SUNRPC: Trace gssproxy upcall results

Record results of a GSS proxy ACCEPT_SEC_CONTEXT upcall and the
svc_authenticate() function to make field debugging of NFS server
Kerberos issues easier.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Bill Baker <bill.baker@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index d11b705..187dd4e 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1337,6 +1337,8 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
 		auth_stat = rpc_autherr_badcred;
 		auth_res = progp->pg_authenticate(rqstp);
 	}
+	if (auth_res != SVC_OK)
+		trace_svc_authenticate(rqstp, auth_res, auth_stat);
 	switch (auth_res) {
 	case SVC_OK:
 		break;