Re: [PATCH] memcg: fix memcg_cache_name() to use cgroup_name()

Glauber Costa
2013-03-27T15:19:58Z

On 03/27/2013 07:11 PM, Michal Hocko wrote:
> On Wed 27-03-13 10:58:25, Johannes Weiner wrote:
>> On Wed, Mar 27, 2013 at 09:36:39AM +0100, Michal Hocko wrote:
> [...]
>>> + /*
>>> + * kmem_cache_create_memcg duplicates the given name and
>>> + * cgroup_name for this name requires RCU context.
>>> + * This static temporary buffer is used to prevent from
>>> + * pointless shortliving allocation.
>>> + */
>>> + if (!tmp_name) {
>>> + tmp_name = kmalloc(PAGE_SIZE, GFP_KERNEL);
>>> + WARN_ON_ONCE(!tmp_name);
>>
>> Just use the page allocator directly and get a free allocation failure
>> warning.
>
> WARN_ON_ONCE is probably pointless.
>
>> Then again, order-0 pages are considered cheap enough that they never
>> even fail in our current implementation.
>>
>> Which brings me to my other point: why not just a simple single-page
>> allocation?
>
> No objection from me. I was previously thinking about the "proper"
> size for something that is a file name. So I originally wanted to use
> PATH_MAX instead but ended up with PAGE_SIZE for reasons I do not
> remember now.

theoretically, this is PATH_MAX + max cache name.