Re: [PATCH 2/2] ksm: cleanup: introduce ksm_check_mm()

[Bob Liu <lliubbo@gmail.com>]

Hi Andrew,

On Fri, Mar 2, 2012 at 4:51 AM, Andrew Morton <akpm@linux-foundation.org> wrote:
> On Thu, 1 Mar 2012 17:32:54 +0800
> Bob Liu <lliubbo@gmail.com> wrote:
>
>> +static int ksm_check_mm(struct mm_struct *mm, struct vm_area_struct *vma,
>> +             unsigned long addr)
>> +{
>> +     if (ksm_test_exit(mm))
>> +             return 0;
>> +     vma = find_vma(mm, addr);
>> +     if (!vma || vma->vm_start > addr)
>> +             return 0;
>> +     if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
>> +             return 0;
>> +     return 1;
>> +}
>
> Can we please think of a suitable name for this check, other than
> "check"?  IOW, give the function a meaningful name which describes what
> it is checking?
>
> And it's not checking the mm, is it?  It is checking the address: to
> see whether it lies within a mergeable anon vma.
>
> So maybe
>
> --- a/mm/ksm.c~ksm-cleanup-introduce-ksm_check_mm-fix
> +++ a/mm/ksm.c
> @@ -375,17 +375,17 @@ static int break_ksm(struct vm_area_stru
>        return (ret & VM_FAULT_OOM) ? -ENOMEM : 0;
>  }
>
> -static int ksm_check_mm(struct mm_struct *mm, struct vm_area_struct *vma,
> -               unsigned long addr)
> +static bool in_mergeable_anon_vma(struct mm_struct *mm,
> +                                struct vm_area_struct *vma, unsigned long addr)
>  {
>        if (ksm_test_exit(mm))
> -               return 0;
> +               return false;
>        vma = find_vma(mm, addr);
>        if (!vma || vma->vm_start > addr)
> -               return 0;
> +               return false;
>        if (!(vma->vm_flags & VM_MERGEABLE) || !vma->anon_vma)
> -               return 0;
> -       return 1;
> +               return false;
> +       return true;
>  }
>
>  static void break_cow(struct rmap_item *rmap_item)
> @@ -401,7 +401,7 @@ static void break_cow(struct rmap_item *
>        put_anon_vma(rmap_item->anon_vma);
>
>        down_read(&mm->mmap_sem);
> -       if (ksm_check_mm(mm, vma, addr))
> +       if (in_mergeable_anon_vma(mm, vma, addr))
>                break_ksm(vma, addr);
>        up_read(&mm->mmap_sem);
>  }
> @@ -428,7 +428,7 @@ static struct page *get_mergeable_page(s
>        struct page *page;
>
>        down_read(&mm->mmap_sem);
> -       if (!ksm_check_mm(mm, vma, addr))
> +       if (!in_mergeable_anon_vma(mm, vma, addr))
>                goto out;
>
>        page = follow_page(vma, addr, FOLL_GET);
> _
>

Yeah, It looks much better than mine, Thanks!

-- 
Regards,
--Bob

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