smb3: add trace point for tree connection

In debugging certain scenarios, especially reconnect cases,
it can be helpful to have a dynamic trace point for the
result of tree connect.  See sample output below
from a reconnect event. The new event is 'smb3_tcon'

            TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
               | |       |   ||||       |         |
           cifsd-6071  [001] ....  2659.897923: smb3_reconnect: server=localhost current_mid=0xa
     kworker/1:1-71    [001] ....  2666.026342: smb3_cmd_done: 	sid=0x0 tid=0x0 cmd=0 mid=0
     kworker/1:1-71    [001] ....  2666.026576: smb3_cmd_err: 	sid=0xc49e1787 tid=0x0 cmd=1 mid=1 status=0xc0000016 rc=-5
     kworker/1:1-71    [001] ....  2666.031677: smb3_cmd_done: 	sid=0xc49e1787 tid=0x0 cmd=1 mid=2
     kworker/1:1-71    [001] ....  2666.031921: smb3_cmd_done: 	sid=0xc49e1787 tid=0x6e78f05f cmd=3 mid=3
     kworker/1:1-71    [001] ....  2666.031923: smb3_tcon: xid=0 sid=0xc49e1787 tid=0x0 unc_name=\\localhost\test rc=0
     kworker/1:1-71    [001] ....  2666.032097: smb3_cmd_done: 	sid=0xc49e1787 tid=0x6e78f05f cmd=11 mid=4
     kworker/1:1-71    [001] ....  2666.032265: smb3_cmd_done: 	sid=0xc49e1787 tid=0x7912332f cmd=3 mid=5
     kworker/1:1-71    [001] ....  2666.032266: smb3_tcon: xid=0 sid=0xc49e1787 tid=0x0 unc_name=\\localhost\IPC$ rc=0
     kworker/1:1-71    [001] ....  2666.032386: smb3_cmd_done: 	sid=0xc49e1787 tid=0x7912332f cmd=11 mid=6
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

fs/cifs/smb2pdu.c

@@ -1512,7 +1512,7 @@ SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
 	rc = cifs_send_recv(xid, ses, &rqst, &resp_buftype, flags, &rsp_iov);
 	cifs_small_buf_release(req);
 	rsp = (struct smb2_tree_connect_rsp *)rsp_iov.iov_base;
-
+	trace_smb3_tcon(xid, tcon->tid, ses->Suid, tree, rc);
 	if (rc != 0) {
 		if (tcon) {
 			cifs_stats_fail_inc(tcon, SMB2_TREE_CONNECT_HE);
@@ -1559,6 +1559,7 @@ SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
 	if (tcon->ses->server->ops->validate_negotiate)
 		rc = tcon->ses->server->ops->validate_negotiate(xid, tcon);
 tcon_exit:
+
 	free_rsp_buf(resp_buftype, rsp);
 	kfree(unc_path);
 	return rc;

fs/cifs/trace.h

@@ -373,6 +373,48 @@ DEFINE_EVENT(smb3_enter_exit_class, smb3_##name,  \
 DEFINE_SMB3_ENTER_EXIT_EVENT(enter);
 DEFINE_SMB3_ENTER_EXIT_EVENT(exit_done);
 
+/*
+ * For SMB2/SMB3 tree connect
+ */
+
+DECLARE_EVENT_CLASS(smb3_tcon_class,
+	TP_PROTO(unsigned int xid,
+		__u32	tid,
+		__u64	sesid,
+		const char *unc_name,
+		int	rc),
+	TP_ARGS(xid, tid, sesid, unc_name, rc),
+	TP_STRUCT__entry(
+		__field(unsigned int, xid)
+		__field(__u32, tid)
+		__field(__u64, sesid)
+		__field(const char *,  unc_name)
+		__field(int, rc)
+	),
+	TP_fast_assign(
+		__entry->xid = xid;
+		__entry->tid = tid;
+		__entry->sesid = sesid;
+		__entry->unc_name = unc_name;
+		__entry->rc = rc;
+	),
+	TP_printk("xid=%u sid=0x%llx tid=0x%x unc_name=%s rc=%d",
+		__entry->xid, __entry->sesid, __entry->tid,
+		__entry->unc_name, __entry->rc)
+)
+
+#define DEFINE_SMB3_TCON_EVENT(name)          \
+DEFINE_EVENT(smb3_tcon_class, smb3_##name,    \
+	TP_PROTO(unsigned int xid,		\
+		__u32	tid,			\
+		__u64	sesid,			\
+		const char *unc_name,		\
+		int	rc),			\
+	TP_ARGS(xid, tid, sesid, unc_name, rc))
+
+DEFINE_SMB3_TCON_EVENT(tcon);
+
+
 /*
  * For smb2/smb3 open call
  */