Index: linux-2.6.11-rc1-ck2/drivers/block/cfq-iosched.c
===================================================================
--- linux-2.6.11-rc1-ck2.orig/drivers/block/cfq-iosched.c	2005-01-19 10:27:53.832219984 +1100
+++ linux-2.6.11-rc1-ck2/drivers/block/cfq-iosched.c	2005-01-19 10:34:12.403668376 +1100
@@ -381,7 +381,8 @@
 	struct cfq_rq *crq_next = NULL, *crq_prev = NULL;
 	struct rb_node *rbnext, *rbprev;
 
-	BUG_ON(!ON_RB(&last->rb_node));
+	if (!ON_RB(&last->rb_node))
+		return NULL;
 
 	if ((rbnext = rb_next(&last->rb_node)) == NULL) {
 		rbnext = rb_first(&cfqq->sort_list[cfqq->dir]);