diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 26adea8..9dec97f 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -204,7 +204,7 @@
  * Returns the global number of pages potentially available for dirty
  * page cache.  This is the base value for the global dirty limits.
  */
-unsigned long global_dirtyable_memory(void)
+static unsigned long global_dirtyable_memory(void)
 {
 	unsigned long x;