diff --git a/[refs] b/[refs]
index dc5b9149b472..3185b5430bb0 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ecb256f815232b35ae8382cff36ca8ce0bbd077e
+refs/heads/master: 240c879f20a605346705be24253bc9fc6fa8a106
diff --git a/trunk/mm/page-writeback.c b/trunk/mm/page-writeback.c
index 28763b8bdbdd..2cb01f6ec5d0 100644
--- a/trunk/mm/page-writeback.c
+++ b/trunk/mm/page-writeback.c
@@ -410,9 +410,12 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
 {
 	unsigned long background;
 	unsigned long dirty;
-	unsigned long available_memory = determine_dirtyable_memory();
+	unsigned long uninitialized_var(available_memory);
 	struct task_struct *tsk;
 
+	if (!vm_dirty_bytes || !dirty_background_bytes)
+		available_memory = determine_dirtyable_memory();
+
 	if (vm_dirty_bytes)
 		dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
 	else