net: fix socket memcg build with !CONFIG_NET

There is still a build bug with the sock memcg code, that triggers
with !CONFIG_NET, that survived my series of randconfig builds.

Signed-off-by: Glauber Costa <[e-mail]>
Reported-by: Randy Dunlap <[e-mail]>
CC: Hiroyouki Kamezawa <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/sock.h

···
 #define sk_refcnt_debug_release(sk) do { } while (0)
 #endif /* SOCK_REFCNT_DEBUG */
 
-#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+#if defined(CONFIG_CGROUP_MEM_RES_CTLR_KMEM) && defined(CONFIG_NET)
 extern struct jump_label_key memcg_socket_limit_enabled;
 static inline struct cg_proto *parent_cg_proto(struct proto *proto,
 					       struct cg_proto *cg_proto)

mm/memcontrol.c

···
 static bool mem_cgroup_is_root(struct mem_cgroup *memcg);
 void sock_update_memcg(struct sock *sk)
 {
-	if (static_branch(&memcg_socket_limit_enabled)) {
+	if (mem_cgroup_sockets_enabled) {
 		struct mem_cgroup *memcg;
 
 		BUG_ON(!sk->sk_prot->proto_cgroup);
···
 
 void sock_release_memcg(struct sock *sk)
 {
-	if (static_branch(&memcg_socket_limit_enabled) && sk->sk_cgrp) {
+	if (mem_cgroup_sockets_enabled && sk->sk_cgrp) {
 		struct mem_cgroup *memcg;
 		WARN_ON(!sk->sk_cgrp->memcg);
 		memcg = sk->sk_cgrp->memcg;