[PATCH] target: Allow for target_submit_cmd() returning errors

[PATCH] target: Allow for target_submit_cmd() returning errors

[Nicholas A. Bellinger]

From: Roland Dreier <roland@purestorage.com>

We want it to be possible for target_submit_cmd() to return errors up
to its fabric module callers.  For now just update the prototype to
return an int, and update all callers to handle non-zero return values
as an error.

This is immediately useful for tcm_qla2xxx to fix a long-standing active
I/O session shutdown race, but tcm_fc, usb-gadget, and sbp-target the
fabric maintainers need to check + ACK that handling a target_submit_cmd()
failure due to session shutdown does not introduce regressions

(nab: Respin against for-next after initial NACK + update docbook comment)

Cc: Chad Dupuis <chad.dupuis@qlogic.com>
Cc: Arun Easi <arun.easi@qlogic.com>
Cc: Chris Boot <bootc@bootc.net>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Mark Rustad <mark.d.rustad@intel.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Andy Grover <agrover@redhat.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
 drivers/scsi/qla2xxx/tcm_qla2xxx.c     |    3 +--
 drivers/target/sbp/sbp_target.c        |    8 +++++---
 drivers/target/target_core_transport.c |   14 +++++++++-----
 drivers/target/tcm_fc/tfc_cmd.c        |    8 +++++---
 drivers/usb/gadget/tcm_usb_gadget.c    |   20 ++++++++------------
 include/target/target_core_fabric.h    |    2 +-
 6 files changed, 29 insertions(+), 26 deletions(-)

diff --git a/drivers/scsi/qla2xxx/tcm_qla2xxx.c b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
index 65a7ed9..4752f65 100644
--- a/drivers/scsi/qla2xxx/tcm_qla2xxx.c
+++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
@@ -597,10 +597,9 @@ static int tcm_qla2xxx_handle_cmd(scsi_qla_host_t *vha, struct qla_tgt_cmd *cmd,
 		return -EINVAL;
 	}
 
-	target_submit_cmd(se_cmd, se_sess, cdb, &cmd->sense_buffer[0],
+	return target_submit_cmd(se_cmd, se_sess, cdb, &cmd->sense_buffer[0],
 				cmd->unpacked_lun, data_length, fcp_task_attr,
 				data_dir, flags);
-	return 0;
 }
 
 static void tcm_qla2xxx_handle_data_work(struct work_struct *work)
diff --git a/drivers/target/sbp/sbp_target.c b/drivers/target/sbp/sbp_target.c
index e10e622..39ddba5 100644
--- a/drivers/target/sbp/sbp_target.c
+++ b/drivers/target/sbp/sbp_target.c
@@ -1235,9 +1235,11 @@ static void sbp_handle_command(struct sbp_target_request *req)
 	pr_debug("sbp_handle_command ORB:0x%llx unpacked_lun:%d data_len:%d data_dir:%d\n",
 			req->orb_pointer, unpacked_lun, data_length, data_dir);
 
-	target_submit_cmd(&req->se_cmd, sess->se_sess, req->cmd_buf,
-			req->sense_buf, unpacked_lun, data_length,
-			MSG_SIMPLE_TAG, data_dir, 0);
+	if (target_submit_cmd(&req->se_cmd, sess->se_sess, req->cmd_buf,
+			      req->sense_buf, unpacked_lun, data_length,
+			      MSG_SIMPLE_TAG, data_dir, 0))
+		goto err;
+
 	return;
 
 err:
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 14e54b4..7647eca 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1447,10 +1447,14 @@ EXPORT_SYMBOL(transport_handle_cdb_direct);
  * @data_dir: DMA data direction
  * @flags: flags for command submission from target_sc_flags_tables
  *
+ * Returns non zero to signal active I/O shutdown failure.  All other
+ * setup exceptions will be returned as a SCSI CHECK_CONDITION response,
+ * but still return zero here.
+ *
  * This may only be called from process context, and also currently
  * assumes internal allocation of fabric payload buffer by target-core.
  **/
-void target_submit_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
+int target_submit_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
 		unsigned char *cdb, unsigned char *sense, u32 unpacked_lun,
 		u32 data_length, int task_attr, int data_dir, int flags)
 {
@@ -1478,7 +1482,7 @@ void target_submit_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
 	 */
 	rc = target_get_sess_cmd(se_sess, se_cmd, (flags & TARGET_SCF_ACK_KREF));
 	if (rc)
-		return;
+		return rc;
 	/*
 	 * Signal bidirectional data payloads to target-core
 	 */
@@ -1491,13 +1495,13 @@ void target_submit_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
 		transport_send_check_condition_and_sense(se_cmd,
 				se_cmd->scsi_sense_reason, 0);
 		target_put_sess_cmd(se_sess, se_cmd);
-		return;
+		return 0;
 	}
 
 	rc = target_setup_cmd_from_cdb(se_cmd, cdb);
 	if (rc != 0) {
 		transport_generic_request_failure(se_cmd);
-		return;
+		return 0;
 	}
 
 	/*
@@ -1507,7 +1511,7 @@ void target_submit_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
 	core_alua_check_nonop_delay(se_cmd);
 
 	transport_handle_cdb_direct(se_cmd);
-	return;
+	return 0;
 }
 EXPORT_SYMBOL(target_submit_cmd);
 
diff --git a/drivers/target/tcm_fc/tfc_cmd.c b/drivers/target/tcm_fc/tfc_cmd.c
index 4ad58ac..b9cb500 100644
--- a/drivers/target/tcm_fc/tfc_cmd.c
+++ b/drivers/target/tcm_fc/tfc_cmd.c
@@ -543,9 +543,11 @@ static void ft_send_work(struct work_struct *work)
 	 * Use a single se_cmd->cmd_kref as we expect to release se_cmd
 	 * directly from ft_check_stop_free callback in response path.
 	 */
-	target_submit_cmd(&cmd->se_cmd, cmd->sess->se_sess, fcp->fc_cdb,
-			&cmd->ft_sense_buffer[0], scsilun_to_int(&fcp->fc_lun),
-			ntohl(fcp->fc_dl), task_attr, data_dir, 0);
+	if (target_submit_cmd(&cmd->se_cmd, cmd->sess->se_sess, fcp->fc_cdb,
+			      &cmd->ft_sense_buffer[0], scsilun_to_int(&fcp->fc_lun),
+			      ntohl(fcp->fc_dl), task_attr, data_dir, 0))
+		goto err;
+
 	pr_debug("r_ctl %x alloc target_submit_cmd\n", fh->fh_r_ctl);
 	return;
 
diff --git a/drivers/usb/gadget/tcm_usb_gadget.c b/drivers/usb/gadget/tcm_usb_gadget.c
index 02ace18..9ddf315 100644
--- a/drivers/usb/gadget/tcm_usb_gadget.c
+++ b/drivers/usb/gadget/tcm_usb_gadget.c
@@ -1060,7 +1060,10 @@ static void usbg_cmd_work(struct work_struct *work)
 	tpg = cmd->fu->tpg;
 	tv_nexus = tpg->tpg_nexus;
 	dir = get_cmd_dir(cmd->cmd_buf);
-	if (dir < 0) {
+	if (dir < 0 ||
+	    target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
+			      cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
+			      0, cmd->prio_attr, dir, TARGET_SCF_UNKNOWN_SIZE)) {
 		transport_init_se_cmd(se_cmd,
 				tv_nexus->tvn_se_sess->se_tpg->se_tpg_tfo,
 				tv_nexus->tvn_se_sess, cmd->data_len, DMA_NONE,
@@ -1069,12 +1072,7 @@ static void usbg_cmd_work(struct work_struct *work)
 		transport_send_check_condition_and_sense(se_cmd,
 				TCM_UNSUPPORTED_SCSI_OPCODE, 1);
 		usbg_cleanup_cmd(cmd);
-		return;
 	}
-
-	target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
-			cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
-			0, cmd->prio_attr, dir, TARGET_SCF_UNKNOWN_SIZE);
 }
 
 static int usbg_submit_command(struct f_uas *fu,
@@ -1172,7 +1170,10 @@ static void bot_cmd_work(struct work_struct *work)
 	tpg = cmd->fu->tpg;
 	tv_nexus = tpg->tpg_nexus;
 	dir = get_cmd_dir(cmd->cmd_buf);
-	if (dir < 0) {
+	if (dir < 0 ||
+	    target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
+			      cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
+			      cmd->data_len, cmd->prio_attr, dir, 0)) {
 		transport_init_se_cmd(se_cmd,
 				tv_nexus->tvn_se_sess->se_tpg->se_tpg_tfo,
 				tv_nexus->tvn_se_sess, cmd->data_len, DMA_NONE,
@@ -1181,12 +1182,7 @@ static void bot_cmd_work(struct work_struct *work)
 		transport_send_check_condition_and_sense(se_cmd,
 				TCM_UNSUPPORTED_SCSI_OPCODE, 1);
 		usbg_cleanup_cmd(cmd);
-		return;
 	}
-
-	target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
-			cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
-			cmd->data_len, cmd->prio_attr, dir, 0);
 }
 
 static int bot_submit_command(struct f_uas *fu,
diff --git a/include/target/target_core_fabric.h b/include/target/target_core_fabric.h
index 815e064..69fb3cf 100644
--- a/include/target/target_core_fabric.h
+++ b/include/target/target_core_fabric.h
@@ -102,7 +102,7 @@ void	transport_init_se_cmd(struct se_cmd *, struct target_core_fabric_ops *,
 		struct se_session *, u32, int, int, unsigned char *);
 int	transport_lookup_cmd_lun(struct se_cmd *, u32);
 int	target_setup_cmd_from_cdb(struct se_cmd *, unsigned char *);
-void	target_submit_cmd(struct se_cmd *, struct se_session *, unsigned char *,
+int	target_submit_cmd(struct se_cmd *, struct se_session *, unsigned char *,
 		unsigned char *, u32, u32, int, int, int);
 int	target_submit_tmr(struct se_cmd *se_cmd, struct se_session *se_sess,
 		unsigned char *sense, u32 unpacked_lun,
-- 
1.7.2.5

Re: [PATCH] target: Allow for target_submit_cmd() returning errors

[Nicholas A. Bellinger]

On Tue, 2012-07-17 at 23:37 +0000, Nicholas A. Bellinger wrote:
> From: Roland Dreier <roland@purestorage.com>
> 
> We want it to be possible for target_submit_cmd() to return errors up
> to its fabric module callers.  For now just update the prototype to
> return an int, and update all callers to handle non-zero return values
> as an error.
> 
> This is immediately useful for tcm_qla2xxx to fix a long-standing active
> I/O session shutdown race, but tcm_fc, usb-gadget, and sbp-target the
> fabric maintainers need to check + ACK that handling a target_submit_cmd()
> failure due to session shutdown does not introduce regressions
> 
> (nab: Respin against for-next after initial NACK + update docbook comment)
> 

<SNIP> + trimming CC to USB folks:

> index 02ace18..9ddf315 100644
> --- a/drivers/usb/gadget/tcm_usb_gadget.c
> +++ b/drivers/usb/gadget/tcm_usb_gadget.c
> @@ -1060,7 +1060,10 @@ static void usbg_cmd_work(struct work_struct *work)
>  	tpg = cmd->fu->tpg;
>  	tv_nexus = tpg->tpg_nexus;
>  	dir = get_cmd_dir(cmd->cmd_buf);
> -	if (dir < 0) {
> +	if (dir < 0 ||
> +	    target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
> +			      cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
> +			      0, cmd->prio_attr, dir, TARGET_SCF_UNKNOWN_SIZE)) {
>  		transport_init_se_cmd(se_cmd,
>  				tv_nexus->tvn_se_sess->se_tpg->se_tpg_tfo,
>  				tv_nexus->tvn_se_sess, cmd->data_len, DMA_NONE,
> @@ -1069,12 +1072,7 @@ static void usbg_cmd_work(struct work_struct *work)
>  		transport_send_check_condition_and_sense(se_cmd,
>  				TCM_UNSUPPORTED_SCSI_OPCODE, 1);
>  		usbg_cleanup_cmd(cmd);
> -		return;
>  	}
> -
> -	target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
> -			cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
> -			0, cmd->prio_attr, dir, TARGET_SCF_UNKNOWN_SIZE);
>  }
>  
>  static int usbg_submit_command(struct f_uas *fu,
> @@ -1172,7 +1170,10 @@ static void bot_cmd_work(struct work_struct *work)
>  	tpg = cmd->fu->tpg;
>  	tv_nexus = tpg->tpg_nexus;
>  	dir = get_cmd_dir(cmd->cmd_buf);
> -	if (dir < 0) {
> +	if (dir < 0 ||
> +	    target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
> +			      cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
> +			      cmd->data_len, cmd->prio_attr, dir, 0)) {
>  		transport_init_se_cmd(se_cmd,
>  				tv_nexus->tvn_se_sess->se_tpg->se_tpg_tfo,
>  				tv_nexus->tvn_se_sess, cmd->data_len, DMA_NONE,
> @@ -1181,12 +1182,7 @@ static void bot_cmd_work(struct work_struct *work)
>  		transport_send_check_condition_and_sense(se_cmd,
>  				TCM_UNSUPPORTED_SCSI_OPCODE, 1);
>  		usbg_cleanup_cmd(cmd);
> -		return;
>  	}
> -
> -	target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
> -			cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
> -			cmd->data_len, cmd->prio_attr, dir, 0);
>  }
>  

Looking at this part again target_submit_cmd() has been moved ahead of
target_init_se_cmd() in the exception path, which ends up getting called
twice during a target_get_sess_cmd() failure..

It looks like usbg_cmd_work() + bot_cmd_work() will need some work if
they intends to use a non zero failure to signal exception here, without
invoking a CHECK_CONDITION and sense.  Actually, I'm not even sure
sending a CHECK_CONDITION here after the target_submit_cmd() is going to
work for other fabrics drivers, but it appears to work with usb-gadget.
(Sebastian..?)

So for the moment, lets fix the double se_cmd init and make things a
little easier to read..   Sebastian, please have a look and double check
that the (dir < 0) + target_submit_cmd() failures cases are both going
to work as expected whilst sending a CHECK_CONDITION response.

Thanks!

--nab

diff --git a/drivers/usb/gadget/tcm_usb_gadget.c b/drivers/usb/gadget/tcm_usb_gadget.c
index 9ddf315..5444866 100644
--- a/drivers/usb/gadget/tcm_usb_gadget.c
+++ b/drivers/usb/gadget/tcm_usb_gadget.c
@@ -1060,19 +1060,25 @@ static void usbg_cmd_work(struct work_struct *work)
        tpg = cmd->fu->tpg;
        tv_nexus = tpg->tpg_nexus;
        dir = get_cmd_dir(cmd->cmd_buf);
-       if (dir < 0 ||
-           target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
-                             cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
-                             0, cmd->prio_attr, dir, TARGET_SCF_UNKNOWN_SIZE)) {
+       if (dir < 0) {
                transport_init_se_cmd(se_cmd,
                                tv_nexus->tvn_se_sess->se_tpg->se_tpg_tfo,
                                tv_nexus->tvn_se_sess, cmd->data_len, DMA_NONE,
                                cmd->prio_attr, cmd->sense_iu.sense);
-
-               transport_send_check_condition_and_sense(se_cmd,
-                               TCM_UNSUPPORTED_SCSI_OPCODE, 1);
-               usbg_cleanup_cmd(cmd);
+               goto out;
        }
+
+       if (target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
+                       cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
+                       0, cmd->prio_attr, dir, TARGET_SCF_UNKNOWN_SIZE) < 0)
+               goto out;
+
+       return;
+
+out:
+       transport_send_check_condition_and_sense(se_cmd,
+                       TCM_UNSUPPORTED_SCSI_OPCODE, 1);
+       usbg_cleanup_cmd(cmd);
 }
 
 static int usbg_submit_command(struct f_uas *fu,
@@ -1170,19 +1176,25 @@ static void bot_cmd_work(struct work_struct *work)
        tpg = cmd->fu->tpg;
        tv_nexus = tpg->tpg_nexus;
        dir = get_cmd_dir(cmd->cmd_buf);
-       if (dir < 0 ||
-           target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
-                             cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
-                             cmd->data_len, cmd->prio_attr, dir, 0)) {
+       if (dir < 0) {
                transport_init_se_cmd(se_cmd,
                                tv_nexus->tvn_se_sess->se_tpg->se_tpg_tfo,
                                tv_nexus->tvn_se_sess, cmd->data_len, DMA_NONE,
                                cmd->prio_attr, cmd->sense_iu.sense);
+               goto out;
+       }
+
+       if (target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
+                       cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
+                       cmd->data_len, cmd->prio_attr, dir, 0) < 0)
+               goto out;
+
+       return;
 
-               transport_send_check_condition_and_sense(se_cmd,
+out:
+       transport_send_check_condition_and_sense(se_cmd,
                                TCM_UNSUPPORTED_SCSI_OPCODE, 1);
-               usbg_cleanup_cmd(cmd);
-       }
+       usbg_cleanup_cmd(cmd);
 }
 
 static int bot_submit_command(struct f_uas *fu,

Re: [PATCH] target: Allow for target_submit_cmd() returning errors

[Sebastian Andrzej Siewior]

On 07/18/2012 02:05 AM, Nicholas A. Bellinger wrote:
>> index 02ace18..9ddf315 100644
>> --- a/drivers/usb/gadget/tcm_usb_gadget.c
>> +++ b/drivers/usb/gadget/tcm_usb_gadget.c
>> @@ -1060,7 +1060,10 @@ static void usbg_cmd_work(struct work_struct *work)
>>   	tpg = cmd->fu->tpg;
>>   	tv_nexus = tpg->tpg_nexus;
>>   	dir = get_cmd_dir(cmd->cmd_buf);
>> -	if (dir<  0) {
>> +	if (dir<  0 ||
>> +	    target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
>> +			      cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
>> +			      0, cmd->prio_attr, dir, TARGET_SCF_UNKNOWN_SIZE)) {
>>   		transport_init_se_cmd(se_cmd,
>>   				tv_nexus->tvn_se_sess->se_tpg->se_tpg_tfo,
>>   				tv_nexus->tvn_se_sess, cmd->data_len, DMA_NONE,
>> @@ -1069,12 +1072,7 @@ static void usbg_cmd_work(struct work_struct *work)
>>   		transport_send_check_condition_and_sense(se_cmd,
>>   				TCM_UNSUPPORTED_SCSI_OPCODE, 1);
>>   		usbg_cleanup_cmd(cmd);
>> -		return;
>>   	}
>> -
>> -	target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
>> -			cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
>> -			0, cmd->prio_attr, dir, TARGET_SCF_UNKNOWN_SIZE);
>>   }
>>
>>   static int usbg_submit_command(struct f_uas *fu,
>
> Looking at this part again target_submit_cmd() has been moved ahead of
> target_init_se_cmd() in the exception path, which ends up getting called
> twice during a target_get_sess_cmd() failure..
>
> It looks like usbg_cmd_work() + bot_cmd_work() will need some work if
> they intends to use a non zero failure to signal exception here, without
> invoking a CHECK_CONDITION and sense.  Actually, I'm not even sure
> sending a CHECK_CONDITION here after the target_submit_cmd() is going to
> work for other fabrics drivers, but it appears to work with usb-gadget.
> (Sebastian..?)

For UAS the status/ sense URB is sent right away (without any data) and
this worked the last time I tested.
For BOT things are a little complicated. What I do is to send empty
data (to fill the data pipe) and send a bad status so the other side
learns that the transfer failed somehow. The sense information is lost.
What I should do is to queue this sense data for the next MODE_SENSE
request which will be coming soon. Right now WinXP repeats a failed
command thrice if MODE_SENSE returns no error. "This" is on my to-fix
list…

> So for the moment, lets fix the double se_cmd init and make things a
> little easier to read..   Sebastian, please have a look and double check
> that the (dir<  0) + target_submit_cmd() failures cases are both going
> to work as expected whilst sending a CHECK_CONDITION response.

The sense code should only be sent once and
transport_send_check_condition_and_sense() sets
SCF_SENT_CHECK_CONDITION and checks for it so doing it twice should not
do any harm right? But grep does not say when this flag gets removed.

>
> Thanks!
>
> --nab

Sebastian
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Re: [PATCH] target: Allow for target_submit_cmd() returning errors

[Nicholas A. Bellinger]

On Wed, 2012-07-18 at 11:10 +0200, Sebastian Andrzej Siewior wrote:
> On 07/18/2012 02:05 AM, Nicholas A. Bellinger wrote:
> >> index 02ace18..9ddf315 100644
> >> --- a/drivers/usb/gadget/tcm_usb_gadget.c
> >> +++ b/drivers/usb/gadget/tcm_usb_gadget.c
> >> @@ -1060,7 +1060,10 @@ static void usbg_cmd_work(struct work_struct *work)
> >>   	tpg = cmd->fu->tpg;
> >>   	tv_nexus = tpg->tpg_nexus;
> >>   	dir = get_cmd_dir(cmd->cmd_buf);
> >> -	if (dir<  0) {
> >> +	if (dir<  0 ||
> >> +	    target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
> >> +			      cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
> >> +			      0, cmd->prio_attr, dir, TARGET_SCF_UNKNOWN_SIZE)) {
> >>   		transport_init_se_cmd(se_cmd,
> >>   				tv_nexus->tvn_se_sess->se_tpg->se_tpg_tfo,
> >>   				tv_nexus->tvn_se_sess, cmd->data_len, DMA_NONE,
> >> @@ -1069,12 +1072,7 @@ static void usbg_cmd_work(struct work_struct *work)
> >>   		transport_send_check_condition_and_sense(se_cmd,
> >>   				TCM_UNSUPPORTED_SCSI_OPCODE, 1);
> >>   		usbg_cleanup_cmd(cmd);
> >> -		return;
> >>   	}
> >> -
> >> -	target_submit_cmd(se_cmd, tv_nexus->tvn_se_sess,
> >> -			cmd->cmd_buf, cmd->sense_iu.sense, cmd->unpacked_lun,
> >> -			0, cmd->prio_attr, dir, TARGET_SCF_UNKNOWN_SIZE);
> >>   }
> >>
> >>   static int usbg_submit_command(struct f_uas *fu,
> >
> > Looking at this part again target_submit_cmd() has been moved ahead of
> > target_init_se_cmd() in the exception path, which ends up getting called
> > twice during a target_get_sess_cmd() failure..
> >
> > It looks like usbg_cmd_work() + bot_cmd_work() will need some work if
> > they intends to use a non zero failure to signal exception here, without
> > invoking a CHECK_CONDITION and sense.  Actually, I'm not even sure
> > sending a CHECK_CONDITION here after the target_submit_cmd() is going to
> > work for other fabrics drivers, but it appears to work with usb-gadget.
> > (Sebastian..?)
> 
> For UAS the status/ sense URB is sent right away (without any data) and
> this worked the last time I tested.

<nod>, thanks for the re-clarification on this..  ;)

> For BOT things are a little complicated. What I do is to send empty
> data (to fill the data pipe) and send a bad status so the other side
> learns that the transfer failed somehow. The sense information is lost.
> What I should do is to queue this sense data for the next MODE_SENSE
> request which will be coming soon. Right now WinXP repeats a failed
> command thrice if MODE_SENSE returns no error. "This" is on my to-fix
> list…
> 

Ok, so I think the special case for usb-gadget where is able to call
transport_send_check_condition_and_sense() should be OK for the single
target_get_sess_cmd() -> target_submit_cmd() failure case..

This is not going to be safe for just about every other fabric AFAICT,
so I think we need a comment here to describe that fact..

> > So for the moment, lets fix the double se_cmd init and make things a
> > little easier to read..   Sebastian, please have a look and double check
> > that the (dir<  0) + target_submit_cmd() failures cases are both going
> > to work as expected whilst sending a CHECK_CONDITION response.
> 
> The sense code should only be sent once and
> transport_send_check_condition_and_sense() sets
> SCF_SENT_CHECK_CONDITION and checks for it so doing it twice should not
> do any harm right? But grep does not say when this flag gets removed.
> 

Correct.  The SCF_SENT_CHECK_CONDITION bit does not get removed ahead of
fabric descriptor release.

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