Re: [PATCH] mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly

[Roman Gushchin]

On Wed, Oct 30, 2019 at 05:03:14PM -0400, Daniel Jordan wrote:
> Hi Roman,
> 
> On Fri, Oct 25, 2019 at 04:27:10PM -0700, Roman Gushchin wrote:
> > page_cgroup_ino() doesn't return a valid memcg pointer for non-compund
> > slab pages, because it depends on PgHead AND PgSlab flags to be set
> > to determine the memory cgroup from the kmem_cache.
> > It's correct for compound pages, but not for generic small pages. Those
> > don't have PgHead set, so it ends up returning zero.
> > 
> > Fix this by replacing the condition to PageSlab() && !PageTail().
> 
> You may also want to update the comment above memcg_from_slab_page():
> 
>  * So this function assumes that the page can pass PageHead() and PageSlab()
>  * checks.

Good catch, thank you! Will send v2 in no time.