linux-kernel - Re: [PATCH v9 02/14] introduce collapse_single_pmd to unify khugepaged and madvise

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Message-ID: <CAA1CXcANV_Y=ka74CYFP0pqPWVYH9S33VzjyDUQ6Nmq1na+QFA@mail.gmail.com>
Date: Tue, 22 Jul 2025 19:56:02 -0600
From: Nico Pache <npache@...hat.com>
To: David Hildenbrand <david@...hat.com>
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Subject: Re: [PATCH v9 02/14] introduce collapse_single_pmd to unify
 khugepaged and madvise_collapse

On Tue, Jul 15, 2025 at 9:54 AM David Hildenbrand <david@...hat.com> wrote:
>
> On 14.07.25 02:31, Nico Pache wrote:
> > The khugepaged daemon and madvise_collapse have two different
> > implementations that do almost the same thing.
> >
> > Create collapse_single_pmd to increase code reuse and create an entry
> > point to these two users.
> >
> > Refactor madvise_collapse and collapse_scan_mm_slot to use the new
> > collapse_single_pmd function. This introduces a minor behavioral change
> > that is most likely an undiscovered bug. The current implementation of
> > khugepaged tests collapse_test_exit_or_disable before calling
> > collapse_pte_mapped_thp, but we weren't doing it in the madvise_collapse
> > case. By unifying these two callers madvise_collapse now also performs
> > this check.
> >
> > Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> > Signed-off-by: Nico Pache <npache@...hat.com>
> > ---
> >   mm/khugepaged.c | 95 +++++++++++++++++++++++++------------------------
> >   1 file changed, 49 insertions(+), 46 deletions(-)
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index eb0babb51868..47a80638af97 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -2362,6 +2362,50 @@ static int collapse_scan_file(struct mm_struct *mm, unsigned long addr,
> >       return result;
> >   }
> >
> > +/*
> > + * Try to collapse a single PMD starting at a PMD aligned addr, and return
> > + * the results.
> > + */
> > +static int collapse_single_pmd(unsigned long addr,
> > +                                struct vm_area_struct *vma, bool *mmap_locked,
> > +                                struct collapse_control *cc)
>
> Nit: we tend to use two-tabs indent here.
Thanks I cleaned up these indentations!
>
> Nice cleanup!
>
> Acked-by: David Hildenbrand <david@...hat.com>
Much appreciated :)
>
> --
> Cheers,
>
> David / dhildenb
>