Re: [PATCH v4 4/4] mm: convert page kmemcg type to a page memcg flag

[Roman Gushchin]

On Thu, Oct 01, 2020 at 07:00:36PM +0200, Michal Koutny wrote:
> Hi.
> 
> On Wed, Sep 30, 2020 at 05:27:10PM -0700, Roman Gushchin <guro@xxxxxx> wrote:
> > @@ -369,8 +371,12 @@ enum page_memcg_data_flags {
> >   */
> >  static inline struct mem_cgroup *page_memcg(struct page *page)
> >  {
> > +	unsigned long memcg_data = page->memcg_data;
> > +
> >  	VM_BUG_ON_PAGE(PageSlab(page), page);
> > -	return (struct mem_cgroup *)page->memcg_data;
> > +	VM_BUG_ON_PAGE(memcg_data & MEMCG_DATA_OBJCGS, page);
> > +
> > +	return (struct mem_cgroup *)(memcg_data & ~MEMCG_DATA_FLAGS_MASK);
> >  }
> Shouldn't this change go also into page_memcg_rcu()? (I don't think the
> current single user (workingset_activation() would pass a non-slab
> kernel page but for consistency sake.)

Yes, a good idea, I will add it.

Thanks!