diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b15a51711bcabd0d797346aedfb4284a07036875..30e07308db24a79d19b8b26b12d64bf588dd19f2 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -19,6 +19,7 @@
 #include <linux/slab.h>
 #include <linux/genhd.h>
 #include <linux/delay.h>
+#include <linux/atomic.h>
 #include "blk-cgroup.h"
 #include "blk.h"
 
@@ -1622,6 +1623,7 @@ static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 static struct cgroup_subsys_state *
 blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 {
+	static atomic64_t id_seq = ATOMIC64_INIT(0);
 	struct blkio_cgroup *blkcg;
 	struct cgroup *parent = cgroup->parent;
 
@@ -1635,6 +1637,7 @@ blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 		return ERR_PTR(-ENOMEM);
 
 	blkcg->weight = BLKIO_WEIGHT_DEFAULT;
+	blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
 done:
 	spin_lock_init(&blkcg->lock);
 	INIT_HLIST_HEAD(&blkcg->blkg_list);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 9df5ab04b6d6ba13d273f641d68f99bc1ed48392..1cb8f764325861283cab4c6a42613ce053e41985 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -116,6 +116,9 @@ struct blkio_cgroup {
 	unsigned int weight;
 	spinlock_t lock;
 	struct hlist_head blkg_list;
+
+	/* for policies to test whether associated blkcg has changed */
+	uint64_t id;
 };
 
 struct blkio_group_stats {