Re: [PATCH 2/2] kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper

[Zi Yan]

On Thu Aug 20, 2026 at 3:40 PM EDT, Yeoreum Yun wrote:
> Since glibc commit 321e1fc73f (“malloc: Enable 2MB THP by default on AArch64”),
> glibc may call madvise(MADV_HUGEPAGE) for sufficiently large allocations
> made by memalign().
>
> The underlying VMA may start at a different address from the aligned
> address returned by memalign(). Furthermore, a subsequent
> madvise(MADV_HUGEPAGE) call does not split the VMA because the flag is
> already set.
>
> This causes split_huge_page_test to fail because the check_huge_xxx()
> helpers incorrectly require the address returned by memalign() to
> match the VMA start address reported in /proc/self/smaps.
>
> Fix this by using /proc/self/pagemap and /proc/kpageflags instead of
> /proc/self/smaps to detect huge pages and change the meaning of
> check_huge_xxx()'s nr_hpages argument:

Have you checked Baolin's patches[1] in mm-new? They resue
gather_after_split_folio_orders() to reimplement check_huge_xxx(), also
based on pagemap and kpageflags. Does it fix the issue?

[1] https://lore.kernel.org/all/cover.1785985999.git.baolin.wang@xxxxxxxxxxxxxxxxx/

>
>   - nr_hpages > 0: check all of pages in the range are huge page.
>   - nr_hpages < 0: check all of pages in the range are not huge page.
>   - nr_hpages == 0: invalid.
>
> Reported-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
> Signed-off-by: Yeoreum Yun <yeoreum.yun@xxxxxxx>
> ---
>  tools/testing/selftests/mm/khugepaged.c           |  26 ++---
>  tools/testing/selftests/mm/split_huge_page_test.c |   6 +-
>  tools/testing/selftests/mm/vm_util.c              | 135 ++++++++++++++++++----
>  tools/testing/selftests/mm/vm_util.h              |   1 +
>  4 files changed, 131 insertions(+), 37 deletions(-)
>


-- 
Best Regards,
Yan, Zi