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Message-ID: <Zn3ffnqsN4pVZA4m@google.com>
Date: Thu, 27 Jun 2024 21:54:06 +0000
From: Igor Pylypiv <ipylypiv@...gle.com>
To: Niklas Cassel <cassel@...nel.org>
Cc: Damien Le Moal <dlemoal@...nel.org>, Tejun Heo <tj@...nel.org>,
Hannes Reinecke <hare@...e.de>, linux-ide@...r.kernel.org,
linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v3 2/6] ata: libata-scsi: Do not overwrite valid sense
data when CK_COND=1
On Thu, Jun 27, 2024 at 04:14:09PM +0200, Niklas Cassel wrote:
> On Wed, Jun 26, 2024 at 11:04:07PM +0000, 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@...r.kernel.org
> > Reviewed-by: Hannes Reinecke <hare@...e.de>
> > Reviewed-by: Damien Le Moal <dlemoal@...nel.org>
> > Signed-off-by: Igor Pylypiv <ipylypiv@...gle.com>
> > ---
> > 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);
>
> This whole logic looks too complicated to me.
>
> Can't we do something to make it easier to read, e.g. something like:
>
>
> {
> if (command_is_ata_passthru(cdb)) {
> handle_passthru_completion(qc);
> ata_qc_done();
> return;
> }
>
> if (need_sense)
> ata_gen_ata_sense(qc);
> else
> /* Keep the SCSI ML and status byte, clear host byte. */
> cmd->result &= 0x0000ffff;
>
> ata_qc_done();
> }
>
> And then put the complicated logic in handle_passthru_command() ?
>
> /* CASES:
> * a) IF error command (ERROR or DF set) and ATA_QCFLAG_SENSE_VALID (SK+ASC+ASCQ) set:
> * - don't touch SK/ASC/ASCQ in sense_buffer
> * - set ATA registers in fixed format or descriptor format (based on dev->flags ATA_DFLAG_D_SENSE)
> * b) IF error command (ERROR or DF set) and ATA_QCFLAG_SENSE_VALID (SK+ASC+ASCQ) not set:
> * - generate the SK+ASC+ASCQ from ATA status and ATA error, and
> * - set CHECK_CONDITION in cmd->result (scsi_build_sense() does this)
> * - set ATA registers in fixed format or descriptor format (based on dev->flags ATA_DFLAG_D_SENSE)
> * c) IF success command (ERROR and DF not set), and ATA_QCFLAG_SENSE_VALID set, CK_COND set:
> * - don't touch SK/ASC/ASCQ in sense_buffer
> * - set ATA registers in fixed format or descriptor format (based on dev->flags ATA_DFLAG_D_SENSE)
> * - we should probably set CHECK_CONDITION status byte in cmd->result here.... but not sure...
> * d) IF success command (ERROR and DF not set), and ATA_QCFLAG_SENSE_VALID set, CK_COND not set:
> * - don't touch SK/ASC/ASCQ in sense_buffer
> * - don't fill ATA registers
> * - keep the SCSI ML and status byte, clear host byte, in cmd->result
> * e) IF success command (ERROR and DF not set), and ATA_QCFLAG_SENSE_VALID not set, CK_COND set:
> * - set SK to "RECOVERED ERROR" ASCQ to "ATA PASS-THROUGH INFORMATION AVAILABLE", ASC to 0.
> * - set ATA registers in fixed format or descriptor format (based on dev->flags ATA_DFLAG_D_SENSE)
> * - set CHECK_CONDITION status byte in cmd->result
> * f) IF success command (ERROR and DF not set), and ATA_QCFLAG_SENSE_VALID not set, CK_COND not set:
> * - keep the SCSI ML and status byte, clear host byte, in cmd->result
> */
> static void ata_handle_passthru_completion(struct ata_queued_cmd *qc);
>
> So we should only copy the ATA registers when CK_COND is set, or if ERROR bit
> or DF bit was set. CK_COND being set in the cdb (input command) basically means
> that the user requested that the ATA registers should be copied into the sense
> buffer (in the result).
>
> The only tricky case is if we should set CHECK_CONDITION in case c) or not.
> All other cases seems quite clear by looking at the SAT spec.
>
Thank you, Niklas! I agree that this code is too complicated and should be
simplified. I don't think we should change the code too much in this patch
since it is going to be backported to stable releases.
Would you mind sending a patch for the proposed simplifications following
this patch series?
I think there are some additional simplifications that can be made,
e.g. both ata_gen_passthru_sense() and ata_gen_ata_sense() contain
the same exact code:
/*
* Use ata_to_sense_error() to map status register bits
* onto sense key, asc & ascq.
*/
if (qc->err_mask ||
tf->status & (ATA_BUSY | ATA_DF | ATA_ERR | ATA_DRQ)) {
ata_to_sense_error(tf->status, tf->error,
&sense_key, &asc, &ascq);
ata_scsi_set_sense(qc->dev, cmd, sense_key, asc, ascq);
} else {
Perhaps it can be moved into a separate function, etc.
Thanks,
Igor
>
> > + } 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
> > --
> > 2.45.2.803.g4e1b14247a-goog
> >
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