linux-kernel - Re: [PATCHv2] mm/khugepaged: Do not fail collapse_pte_mapped_thp() on SCAN_PMD

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Message-ID: <1a93bd0c-d673-475e-a28b-0a6d0d2e865b@lucifer.local>
Date: Thu, 18 Sep 2025 13:16:03 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Kiryl Shutsemau <kirill@...temov.name>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>, Zi Yan <ziy@...dia.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
        Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2] mm/khugepaged: Do not fail collapse_pte_mapped_thp()
 on SCAN_PMD_NULL

Sorry mutt hid this reply from me...

On Wed, Sep 17, 2025 at 11:43:08AM +0100, Kiryl Shutsemau wrote:
> On Tue, Sep 16, 2025 at 10:54:12AM +0100, Lorenzo Stoakes wrote:
> > There was a v1 with tags, you've not propagated any of them? Did you feel
> > the change was enough to remove them?
>
> I moved code around and was not comfortable to carry tags over.

Ack.

>
> > Anyway, LGTM so:
> >
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> >
> > > ---
> > >
> > > v2:
> > >  - Modify set_huge_pmd() instead of introducing install_huge_pmd();
> > >
> > > ---
> > >  mm/khugepaged.c | 20 +++++++++++++++++++-
> > >  1 file changed, 19 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > > index b486c1d19b2d..986718599355 100644
> > > --- a/mm/khugepaged.c
> > > +++ b/mm/khugepaged.c
> > > @@ -1472,15 +1472,32 @@ static void collect_mm_slot(struct khugepaged_mm_slot *mm_slot)
> > >  static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
> > >  			pmd_t *pmdp, struct folio *folio, struct page *page)
> > >  {
> > > +	struct mm_struct *mm = vma->vm_mm;
> > >  	struct vm_fault vmf = {
> > >  		.vma = vma,
> > >  		.address = addr,
> > >  		.flags = 0,
> > > -		.pmd = pmdp,
> > >  	};
> > > +	pgd_t *pgdp;
> > > +	p4d_t *p4dp;
> > > +	pud_t *pudp;
> > >
> > >  	mmap_assert_locked(vma->vm_mm);
> >
> > NIT: you have mm as a local var should use here too. Not a big deal though
> > obviously...
>
> Do you want v3 for this?

No, this is not a big deal.