diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index c28a47c..97967ce 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -24,6 +24,7 @@
 	return bdi;
 }
 
+struct backing_dev_info *bdi_get_by_id(u64 id);
 void bdi_put(struct backing_dev_info *bdi);
 
 __printf(2, 3)
@@ -44,10 +45,13 @@
 void wb_workfn(struct work_struct *work);
 void wb_wakeup_delayed(struct bdi_writeback *wb);
 
+void wb_wait_for_completion(struct wb_completion *done);
+
 extern spinlock_t bdi_lock;
 extern struct list_head bdi_list;
 
 extern struct workqueue_struct *bdi_wq;
+extern struct workqueue_struct *bdi_async_bio_wq;
 
 static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
 {
@@ -226,6 +230,8 @@
 struct bdi_writeback_congested *
 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp);
 void wb_congested_put(struct bdi_writeback_congested *congested);
+struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
+				    struct cgroup_subsys_state *memcg_css);
 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 				    struct cgroup_subsys_state *memcg_css,
 				    gfp_t gfp);
@@ -365,7 +371,7 @@
 	rcu_read_lock();
 
 	/*
-	 * Paired with store_release in inode_switch_wb_work_fn() and
+	 * Paired with store_release in inode_switch_wbs_work_fn() and
 	 * ensures that we see the new wb if we see cleared I_WB_SWITCH.
 	 */
 	cookie->locked = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;