SUNRPC: Make the svc_authenticate tracepoint conditional

Clean up: Simplify the tracepoint's only call site.

Also, I noticed that when svc_authenticate() returns SVC_COMPLETE,
it leaves rq_auth_stat set to an error value. That doesn't need to
be recorded in the trace log.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>

include/trace/events/sunrpc.h

@@ -1666,11 +1666,13 @@ TRACE_DEFINE_ENUM(SVC_COMPLETE);
 #define SVC_RQST_ENDPOINT_VARARGS \
 		__entry->xid, __get_sockaddr(server), __get_sockaddr(client)
 
-TRACE_EVENT(svc_authenticate,
+TRACE_EVENT_CONDITION(svc_authenticate,
 	TP_PROTO(const struct svc_rqst *rqst, int auth_res),
 
 	TP_ARGS(rqst, auth_res),
 
+	TP_CONDITION(auth_res != SVC_OK && auth_res != SVC_COMPLETE),
+
 	TP_STRUCT__entry(
 		SVC_RQST_ENDPOINT_FIELDS(rqst)
 

net/sunrpc/svc.c

@@ -1280,8 +1280,7 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 	/* Also give the program a chance to reject this call: */
 	if (auth_res == SVC_OK && progp)
 		auth_res = progp->pg_authenticate(rqstp);
-	if (auth_res != SVC_OK)
-		trace_svc_authenticate(rqstp, auth_res);
+	trace_svc_authenticate(rqstp, auth_res);
 	switch (auth_res) {
 	case SVC_OK:
 		break;