scsi: target: core: Add CONTROL field for trace events

trace-cmd report doesn't show events from target subsystem because
scsi_command_size() leaks through event format string:

  [target:target_sequencer_start] function scsi_command_size not defined
  [target:target_cmd_complete] function scsi_command_size not defined

Addition of scsi_command_size() to plugin_scsi.c in trace-cmd doesn't
help because an expression is used inside TP_printk(). trace-cmd event
parser doesn't understand minus sign inside [ ]:

  Error: expected ']' but read '-'

Rather than duplicating kernel code in plugin_scsi.c, provide a dedicated
field for CONTROL byte.

Link: https://lore.kernel.org/r/20200929125957.83069-1-r.bolshakov@yadro.comReviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

include/scsi/scsi_common.h

@@ -25,6 +25,13 @@ scsi_command_size(const unsigned char *cmnd)
 		scsi_varlen_cdb_length(cmnd) : COMMAND_SIZE(cmnd[0]);
 }
 
+static inline unsigned char
+scsi_command_control(const unsigned char *cmnd)
+{
+	return (cmnd[0] == VARIABLE_LENGTH_CMD) ?
+		cmnd[1] : cmnd[COMMAND_SIZE(cmnd[0]) - 1];
+}
+
 /* Returns a human-readable name for the device */
 extern const char *scsi_device_type(unsigned type);
 

include/trace/events/target.h

@@ -141,6 +141,7 @@ TRACE_EVENT(target_sequencer_start,
 		__field( unsigned int,	opcode		)
 		__field( unsigned int,	data_length	)
 		__field( unsigned int,	task_attribute  )
+		__field( unsigned char,	control		)
 		__array( unsigned char,	cdb, TCM_MAX_COMMAND_SIZE	)
 		__string( initiator,	cmd->se_sess->se_node_acl->initiatorname	)
 	),
@@ -151,6 +152,7 @@ TRACE_EVENT(target_sequencer_start,
 		__entry->opcode		= cmd->t_task_cdb[0];
 		__entry->data_length	= cmd->data_length;
 		__entry->task_attribute	= cmd->sam_task_attr;
+		__entry->control	= scsi_command_control(cmd->t_task_cdb);
 		memcpy(__entry->cdb, cmd->t_task_cdb, TCM_MAX_COMMAND_SIZE);
 		__assign_str(initiator, cmd->se_sess->se_node_acl->initiatorname);
 	),
@@ -160,9 +162,7 @@ TRACE_EVENT(target_sequencer_start,
 		  __entry->tag, show_opcode_name(__entry->opcode),
 		  __entry->data_length, __print_hex(__entry->cdb, 16),
 		  show_task_attribute_name(__entry->task_attribute),
-		  scsi_command_size(__entry->cdb) <= 16 ?
-			__entry->cdb[scsi_command_size(__entry->cdb) - 1] :
-			__entry->cdb[1]
+		  __entry->control
 	)
 );
 
@@ -178,6 +178,7 @@ TRACE_EVENT(target_cmd_complete,
 		__field( unsigned int,	opcode		)
 		__field( unsigned int,	data_length	)
 		__field( unsigned int,	task_attribute  )
+		__field( unsigned char,	control		)
 		__field( unsigned char,	scsi_status	)
 		__field( unsigned char,	sense_length	)
 		__array( unsigned char,	cdb, TCM_MAX_COMMAND_SIZE	)
@@ -191,6 +192,7 @@ TRACE_EVENT(target_cmd_complete,
 		__entry->opcode		= cmd->t_task_cdb[0];
 		__entry->data_length	= cmd->data_length;
 		__entry->task_attribute	= cmd->sam_task_attr;
+		__entry->control	= scsi_command_control(cmd->t_task_cdb);
 		__entry->scsi_status	= cmd->scsi_status;
 		__entry->sense_length	= cmd->scsi_status == SAM_STAT_CHECK_CONDITION ?
 			min(18, ((u8 *) cmd->sense_buffer)[SPC_ADD_SENSE_LEN_OFFSET] + 8) : 0;
@@ -208,9 +210,7 @@ TRACE_EVENT(target_cmd_complete,
 		  show_opcode_name(__entry->opcode),
 		  __entry->data_length, __print_hex(__entry->cdb, 16),
 		  show_task_attribute_name(__entry->task_attribute),
-		  scsi_command_size(__entry->cdb) <= 16 ?
-			__entry->cdb[scsi_command_size(__entry->cdb) - 1] :
-			__entry->cdb[1]
+		  __entry->control
 	)
 );