+static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
+{
+ if (mem_cgroup_disabled())
+ return 0;
+
+ return memcg->css.id;
+}
+
+/**
+ * mem_cgroup_from_id - look up a memcg from an id
+ * @id: the id to look up
+ *
+ * Caller must hold rcu_read_lock() and use css_tryget() as necessary.
+ */
+static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
+{
+ struct cgroup_subsys_state *css;
+
+ css = css_from_id(id, &memory_cgrp_subsys);
+ return mem_cgroup_from_css(css);
+}
+