diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index e047b49..a48d90e 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -219,6 +219,17 @@
 		percpu_ref_put(&wb->refcnt);
 }
 
+/**
+ * wb_dying - is a wb dying?
+ * @wb: bdi_writeback of interest
+ *
+ * Returns whether @wb is unlinked and being drained.
+ */
+static inline bool wb_dying(struct bdi_writeback *wb)
+{
+	return percpu_ref_is_dying(&wb->refcnt);
+}
+
 #else	/* CONFIG_CGROUP_WRITEBACK */
 
 static inline bool wb_tryget(struct bdi_writeback *wb)
@@ -234,6 +245,11 @@
 {
 }
 
+static inline bool wb_dying(struct bdi_writeback *wb)
+{
+	return false;
+}
+
 #endif	/* CONFIG_CGROUP_WRITEBACK */
 
 #endif	/* __LINUX_BACKING_DEV_DEFS_H */