Re: [PATCH v5 5/5] mm: rmap: support batched unmapping for file large folios

[Barry Song <21cnbao@gmail.com>]

>
> Thanks for catching this, Dev. I already filter out some of the more
> complex cases, for example:
> if (pte_unused(pte))
>         return 1;
>
> Since the userfaultfd write-protection case is also a corner case,
> could we filter it out as well?
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index c86f1135222b..6bb8ba6f046e 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1870,6 +1870,9 @@ static inline unsigned int
> folio_unmap_pte_batch(struct folio *folio,
>         if (pte_unused(pte))
>                 return 1;
>
> +       if (userfaultfd_wp(vma))
> +               return 1;
> +
>         return folio_pte_batch(folio, pvmw->pte, pte, max_nr);
> }
>
> Just offering a second option — yours is probably better.

Sorry for replying in the wrong place. The above reply was actually meant
for your fix-patch below[1]:

"mm: Fix uffd-wp bit loss when batching file folio unmapping"

[1] https://lore.kernel.org/linux-mm/20260116082721.275178-1-dev.jain@arm.com/

Thanks
Barry