linux-kernel - Re: [PATCH] mm/shmem.c: use helper transhuge_vma

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Date:   Wed, 15 Jun 2022 17:40:23 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     Hugh Dickins <hughd@...gle.com>, Miaohe Lin <linmiaohe@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/shmem.c: use helper transhuge_vma_enabled()

On Tue, Jun 14, 2022 at 10:02 PM Anshuman Khandual
<anshuman.khandual@....com> wrote:
>
>
>
> On 6/11/22 08:44, Hugh Dickins wrote:
> > On Sat, 11 Jun 2022, Miaohe Lin wrote:
> >
> >> Use helper transhuge_vma_enabled() to check whether transhuge is enable
> >> on vma. Minor readability improvement.
> >>
> >> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> >
> > No thanks, that's a readability regression, forcing reader
> > to go and look up what transhuge_vma_enabled() actually means.
> >
> > What you call a helper, I call an obfuscator - as I implied in
> > b9e2faaf6fa0 ("huge tmpfs: revert shmem's use of transhuge_vma_enabled()")
>
> The same reasoning should also be applicable for other calls sites
> for transhuge_vma_enabled(). Should not they be dropped as well ?

Yes, the only caller was hugepage_vma_check(). It was changed to
open-code and the helper was removed by series:
https://lore.kernel.org/linux-mm/20220615172926.546974-1-shy828301@gmail.com/T/#m7610c2a4e5dda753cbc850986d5486f59a821c1a

>
> >
> > Hugh
> >
> >> ---
> >>  mm/shmem.c | 3 +--
> >>  1 file changed, 1 insertion(+), 2 deletions(-)
> >>
> >> diff --git a/mm/shmem.c b/mm/shmem.c
> >> index 133c67057d41..59cc2e980c95 100644
> >> --- a/mm/shmem.c
> >> +++ b/mm/shmem.c
> >> @@ -480,8 +480,7 @@ bool shmem_is_huge(struct vm_area_struct *vma,
> >>              return false;
> >>      if (shmem_huge == SHMEM_HUGE_DENY)
> >>              return false;
> >> -    if (vma && ((vma->vm_flags & VM_NOHUGEPAGE) ||
> >> -        test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)))
> >> +    if (vma && !transhuge_vma_enabled(vma, vma->vm_flags))
> >>              return false;
> >>      if (shmem_huge == SHMEM_HUGE_FORCE)
> >>              return true;
> >> --
> >> 2.23.0
> >
>