Re: [PATCH v2 06/10] mm: memory: use a folio in zap_pte_range()

[Kefeng Wang]

On 2023/11/5 1:20, Matthew Wilcox wrote:
> On Sat, Nov 04, 2023 at 11:55:18AM +0800, Kefeng Wang wrote:
> > -/* Decides whether we should zap this page with the page pointer specified */
> > -static inline bool should_zap_page(struct zap_details *details, struct page *page)
> > +/* Decides whether we should zap this folio with the folio pointer specified */
> > +static inline bool should_zap_page(struct zap_details *details, struct folio *folio)
>
> Surely we should rename this to should_zap_folio()?
Will update.
> > @@ -1487,10 +1492,10 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> >   			 * see zap_install_uffd_wp_if_needed().
> >   			 */
> >   			WARN_ON_ONCE(!vma_is_anonymous(vma));
> > -			rss[mm_counter(page)]--;
> > +			rss[mm_counter(&folio->page)]--;
> >   			if (is_device_private_entry(entry))
> > -				page_remove_rmap(page, vma, false);
> > -			put_page(page);
> > +				page_remove_rmap(&folio->page, vma, false);
> > +			folio_put(folio);
>
> This is wrong.  If we have a PTE-mapped THP, you'll remove the head page
> N times instead of removing each of N pages.

This is device private entry, I suppose that it won't be a THP and large 
folio when check migrate_vma_check_page() and migrate_vma_insert_page(),
right?

> I suspect you're going to collide with Ryan's work by doing this ...
Maybe not if the above is true, at least for now.

Thanks.