diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 8137482..c689b60 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -69,6 +69,12 @@
 int dirty_background_ratio = 5;
 
 /*
+ * free highmem will not be subtracted from the total free memory
+ * for calculating free ratios if vm_highmem_is_dirtyable is true
+ */
+int vm_highmem_is_dirtyable;
+
+/*
  * The generator of dirty data starts writeback at this percentage
  */
 int vm_dirty_ratio = 10;
@@ -287,7 +293,10 @@
 	x = global_page_state(NR_FREE_PAGES)
 		+ global_page_state(NR_INACTIVE)
 		+ global_page_state(NR_ACTIVE);
-	x -= highmem_dirtyable_memory(x);
+
+	if (!vm_highmem_is_dirtyable)
+		x -= highmem_dirtyable_memory(x);
+
 	return x + 1;	/* Ensure that we never return 0 */
 }