linux-kernel - Re: [v3 PATCH 1/7] mm: khugepaged: check THP flag in hugepage_vma

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Date:   Thu, 9 Jun 2022 10:49:19 -0700
From:   "Zach O'Keefe" <zokeefe@...gle.com>
To:     Yang Shi <shy828301@...il.com>
Cc:     vbabka@...e.cz, kirill.shutemov@...ux.intel.com,
        willy@...radead.org, akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [v3 PATCH 1/7] mm: khugepaged: check THP flag in hugepage_vma_check()

Reviewed-by: Zach O'Keefe <zokeefe@...gle.com>

On Mon, Jun 6, 2022 at 2:44 PM Yang Shi <shy828301@...il.com> wrote:
>
> Currently the THP flag check in hugepage_vma_check() will fallthrough if
> the flag is NEVER and VM_HUGEPAGE is set.  This is not a problem for now
> since all the callers have the flag checked before or can't be invoked if
> the flag is NEVER.
>
> However, the following patch will call hugepage_vma_check() in more
> places, for example, page fault, so this flag must be checked in
> hugepge_vma_check().
>
> Signed-off-by: Yang Shi <shy828301@...il.com>
> ---
>  mm/khugepaged.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 671ac7800e53..84b9cf4b9be9 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -458,6 +458,9 @@ bool hugepage_vma_check(struct vm_area_struct *vma,
>         if (shmem_file(vma->vm_file))
>                 return shmem_huge_enabled(vma);
>
> +       if (!khugepaged_enabled())
> +               return false;
> +
>         /* THP settings require madvise. */
>         if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always())
>                 return false;
> --
> 2.26.3
>
>