diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 6301af28da21..682e3a6a8b2e 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1723,14 +1723,20 @@ void laptop_mode_timer_fn(unsigned long data)
 	struct request_queue *q = (struct request_queue *)data;
 	int nr_pages = global_page_state(NR_FILE_DIRTY) +
 		global_page_state(NR_UNSTABLE_NFS);
+	struct bdi_writeback *wb;
+	struct wb_iter iter;
 
 	/*
 	 * We want to write everything out, not just down to the dirty
 	 * threshold
 	 */
-	if (bdi_has_dirty_io(&q->backing_dev_info))
-		wb_start_writeback(&q->backing_dev_info.wb, nr_pages, true,
-				   WB_REASON_LAPTOP_TIMER);
+	if (!bdi_has_dirty_io(&q->backing_dev_info))
+		return;
+
+	bdi_for_each_wb(wb, &q->backing_dev_info, &iter, 0)
+		if (wb_has_dirty_io(wb))
+			wb_start_writeback(wb, nr_pages, true,
+					   WB_REASON_LAPTOP_TIMER);
 }
 
 /*