[PATCH 2/2] mm: introduce mem_cgroup_put() helper

[Roman Gushchin]

Introduce the mem_cgroup_put() helper, which helps to eliminate
guarding memcg css release with "#ifdef CONFIG_MEMCG" in multiple
places.

Signed-off-by: Roman Gushchin <guro@xxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 include/linux/memcontrol.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index cf1c3555328f..3607913032be 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -383,6 +383,11 @@ struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *css){
 	return css ? container_of(css, struct mem_cgroup, css) : NULL;
 }
 
+static inline void mem_cgroup_put(struct mem_cgroup *memcg)
+{
+	css_put(&memcg->css);
+}
+
 #define mem_cgroup_from_counter(counter, member)	\
 	container_of(counter, struct mem_cgroup, member)
 
@@ -852,6 +857,10 @@ static inline bool task_in_mem_cgroup(struct task_struct *task,
 	return true;
 }
 
+static inline void mem_cgroup_put(struct mem_cgroup *memcg)
+{
+}
+
 static inline struct mem_cgroup *
 mem_cgroup_iter(struct mem_cgroup *root,
 		struct mem_cgroup *prev,
-- 
2.14.4