mm: introduce mem_cgroup_put() helper

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

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Roman Gushchin <[email protected]>
Reviewed-by: Shakeel Butt <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 680d3395fc838269870fb836664826fa296cc9e9..42f4719def3205cfc77284507665da719954e132 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -378,6 +378,11 @@ 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)
 
@@ -850,6 +855,10 @@ 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,