[SOCK]: Enumerate struct proto-s to facilitate percpu inuse accounting (v2).

The inuse counters are going to become a per-cpu array.  Introduce an
index for this array on the struct proto.

To handle the case of proto register-unregister-register loop the
bitmap is used. All its bits manipulations are protected with
proto_list_lock and a sanity check for the bitmap being exhausted is
also added.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sock.h b/include/net/sock.h
index 1c9d059..abc6341 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -562,6 +562,7 @@
 
 	/* Keeping track of sockets in use */
 #ifdef CONFIG_PROC_FS
+	unsigned int		inuse_idx;
 	struct pcounter		inuse;
 #endif