SUNRPC: Optimise away svc_recv_available

We really do not want to do ioctls in the server's fast path. Instead, let's
use the fact that we managed to read a full record as the indicator that
we should try to read the socket again.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

net/sunrpc/svcsock.c

@@ -311,19 +311,6 @@ static int svc_one_sock_name(struct svc_sock *svsk, char *buf, int remaining)
 	return len;
 }
 
-/*
- * Check input queue length
- */
-static int svc_recv_available(struct svc_sock *svsk)
-{
-	struct socket	*sock = svsk->sk_sock;
-	int		avail, err;
-
-	err = kernel_sock_ioctl(sock, TIOCINQ, (unsigned long) &avail);
-
-	return (err >= 0)? avail : err;
-}
-
 /*
  * Generic recvfrom routine.
  */
@@ -339,8 +326,14 @@ static int svc_recvfrom(struct svc_rqst *rqstp, struct kvec *iov, int nr,
 
 	rqstp->rq_xprt_hlen = 0;
 
+	clear_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
 	len = kernel_recvmsg(svsk->sk_sock, &msg, iov, nr, buflen,
 				msg.msg_flags);
+	/* If we read a full record, then assume there may be more
+	 * data to read (stream based sockets only!)
+	 */
+	if (len == buflen)
+		set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
 
 	dprintk("svc: socket %p recvfrom(%p, %Zu) = %d\n",
 		svsk, iov[0].iov_base, iov[0].iov_len, len);
@@ -980,8 +973,6 @@ static int svc_tcp_recv_record(struct svc_sock *svsk, struct svc_rqst *rqstp)
 	unsigned int want;
 	int len;
 
-	clear_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
-
 	if (svsk->sk_tcplen < sizeof(rpc_fraghdr)) {
 		struct kvec	iov;
 
@@ -1073,8 +1064,6 @@ static int copy_pages_to_kvecs(struct kvec *vec, struct page **pages, int len)
 static void svc_tcp_fragment_received(struct svc_sock *svsk)
 {
 	/* If we have more data, signal svc_xprt_enqueue() to try again */
-	if (svc_recv_available(svsk) > sizeof(rpc_fraghdr))
-		set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags);
 	dprintk("svc: TCP %s record (%d bytes)\n",
 		svc_sock_final_rec(svsk) ? "final" : "nonfinal",
 		svc_sock_reclen(svsk));