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

Johannes Weiner
2013-03-27T15:32:26Z

On Wed, Mar 27, 2013 at 04:11:04PM +0100, 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. Maybe we can use NAME_MAX instead. I just do not like to
> use page allocator directly when allocatating something like strings
> etc...

Don't grep for GFP_TEMPORARY then, we do it in a couple places :-)
NAME_MAX is just for single dentry names, not path names, no? Might
be a little short.

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