Re: [PATCH RESEND] userfaultfd: snapshot VMA state across UFFDIO_COPY retry

[Mike Rapoport]

Hi David,

On Tue, May 19, 2026 at 06:36:23AM +0100, David CARLIER wrote:
> On Tue, 19 May 2026 at 06:25, Mike Rapoport <rppt@xxxxxxxxxx> wrote:
>
> > @@ -69,6 +71,24 @@ static const struct vm_uffd_ops *vma_uffd_ops(struct vm_area_struct *vma)
> >         return vma->vm_ops ? vma->vm_ops->uffd_ops : NULL;
> >  }
> >
> > +static const struct vm_uffd_ops *vma_uffd_copy_ops(struct vm_area_struct *vma)
> 
> 
> My only 2 cent, I would name it vma_uffd_effective_copy_ops() instead or
> a comment to highlight it is about "UFFDIO_COPY into a MAP_PRIVATE file-backed"
 
Too long for my taste :)
And comment is useful anyway as it explains why we override the ops at all.
 
> > +{
> > +       const struct vm_uffd_ops *ops = vma_uffd_ops(vma);
> > +
> > +       if (!ops)
> > +               return NULL;
> > +
> > +       /*
> > +        * UFFDIO_COPY fills MAP_PRIVATE file-backed mappings as anonymous
> > +        * memory. This is an effective ops override, so retry validation must
> > +        * compare the override result, not just vma->vm_ops->uffd_ops.
> > +        */
> > +       if (!(vma->vm_flags & VM_SHARED))
> > +               return &anon_uffd_ops;
> > +
> > +       return ops;
> > +}

-- 
Sincerely yours,
Mike.