Re: [PATCH v3 2/2] selftests/damon/sysfs.py: validate memcg_path staging readback

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The test fails if CONFIG_MEMCG is disabled because stopping an unstarted kdamond returns an error, defeating the intent of ignoring start failures.
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commit 82e2d2dc23cd1bb3cb389943f0bf754e63c68c96
Author: Cheng Nie <niecheng1@uniontech.com>

selftests/damon/sysfs.py: validate memcg_path staging readback

This commit adds a test to validate the staging readback of memcg_path in
DAMON sysfs without committing it. It configures the memcg filter, verifies
the readback, and attempts to ignore start() failures to avoid depending on
CONFIG_MEMCG or cgroup layout.

> diff --git a/tools/testing/selftests/damon/sysfs.py b/tools/testing/selftests/damon/sysfs.py
> index aa03a1187489f..7a17ab88361bc 100755
> --- a/tools/testing/selftests/damon/sysfs.py
> +++ b/tools/testing/selftests/damon/sysfs.py
> @@ -250,6 +250,38 @@ def assert_ctxs_committed(kdamonds):
[ ... ]
> +def test_memcg_filter_memcg_path_staging():
> +    global kdamonds
> +    memcg_filter = _damon_sysfs.DamosFilter(
> +            type_='memcg', matching=True, allow=True, memcg_path='/')
> +    kdamonds = _damon_sysfs.Kdamonds(
> +            [_damon_sysfs.Kdamond(
> +                contexts=[_damon_sysfs.DamonCtx(
> +                    targets=[_damon_sysfs.DamonTarget(pid=-1)],
> +                    schemes=[_damon_sysfs.Damos(
> +                        ops_filters=[memcg_filter])],
> +                    )])])
> +    kdamonds.start()
[ ... ]
> +    err = kdamonds.stop()
> +    if err is not None:
> +        print('memcg_path staging: kdamond stop (%s)' % err)
> +        exit(1)

[Severity: Medium]
The commit message mentions ignoring start() failures so the test does not
depend on CONFIG_MEMCG or cgroup layout. However, if start() fails,
kdamonds.stop() will return an error because the kernel's
damon_sysfs_turn_damon_off() returns -EINVAL when kdamond->damon_ctx is
NULL.

Does this cause the test to exit(1) and fail anyway on environments without
CONFIG_MEMCG when checking the return value of stop() here?

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Sashiko AI review · https://sashiko.dev/#/patchset/D4787203018006D6+20260601073635.200015-1-niecheng1@uniontech.com?part=2