scsi: iscsi: Capture iscsi debug messages using tracepoints

This commit enhances iscsi initiator modules to capture iscsi debug
messages using linux kernel tracepoint facility:

https://www.kernel.org/doc/Documentation/trace/tracepoints.txt

The following tracepoint events have been created under the iscsi
tracepoint event group:

iscsi_dbg_conn - to capture connection debug messages (libiscsi module)

iscsi_dbg_session - to capture session debug messages (libiscsi module)

iscsi_dbg_eh - to capture error handling debug messages (libiscsi module)

iscsi_dbg_tcp - to capture iscsi tcp debug messages (libiscsi_tcp module)

iscsi_dbg_sw_tcp - to capture iscsi sw tcp debug messages (iscsi_tcp module)

iscsi_dbg_trans_session - to cpature iscsi transsport sess debug messages
	(scsi_transport_iscsi module)

iscsi_dbg_trans_conn - to capture iscsi transport conn debug messages
	(scsi_transport_iscsi module)

[mkp: typos]

Signed-off-by: Fred Herard <fred.herard@oracle.com>
Reviewed-by: Rajan Shanmugavelu <rajan.shanmugavelu@oracle.com>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/drivers/scsi/libiscsi_tcp.c b/drivers/scsi/libiscsi_tcp.c
index 4fcb9e6..8a6b1b3f 100644
--- a/drivers/scsi/libiscsi_tcp.c
+++ b/drivers/scsi/libiscsi_tcp.c
@@ -43,6 +43,7 @@
 #include <scsi/scsi_host.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_transport_iscsi.h>
+#include <trace/events/iscsi.h>
 
 #include "iscsi_tcp.h"
 
@@ -65,6 +66,9 @@ MODULE_PARM_DESC(debug_libiscsi_tcp, "Turn on debugging for libiscsi_tcp "
 			iscsi_conn_printk(KERN_INFO, _conn,	\
 					     "%s " dbg_fmt,	\
 					     __func__, ##arg);	\
+		iscsi_dbg_trace(trace_iscsi_dbg_tcp,		\
+				&(_conn)->cls_conn->dev,	\
+				"%s " dbg_fmt, __func__, ##arg);\
 	} while (0);
 
 static int iscsi_tcp_hdr_recv_done(struct iscsi_tcp_conn *tcp_conn,