Index: generic/include/mm/as.h
===================================================================
--- generic/include/mm/as.h	(revision c1982e45cfd67b998329f3d32f3b52cbbc6caa5b)
+++ generic/include/mm/as.h	(revision 2a1803ebc9ca7186c0252f445083c2f952ae7cad)
@@ -35,5 +35,4 @@
 #define AS_AREA_EXEC	4
 #define AS_AREA_DEVICE	8
-
 
 #ifdef KERNEL
@@ -84,4 +83,5 @@
 	count_t pages;		/**< Size of this area in multiples of PAGE_SIZE. */
 	__address base;		/**< Base address of this area. */
+	btree_t used_space;	/**< Map of used space. */
 };