memcg: cleanup kmem tcp ifdefs

TCP kmem accounting is currently guarded by CONFIG_MEMCG_KMEM ifdefs but
the code is not used if !CONFIG_INET so we should rather test for both.
The same applies to net/sock.h, net/ip.h and net/tcp_memcontrol.h but
let's keep those outside of any ifdefs because it is considered safer wrt.
 future maintainability.

Tested with
- CONFIG_INET && CONFIG_MEMCG_KMEM
- !CONFIG_INET && CONFIG_MEMCG_KMEM
- CONFIG_INET && !CONFIG_MEMCG_KMEM
- !CONFIG_INET && !CONFIG_MEMCG_KMEM

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -51,6 +51,7 @@
 #include <linux/oom.h>
 #include "internal.h"
 #include <net/sock.h>
+#include <net/ip.h>
 #include <net/tcp_memcontrol.h>
 
 #include <asm/uaccess.h>
@@ -326,7 +327,7 @@ struct mem_cgroup {
 	struct mem_cgroup_stat_cpu nocpu_base;
 	spinlock_t pcp_counter_lock;
 
-#ifdef CONFIG_INET
+#if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_INET)
 	struct tcp_memcontrol tcp_mem;
 #endif
 };
@@ -412,9 +413,7 @@ struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *s)
 }
 
 /* Writing them here to avoid exposing memcg's inner layout */
-#ifdef CONFIG_MEMCG_KMEM
-#include <net/sock.h>
-#include <net/ip.h>
+#if defined(CONFIG_INET) && defined(CONFIG_MEMCG_KMEM)
 
 static bool mem_cgroup_is_root(struct mem_cgroup *memcg);
 void sock_update_memcg(struct sock *sk)
@@ -461,7 +460,6 @@ void sock_release_memcg(struct sock *sk)
 	}
 }
 
-#ifdef CONFIG_INET
 struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg)
 {
 	if (!memcg || mem_cgroup_is_root(memcg))
@@ -470,10 +468,7 @@ struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg)
 	return &memcg->tcp_mem.cg_proto;
 }
 EXPORT_SYMBOL(tcp_proto_cgroup);
-#endif /* CONFIG_INET */
-#endif /* CONFIG_MEMCG_KMEM */
 
-#if defined(CONFIG_INET) && defined(CONFIG_MEMCG_KMEM)
 static void disarm_sock_keys(struct mem_cgroup *memcg)
 {
 	if (!memcg_proto_activated(&memcg->tcp_mem.cg_proto))