diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 15261d74baa4aed19034e6a8938f9beb341ea1b3..6f0766ea159b3a98362892f731a1d3ce54eda8af 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -141,6 +141,9 @@ struct cgroup_subsys_state {
 	 */
 	int id;
 
+	/* number of tasks under this css and its descendants */
+	int nr_tasks;
+
 	unsigned int flags;
 
 	/*
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 474a23b1582209c9fd8110c7e6bd3adac4a45ead..237080ee3305cf140f66db07ac4cce872472f379 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1796,6 +1796,24 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
 	return 0;
 }
 
+static void css_account_tasks(struct css_set *cset, int num)
+{
+	struct cgroup_subsys *ss;
+	int ssid;
+
+	for_each_subsys(ss, ssid) {
+		struct cgroup_subsys_state *css = cset->subsys[ssid];
+
+		if (!css)
+			continue;
+		css->nr_tasks += num;
+		while (css->parent) {
+			css = css->parent;
+			css->nr_tasks += num;
+		}
+	}
+}
+
 /*
  * To reduce the fork() overhead for systems that are not actually using
  * their cgroups capability, we don't maintain the lists running through
@@ -1847,6 +1865,7 @@ static void cgroup_enable_task_cg_lists(void)
 			list_add_tail(&p->cg_list, &cset->tasks);
 			get_css_set(cset);
 			cset->nr_tasks++;
+			css_account_tasks(cset, 1);
 		}
 		spin_unlock(&p->sighand->siglock);
 	} while_each_thread(g, p);
@@ -2339,9 +2358,11 @@ static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx)
 
 			get_css_set(to_cset);
 			to_cset->nr_tasks++;
+			css_account_tasks(to_cset, 1);
 			css_set_move_task(task, from_cset, to_cset, true);
 			put_css_set_locked(from_cset);
 			from_cset->nr_tasks--;
+			css_account_tasks(from_cset, -1);
 		}
 	}
 	spin_unlock_irq(&css_set_lock);
@@ -5828,6 +5849,7 @@ void cgroup_post_fork(struct task_struct *child)
 		if (list_empty(&child->cg_list)) {
 			get_css_set(cset);
 			cset->nr_tasks++;
+			css_account_tasks(cset, 1);
 			css_set_move_task(child, NULL, cset, false);
 		}
 		spin_unlock_irq(&css_set_lock);
@@ -5879,6 +5901,7 @@ void cgroup_exit(struct task_struct *tsk)
 		css_set_move_task(tsk, cset, NULL, false);
 		list_add_tail(&tsk->cg_list, &cset->dying_tasks);
 		cset->nr_tasks--;
+		css_account_tasks(cset, -1);
 		spin_unlock_irq(&css_set_lock);
 	} else {
 		get_css_set(cset);