+static int blkcg_css_online(struct cgroup_subsys_state *css)
+{
+ struct blkcg *blkcg = css_to_blkcg(css);
+ struct blkcg *parent = blkcg_parent(blkcg);
+
+ /*
+ * blkcg_pin_online() is used to delay blkcg offline so that blkgs
+ * don't go offline while cgwbs are still active on them. Pin the
+ * parent so that offline always happens towards the root.
+ */
+ if (parent)
+ blkcg_pin_online(parent);
+ return 0;
+}
+