SUNRPC: Chunk reading of replies from the server

Read the TCP data in chunks of max 2MB so that we do not hog the
socket lock.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

net/sunrpc/xprtsock.c

@@ -52,6 +52,8 @@
 
 #include "sunrpc.h"
 
+#define RPC_TCP_READ_CHUNK_SZ	(3*512*1024)
+
 static void xs_close(struct rpc_xprt *xprt);
 static void xs_tcp_set_socket_timeouts(struct rpc_xprt *xprt,
 		struct socket *sock);
@@ -1479,6 +1481,7 @@ static int xs_tcp_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb, uns
 		.offset	= offset,
 		.count	= len,
 	};
+	size_t ret;
 
 	dprintk("RPC:       xs_tcp_data_recv started\n");
 	do {
@@ -1507,9 +1510,14 @@ static int xs_tcp_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb, uns
 		/* Skip over any trailing bytes on short reads */
 		xs_tcp_read_discard(transport, &desc);
 	} while (desc.count);
+	ret = len - desc.count;
+	if (ret < rd_desc->count)
+		rd_desc->count -= ret;
+	else
+		rd_desc->count = 0;
 	trace_xs_tcp_data_recv(transport);
 	dprintk("RPC:       xs_tcp_data_recv done\n");
-	return len - desc.count;
+	return ret;
 }
 
 static void xs_tcp_data_receive(struct sock_xprt *transport)
@@ -1517,7 +1525,6 @@ static void xs_tcp_data_receive(struct sock_xprt *transport)
 	struct rpc_xprt *xprt = &transport->xprt;
 	struct sock *sk;
 	read_descriptor_t rd_desc = {
-		.count = 2*1024*1024,
 		.arg.data = xprt,
 	};
 	unsigned long total = 0;
@@ -1531,16 +1538,16 @@ static void xs_tcp_data_receive(struct sock_xprt *transport)
 
 	/* We use rd_desc to pass struct xprt to xs_tcp_data_recv */
 	for (loop = 0; loop < 64; loop++) {
+		rd_desc.count = RPC_TCP_READ_CHUNK_SZ;
 		lock_sock(sk);
 		read = tcp_read_sock(sk, &rd_desc, xs_tcp_data_recv);
-		if (read <= 0) {
+		if (rd_desc.count != 0 || read < 0) {
 			clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state);
 			release_sock(sk);
 			break;
 		}
 		release_sock(sk);
 		total += read;
-		rd_desc.count = 65536;
 	}
 	if (test_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
 		queue_work(xprtiod_workqueue, &transport->recv_worker);