linux-kernel - Re: [PATCH v5 68/70] mm: Remove the vma linked list

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Date:   Thu, 3 Feb 2022 12:08:25 +0000
From:   Mark Hemment <markhemm@...glemail.com>
To:     Liam Howlett <liam.howlett@...cle.com>
Cc:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v5 68/70] mm: Remove the vma linked list

On Wed, 2 Feb 2022 at 02:43, Liam Howlett <liam.howlett@...cle.com> wrote:
>
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
>
> Replace any vm_next use with vma_find().
>
> Update free_pgtables(), unmap_vmas(), and zap_page_range() to use the
> maple tree.
>
> Use the new free_pgtables() and unmap_vmas() in do_mas_align_munmap().
> At the same time, alter the loop to be more compact.
>
> Now that free_pgtables() and unmap_vmas() take a maple tree as an
> argument, rearrange do_mas_align_munmap() to use the new tree to hold
> the vmas to remove.
>
> Remove __vma_link_list() and __vma_unlink_list() as they are exclusively
> used to update the linked list
>
> Drop linked list update from __insert_vm_struct().
>
> Rework validation of tree as it was depending on the linked list.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> ---
>  include/linux/mm.h       |   5 +-
>  include/linux/mm_types.h |   4 -
>  kernel/fork.c            |  13 +-
>  mm/debug.c               |  14 +-
>  mm/gup.c                 |   2 +-
>  mm/internal.h            |  10 +-
>  mm/memory.c              |  33 ++-
>  mm/mmap.c                | 518 +++++++++++++++++----------------------
>  mm/nommu.c               |   2 -
>  mm/util.c                |  40 ---
>  10 files changed, 264 insertions(+), 377 deletions(-)
...
> -static inline int
> -unlock_range(struct vm_area_struct *start, struct vm_area_struct **tail,
> -            unsigned long limit)
> -{
> -       struct mm_struct *mm = start->vm_mm;
> -       struct vm_area_struct *tmp = start;
> -       int count = 0;
> -
> -       while (tmp && tmp->vm_start < limit) {
> -               *tail = tmp;
> -               count++;
> -               if (tmp->vm_flags & VM_LOCKED) {
> -                       mm->locked_vm -= vma_pages(tmp);
> -                       munlock_vma_pages_all(tmp);
> -               }
> -
> -               tmp = tmp->vm_next;
> -       }
> -
> -       return count;
> -}

Trivial: Comment in exit_mmap(), for oom-victim case, has a reference
to this removed function (unlock_range()).

Cheers,
Mark