linux-kernel - Re: [PATCH v7 03/12] khugepaged: generalize hugepage_vma

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Message-ID: <CAA1CXcBQzgTeKcDN+p9fF14SmMJSzkRcKwdUB0jr_72etc+Rdw@mail.gmail.com>
Date: Sun, 29 Jun 2025 00:52:13 -0600
From: Nico Pache <npache@...hat.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>, linux-mm@...ck.org, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
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Subject: Re: [PATCH v7 03/12] khugepaged: generalize hugepage_vma_revalidate
 for mTHP support

On Fri, May 16, 2025 at 11:15 AM Liam R. Howlett
<Liam.Howlett@...cle.com> wrote:
>
> * Nico Pache <npache@...hat.com> [250514 23:23]:
> > For khugepaged to support different mTHP orders, we must generalize this
> > to check if the PMD is not shared by another VMA and the order is
> > enabled.
> >
> > No functional change in this patch.
>
> This patch needs to be with the functional change for git blame and
> reviewing the changes.
I don't think that is the case. I've seen many series' that piecemeal
their changes including separating out nonfunctional changes before
the actual functional change. A lot of small changes were required to
generalize this for mTHP collapse. Doing it all in one patch would
have made the mTHP support patch huge and noisy. I tried to make that
patch cleaner (for review purposes) by separating out some of the
noise.


-- Nico
>
> >
> > Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> > Co-developed-by: Dev Jain <dev.jain@....com>
> > Signed-off-by: Dev Jain <dev.jain@....com>
> > Signed-off-by: Nico Pache <npache@...hat.com>
> > ---
> >  mm/khugepaged.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 5457571d505a..0c4d6a02d59c 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -920,7 +920,7 @@ static int khugepaged_find_target_node(struct collapse_control *cc)
> >  static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
> >                                  bool expect_anon,
> >                                  struct vm_area_struct **vmap,
> > -                                struct collapse_control *cc)
> > +                                struct collapse_control *cc, int order)
> >  {
> >       struct vm_area_struct *vma;
> >       unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
> > @@ -934,7 +934,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
> >
> >       if (!thp_vma_suitable_order(vma, address, PMD_ORDER))
> >               return SCAN_ADDRESS_RANGE;
> > -     if (!thp_vma_allowable_order(vma, vma->vm_flags, tva_flags, PMD_ORDER))
> > +     if (!thp_vma_allowable_order(vma, vma->vm_flags, tva_flags, order))
> >               return SCAN_VMA_CHECK;
> >       /*
> >        * Anon VMA expected, the address may be unmapped then
> > @@ -1130,7 +1130,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> >               goto out_nolock;
> >
> >       mmap_read_lock(mm);
> > -     result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
> > +     result = hugepage_vma_revalidate(mm, address, true, &vma, cc, HPAGE_PMD_ORDER);
> >       if (result != SCAN_SUCCEED) {
> >               mmap_read_unlock(mm);
> >               goto out_nolock;
> > @@ -1164,7 +1164,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> >        * mmap_lock.
> >        */
> >       mmap_write_lock(mm);
> > -     result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
> > +     result = hugepage_vma_revalidate(mm, address, true, &vma, cc, HPAGE_PMD_ORDER);
> >       if (result != SCAN_SUCCEED)
> >               goto out_up_write;
> >       /* check if the pmd is still valid */
> > @@ -2782,7 +2782,7 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
> >                       mmap_read_lock(mm);
> >                       mmap_locked = true;
> >                       result = hugepage_vma_revalidate(mm, addr, false, &vma,
> > -                                                      cc);
> > +                                                      cc, HPAGE_PMD_ORDER);
> >                       if (result  != SCAN_SUCCEED) {
> >                               last_fail = result;
> >                               goto out_nolock;
> > --
> > 2.49.0
> >
>