diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 8c857d7..97a92fa 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -155,6 +155,8 @@
 	struct rb_root cgwb_congested_tree; /* their congested states */
 	atomic_t usage_cnt; /* counts both cgwbs and cgwb_contested's */
 #endif
+	wait_queue_head_t wb_waitq;
+
 	struct device *dev;
 
 	struct timer_list laptop_mode_wb_timer;