[NETNS][FRAGS]: Make the pernet subsystem for fragments.

On namespace start we mainly prepare the ctl variables.

When the namespace is stopped we have to kill all the fragments that
point to this namespace.  The inet_frags_exit_net() handles it.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 0c4bc46..f936d04 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -728,6 +728,17 @@
 	return ip6_frags_sysctl_register(net);
 }
 
+static void ipv6_frags_exit_net(struct net *net)
+{
+	ip6_frags_sysctl_unregister(net);
+	inet_frags_exit_net(&net->ipv6.frags, &ip6_frags);
+}
+
+static struct pernet_operations ip6_frags_ops = {
+	.init = ipv6_frags_init_net,
+	.exit = ipv6_frags_exit_net,
+};
+
 int __init ipv6_frag_init(void)
 {
 	int ret;
@@ -736,7 +747,7 @@
 	if (ret)
 		goto out;
 
-	ipv6_frags_init_net(&init_net);
+	register_pernet_subsys(&ip6_frags_ops);
 
 	ip6_frags.hashfn = ip6_hashfn;
 	ip6_frags.constructor = ip6_frag_init;
@@ -754,5 +765,6 @@
 void ipv6_frag_exit(void)
 {
 	inet_frags_fini(&ip6_frags);
+	unregister_pernet_subsys(&ip6_frags_ops);
 	inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
 }