[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/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c
index f1b95e1..724d69a 100644
--- a/net/ipv4/inet_fragment.c
+++ b/net/ipv4/inet_fragment.c
@@ -83,6 +83,13 @@
 }
 EXPORT_SYMBOL(inet_frags_fini);
 
+void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f)
+{
+	nf->low_thresh = 0;
+	inet_frag_evictor(nf, f);
+}
+EXPORT_SYMBOL(inet_frags_exit_net);
+
 static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f)
 {
 	write_lock(&f->lock);