From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx188.postini.com [74.125.245.188]) by kanga.kvack.org (Postfix) with SMTP id 55DA46B002B for ; Wed, 26 Sep 2012 04:46:52 -0400 (EDT) Message-ID: <5062C029.308@parallels.com> Date: Wed, 26 Sep 2012 12:43:21 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCH] slab: Ignore internal flags in cache creation References: <1348571866-31738-1-git-send-email-glommer@parallels.com> <00000139fe408877-40bc98e3-322c-4ba2-be72-e298ff28e694-000000@email.amazonses.com> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Christoph Lameter , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Pekka Enberg On 09/26/2012 04:46 AM, David Rientjes wrote: > On Tue, 25 Sep 2012, Christoph Lameter wrote: > >>> No cache should ever pass those as a creation flags. We can just ignore >>> this bit if it happens to be passed (such as when duplicating a cache in >>> the kmem memcg patches) >> >> Acked-by: Christoph Lameter >> > > Nack, this is already handled by CREATE_MASK in the mm/slab.c allocator; > the flag extensions beyond those defined in the generic slab.h header are > implementation defined. It may be true that SLAB uses a bit only > internally (and already protects it with a BUG_ON() in > __kmem_cache_create()) but that doesn't mean other implementations can't > use such a flag that would be a no-op on another allocator. > So the problem I am facing here is that when I am creating caches from memcg, I would very much like to reuse their flags fields. They are stored in the cache itself, so this is not a problem. But slab also stores that flag, leading to the precise BUG_ON() on CREATE_MASK that you quoted. In this context, passing this flag becomes completely valid, I just need that to be explicitly masked out. What is your suggestion to handle this ? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org