Re: [PATCH v20 2/5] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs

[Michał Mirosław]

On Wed, 21 Jun 2023 at 09:24, Muhammad Usama Anjum
<usama.anjum@xxxxxxxxxxxxx> wrote:
[...]
> +static int pagemap_scan_test_walk(unsigned long start, unsigned long end,
> +                                 struct mm_walk *walk)
> +{
> +       struct pagemap_scan_private *p = walk->private;
> +       struct vm_area_struct *vma = walk->vma;
> +
> +       if ((p->flags & PM_SCAN_REQUIRE_UFFD) && (!userfaultfd_wp_async(vma) ||
> +           !userfaultfd_wp_use_markers(vma)))
> +               return -EPERM;
> +
> +       if (vma->vm_flags & VM_PFNMAP)
> +               return 1;
> +
> +       return 0;
> +}

This could actually short-circuit all vma flags (e.g. IS_FILE): if
(required_mask & IS_FILE && vma is not file-backed) return 0;

Best Regards
Michał Mirosław