smb3: add dynamic trace point to trace when credits obtained

SMB3 crediting is used for flow control, and it can be useful to
trace for problem determination how many credits were acquired
and for which operation.

Here is an example ("trace-cmd record -e *add_credits"):
cifsd-9522    [010] ....  5995.202712: smb3_add_credits:
	server=localhost current_mid=0x12 credits=373 credits_to_add=10
cifsd-9522    [010] ....  5995.204040: smb3_add_credits:
	server=localhost current_mid=0x15 credits=400 credits_to_add=30
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2ops.c

@@ -72,7 +72,7 @@ smb2_add_credits(struct TCP_Server_Info *server,
 	/* eg found case where write overlapping reconnect messed up credits */
 	if (((optype & CIFS_OP_MASK) == CIFS_NEG_OP) && (*val != 0))
 		trace_smb3_reconnect_with_invalid_credits(server->CurrentMid,
-			server->hostname, *val);
+			server->hostname, *val, add);
 	if ((instance == 0) || (instance == server->reconnect_instance))
 		*val += add;
 	else
@@ -121,6 +121,8 @@ smb2_add_credits(struct TCP_Server_Info *server,
 		cifs_dbg(FYI, "disabling oplocks\n");
 		break;
 	default:
+		trace_smb3_add_credits(server->CurrentMid,
+			server->hostname, rc, add);
 		cifs_dbg(FYI, "add %u credits total=%d\n", add, rc);
 	}
 }

fs/cifs/trace.h

@@ -878,33 +878,39 @@ DEFINE_SMB3_RECONNECT_EVENT(partial_send_reconnect);
 DECLARE_EVENT_CLASS(smb3_credit_class,
 	TP_PROTO(__u64	currmid,
 		char *hostname,
-		int credits),
-	TP_ARGS(currmid, hostname, credits),
+		int credits,
+		int credits_to_add),
+	TP_ARGS(currmid, hostname, credits, credits_to_add),
 	TP_STRUCT__entry(
 		__field(__u64, currmid)
 		__field(char *, hostname)
 		__field(int, credits)
+		__field(int, credits_to_add)
 	),
 	TP_fast_assign(
 		__entry->currmid = currmid;
 		__entry->hostname = hostname;
 		__entry->credits = credits;
+		__entry->credits_to_add = credits_to_add;
 	),
-	TP_printk("server=%s current_mid=0x%llx credits=%d",
+	TP_printk("server=%s current_mid=0x%llx credits=%d credits_to_add=%d",
 		__entry->hostname,
 		__entry->currmid,
-		__entry->credits)
+		__entry->credits,
+		__entry->credits_to_add)
 )
 
 #define DEFINE_SMB3_CREDIT_EVENT(name)        \
 DEFINE_EVENT(smb3_credit_class, smb3_##name,  \
 	TP_PROTO(__u64	currmid,		\
 		char *hostname,			\
-		int  credits),			\
-	TP_ARGS(currmid, hostname, credits))
+		int  credits,			\
+		int  credits_to_add),		\
+	TP_ARGS(currmid, hostname, credits, credits_to_add))
 
 DEFINE_SMB3_CREDIT_EVENT(reconnect_with_invalid_credits);
 DEFINE_SMB3_CREDIT_EVENT(credit_timeout);
+DEFINE_SMB3_CREDIT_EVENT(add_credits);
 
 #endif /* _CIFS_TRACE_H */
 

fs/cifs/transport.c

@@ -563,7 +563,7 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 			cifs_num_waiters_dec(server);
 			if (!rc) {
 				trace_smb3_credit_timeout(server->CurrentMid,
-					server->hostname, num_credits);
+					server->hostname, num_credits, 0);
 				cifs_server_dbg(VFS, "wait timed out after %d ms\n",
 					 timeout);
 				return -ENOTSUPP;
@@ -604,7 +604,8 @@ wait_for_free_credits(struct TCP_Server_Info *server, const int num_credits,
 				if (!rc) {
 					trace_smb3_credit_timeout(
 						server->CurrentMid,
-						server->hostname, num_credits);
+						server->hostname, num_credits,
+						0);
 					cifs_server_dbg(VFS, "wait timed out after %d ms\n",
 						 timeout);
 					return -ENOTSUPP;