From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH v2 04/29] slub: always get the cache from its page in kfree Date: Fri, 11 May 2012 15:11:56 -0300 Message-ID: <4FAD566C.3000804@parallels.com> References: <1336758272-24284-1-git-send-email-glommer@parallels.com> <1336758272-24284-5-git-send-email-glommer@parallels.com> <4FAD531D.6030007@parallels.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Christoph Lameter Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, Tejun Heo , Li Zefan , Greg Thelen , Suleiman Souhlal , Michal Hocko , Johannes Weiner , devel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, Pekka Enberg On 05/11/2012 03:06 PM, Christoph Lameter wrote: > On Fri, 11 May 2012, Glauber Costa wrote: > >>> Adding a VM_BUG_ON may be useful to make sure that kmem_cache_free is >>> always passed the correct slab cache. >> >> Well, problem is , it isn't always passed the "correct" slab cache. >> At least not after this series, since we'll have child caches associated with >> the main cache. >> >> So we'll pass, for instance, kmem_cache_free(dentry_cache...), but will in >> fact free from the memcg copy of the dentry cache. > > Urg. But then please only do this for the MEMCG case and add a fat big > warning in kmem_cache_free. I can do that, of course. Another option if you don't oppose, is to add another field in the kmem_cache structure (I tried to keep them at a minimum), to record the parent cache we got created from. Then, it gets trivial to do the following: VM_BUG_ON(page->slab != s && page->slab != s->parent_cache);