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

Peter Xu
2023-09-28T16:25:42Z

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