Merge branch 'tipc-refactor-socket-receive-functions'

Jon Maloy says:

====================
tipc: refactor socket receive functions

We try to make the functions tipc_sk_recvmsg() and
tipc_sk_recvstream() more readable.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/socket.c

@@ -51,6 +51,7 @@
 #define TIPC_FWD_MSG		1
 #define TIPC_MAX_PORT		0xffffffff
 #define TIPC_MIN_PORT		1
+#define TIPC_ACK_RATE		4       /* ACK at 1/4 of of rcv window size */
 
 enum {
 	TIPC_LISTEN = TCP_LISTEN,
@@ -1290,7 +1291,7 @@ static int tipc_wait_for_rcvmsg(struct socket *sock, long *timeop)
 /**
  * tipc_recvmsg - receive packet-oriented message
  * @m: descriptor for message info
- * @buf_len: total size of user buffer area
+ * @buflen: length of user buffer area
  * @flags: receive flags
  *
  * Used for SOCK_DGRAM, SOCK_RDM, and SOCK_SEQPACKET messages.
@@ -1298,95 +1299,85 @@ static int tipc_wait_for_rcvmsg(struct socket *sock, long *timeop)
  *
  * Returns size of returned message data, errno otherwise
  */
-static int tipc_recvmsg(struct socket *sock, struct msghdr *m, size_t buf_len,
-			int flags)
+static int tipc_recvmsg(struct socket *sock, struct msghdr *m,
+			size_t buflen,	int flags)
 {
 	struct sock *sk = sock->sk;
 	struct tipc_sock *tsk = tipc_sk(sk);
-	struct sk_buff *buf;
-	struct tipc_msg *msg;
-	bool is_connectionless = tipc_sk_type_connectionless(sk);
-	long timeo;
-	unsigned int sz;
-	u32 err;
-	int res, hlen;
+	struct sk_buff *skb;
+	struct tipc_msg *hdr;
+	bool connected = !tipc_sk_type_connectionless(sk);
+	int rc, err, hlen, dlen, copy;
+	long timeout;
 
 	/* Catch invalid receive requests */
-	if (unlikely(!buf_len))
+	if (unlikely(!buflen))
 		return -EINVAL;
 
 	lock_sock(sk);
-
-	if (!is_connectionless && unlikely(sk->sk_state == TIPC_OPEN)) {
-		res = -ENOTCONN;
+	if (unlikely(connected && sk->sk_state == TIPC_OPEN)) {
+		rc = -ENOTCONN;
 		goto exit;
 	}
+	timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 
-	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
-restart:
-
-	/* Look for a message in receive queue; wait if necessary */
-	res = tipc_wait_for_rcvmsg(sock, &timeo);
-	if (res)
+	do {
+		/* Look at first msg in receive queue; wait if necessary */
+		rc = tipc_wait_for_rcvmsg(sock, &timeout);
+		if (unlikely(rc))
 			goto exit;
-
-	/* Look at first message in receive queue */
-	buf = skb_peek(&sk->sk_receive_queue);
-	msg = buf_msg(buf);
-	sz = msg_data_sz(msg);
-	hlen = msg_hdr_sz(msg);
-	err = msg_errcode(msg);
-
-	/* Discard an empty non-errored message & try again */
-	if ((!sz) && (!err)) {
+		skb = skb_peek(&sk->sk_receive_queue);
+		hdr = buf_msg(skb);
+		dlen = msg_data_sz(hdr);
+		hlen = msg_hdr_sz(hdr);
+		err = msg_errcode(hdr);
+		if (likely(dlen || err))
+			break;
 		tsk_advance_rx_queue(sk);
-		goto restart;
-	}
+	} while (1);
 
-	/* Capture sender's address (optional) */
-	set_orig_addr(m, msg);
-
-	/* Capture ancillary data (optional) */
-	res = tipc_sk_anc_data_recv(m, msg, tsk);
-	if (res)
+	/* Collect msg meta data, including error code and rejected data */
+	set_orig_addr(m, hdr);
+	rc = tipc_sk_anc_data_recv(m, hdr, tsk);
+	if (unlikely(rc))
 		goto exit;
 
-	/* Capture message data (if valid) & compute return value (always) */
-	if (!err) {
-		if (unlikely(buf_len < sz)) {
-			sz = buf_len;
+	/* Capture data if non-error msg, otherwise just set return value */
+	if (likely(!err)) {
+		copy = min_t(int, dlen, buflen);
+		if (unlikely(copy != dlen))
 			m->msg_flags |= MSG_TRUNC;
-		}
-		res = skb_copy_datagram_msg(buf, hlen, m, sz);
-		if (res)
-			goto exit;
-		res = sz;
+		rc = skb_copy_datagram_msg(skb, hlen, m, copy);
 	} else {
-		if (is_connectionless || err == TIPC_CONN_SHUTDOWN ||
-		    m->msg_control)
-			res = 0;
-		else
-			res = -ECONNRESET;
+		copy = 0;
+		rc = 0;
+		if (err != TIPC_CONN_SHUTDOWN && connected && !m->msg_control)
+			rc = -ECONNRESET;
 	}
+	if (unlikely(rc))
+		goto exit;
 
+	/* Caption of data or error code/rejected data was successful */
 	if (unlikely(flags & MSG_PEEK))
 		goto exit;
 
-	if (likely(!is_connectionless)) {
-		tsk->rcv_unacked += tsk_inc(tsk, hlen + sz);
-		if (unlikely(tsk->rcv_unacked >= (tsk->rcv_win / 4)))
-			tipc_sk_send_ack(tsk);
-	}
 	tsk_advance_rx_queue(sk);
+	if (likely(!connected))
+		goto exit;
+
+	/* Send connection flow control ack when applicable */
+	tsk->rcv_unacked += tsk_inc(tsk, hlen + dlen);
+	if (tsk->rcv_unacked >= tsk->rcv_win / TIPC_ACK_RATE)
+		tipc_sk_send_ack(tsk);
 exit:
 	release_sock(sk);
-	return res;
+	return rc ? rc : copy;
 }
 
 /**
- * tipc_recv_stream - receive stream-oriented data
+ * tipc_recvstream - receive stream-oriented data
  * @m: descriptor for message info
- * @buf_len: total size of user buffer area
+ * @buflen: total size of user buffer area
  * @flags: receive flags
  *
  * Used for SOCK_STREAM messages only.  If not enough data is available
@@ -1394,111 +1385,98 @@ static int tipc_recvmsg(struct socket *sock, struct msghdr *m, size_t buf_len,
  *
  * Returns size of returned message data, errno otherwise
  */
-static int tipc_recv_stream(struct socket *sock, struct msghdr *m,
-			    size_t buf_len, int flags)
+static int tipc_recvstream(struct socket *sock, struct msghdr *m,
+			   size_t buflen, int flags)
 {
 	struct sock *sk = sock->sk;
 	struct tipc_sock *tsk = tipc_sk(sk);
-	struct sk_buff *buf;
-	struct tipc_msg *msg;
-	long timeo;
-	unsigned int sz;
-	int target;
-	int sz_copied = 0;
-	u32 err;
-	int res = 0, hlen;
+	struct sk_buff *skb;
+	struct tipc_msg *hdr;
+	struct tipc_skb_cb *skb_cb;
+	bool peek = flags & MSG_PEEK;
+	int offset, required, copy, copied = 0;
+	int hlen, dlen, err, rc;
+	long timeout;
 
 	/* Catch invalid receive attempts */
-	if (unlikely(!buf_len))
+	if (unlikely(!buflen))
 		return -EINVAL;
 
 	lock_sock(sk);
 
 	if (unlikely(sk->sk_state == TIPC_OPEN)) {
-		res = -ENOTCONN;
+		rc = -ENOTCONN;
 		goto exit;
 	}
+	required = sock_rcvlowat(sk, flags & MSG_WAITALL, buflen);
+	timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 
-	target = sock_rcvlowat(sk, flags & MSG_WAITALL, buf_len);
-	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
-
-restart:
-	/* Look for a message in receive queue; wait if necessary */
-	res = tipc_wait_for_rcvmsg(sock, &timeo);
-	if (res)
-		goto exit;
-
-	/* Look at first message in receive queue */
-	buf = skb_peek(&sk->sk_receive_queue);
-	msg = buf_msg(buf);
-	sz = msg_data_sz(msg);
-	hlen = msg_hdr_sz(msg);
-	err = msg_errcode(msg);
-
-	/* Discard an empty non-errored message & try again */
-	if ((!sz) && (!err)) {
+	do {
+		/* Look at first msg in receive queue; wait if necessary */
+		rc = tipc_wait_for_rcvmsg(sock, &timeout);
+		if (unlikely(rc))
+			break;
+		skb = skb_peek(&sk->sk_receive_queue);
+		skb_cb = TIPC_SKB_CB(skb);
+		hdr = buf_msg(skb);
+		dlen = msg_data_sz(hdr);
+		hlen = msg_hdr_sz(hdr);
+		err = msg_errcode(hdr);
+
+		/* Discard any empty non-errored (SYN-) message */
+		if (unlikely(!dlen && !err)) {
 			tsk_advance_rx_queue(sk);
-		goto restart;
+			continue;
 		}
 
-	/* Optionally capture sender's address & ancillary data of first msg */
-	if (sz_copied == 0) {
-		set_orig_addr(m, msg);
-		res = tipc_sk_anc_data_recv(m, msg, tsk);
-		if (res)
-			goto exit;
+		/* Collect msg meta data, incl. error code and rejected data */
+		if (!copied) {
+			set_orig_addr(m, hdr);
+			rc = tipc_sk_anc_data_recv(m, hdr, tsk);
+			if (rc)
+				break;
 		}
 
-	/* Capture message data (if valid) & compute return value (always) */
-	if (!err) {
-		u32 offset = TIPC_SKB_CB(buf)->bytes_read;
-		u32 needed;
-		int sz_to_copy;
-
-		sz -= offset;
-		needed = (buf_len - sz_copied);
-		sz_to_copy = min(sz, needed);
-
-		res = skb_copy_datagram_msg(buf, hlen + offset, m, sz_to_copy);
-		if (res)
-			goto exit;
-
-		sz_copied += sz_to_copy;
-
-		if (sz_to_copy < sz) {
-			if (!(flags & MSG_PEEK))
-				TIPC_SKB_CB(buf)->bytes_read =
-					offset + sz_to_copy;
-			goto exit;
+		/* Copy data if msg ok, otherwise return error/partial data */
+		if (likely(!err)) {
+			offset = skb_cb->bytes_read;
+			copy = min_t(int, dlen - offset, buflen - copied);
+			rc = skb_copy_datagram_msg(skb, hlen + offset, m, copy);
+			if (unlikely(rc))
+				break;
+			copied += copy;
+			offset += copy;
+			if (unlikely(offset < dlen)) {
+				if (!peek)
+					skb_cb->bytes_read = offset;
+				break;
 			}
 		} else {
-		if (sz_copied != 0)
-			goto exit; /* can't add error msg to valid data */
-
-		if ((err == TIPC_CONN_SHUTDOWN) || m->msg_control)
-			res = 0;
-		else
-			res = -ECONNRESET;
+			rc = 0;
+			if ((err != TIPC_CONN_SHUTDOWN) && !m->msg_control)
+				rc = -ECONNRESET;
+			if (copied || rc)
+				break;
 		}
 
-	if (unlikely(flags & MSG_PEEK))
-		goto exit;
+		if (unlikely(peek))
+			break;
 
-	tsk->rcv_unacked += tsk_inc(tsk, hlen + msg_data_sz(msg));
-	if (unlikely(tsk->rcv_unacked >= (tsk->rcv_win / 4)))
-		tipc_sk_send_ack(tsk);
 		tsk_advance_rx_queue(sk);
 
-	/* Loop around if more data is required */
-	if ((sz_copied < buf_len) &&	/* didn't get all requested data */
-	    (!skb_queue_empty(&sk->sk_receive_queue) ||
-	    (sz_copied < target)) &&	/* and more is ready or required */
-	    (!err))			/* and haven't reached a FIN */
-		goto restart;
+		/* Send connection flow control advertisement when applicable */
+		tsk->rcv_unacked += tsk_inc(tsk, hlen + dlen);
+		if (unlikely(tsk->rcv_unacked >= tsk->rcv_win / TIPC_ACK_RATE))
+			tipc_sk_send_ack(tsk);
+
+		/* Exit if all requested data or FIN/error received */
+		if (copied == buflen || err)
+			break;
 
+	} while (!skb_queue_empty(&sk->sk_receive_queue) || copied < required);
 exit:
 	release_sock(sk);
-	return sz_copied ? sz_copied : res;
+	return copied ? copied : rc;
 }
 
 /**
@@ -2593,7 +2571,7 @@ static const struct proto_ops stream_ops = {
 	.setsockopt	= tipc_setsockopt,
 	.getsockopt	= tipc_getsockopt,
 	.sendmsg	= tipc_sendstream,
-	.recvmsg	= tipc_recv_stream,
+	.recvmsg	= tipc_recvstream,
 	.mmap		= sock_no_mmap,
 	.sendpage	= sock_no_sendpage
 };