Re: [PATCH v4 2/7] mm/khugepaged: extract reference check into folio_pte_referenced() helper

[Lorenzo Stoakes (ARM)]

On Wed, Aug 12, 2026 at 06:19:01PM -0600, Nico Pache (Red Hat) wrote:
>
>
> On 8/11/26 9:47 AM, David Hildenbrand (Arm) wrote:
> > On 8/11/26 14:48, Nico Pache (Red Hat) wrote:
> >> This change deduplicates the "is this PTE/folio referenced enough to be
> >> considered for a collapse" condition that was repeated in both
> >> __collapse_huge_page_isolate() and collapse_scan_pmd(), extracting it into
> >> a single inline helper function.
> >>
> >> Also move the comment and use it as the function header. While we are at
> >> it, updated the comment to clarify that a young pte is a recently accessed
> >> one.
> >>
> >> Acked-by: Usama Arif <usama.arif@xxxxxxxxx>
> >> Signed-off-by: Nico Pache (Red Hat) <nico.pache@xxxxxxxxx>
> >> ---
> >>  mm/khugepaged.c | 32 ++++++++++++++++++--------------
> >>  1 file changed, 18 insertions(+), 14 deletions(-)
> >>
> >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> >> index 1e26ea97381a..8babd4c97db6 100644
> >> --- a/mm/khugepaged.c
> >> +++ b/mm/khugepaged.c
> >> @@ -672,6 +672,22 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte,
> >>  	}
> >>  }
> >>
> >> +/*
> >> + * folio_pte_referenced() - Check if a folio or its PTE mapping was recently used
> >> + *
> >> + * Return: true if recent access was observed through either the folio state
> >> + * or the current PTE mapping.
> >> + */
> >
> > No need for doc for such a trivial internal helper :)
>
> Ok sounds good I can send a fixup to remove it. Lorenzo has often asked for
> these when I've introduced functions, so I've got in the habit of including them.

Yeah here it's probably not so necessary as what it does is somewhat inferred,
more so useful for shared functions and those which have more complicated/less
clear logic :)

>
> >
> >> +static inline bool folio_pte_referenced(struct folio *folio,
> >> +		struct vm_area_struct *vma, unsigned long addr, pte_t pteval)
> >> +{
> >> +	/* The folio was referenced previously ... */
> >> +	if (folio_test_young(folio) || folio_test_referenced(folio))
> >> +		return true;
> >> +	/* ... or the PTE mapping was recently used */
> >> +	return pte_young(pteval) || mmu_notifier_test_young(vma->vm_mm, addr);
> >> +}
> >> +
> >
> > Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
>
> Thank you :)
>
> >
>

--
Cheers, Lorenzo