[NET]: Hide the dead code in the net_namespace.c

The namespace creation/destruction code is never called
if the CONFIG_NET_NS is n, so it's OK to move it under
appropriate ifdef.

The copy_net_ns() in the "n" case checks for flags and
returns -EINVAL when new net ns is requested. In a perfect
world this stub must be in net_namespace.h, but this
function need to know the CLONE_NEWNET value and thus
requires sched.h. On the other hand this header is to be
injected into almost every .c file in the networking code,
and making all this code depend on the sched.h is a
suicidal attempt.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/net_namespace.c

@@ -22,11 +22,84 @@ static struct kmem_cache *net_cachep;
 struct net init_net;
 EXPORT_SYMBOL_GPL(init_net);
 
+/*
+ * setup_net runs the initializers for the network namespace object.
+ */
+static int setup_net(struct net *net)
+{
+	/* Must be called with net_mutex held */
+	struct pernet_operations *ops;
+	int error;
+
+	atomic_set(&net->count, 1);
+	atomic_set(&net->use_count, 0);
+
+	error = 0;
+	list_for_each_entry(ops, &pernet_list, list) {
+		if (ops->init) {
+			error = ops->init(net);
+			if (error < 0)
+				goto out_undo;
+		}
+	}
+out:
+	return error;
+
+out_undo:
+	/* Walk through the list backwards calling the exit functions
+	 * for the pernet modules whose init functions did not fail.
+	 */
+	list_for_each_entry_continue_reverse(ops, &pernet_list, list) {
+		if (ops->exit)
+			ops->exit(net);
+	}
+
+	rcu_barrier();
+	goto out;
+}
+
+#ifdef CONFIG_NET_NS
 static struct net *net_alloc(void)
 {
 	return kmem_cache_zalloc(net_cachep, GFP_KERNEL);
 }
 
+struct net *copy_net_ns(unsigned long flags, struct net *old_net)
+{
+	struct net *new_net = NULL;
+	int err;
+
+	get_net(old_net);
+
+	if (!(flags & CLONE_NEWNET))
+		return old_net;
+
+	err = -ENOMEM;
+	new_net = net_alloc();
+	if (!new_net)
+		goto out;
+
+	mutex_lock(&net_mutex);
+	err = setup_net(new_net);
+	if (err)
+		goto out_unlock;
+
+	rtnl_lock();
+	list_add_tail(&new_net->list, &net_namespace_list);
+	rtnl_unlock();
+
+
+out_unlock:
+	mutex_unlock(&net_mutex);
+out:
+	put_net(old_net);
+	if (err) {
+		net_free(new_net);
+		new_net = ERR_PTR(err);
+	}
+	return new_net;
+}
+
 static void net_free(struct net *net)
 {
 	if (!net)
@@ -72,7 +145,6 @@ static void cleanup_net(struct work_struct *work)
 	net_free(net);
 }
 
-
 void __put_net(struct net *net)
 {
 	/* Cleanup the network namespace in process context */
@@ -81,81 +153,14 @@ void __put_net(struct net *net)
 }
 EXPORT_SYMBOL_GPL(__put_net);
 
-/*
+#else
- * setup_net runs the initializers for the network namespace object.
- */
-static int setup_net(struct net *net)
-{
-	/* Must be called with net_mutex held */
-	struct pernet_operations *ops;
-	int error;
-
-	atomic_set(&net->count, 1);
-	atomic_set(&net->use_count, 0);
-
-	error = 0;
-	list_for_each_entry(ops, &pernet_list, list) {
-		if (ops->init) {
-			error = ops->init(net);
-			if (error < 0)
-				goto out_undo;
-		}
-	}
-out:
-	return error;
-
-out_undo:
-	/* Walk through the list backwards calling the exit functions
-	 * for the pernet modules whose init functions did not fail.
-	 */
-	list_for_each_entry_continue_reverse(ops, &pernet_list, list) {
-		if (ops->exit)
-			ops->exit(net);
-	}
-
-	rcu_barrier();
-	goto out;
-}
-
 struct net *copy_net_ns(unsigned long flags, struct net *old_net)
 {
-	struct net *new_net = NULL;
+	if (flags & CLONE_NEWNET)
-	int err;
+		return ERR_PTR(-EINVAL);
-
+	return old_net;
-	get_net(old_net);
-
-	if (!(flags & CLONE_NEWNET))
-		return old_net;
-
-#ifndef CONFIG_NET_NS
-	return ERR_PTR(-EINVAL);
-#endif
-
-	err = -ENOMEM;
-	new_net = net_alloc();
-	if (!new_net)
-		goto out;
-
-	mutex_lock(&net_mutex);
-	err = setup_net(new_net);
-	if (err)
-		goto out_unlock;
-
-	rtnl_lock();
-	list_add_tail(&new_net->list, &net_namespace_list);
-	rtnl_unlock();
-
-
-out_unlock:
-	mutex_unlock(&net_mutex);
-out:
-	put_net(old_net);
-	if (err) {
-		net_free(new_net);
-		new_net = ERR_PTR(err);
-	}
-	return new_net;
 }
+#endif
 
 static int __init net_ns_init(void)
 {