[SOCK][NETNS]: Add the percpu prot_inuse counter in the struct net.

Such an accounting would cost us two more dereferences to get the
percpu variable from the struct net, so I make sock_prot_inuse_get
and _add calls work differently depending on CONFIG_NET_NS - without
it old optimized routines are used.

The per-cpu counter for init_net is prepared in core_initcall, so
that even af_inet, that starts as fs_initcall, will already have the
init_net prepared.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/netns/core.h

@@ -2,12 +2,15 @@
 #define __NETNS_CORE_H__
 
 struct ctl_table_header;
+struct prot_inuse;
 
 struct netns_core {
 	/* core sysctls */
 	struct ctl_table_header	*sysctl_hdr;
 
 	int	sysctl_somaxconn;
+
+	struct prot_inuse	*inuse;
 };
 
 #endif

net/core/sock.c

@@ -1947,6 +1947,53 @@ struct prot_inuse {
 };
 
 static DECLARE_BITMAP(proto_inuse_idx, PROTO_INUSE_NR);
+
+#ifdef CONFIG_NET_NS
+void sock_prot_inuse_add(struct net *net, struct proto *prot, int val)
+{
+	int cpu = smp_processor_id();
+	per_cpu_ptr(net->core.inuse, cpu)->val[prot->inuse_idx] += val;
+}
+EXPORT_SYMBOL_GPL(sock_prot_inuse_add);
+
+int sock_prot_inuse_get(struct net *net, struct proto *prot)
+{
+	int cpu, idx = prot->inuse_idx;
+	int res = 0;
+
+	for_each_possible_cpu(cpu)
+		res += per_cpu_ptr(net->core.inuse, cpu)->val[idx];
+
+	return res >= 0 ? res : 0;
+}
+EXPORT_SYMBOL_GPL(sock_prot_inuse_get);
+
+static int sock_inuse_init_net(struct net *net)
+{
+	net->core.inuse = alloc_percpu(struct prot_inuse);
+	return net->core.inuse ? 0 : -ENOMEM;
+}
+
+static void sock_inuse_exit_net(struct net *net)
+{
+	free_percpu(net->core.inuse);
+}
+
+static struct pernet_operations net_inuse_ops = {
+	.init = sock_inuse_init_net,
+	.exit = sock_inuse_exit_net,
+};
+
+static __init int net_inuse_init(void)
+{
+	if (register_pernet_subsys(&net_inuse_ops))
+		panic("Cannot initialize net inuse counters");
+
+	return 0;
+}
+
+core_initcall(net_inuse_init);
+#else
 static DEFINE_PER_CPU(struct prot_inuse, prot_inuse);
 
 void sock_prot_inuse_add(struct net *net, struct proto *prot, int val)
@@ -1966,6 +2013,7 @@ int sock_prot_inuse_get(struct net *net, struct proto *prot)
 	return res >= 0 ? res : 0;
 }
 EXPORT_SYMBOL_GPL(sock_prot_inuse_get);
+#endif
 
 static void assign_proto_idx(struct proto *prot)
 {