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

[Baolin Wang]

On 9/25/26 3:11 AM, 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@xxxxxxxxxx>
> Signed-off-by: Yeoreum Yun <yeoreum.yun@xxxxxxx>
> ---

With comments from Sarthak addressed,
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Tested-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>