target: Add tracepoints for SCSI commands being processed

This patch adds tracepoints to the target code for commands being
received and being completed, which is quite useful for debugging
interactions with initiators. For example, one can do something like the
following to watch commands that are completing unsuccessfully:

    # echo 'scsi_status!=0' > /sys/kernel/debug/tracing/events/target/target_cmd_complete/filter
    # echo 1 > /sys/kernel/debug/tracing/events/target/target_cmd_complete/enable

        <run command that fails>

    # cat /sys/kernel/debug/tracing/trace
         iscsi_trx-0-1902  [003] ...1 990185.810385: target_cmd_complete: iqn.1993-08.org.debian:01:e51ede6aacfd <- LUN 001 status CHECK CONDITION (sense len 18 / 70 00 05 00 00 00 00 0a 00 00 00 00 20 00 00 00 00 00)  0x95 data_length    512  CDB 95 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  (TA:SIMPLE C:00)

(v2: Drop undefined COMPARE_AND_WRITE)

Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 15 insertions, 1 deletions

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index ae40addd4ce0..7172d005d063 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -52,6 +52,9 @@
 #include "target_core_pr.h"
 #include "target_core_ua.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/target.h>
+
 static struct workqueue_struct *target_completion_wq;
 static struct kmem_cache *se_sess_cache;
 struct kmem_cache *se_ua_cache;
@@ -1123,6 +1126,8 @@ target_setup_cmd_from_cdb(struct se_cmd *cmd, unsigned char *cdb)
 	 */
 	memcpy(cmd->t_task_cdb, cdb, scsi_command_size(cdb));
 
+	trace_target_sequencer_start(cmd);
+
 	/*
 	 * Check for an existing UNIT ATTENTION condition
 	 */
@@ -1546,7 +1551,8 @@ void transport_generic_request_failure(struct se_cmd *cmd,
 				cmd->orig_fe_lun, 0x2C,
 				ASCQ_2CH_PREVIOUS_RESERVATION_CONFLICT_STATUS);
 
-		ret = cmd->se_tfo->queue_status(cmd);
+		trace_target_cmd_complete(cmd);
+		ret = cmd->se_tfo-> queue_status(cmd);
 		if (ret == -EAGAIN || ret == -ENOMEM)
 			goto queue_full;
 		goto check_stop;
@@ -1766,6 +1772,7 @@ static void transport_complete_qf(struct se_cmd *cmd)
 	transport_complete_task_attr(cmd);
 
 	if (cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) {
+		trace_target_cmd_complete(cmd);
 		ret = cmd->se_tfo->queue_status(cmd);
 		if (ret)
 			goto out;
@@ -1773,6 +1780,7 @@ static void transport_complete_qf(struct se_cmd *cmd)
 
 	switch (cmd->data_direction) {
 	case DMA_FROM_DEVICE:
+		trace_target_cmd_complete(cmd);
 		ret = cmd->se_tfo->queue_data_in(cmd);
 		break;
 	case DMA_TO_DEVICE:
@@ -1783,6 +1791,7 @@ static void transport_complete_qf(struct se_cmd *cmd)
 		}
 		/* Fall through for DMA_TO_DEVICE */
 	case DMA_NONE:
+		trace_target_cmd_complete(cmd);
 		ret = cmd->se_tfo->queue_status(cmd);
 		break;
 	default:
@@ -1861,6 +1870,7 @@ static void target_complete_ok_work(struct work_struct *work)
 		}
 		spin_unlock(&cmd->se_lun->lun_sep_lock);
 
+		trace_target_cmd_complete(cmd);
 		ret = cmd->se_tfo->queue_data_in(cmd);
 		if (ret == -EAGAIN || ret == -ENOMEM)
 			goto queue_full;
@@ -1889,6 +1899,7 @@ static void target_complete_ok_work(struct work_struct *work)
 		}
 		/* Fall through for DMA_TO_DEVICE */
 	case DMA_NONE:
+		trace_target_cmd_complete(cmd);
 		ret = cmd->se_tfo->queue_status(cmd);
 		if (ret == -EAGAIN || ret == -ENOMEM)
 			goto queue_full;
@@ -2745,6 +2756,7 @@ transport_send_check_condition_and_sense(struct se_cmd *cmd,
 	cmd->scsi_sense_length  = TRANSPORT_SENSE_BUFFER;
 
 after_reason:
+	trace_target_cmd_complete(cmd);
 	return cmd->se_tfo->queue_status(cmd);
 }
 EXPORT_SYMBOL(transport_send_check_condition_and_sense);
@@ -2761,6 +2773,7 @@ int transport_check_aborted_status(struct se_cmd *cmd, int send_status)
 		 cmd->t_task_cdb[0], cmd->se_tfo->get_task_tag(cmd));
 
 	cmd->se_cmd_flags |= SCF_SENT_DELAYED_TAS;
+	trace_target_cmd_complete(cmd);
 	cmd->se_tfo->queue_status(cmd);
 
 	return 1;
@@ -2798,6 +2811,7 @@ void transport_send_task_abort(struct se_cmd *cmd)
 		" ITT: 0x%08x\n", cmd->t_task_cdb[0],
 		cmd->se_tfo->get_task_tag(cmd));
 
+	trace_target_cmd_complete(cmd);
 	cmd->se_tfo->queue_status(cmd);
 }