dlm: fix connection close handling

Closing a connection to a node can create problems if there are
outstanding messages for that node.  The problems include dlm_send
spinning attempting to reconnect, or BUG from tcp_connect_to_sock()
attempting to use a partially closed connection.

To cleanly close a connection, we now first attempt to send any pending
messages, cancel any remaining workqueue work, and flag the connection
as closed to avoid reconnect attempts.

Signed-off-by: Lars Marowsky-Bree <lmb@suse.de>
Signed-off-by: Christine Caulfield <ccaulfie@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/lowcomms.c

@@ -106,6 +106,7 @@ struct connection {
 #define CF_CONNECT_PENDING 3
 #define CF_INIT_PENDING 4
 #define CF_IS_OTHERCON 5
+#define CF_CLOSE 6
 	struct list_head writequeue;  /* List of outgoing writequeue_entries */
 	spinlock_t writequeue_lock;
 	int (*rx_action) (struct connection *);	/* What to do when active */
@@ -299,6 +300,8 @@ static void lowcomms_write_space(struct sock *sk)
 
 static inline void lowcomms_connect_sock(struct connection *con)
 {
+	if (test_bit(CF_CLOSE, &con->flags))
+		return;
 	if (!test_and_set_bit(CF_CONNECT_PENDING, &con->flags))
 		queue_work(send_workqueue, &con->swork);
 }
@@ -1368,6 +1371,13 @@ int dlm_lowcomms_close(int nodeid)
 	log_print("closing connection to node %d", nodeid);
 	con = nodeid2con(nodeid, 0);
 	if (con) {
+		clear_bit(CF_CONNECT_PENDING, &con->flags);
+		clear_bit(CF_WRITE_PENDING, &con->flags);
+		set_bit(CF_CLOSE, &con->flags);
+		if (cancel_work_sync(&con->swork))
+			log_print("canceled swork for node %d", nodeid);
+		if (cancel_work_sync(&con->rwork))
+			log_print("canceled rwork for node %d", nodeid);
 		clean_one_writequeue(con);
 		close_connection(con, true);
 	}
@@ -1393,9 +1403,10 @@ static void process_send_sockets(struct work_struct *work)
 
 	if (test_and_clear_bit(CF_CONNECT_PENDING, &con->flags)) {
 		con->connect_action(con);
+		set_bit(CF_WRITE_PENDING, &con->flags);
 	}
-	clear_bit(CF_WRITE_PENDING, &con->flags);
-	send_to_sock(con);
+	if (test_and_clear_bit(CF_WRITE_PENDING, &con->flags))
+		send_to_sock(con);
 }