diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index e9d371b..b625073 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -7,6 +7,27 @@
 #include <linux/sched.h>
 #include <linux/fs.h>
 
+/*
+ * The 1/16 region above the global dirty limit will be put to maximum pauses:
+ *
+ *	(limit, limit + limit/DIRTY_MAXPAUSE_AREA)
+ *
+ * The 1/16 region above the max-pause region, dirty exceeded bdi's will be put
+ * to loops:
+ *
+ *	(limit + limit/DIRTY_MAXPAUSE_AREA, limit + limit/DIRTY_PASSGOOD_AREA)
+ *
+ * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
+ * time) for the dirty pages to drop, unless written enough pages.
+ *
+ * The global dirty threshold is normally equal to the global dirty limit,
+ * except when the system suddenly allocates a lot of anonymous memory and
+ * knocks down the global dirty threshold quickly, in which case the global
+ * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
+ */
+#define DIRTY_MAXPAUSE_AREA		16
+#define DIRTY_PASSGOOD_AREA		8
+
 struct backing_dev_info;
 
 /*