cifs: fix string declarations and assignments in tracepoints

We missed using the variable length string macros in several
tracepoints. Fixed them in this change.

There's probably more useful macros that we can use to print
others like flags etc. But I'll submit sepawrate patches for
those at a future date.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Cc: <stable@vger.kernel.org> # v5.12
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/trace.h

@@ -12,6 +12,11 @@
 
 #include <linux/tracepoint.h>
 
+/*
+ * Please use this 3-part article as a reference for writing new tracepoints:
+ * https://lwn.net/Articles/379903/
+ */
+
 /* For logging errors in read or write */
 DECLARE_EVENT_CLASS(smb3_rw_err_class,
 	TP_PROTO(unsigned int xid,
@@ -529,16 +534,16 @@ DECLARE_EVENT_CLASS(smb3_exit_err_class,
 	TP_ARGS(xid, func_name, rc),
 	TP_STRUCT__entry(
 		__field(unsigned int, xid)
-		__field(const char *, func_name)
+		__string(func_name, func_name)
 		__field(int, rc)
 	),
 	TP_fast_assign(
 		__entry->xid = xid;
-		__entry->func_name = func_name;
+		__assign_str(func_name, func_name);
 		__entry->rc = rc;
 	),
 	TP_printk("\t%s: xid=%u rc=%d",
-		__entry->func_name, __entry->xid, __entry->rc)
+		__get_str(func_name), __entry->xid, __entry->rc)
 )
 
 #define DEFINE_SMB3_EXIT_ERR_EVENT(name)          \
@@ -583,14 +588,14 @@ DECLARE_EVENT_CLASS(smb3_enter_exit_class,
 	TP_ARGS(xid, func_name),
 	TP_STRUCT__entry(
 		__field(unsigned int, xid)
-		__field(const char *, func_name)
+		__string(func_name, func_name)
 	),
 	TP_fast_assign(
 		__entry->xid = xid;
-		__entry->func_name = func_name;
+		__assign_str(func_name, func_name);
 	),
 	TP_printk("\t%s: xid=%u",
-		__entry->func_name, __entry->xid)
+		__get_str(func_name), __entry->xid)
 )
 
 #define DEFINE_SMB3_ENTER_EXIT_EVENT(name)        \
@@ -857,16 +862,16 @@ DECLARE_EVENT_CLASS(smb3_reconnect_class,
 	TP_STRUCT__entry(
 		__field(__u64, currmid)
 		__field(__u64, conn_id)
-		__field(char *, hostname)
+		__string(hostname, hostname)
 	),
 	TP_fast_assign(
 		__entry->currmid = currmid;
 		__entry->conn_id = conn_id;
-		__entry->hostname = hostname;
+		__assign_str(hostname, hostname);
 	),
 	TP_printk("conn_id=0x%llx server=%s current_mid=%llu",
 		__entry->conn_id,
-		__entry->hostname,
+		__get_str(hostname),
 		__entry->currmid)
 )
 
@@ -891,23 +896,23 @@ DECLARE_EVENT_CLASS(smb3_credit_class,
 	TP_STRUCT__entry(
 		__field(__u64, currmid)
 		__field(__u64, conn_id)
-		__field(char *, hostname)
+		__string(hostname, hostname)
 		__field(int, credits)
 		__field(int, credits_to_add)
 		__field(int, in_flight)
 	),
 	TP_fast_assign(
 		__entry->currmid = currmid;
 		__entry->conn_id = conn_id;
-		__entry->hostname = hostname;
+		__assign_str(hostname, hostname);
 		__entry->credits = credits;
 		__entry->credits_to_add = credits_to_add;
 		__entry->in_flight = in_flight;
 	),
 	TP_printk("conn_id=0x%llx server=%s current_mid=%llu "
 			"credits=%d credit_change=%d in_flight=%d",
 		__entry->conn_id,
-		__entry->hostname,
+		__get_str(hostname),
 		__entry->currmid,
 		__entry->credits,
 		__entry->credits_to_add,