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

Matthew Wilcox
2023-11-06T14:21:07Z

On Mon, Nov 06, 2023 at 10:30:59AM +0800, Kefeng Wang wrote:
> On 2023/11/5 1:20, Matthew Wilcox wrote:
> > > - 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 don't want to leave that kind of booby-trap in the code. Both places
which currently call page_remove_rmap() should be left as referring to
the page, not the folio.