[Devel] Re: [PATCH v2 04/29] slub: always get the cache from its page in kfree

[Glauber Costa]

On 05/11/2012 03:17 PM, Christoph Lameter wrote:
> On Fri, 11 May 2012, Glauber Costa wrote:
>
>> 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);
>
> Sounds ok but I need to catch up on what this whole memcg thing in slab
> allocators should accomplish in order to say something definite.
>
Fair enough.

Thank you in advance for your time reviewing this!