Re: [PATCH v2 2/3] userfaultfd: UFFDIO_REMAP uABI

[Peter Xu]

On Wed, Sep 27, 2023 at 03:29:35PM +0200, David Hildenbrand wrote:
> > > +       if (!pte_same(*src_pte, orig_src_pte) ||
> > > +           !pte_same(*dst_pte, orig_dst_pte) ||
> > > +           folio_test_large(src_folio) ||
> > > +           folio_estimated_sharers(src_folio) != 1) {
> 
> ^ here you should check PageAnonExclusive. Please get rid of any implicit
> explicit/implcit mapcount checks.

David, is PageAnon 100% accurate now in the current tree?

IOW, can it be possible that the page has total_mapcount==1 but missing
AnonExclusive bit in any possible way?

Thanks,

-- 
Peter Xu