[NETNS]: struct net content re-work (v3)

Recently David Miller and Herbert Xu pointed out that struct net becomes
overbloated and un-maintainable. There are two solutions:
- provide a pointer to a network subsystem definition from struct net.
  This costs an additional dereferrence
- place sub-system definition into the structure itself. This will speedup
  run-time access at the cost of recompilation time

The second approach looks better for us. Other sub-systems will follow.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Acked-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/net_namespace.h

@@ -8,6 +8,8 @@
 #include <linux/workqueue.h>
 #include <linux/list.h>
 
+#include <net/netns/unix.h>
+
 struct proc_dir_entry;
 struct net_device;
 struct sock;
@@ -45,9 +47,7 @@ struct net {
 	rwlock_t		packet_sklist_lock;
 	struct hlist_head	packet_sklist;
 
-	/* unix sockets */
-	int			sysctl_unix_max_dgram_qlen;
-	struct ctl_table_header	*unix_ctl;
+	struct netns_unix	unx;
 };
 
 #ifdef CONFIG_NET