SUNRPC: Tracepoint to record errors in svc_xpo_create()

Capture transport creation failures.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

include/trace/events/sunrpc.h

@@ -1167,6 +1167,35 @@ DEFINE_EVENT(svc_rqst_status, svc_send,
 		{ (1UL << XPT_KILL_TEMP),	"XPT_KILL_TEMP"},	\
 		{ (1UL << XPT_CONG_CTRL),	"XPT_CONG_CTRL"})
 
+TRACE_EVENT(svc_xprt_create_err,
+	TP_PROTO(
+		const char *program,
+		const char *protocol,
+		struct sockaddr *sap,
+		const struct svc_xprt *xprt
+	),
+
+	TP_ARGS(program, protocol, sap, xprt),
+
+	TP_STRUCT__entry(
+		__field(long, error)
+		__string(program, program)
+		__string(protocol, protocol)
+		__array(unsigned char, addr, sizeof(struct sockaddr_in6))
+	),
+
+	TP_fast_assign(
+		__entry->error = PTR_ERR(xprt);
+		__assign_str(program, program);
+		__assign_str(protocol, protocol);
+		memcpy(__entry->addr, sap, sizeof(__entry->addr));
+	),
+
+	TP_printk("addr=%pISpc program=%s protocol=%s error=%ld",
+		__entry->addr, __get_str(program), __get_str(protocol),
+		__entry->error)
+);
+
 TRACE_EVENT(svc_xprt_do_enqueue,
 	TP_PROTO(struct svc_xprt *xprt, struct svc_rqst *rqst),
 

net/sunrpc/svc_xprt.c

@@ -206,6 +206,7 @@ static struct svc_xprt *__svc_xpo_create(struct svc_xprt_class *xcl,
 		.sin6_port		= htons(port),
 	};
 #endif
+	struct svc_xprt *xprt;
 	struct sockaddr *sap;
 	size_t len;
 
@@ -224,7 +225,11 @@ static struct svc_xprt *__svc_xpo_create(struct svc_xprt_class *xcl,
 		return ERR_PTR(-EAFNOSUPPORT);
 	}
 
-	return xcl->xcl_ops->xpo_create(serv, net, sap, len, flags);
+	xprt = xcl->xcl_ops->xpo_create(serv, net, sap, len, flags);
+	if (IS_ERR(xprt))
+		trace_svc_xprt_create_err(serv->sv_program->pg_name,
+					  xcl->xcl_name, sap, xprt);
+	return xprt;
 }
 
 /*