Re: [PATCH mm-new 2/2] mm/khugepaged: merge PTE scanning logic into a new helper

[Dev Jain]

On 02/10/25 1:02 pm, Lance Yang wrote:
> From: Lance Yang <lance.yang@xxxxxxxxx>
>
> As David suggested, the PTE scanning logic in hpage_collapse_scan_pmd()
> and __collapse_huge_page_isolate() was almost duplicated.
>
> This patch cleans things up by moving all the common PTE checking logic
> into a new shared helper, thp_collapse_check_pte().
>
> Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Lance Yang <lance.yang@xxxxxxxxx>
> ---
>   

In hpage_collapse_scan_pmd(), we enter with mmap lock held, so for
an anonymous vma, is it even possible to hit if (!folio_test_anon(folio))?
In which case we can replace this with VM_BUG_ON_FOLIO and abstract away
till the folio_maybe_mapped_shared() block?