On Fri, Sep 25, 2026 at 06:08:44PM +0530, Sarthak Sharma wrote:
>
>
> On 9/25/26 12:41 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.
>
> s/accroding/according
Okay.
>
> >
> > 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")
>
> Checkpatch gives a warning saying it requires atleast 12 characters of
> commit SHA.
Oops. I'll update.
>
> > Suggested-by: David Hildenbrand (Arm) <[email protected]>
> > Signed-off-by: Yeoreum Yun <[email protected]>
> > ---
>
> [...]
>
> > +static bool __check_pmd_huge(void *addr, size_t len, int nr_hpages,
> > + uint64_t hpage_size, enum check_huge_type type)
> > +{
> > + int pagemap_fd;
> > + int nr_pmd_mappings = 0;
> > + uint64_t categories;
> > + char *start = addr;
> > + char *end = start + len;
> > +
> > + pagemap_fd = open(PAGEMAP_PATH, O_RDONLY);
> > + if (pagemap_fd < 0)
> > + ksft_exit_fail_msg("open pagemap fail\n");
>
> Can we use ksft_exit_fail_perror("open pagemap") here? Will help in
> diagnosing failures as well.
I see thanks!
>
> Apart from these nits, rest looks good.
>
> Reviewed-by: Sarthak Sharma <[email protected]>
--
Sincerely,
Yeoreum Yun
