linux-kernel - [PATCH 0/3] selftests/mm: hugetlb cgroup charging: robustness fixes

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Message-ID: <20251220111645.2246009-1-liwang@redhat.com>
Date: Sat, 20 Dec 2025 19:16:42 +0800
From: Li Wang <liwang@...hat.com>
To: linux-kselftest@...r.kernel.org,
	akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH 0/3] selftests/mm: hugetlb cgroup charging: robustness fixes

This series fixes a few issues in the hugetlb cgroup charging selftests
(write_to_hugetlbfs.c + charge_reserved_hugetlb.sh) that show up on systems
with large hugepages (e.g. 512MB) and when failures cause the test to wait
indefinitely.

On an aarch64 64k page kernel with 512MB hugepages, the test consistently
fails in write_to_hugetlbfs with ENOMEM and then hangs waiting for the
expected usage values. The root cause is that charge_reserved_hugetlb.sh
mounts hugetlbfs with a fixed size=256M, which is smaller than a single
hugepage, resulting in a mount with size=0 capacity.

In addition, write_to_hugetlbfs previously parsed -s via atoi() into an
int, which can overflow and print negative sizes.

Reproducer / environment:
  - Kernel: 6.12.0-xxx.el10.aarch64+64k
  - Hugepagesize: 524288 kB (512MB)
  - ./charge_reserved_hugetlb.sh -cgroup-v2
  - Observed mount: pagesize=512M,size=0 before this series

After applying the series, the test completes successfully on the above setup.

Li Wang (3):
  selftests/mm/write_to_hugetlbfs: parse -s with strtoull and use size_t
  selftests/mm/charge_reserved_hugetlb.sh: add waits with timeout helper
  selftests/mm/charge_reserved_hugetlb: fix hugetlbfs mount size for
    large hugepages

 .../selftests/mm/charge_reserved_hugetlb.sh   | 49 ++++++++++---------
 .../testing/selftests/mm/write_to_hugetlbfs.c | 19 +++++--
 2 files changed, 43 insertions(+), 25 deletions(-)

-- 
2.49.0