linux-kernel - Re: [PATCH v3 03/16] mm/mmap: Introduce vmi_complete_munmap

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Message-ID: <CAJuCfpHPWm2Bj+CZJyZQrwOBEP76M_xsdH3DG8CuUS=Onv+c8w@mail.gmail.com>
Date: Wed, 10 Jul 2024 09:07:01 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, 
	Vlastimil Babka <vbabka@...e.cz>, Lorenzo Stoakes <lstoakes@...il.com>, 
	Matthew Wilcox <willy@...radead.org>, sidhartha.kumar@...cle.com, 
	"Paul E . McKenney" <paulmck@...nel.org>, Bert Karwatzki <spasswolf@....de>, Jiri Olsa <olsajiri@...il.com>, 
	linux-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v3 03/16] mm/mmap: Introduce vmi_complete_munmap_vmas()

On Thu, Jul 4, 2024 at 11:27 AM Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
>
> Extract all necessary operations that need to be completed after the vma
> maple tree is updated from a munmap() operation.  Extracting this makes
> the later patch in the series easier to understand.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> ---
>  mm/mmap.c | 79 +++++++++++++++++++++++++++++++++++++------------------
>  1 file changed, 53 insertions(+), 26 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index d572e1ff8255..411798f46932 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2605,6 +2605,56 @@ static inline void abort_munmap_vmas(struct ma_state *mas_detach)
>         __mt_destroy(mas_detach->tree);
>  }
>
> +/*
> + * vmi_complete_munmap_vmas() - Finish the munmap() operation
> + * @vmi: The vma iterator

You are missing vma and mm documentation. With that fixed

Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>


> + * @start: The start address
> + * @end: The end address
> + * @unlock: Unlock the mm or not
> + * @mas_detach: them maple state of the detached vma maple tree
> + * @locked_vm: The locked_vm count in the detached vmas
> + *
> + * This function updates the mm_struct, unmaps the region, frees the resources
> + * used for the munmap() and may downgrade the lock - if requested.  Everything
> + * needed to be done once the vma maple tree is updated.
> + */
> +static void
> +vmi_complete_munmap_vmas(struct vma_iterator *vmi, struct vm_area_struct *vma,
> +               struct mm_struct *mm, unsigned long start,
> +               unsigned long end, bool unlock, struct ma_state *mas_detach,
> +               unsigned long locked_vm)
> +{
> +       struct vm_area_struct *prev, *next;
> +       int count;
> +
> +       count = mas_detach->index + 1;
> +       mm->map_count -= count;
> +       mm->locked_vm -= locked_vm;
> +       if (unlock)
> +               mmap_write_downgrade(mm);
> +
> +       prev = vma_iter_prev_range(vmi);
> +       next = vma_next(vmi);
> +       if (next)
> +               vma_iter_prev_range(vmi);
> +
> +       /*
> +        * We can free page tables without write-locking mmap_lock because VMAs
> +        * were isolated before we downgraded mmap_lock.
> +        */
> +       mas_set(mas_detach, 1);
> +       unmap_region(mm, mas_detach, vma, prev, next, start, end, count,
> +                    !unlock);
> +       /* Statistics and freeing VMAs */
> +       mas_set(mas_detach, 0);
> +       remove_mt(mm, mas_detach);
> +       validate_mm(mm);
> +       if (unlock)
> +               mmap_read_unlock(mm);
> +
> +       __mt_destroy(mas_detach->tree);
> +}
> +
>  /*
>   * do_vmi_align_munmap() - munmap the aligned region from @start to @end.
>   * @vmi: The vma iterator
> @@ -2624,7 +2674,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
>                     struct mm_struct *mm, unsigned long start,
>                     unsigned long end, struct list_head *uf, bool unlock)
>  {
> -       struct vm_area_struct *prev, *next = NULL;
> +       struct vm_area_struct *next = NULL;
>         struct maple_tree mt_detach;
>         int count = 0;
>         int error = -ENOMEM;
> @@ -2728,31 +2778,8 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
>                 goto clear_tree_failed;
>
>         /* Point of no return */
> -       mm->locked_vm -= locked_vm;
> -       mm->map_count -= count;
> -       if (unlock)
> -               mmap_write_downgrade(mm);
> -
> -       prev = vma_iter_prev_range(vmi);
> -       next = vma_next(vmi);
> -       if (next)
> -               vma_iter_prev_range(vmi);
> -
> -       /*
> -        * We can free page tables without write-locking mmap_lock because VMAs
> -        * were isolated before we downgraded mmap_lock.
> -        */
> -       mas_set(&mas_detach, 1);
> -       unmap_region(mm, &mas_detach, vma, prev, next, start, end, count,
> -                    !unlock);
> -       /* Statistics and freeing VMAs */
> -       mas_set(&mas_detach, 0);
> -       remove_mt(mm, &mas_detach);
> -       validate_mm(mm);
> -       if (unlock)
> -               mmap_read_unlock(mm);
> -
> -       __mt_destroy(&mt_detach);
> +       vmi_complete_munmap_vmas(vmi, vma, mm, start, end, unlock, &mas_detach,
> +                                locked_vm);
>         return 0;
>
>  clear_tree_failed:
> --
> 2.43.0
>