mm: memcontrol: avoid unused function warning

A bugfix in v4.8-rc2 introduced a harmless warning when
CONFIG_MEMCG_SWAP is disabled but CONFIG_MEMCG is enabled:

  mm/memcontrol.c:4085:27: error: 'mem_cgroup_id_get_online' defined but not used [-Werror=unused-function]
   static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)

This moves the function inside of the #ifdef block that hides the
calling function, to avoid the warning.

Fixes: 1f47b61fb407 ("mm: memcontrol: fix swap counter leak on swapout from offline cgroup")
Link: http://lkml.kernel.org/r/20160824113733.2776701-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2ff0289..9a6a51a 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4082,24 +4082,6 @@ static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n)
        atomic_add(n, &memcg->id.ref);
 }
 
-static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
-{
-       while (!atomic_inc_not_zero(&memcg->id.ref)) {
-               /*
-                * The root cgroup cannot be destroyed, so it's refcount must
-                * always be >= 1.
-                */
-               if (WARN_ON_ONCE(memcg == root_mem_cgroup)) {
-                       VM_BUG_ON(1);
-                       break;
-               }
-               memcg = parent_mem_cgroup(memcg);
-               if (!memcg)
-                       memcg = root_mem_cgroup;
-       }
-       return memcg;
-}
-
 static void mem_cgroup_id_put_many(struct mem_cgroup *memcg, unsigned int n)
 {
        if (atomic_sub_and_test(n, &memcg->id.ref)) {
@@ -5821,6 +5803,24 @@ static int __init mem_cgroup_init(void)
 subsys_initcall(mem_cgroup_init);
 
 #ifdef CONFIG_MEMCG_SWAP
+static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
+{
+       while (!atomic_inc_not_zero(&memcg->id.ref)) {
+               /*
+                * The root cgroup cannot be destroyed, so it's refcount must
+                * always be >= 1.
+                */
+               if (WARN_ON_ONCE(memcg == root_mem_cgroup)) {
+                       VM_BUG_ON(1);
+                       break;
+               }
+               memcg = parent_mem_cgroup(memcg);
+               if (!memcg)
+                       memcg = root_mem_cgroup;
+       }
+       return memcg;
+}
+
 /**
  * mem_cgroup_swapout - transfer a memsw charge to swap
  * @page: page whose memsw charge to transfer