SLUB: Fix validation

Some parts of object validation will never occur because on_freelist
does return the wrong exit code for a NULL object.

Fix that.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.21-rc6/mm/slub.c
===================================================================
--- linux-2.6.21-rc6.orig/mm/slub.c	2007-04-12 15:06:54.000000000 -0700
+++ linux-2.6.21-rc6/mm/slub.c	2007-04-12 15:07:23.000000000 -0700
@@ -588,7 +588,7 @@ static int on_freelist(struct kmem_cache
 			s->objects - nr);
 		page->inuse = s->objects - nr;
 	}
-	return 0;
+	return search == NULL;
 }
 
 /*