[PATCH v2 0/2] kselftest: mm: fix some failure of split_huge_page_test

[Yeoreum Yun <yeoreum.yun@arm.com>]

split_huge_page_test can fail for the following reasons:

  1. During the test, khugepaged may collapse previously split pages again,
     causing intermittent failures.

  2. 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(). Moreover, a subsequent
     madvise(MADV_HUGEPAGE) call does not split the VMA because it already
     has the same advice.

     This causes the 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.

Address these issues by applying MADV_NOHUGEPAGE after faulting in the
huge page, preventing khugepaged from collapsing it again, and by replacing
the use of /proc/self/smaps in the check_huge_xxx() helpers with
/proc/self/pagemap and /proc/kpageflags.

This patch based on mm-unstable

---
Changes in v2:
  - rebase to mm-unstable.
  - add message in case of failure of madvise() with MADV_NOHUGEPAGE.
  - fix wrong setup expected_huge in check_huge_shmem().
  - Link to v1: https://lore.kernel.org/r/20260820-fix_split-v1-0-ab430c58c7cf@arm.com

---
Yeoreum Yun (2):
      kselftest: mm: prevent random failure of huge page split for khugepaged
      kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper

 tools/testing/selftests/mm/split_huge_page_test.c |  15 +++
 tools/testing/selftests/mm/vm_util.c              | 130 +++++++++++++---------
 tools/testing/selftests/mm/vm_util.h              |   1 +
 3 files changed, 92 insertions(+), 54 deletions(-)
---
base-commit: 169393fff5d1ec2690934067eeb95544ff5ebdd7
change-id: 20260820-fix_split-f44939ec44b8

Best regards,
-- 
Sincerely,
Yeoreum Yun