Index: kernel/generic/src/mm/backend_phys.c
===================================================================
--- kernel/generic/src/mm/backend_phys.c	(revision aafed151536405cdb1390b88b7e4ac7c285dd53e)
+++ kernel/generic/src/mm/backend_phys.c	(revision fa603e9908d894356690de9782e4735496a91a8a)
@@ -143,5 +143,5 @@
 	    as_area_get_flags(area));
 
-	if (!used_space_insert(area, upage, 1))
+	if (!used_space_insert(&area->used_space, upage, 1))
 		panic("Cannot insert used space.");