SUNRPC: use request size to initialize bio_vec in svc_udp_sendto()

Use the proper size when setting up the bio_vec, as otherwise only
zero-length UDP packets will be sent.

Fixes: baabf59 ("SUNRPC: Convert svc_udp_sendto() to use the per-socket bio_vec array")
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

net/sunrpc/svcsock.c

@@ -717,12 +717,12 @@ static int svc_udp_sendto(struct svc_rqst *rqstp)
 				ARRAY_SIZE(rqstp->rq_bvec), xdr);
 
 	iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
-		      count, 0);
+		      count, rqstp->rq_res.len);
 	err = sock_sendmsg(svsk->sk_sock, &msg);
 	if (err == -ECONNREFUSED) {
 		/* ICMP error on earlier request. */
 		iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
-			      count, 0);
+			      count, rqstp->rq_res.len);
 		err = sock_sendmsg(svsk->sk_sock, &msg);
 	}