Re: [PATCH v8 2/4] kselftest: mm: replace usage of /proc/self/smaps for __check_pmd_huge()

[Zi Yan <ziy@nvidia.com>]

On 24 Sep 2026, at 15:11, 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_pmd_huge()
> helpers incorrectly require the address returned by memalign() to
> match the VMA start address reported in /proc/self/smaps.
>
> Instead of relying on /proc/self/smaps, use /proc/self/pagemap and
> /proc/kpageflags to detect huge-page mappings checking PAGE_IS_HUGE
> and PAGE_IS_FILE accroding to type of huge page.
>
> Since shmem pages are also file-backed, simply check whether the page
> is file-backed.
>
> Fixes: 642bc52aed9 ("selftests: vm: bring common functions to a new file")
> Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
> Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> ---
>  tools/testing/selftests/mm/vm_util.c | 78 ++++++++++++++++++++++--------------
>  1 file changed, 49 insertions(+), 29 deletions(-)
>
LGTM.

Acked-by: Zi Yan <ziy@nvidia.com>


Best Regards,
Yan, Zi