Index: linux/mm/page_alloc.c
===================================================================
--- linux.orig/mm/page_alloc.c
+++ linux/mm/page_alloc.c
@@ -875,6 +875,7 @@ unsigned int nr_free_buffer_pages(void)
 {
 	return nr_free_zone_pages(GFP_USER & GFP_ZONEMASK);
 }
+EXPORT_SYMBOL(nr_free_buffer_pages);
 
 /*
  * Amount of free RAM allocatable within all zones