linux-kernel - Re: [PATCH 04/16] huge tmpfs: revert shmem's use of transhuge_vma

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Date:   Fri, 30 Jul 2021 14:56:12 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...e.com>,
        Rik van Riel <riel@...riel.com>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Alexey Gladkov <legion@...nel.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Matthew Auld <matthew.auld@...el.com>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org, Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH 04/16] huge tmpfs: revert shmem's use of transhuge_vma_enabled()

On Fri, Jul 30, 2021 at 12:36 AM Hugh Dickins <hughd@...gle.com> wrote:
>
> 5.14 commit e6be37b2e7bd ("mm/huge_memory.c: add missing read-only THP
> checking in transparent_hugepage_enabled()") added transhuge_vma_enabled()
> as a wrapper for two very different checks: shmem_huge_enabled() prefers
> to show those two checks explicitly, as before.

Basically I have no objection to separating them again. But IMHO they
seem not very different. Or just makes things easier for the following
patches?

>
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> ---
>  mm/shmem.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index ce3ccaac54d6..c6fa6f4f2db8 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -4003,7 +4003,8 @@ bool shmem_huge_enabled(struct vm_area_struct *vma)
>         loff_t i_size;
>         pgoff_t off;
>
> -       if (!transhuge_vma_enabled(vma, vma->vm_flags))
> +       if ((vma->vm_flags & VM_NOHUGEPAGE) ||
> +           test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
>                 return false;
>         if (shmem_huge == SHMEM_HUGE_FORCE)
>                 return true;
> --
> 2.26.2
>