debugobjects: avoid recursive calls with kmemleak

CONFIG_DEBUG_OBJECTS_RCU_HEAD does not play well with kmemleak due to
recursive calls.

fill_pool
  kmemleak_ignore
    make_black_object
      put_object
        __call_rcu (kernel/rcu/tree.c)
          debug_rcu_head_queue
            debug_object_activate
              debug_object_init
                fill_pool
                  kmemleak_ignore
                    make_black_object
                      ...

So add SLAB_NOLEAKTRACE to kmem_cache_create() to not register newly
allocated debug objects at all.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Qian Cai <[email protected]>
Suggested-by: Catalin Marinas <[email protected]>
Acked-by: Waiman Long <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Yang Shi <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

lib/debugobjects.c

@@ -135,7 +135,6 @@ static void fill_pool(void)
 		if (!new)
 			return;
 
-		kmemleak_ignore(new);
 		raw_spin_lock_irqsave(&pool_lock, flags);
 		hlist_add_head(&new->node, &obj_pool);
 		debug_objects_allocated++;
@@ -1128,7 +1127,6 @@ static int __init debug_objects_replace_static_objects(void)
 		obj = kmem_cache_zalloc(obj_cache, GFP_KERNEL);
 		if (!obj)
 			goto free;
-		kmemleak_ignore(obj);
 		hlist_add_head(&obj->node, &objects);
 	}
 
@@ -1184,7 +1182,8 @@ void __init debug_objects_mem_init(void)
 
 	obj_cache = kmem_cache_create("debug_objects_cache",
 				      sizeof (struct debug_obj), 0,
-				      SLAB_DEBUG_OBJECTS, NULL);
+				      SLAB_DEBUG_OBJECTS | SLAB_NOLEAKTRACE,
+				      NULL);
 
 	if (!obj_cache || debug_objects_replace_static_objects()) {
 		debug_objects_enabled = 0;