[PATCH v1 2/9] mm/mmap: Abstract vma clean up from exit_mmap()

[Suren Baghdasaryan]

On Tue, Sep 9, 2025 at 12:09 PM Liam R. Howlett <Liam.Howlett at oracle.com> wrote:
>
> Create the new function tear_down_vmas() to remove a range of vmas.
> exit_mmap() will be removing all the vmas.
>
> This is necessary for future patches.
>
> No functional changes intended.
>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes at oracle.com>
> Signed-off-by: Liam R. Howlett <Liam.Howlett at oracle.com>

Reviewed-by: Suren Baghdasaryan <surenb at google.com>

> ---
>  mm/mmap.c | 37 ++++++++++++++++++++++++-------------
>  1 file changed, 24 insertions(+), 13 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index b07b3ec5e28f5..a290448a53bb2 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1250,6 +1250,29 @@ int vm_brk_flags(unsigned long addr, unsigned long request, vm_flags_t vm_flags)
>  }
>  EXPORT_SYMBOL(vm_brk_flags);
>
> +static inline

nit: Maybe let the compiler decide whether to inline this one?

> +unsigned long tear_down_vmas(struct mm_struct *mm, struct vma_iterator *vmi,
> +               struct vm_area_struct *vma, unsigned long max)
> +{
> +       unsigned long nr_accounted = 0;
> +       int count = 0;
> +
> +       mmap_assert_write_locked(mm);
> +       vma_iter_set(vmi, vma->vm_end);
> +       do {
> +               if (vma->vm_flags & VM_ACCOUNT)
> +                       nr_accounted += vma_pages(vma);
> +               vma_mark_detached(vma);
> +               remove_vma(vma);
> +               count++;
> +               cond_resched();
> +               vma = vma_next(vmi);
> +       } while (vma && vma->vm_end <= max);
> +
> +       WARN_ON_ONCE(count != mm->map_count);
> +       return nr_accounted;
> +}
> +
>  /* Release all mmaps. */
>  void exit_mmap(struct mm_struct *mm)
>  {
> @@ -1257,7 +1280,6 @@ void exit_mmap(struct mm_struct *mm)
>         struct vm_area_struct *vma;
>         unsigned long nr_accounted = 0;
>         VMA_ITERATOR(vmi, mm, 0);
> -       int count = 0;
>
>         /* mm's last user has gone, and its about to be pulled down */
>         mmu_notifier_release(mm);
> @@ -1297,18 +1319,7 @@ void exit_mmap(struct mm_struct *mm)
>          * enabled, without holding any MM locks besides the unreachable
>          * mmap_write_lock.
>          */
> -       vma_iter_set(&vmi, vma->vm_end);
> -       do {
> -               if (vma->vm_flags & VM_ACCOUNT)
> -                       nr_accounted += vma_pages(vma);
> -               vma_mark_detached(vma);
> -               remove_vma(vma);
> -               count++;
> -               cond_resched();
> -               vma = vma_next(&vmi);
> -       } while (vma && likely(!xa_is_zero(vma)));
> -
> -       BUG_ON(count != mm->map_count);
> +       nr_accounted = tear_down_vmas(mm, &vmi, vma, ULONG_MAX);
>
>  destroy:
>         __mt_destroy(&mm->mm_mt);
> --
> 2.47.2
>