target: Allow for target_submit_cmd() returning errors

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 +
      fix double se_cmd init in exception path for usb-gadget)

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

@@ -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)

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,
+	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);
+			      MSG_SIMPLE_TAG, data_dir, 0))
+		goto err;
+
 	return;
 
 err:

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);
 

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,
+	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);
+			      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;
 

drivers/usb/gadget/tcm_usb_gadget.c

@@ -1065,16 +1065,20 @@ static void usbg_cmd_work(struct work_struct *work)
 				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,
+			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);
-		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,
@@ -1177,16 +1181,20 @@ static void bot_cmd_work(struct work_struct *work)
 				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;
 
+out:
 	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,

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,