DLM: fix to use sk_callback_lock correctly

In the current implementation, we think that exclusion control between
processing to set the callback function to the connection structure and
processing to refer to the connection structure from the callback function
was not enough. We fix them.
Signed-off-by: Tadashi Miyauchi <miyauchi@toshiba-tops.co.jp>
Signed-off-by: Tsutomu Owa <tsutomu.owa@toshiba.co.jp>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/lowcomms.c

@@ -411,17 +411,23 @@ int dlm_lowcomms_addr(int nodeid, struct sockaddr_storage *addr, int len)
 /* Data available on socket or listen socket received a connect */
 static void lowcomms_data_ready(struct sock *sk)
 {
-	struct connection *con = sock2con(sk);
+	struct connection *con;
+
+	read_lock_bh(&sk->sk_callback_lock);
+	con = sock2con(sk);
 	if (con && !test_and_set_bit(CF_READ_PENDING, &con->flags))
 		queue_work(recv_workqueue, &con->rwork);
+	read_unlock_bh(&sk->sk_callback_lock);
 }
 
 static void lowcomms_write_space(struct sock *sk)
 {
-	struct connection *con = sock2con(sk);
+	struct connection *con;
 
+	read_lock_bh(&sk->sk_callback_lock);
+	con = sock2con(sk);
 	if (!con)
-		return;
+		goto out;
 
 	clear_bit(SOCK_NOSPACE, &con->sock->flags);
 
@@ -431,6 +437,8 @@ static void lowcomms_write_space(struct sock *sk)
 	}
 
 	queue_work(send_workqueue, &con->swork);
+out:
+	read_unlock_bh(&sk->sk_callback_lock);
 }
 
 static inline void lowcomms_connect_sock(struct connection *con)
@@ -797,8 +805,6 @@ static int tcp_accept_from_sock(struct connection *con)
 		mutex_lock_nested(&othercon->sock_mutex, 2);
 		if (!othercon->sock) {
 			newcon->othercon = othercon;
-			othercon->sock = newsock;
-			newsock->sk->sk_user_data = othercon;
 			add_sock(newsock, othercon);
 			addcon = othercon;
 			mutex_unlock(&othercon->sock_mutex);
@@ -812,7 +818,6 @@ static int tcp_accept_from_sock(struct connection *con)
 		}
 	}
 	else {
-		newsock->sk->sk_user_data = newcon;
 		newcon->rx_action = receive_from_sock;
 		/* accept copies the sk after we've saved the callbacks, so we
 		   don't want to save them a second time or comm errors will
@@ -918,8 +923,6 @@ static int sctp_accept_from_sock(struct connection *con)
 		mutex_lock_nested(&othercon->sock_mutex, 2);
 		if (!othercon->sock) {
 			newcon->othercon = othercon;
-			othercon->sock = newsock;
-			newsock->sk->sk_user_data = othercon;
 			add_sock(newsock, othercon);
 			addcon = othercon;
 			mutex_unlock(&othercon->sock_mutex);
@@ -931,7 +934,6 @@ static int sctp_accept_from_sock(struct connection *con)
 			goto accept_err;
 		}
 	} else {
-		newsock->sk->sk_user_data = newcon;
 		newcon->rx_action = receive_from_sock;
 		add_sock(newsock, newcon);
 		addcon = newcon;
@@ -1058,7 +1060,6 @@ static void sctp_connect_to_sock(struct connection *con)
 	if (result < 0)
 		goto socket_err;
 
-	sock->sk->sk_user_data = con;
 	con->rx_action = receive_from_sock;
 	con->connect_action = sctp_connect_to_sock;
 	add_sock(sock, con);
@@ -1143,7 +1144,6 @@ static void tcp_connect_to_sock(struct connection *con)
 		goto out_err;
 	}
 
-	sock->sk->sk_user_data = con;
 	con->rx_action = receive_from_sock;
 	con->connect_action = tcp_connect_to_sock;
 	add_sock(sock, con);
@@ -1233,10 +1233,12 @@ static struct socket *tcp_create_listen_sock(struct connection *con,
 	if (result < 0) {
 		log_print("Failed to set SO_REUSEADDR on socket: %d", result);
 	}
+	write_lock_bh(&sock->sk->sk_callback_lock);
 	sock->sk->sk_user_data = con;
 	save_listen_callbacks(sock);
 	con->rx_action = tcp_accept_from_sock;
 	con->connect_action = tcp_connect_to_sock;
+	write_unlock_bh(&sock->sk->sk_callback_lock);
 
 	/* Bind to our port */
 	make_sockaddr(saddr, dlm_config.ci_tcp_port, &addr_len);
@@ -1639,8 +1641,11 @@ static void _stop_conn(struct connection *con, bool and_other)
 	set_bit(CF_CLOSE, &con->flags);
 	set_bit(CF_READ_PENDING, &con->flags);
 	set_bit(CF_WRITE_PENDING, &con->flags);
-	if (con->sock && con->sock->sk)
+	if (con->sock && con->sock->sk) {
+		write_lock_bh(&con->sock->sk->sk_callback_lock);
 		con->sock->sk->sk_user_data = NULL;
+		write_unlock_bh(&con->sock->sk->sk_callback_lock);
+	}
 	if (con->othercon && and_other)
 		_stop_conn(con->othercon, false);
 	mutex_unlock(&con->sock_mutex);