le Moal]

On 6/27/24 08:04, Igor Pylypiv wrote:
> Current ata_gen_passthru_sense() code performs two actions:
> 1. Generates sense data based on the ATA 'status' and ATA 'error' fields.
> 2. Populates "ATA Status Return sense data descriptor" / "Fixed format
>    sense data" with ATA taskfile fields.
> 
> The problem is that #1 generates sense data even when a valid sense data
> is already present (ATA_QCFLAG_SENSE_VALID is set). Factoring out #2 into
> a separate function allows us to generate sense data only when there is
> no valid sense data (ATA_QCFLAG_SENSE_VALID is not set).
> 
> As a bonus, we can now delete a FIXME comment in atapi_qc_complete()
> which states that we don't want to translate taskfile registers into
> sense descriptors for ATAPI.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
> Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
> Signed-off-by: Igor Pylypiv <ipylypiv@xxxxxxxxxx>

I wonder if we can find the patch that introduced the bug in the first place so
that we can add a Fixes tag. I have not checked. This may have been wrong since
a long time ago...

> ---
>  drivers/ata/libata-scsi.c | 158 +++++++++++++++++++++-----------------
>  1 file changed, 86 insertions(+), 72 deletions(-)
> 
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index a9e44ad4c2de..26b1263f5c7c 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -230,6 +230,80 @@ void ata_scsi_set_sense_information(struct ata_device *dev,
>  				   SCSI_SENSE_BUFFERSIZE, information);
>  }
>  
> +/**
> + *	ata_scsi_set_passthru_sense_fields - Set ATA fields in sense buffer
> + *	@qc: ATA PASS-THROUGH command.
> + *
> + *	Populates "ATA Status Return sense data descriptor" / "Fixed format
> + *	sense data" with ATA taskfile fields.
> + *
> + *	LOCKING:
> + *	None.
> + */
> +static void ata_scsi_set_passthru_sense_fields(struct ata_queued_cmd *qc)
> +{
> +	struct scsi_cmnd *cmd = qc->scsicmd;
> +	struct ata_taskfile *tf = &qc->result_tf;
> +	unsigned char *sb = cmd->sense_buffer;
> +
> +	if ((sb[0] & 0x7f) >= 0x72) {
> +		unsigned char *desc;
> +		u8 len;
> +
> +		/* descriptor format */
> +		len = sb[7];
> +		desc = (char *)scsi_sense_desc_find(sb, len + 8, 9);
> +		if (!desc) {
> +			if (SCSI_SENSE_BUFFERSIZE < len + 14)
> +				return;
> +			sb[7] = len + 14;
> +			desc = sb + 8 + len;
> +		}
> +		desc[0] = 9;
> +		desc[1] = 12;
> +		/*
> +		 * Copy registers into sense buffer.
> +		 */
> +		desc[2] = 0x00;
> +		desc[3] = tf->error;
> +		desc[5] = tf->nsect;
> +		desc[7] = tf->lbal;
> +		desc[9] = tf->lbam;
> +		desc[11] = tf->lbah;
> +		desc[12] = tf->device;
> +		desc[13] = tf->status;
> +
> +		/*
> +		 * Fill in Extend bit, and the high order bytes
> +		 * if applicable.
> +		 */
> +		if (tf->flags & ATA_TFLAG_LBA48) {
> +			desc[2] |= 0x01;
> +			desc[4] = tf->hob_nsect;
> +			desc[6] = tf->hob_lbal;
> +			desc[8] = tf->hob_lbam;
> +			desc[10] = tf->hob_lbah;
> +		}
> +	} else {
> +		/* Fixed sense format */
> +		sb[0] |= 0x80;
> +		sb[3] = tf->error;
> +		sb[4] = tf->status;
> +		sb[5] = tf->device;
> +		sb[6] = tf->nsect;
> +		if (tf->flags & ATA_TFLAG_LBA48)  {
> +			sb[8] |= 0x80;
> +			if (tf->hob_nsect)
> +				sb[8] |= 0x40;
> +			if (tf->hob_lbal || tf->hob_lbam || tf->hob_lbah)
> +				sb[8] |= 0x20;
> +		}
> +		sb[9] = tf->lbal;
> +		sb[10] = tf->lbam;
> +		sb[11] = tf->lbah;
> +	}
> +}
> +
>  static void ata_scsi_set_invalid_field(struct ata_device *dev,
>  				       struct scsi_cmnd *cmd, u16 field, u8 bit)
>  {
> @@ -837,10 +911,8 @@ static void ata_to_sense_error(unsigned id, u8 drv_stat, u8 drv_err, u8 *sk,
>   *	ata_gen_passthru_sense - Generate check condition sense block.
>   *	@qc: Command that completed.
>   *
> - *	This function is specific to the ATA descriptor format sense
> - *	block specified for the ATA pass through commands.  Regardless
> - *	of whether the command errored or not, return a sense
> - *	block. Copy all controller registers into the sense
> + *	This function is specific to the ATA pass through commands.
> + *	Regardless of whether the command errored or not, return a sense
>   *	block. If there was no error, we get the request from an ATA
>   *	passthrough command, so we use the following sense data:
>   *	sk = RECOVERED ERROR
> @@ -875,63 +947,6 @@ static void ata_gen_passthru_sense(struct ata_queued_cmd *qc)
>  		 */
>  		scsi_build_sense(cmd, 1, RECOVERED_ERROR, 0, 0x1D);
>  	}
> -
> -	if ((sb[0] & 0x7f) >= 0x72) {
> -		unsigned char *desc;
> -		u8 len;
> -
> -		/* descriptor format */
> -		len = sb[7];
> -		desc = (char *)scsi_sense_desc_find(sb, len + 8, 9);
> -		if (!desc) {
> -			if (SCSI_SENSE_BUFFERSIZE < len + 14)
> -				return;
> -			sb[7] = len + 14;
> -			desc = sb + 8 + len;
> -		}
> -		desc[0] = 9;
> -		desc[1] = 12;
> -		/*
> -		 * Copy registers into sense buffer.
> -		 */
> -		desc[2] = 0x00;
> -		desc[3] = tf->error;
> -		desc[5] = tf->nsect;
> -		desc[7] = tf->lbal;
> -		desc[9] = tf->lbam;
> -		desc[11] = tf->lbah;
> -		desc[12] = tf->device;
> -		desc[13] = tf->status;
> -
> -		/*
> -		 * Fill in Extend bit, and the high order bytes
> -		 * if applicable.
> -		 */
> -		if (tf->flags & ATA_TFLAG_LBA48) {
> -			desc[2] |= 0x01;
> -			desc[4] = tf->hob_nsect;
> -			desc[6] = tf->hob_lbal;
> -			desc[8] = tf->hob_lbam;
> -			desc[10] = tf->hob_lbah;
> -		}
> -	} else {
> -		/* Fixed sense format */
> -		sb[0] |= 0x80;
> -		sb[3] = tf->error;
> -		sb[4] = tf->status;
> -		sb[5] = tf->device;
> -		sb[6] = tf->nsect;
> -		if (tf->flags & ATA_TFLAG_LBA48)  {
> -			sb[8] |= 0x80;
> -			if (tf->hob_nsect)
> -				sb[8] |= 0x40;
> -			if (tf->hob_lbal || tf->hob_lbam || tf->hob_lbah)
> -				sb[8] |= 0x20;
> -		}
> -		sb[9] = tf->lbal;
> -		sb[10] = tf->lbam;
> -		sb[11] = tf->lbah;
> -	}
>  }
>  
>  /**
> @@ -1634,6 +1649,8 @@ static void ata_scsi_qc_complete(struct ata_queued_cmd *qc)
>  	u8 *cdb = cmd->cmnd;
>  	int need_sense = (qc->err_mask != 0) &&
>  		!(qc->flags & ATA_QCFLAG_SENSE_VALID);
> +	int need_passthru_sense = (qc->err_mask != 0) ||
> +		(qc->flags & ATA_QCFLAG_SENSE_VALID);
>  
>  	/* For ATA pass thru (SAT) commands, generate a sense block if
>  	 * user mandated it or if there's an error.  Note that if we
> @@ -1645,13 +1662,16 @@ static void ata_scsi_qc_complete(struct ata_queued_cmd *qc)
>  	 * asc,ascq = ATA PASS-THROUGH INFORMATION AVAILABLE
>  	 */
>  	if (((cdb[0] == ATA_16) || (cdb[0] == ATA_12)) &&
> -	    ((cdb[2] & 0x20) || need_sense))
> -		ata_gen_passthru_sense(qc);
> -	else if (need_sense)
> +	    ((cdb[2] & 0x20) || need_passthru_sense)) {
> +		if (!(qc->flags & ATA_QCFLAG_SENSE_VALID))
> +			ata_gen_passthru_sense(qc);
> +		ata_scsi_set_passthru_sense_fields(qc);
> +	} else if (need_sense) {
>  		ata_gen_ata_sense(qc);
> -	else
> +	} else {
>  		/* Keep the SCSI ML and status byte, clear host byte. */
>  		cmd->result &= 0x0000ffff;
> +	}
>  
>  	ata_qc_done(qc);
>  }
> @@ -2590,14 +2610,8 @@ static void atapi_qc_complete(struct ata_queued_cmd *qc)
>  	/* handle completion from EH */
>  	if (unlikely(err_mask || qc->flags & ATA_QCFLAG_SENSE_VALID)) {
>  
> -		if (!(qc->flags & ATA_QCFLAG_SENSE_VALID)) {
> -			/* FIXME: not quite right; we don't want the
> -			 * translation of taskfile registers into a
> -			 * sense descriptors, since that's only
> -			 * correct for ATA, not ATAPI
> -			 */
> +		if (!(qc->flags & ATA_QCFLAG_SENSE_VALID))
>  			ata_gen_passthru_sense(qc);
> -		}
>  
>  		/* SCSI EH automatically locks door if sdev->locked is
>  		 * set.  Sometimes door lock request continues to

-- 
Damien Le Moal
Western Digital Research