[NET]: Cleanup pernet operation without CONFIG_NET_NS

If CONFIG_NET_NS is not set, the only namespace is possible.

This patch removes list of pernet_operations and cleanups code a bit.
This list is not needed if there are no namespaces. We should just call
->init method.

Additionally, the ->exit will be called on module unloading only. This
case is safe - the code is not discarded. For the in/kernel code, ->exit
should never be called.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: dlunev

net/core/net_namespace.c

@@ -188,6 +188,7 @@ static int __init net_ns_init(void)
 
 pure_initcall(net_ns_init);
 
+#ifdef CONFIG_NET_NS
 static int register_pernet_operations(struct list_head *list,
 				      struct pernet_operations *ops)
 {
@@ -228,6 +229,23 @@ static void unregister_pernet_operations(struct pernet_operations *ops)
 			ops->exit(net);
 }
 
+#else
+
+static int register_pernet_operations(struct list_head *list,
+				      struct pernet_operations *ops)
+{
+	if (ops->init == NULL)
+		return 0;
+	return ops->init(&init_net);
+}
+
+static void unregister_pernet_operations(struct pernet_operations *ops)
+{
+	if (ops->exit)
+		ops->exit(&init_net);
+}
+#endif
+
 /**
  *      register_pernet_subsys - register a network namespace subsystem
  *	@ops:  pernet operations structure for the subsystem