[INET]: Collect frag queues management objects together

There are some objects that are common in all the places
which are used to keep track of frag queues, they are:

 * hash table
 * LRU list
 * rw lock
 * rnd number for hash function
 * the number of queues
 * the amount of memory occupied by queues
 * secret timer

Move all this stuff into one structure (struct inet_frags)
to make it possible use them uniformly in the future. Like
with the previous patch this mostly consists of hunks like

-    write_lock(&ipfrag_lock);
+    write_lock(&ip4_frags.lock);

To address the issue with exporting the number of queues and
the amount of memory occupied by queues outside the .c file
they are declared in, I introduce a couple of helpers.

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

net/ipv4/inet_fragment.c

@@ -0,0 +1,44 @@
+/*
+ * inet fragments management
+ *
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ *
+ * 		Authors:	Pavel Emelyanov <xemul@openvz.org>
+ *				Started as consolidation of ipv4/ip_fragment.c,
+ *				ipv6/reassembly. and ipv6 nf conntrack reassembly
+ */
+
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/module.h>
+#include <linux/timer.h>
+#include <linux/mm.h>
+
+#include <net/inet_frag.h>
+
+void inet_frags_init(struct inet_frags *f)
+{
+	int i;
+
+	for (i = 0; i < INETFRAGS_HASHSZ; i++)
+		INIT_HLIST_HEAD(&f->hash[i]);
+
+	INIT_LIST_HEAD(&f->lru_list);
+	rwlock_init(&f->lock);
+
+	f->rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
+				   (jiffies ^ (jiffies >> 6)));
+
+	f->nqueues = 0;
+	atomic_set(&f->mem, 0);
+
+}
+EXPORT_SYMBOL(inet_frags_init);
+
+void inet_frags_fini(struct inet_frags *f)
+{
+}
+EXPORT_SYMBOL(inet_frags_fini);