Signed-off-by: Waiman Long <longman@redhat.com>
---
 include/linux/memcontrol.h |  3 +++
 mm/memcontrol.c            | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 1dcb763bb610..0e31418e5a47 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h

@@ -1268,6 +1268,9 @@ static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
 struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep);
 void memcg_kmem_put_cache(struct kmem_cache *cachep);
 
+extern void memcg_iterate_all(void (*callback)(struct mem_cgroup *memcg,
+					       void *arg), void *arg);
+
 #ifdef CONFIG_MEMCG_KMEM
 int __memcg_kmem_charge(struct page *page, gfp_t gfp, int order);
 void __memcg_kmem_uncharge(struct page *page, int order);

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ba9138a4a1de..c1c4706f7696 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -443,6 +443,19 @@ static int memcg_alloc_shrinker_maps(struct mem_cgroup *memcg)
 static void memcg_free_shrinker_maps(struct mem_cgroup *memcg) { }
 #endif /* CONFIG_MEMCG_KMEM */
 
+/*
+ * Iterate all the memory cgroups and call the given callback function
+ * for each of the memory cgroups.
+ */
+void memcg_iterate_all(void (*callback)(struct mem_cgroup *memcg, void *arg),
+		       void *arg)
+{
+	struct mem_cgroup *memcg;
+
+	for_each_mem_cgroup(memcg)
+		callback(memcg, arg);
+}
+
 /**
  * mem_cgroup_css_from_page - css of the memcg associated with a page
  * @page: page of interest

-- 
2.18.1