drbd: Keep the listening socket open while trying to connect to the peer

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_receiver.c

@@ -666,7 +666,32 @@ out:
 	return sock;
 }
 
-static struct socket *prepare_listen_socket(struct drbd_tconn *tconn)
+struct accept_wait_data {
+	struct drbd_tconn *tconn;
+	struct socket *s_listen;
+	struct completion door_bell;
+	void (*original_sk_state_change)(struct sock *sk);
+
+};
+
+static void incomming_connection(struct sock *sk)
+{
+	struct accept_wait_data *ad = sk->sk_user_data;
+	struct drbd_tconn *tconn = ad->tconn;
+
+	if (sk->sk_state != TCP_ESTABLISHED)
+		conn_warn(tconn, "unexpected tcp state change. sk_state = %d\n", sk->sk_state);
+
+	write_lock_bh(&sk->sk_callback_lock);
+	sk->sk_state_change = ad->original_sk_state_change;
+	sk->sk_user_data = NULL;
+	write_unlock_bh(&sk->sk_callback_lock);
+
+	sk->sk_state_change(sk);
+	complete(&ad->door_bell);
+}
+
+static int prepare_listen_socket(struct drbd_tconn *tconn, struct accept_wait_data *ad)
 {
 	int err, sndbuf_size, rcvbuf_size, my_addr_len;
 	struct sockaddr_in6 my_addr;
@@ -678,7 +703,7 @@ static struct socket *prepare_listen_socket(struct drbd_tconn *tconn)
 	nc = rcu_dereference(tconn->net_conf);
 	if (!nc) {
 		rcu_read_unlock();
-		return NULL;
+		return -EIO;
 	}
 	sndbuf_size = nc->sndbuf_size;
 	rcvbuf_size = nc->rcvbuf_size;
@@ -703,12 +728,19 @@ static struct socket *prepare_listen_socket(struct drbd_tconn *tconn)
 	if (err < 0)
 		goto out;
 
+	ad->s_listen = s_listen;
+	write_lock_bh(&s_listen->sk->sk_callback_lock);
+	ad->original_sk_state_change = s_listen->sk->sk_state_change;
+	s_listen->sk->sk_state_change = incomming_connection;
+	s_listen->sk->sk_user_data = ad;
+	write_unlock_bh(&s_listen->sk->sk_callback_lock);
+
 	what = "listen";
 	err = s_listen->ops->listen(s_listen, 5);
 	if (err < 0)
 		goto out;
 
-	return s_listen;
+	return 0;
 out:
 	if (s_listen)
 		sock_release(s_listen);
@@ -719,14 +751,13 @@ out:
 		}
 	}
 
-	return NULL;
+	return -EIO;
 }
 
-static struct socket *drbd_wait_for_connect(struct drbd_tconn *tconn)
+static struct socket *drbd_wait_for_connect(struct drbd_tconn *tconn, struct accept_wait_data *ad)
 {
 	int timeo, connect_int, err = 0;
 	struct socket *s_estab = NULL;
-	struct socket *s_listen;
 	struct net_conf *nc;
 
 	rcu_read_lock();
@@ -741,18 +772,11 @@ static struct socket *drbd_wait_for_connect(struct drbd_tconn *tconn)
 	timeo = connect_int * HZ;
 	timeo += (random32() & 1) ? timeo / 7 : -timeo / 7; /* 28.5% random jitter */
 
-	s_listen = prepare_listen_socket(tconn);
-	if (!s_listen)
-		goto out;
-
-	s_listen->sk->sk_rcvtimeo = timeo;
-	s_listen->sk->sk_sndtimeo = timeo;
-
-	err = kernel_accept(s_listen, &s_estab, 0);
+	err = wait_for_completion_interruptible_timeout(&ad->door_bell, timeo);
+	if (err <= 0)
+		return NULL;
 
-out:
-	if (s_listen)
-		sock_release(s_listen);
+	err = kernel_accept(ad->s_listen, &s_estab, 0);
 	if (err < 0) {
 		if (err != -EAGAIN && err != -EINTR && err != -ERESTARTSYS) {
 			conn_err(tconn, "accept failed, err = %d\n", err);
@@ -855,6 +879,10 @@ static int conn_connect(struct drbd_tconn *tconn)
 	int vnr, timeout, try, h, ok;
 	bool discard_my_data;
 	enum drbd_state_rv rv;
+	struct accept_wait_data ad = {
+		.tconn = tconn,
+		.door_bell = COMPLETION_INITIALIZER_ONSTACK(ad.door_bell),
+	};
 
 	if (conn_request_state(tconn, NS(conn, C_WF_CONNECTION), CS_VERBOSE) < SS_SUCCESS)
 		return -2;
@@ -873,6 +901,9 @@ static int conn_connect(struct drbd_tconn *tconn)
 	/* Assume that the peer only understands protocol 80 until we know better.  */
 	tconn->agreed_pro_version = 80;
 
+	if (prepare_listen_socket(tconn, &ad))
+		return 0;
+
 	do {
 		struct socket *s;
 
@@ -911,7 +942,7 @@ static int conn_connect(struct drbd_tconn *tconn)
 		}
 
 retry:
-		s = drbd_wait_for_connect(tconn);
+		s = drbd_wait_for_connect(tconn, &ad);
 		if (s) {
 			try = receive_first_packet(tconn, s);
 			drbd_socket_okay(&sock.socket);
@@ -957,6 +988,9 @@ retry:
 		}
 	} while (1);
 
+	if (ad.s_listen)
+		sock_release(ad.s_listen);
+
 	sock.socket->sk->sk_reuse = 1; /* SO_REUSEADDR */
 	msock.socket->sk->sk_reuse = 1; /* SO_REUSEADDR */
 
@@ -1052,6 +1086,8 @@ retry:
 	return h;
 
 out_release_sockets:
+	if (ad.s_listen)
+		sock_release(ad.s_listen);
 	if (sock.socket)
 		sock_release(sock.socket);
 	if (msock.socket)