test_hugetlb_memcg creates a child cgroup and then writes memory.max and
memory.swap.max. When the test is run standalone, the memory controller
may not be enabled in the test root cgroup's subtree_control.

In that case, the child cgroup is created without the memory control
files, and the test fails during setup before reaching the hugetlb memcg
accounting checks.

Skip the test when the memory controller is unavailable. Otherwise, enable
it in subtree_control before creating the test cgroup.

Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
---
Tested with a cgroup namespace where memory is available in
cgroup.controllers but not enabled in cgroup.subtree_control:

  before: test_hugetlb_memcg failed with "fail to set cgroup memory limit"
  after:  test_hugetlb_memcg passed and cgroup.subtree_control contained memory

 tools/testing/selftests/cgroup/test_hugetlb_memcg.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/testing/selftests/cgroup/test_hugetlb_memcg.c b/tools/testing/selftests/cgroup/test_hugetlb_memcg.c
index f451aa449be6..b627d84358b1 100644
--- a/tools/testing/selftests/cgroup/test_hugetlb_memcg.c
+++ b/tools/testing/selftests/cgroup/test_hugetlb_memcg.c
@@ -217,6 +217,14 @@ int main(int argc, char **argv)
 	if (cg_find_unified_root(root, sizeof(root), NULL))
 		ksft_exit_skip("cgroup v2 isn't mounted\n");
 
+	if (cg_read_strstr(root, "cgroup.controllers", "memory"))
+		ksft_exit_skip("memory controller isn't available\n");
+
+	if (cg_read_strstr(root, "cgroup.subtree_control", "memory")) {
+		if (cg_write(root, "cgroup.subtree_control", "+memory"))
+			ksft_exit_skip("Failed to set memory controller\n");
+	}
+
 	switch (test_hugetlb_memcg(root)) {
 	case KSFT_PASS:
 		ksft_test_result_pass("test_hugetlb_memcg\n");
-- 
2.43.0

Hello,

Applied to cgroup/for-7.2.

Thanks.

--
tejun

On Wed, May 20, 2026 at 05:31:30PM +0800, Guopeng Zhang <zhangguopeng@kylinos.cn> wrote:
> test_hugetlb_memcg creates a child cgroup and then writes memory.max and
> memory.swap.max. When the test is run standalone, the memory controller
> may not be enabled in the test root cgroup's subtree_control.
> 
> In that case, the child cgroup is created without the memory control
> files, and the test fails during setup before reaching the hugetlb memcg
> accounting checks.
> 
> Skip the test when the memory controller is unavailable. Otherwise, enable
> it in subtree_control before creating the test cgroup.

Makes sense.

> Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
> ---
> Tested with a cgroup namespace where memory is available in
> cgroup.controllers but not enabled in cgroup.subtree_control:
> 
>   before: test_hugetlb_memcg failed with "fail to set cgroup memory limit"
>   after:  test_hugetlb_memcg passed and cgroup.subtree_control contained memory
> 
>  tools/testing/selftests/cgroup/test_hugetlb_memcg.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

Acked-by: Michal Koutný <mkoutny@suse.com>