Re: [RFC PATCH 6/6] selftests/damon/sysfs.py: test damon probes

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] DamonProbe.stage() completely ignores the error returned when writing to the 'weight' sysfs file, masking potential write failures.
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--- Patch [6]: [RFC PATCH 6/6] selftests/damon/sysfs.py: test damon probes ---
commit e47c18c7c1e4b19237b2738bc5c072c3c570dcc9
Author: SJ Park <[email protected]>

selftests/damon/sysfs.py: test damon probes

This commit extends sysfs.py to test DAMON probes by committing them via
sysfs and checking the in-kernel status using drgn.

> diff --git a/tools/testing/selftests/damon/sysfs.py b/tools/testing/selftests/damon/sysfs.py
> index 8c2dfc5ed8e04..852b6887a75ce 100755
> --- a/tools/testing/selftests/damon/sysfs.py
> +++ b/tools/testing/selftests/damon/sysfs.py
> @@ -319,7 +319,21 @@ def main():
>                  intervals_goal=_damon_sysfs.IntervalsGoal(
>                      access_bp=400, aggrs=3, min_sample_us=5000,
>                      max_sample_us=10000000),
> -                update_us=2000000),
> +                update_us=2000000,
> +                probes=_damon_sysfs.DamonProbes(
> +                    probes=[_damon_sysfs.DamonProbe(
> +                        weight=42,

[Severity: Medium]
Will this properly catch setup failures when setting the probe weight?

When testing DamonProbes, DamonProbe.stage() writes the weight to sysfs
but overwrites the returned error status without checking it:

tools/testing/selftests/damon/_damon_sysfs.py:DamonProbe.stage()

    def stage(self):
        err = write_file(
                os.path.join(self.sysfs_dir(), 'weight'), '%d' % self.weight)
        return self.filters.stage()

If the sysfs write fails, such as the kernel rejecting the weight value
or the sysfs node being absent, the error is silently ignored. Could this
cause the test suite to proceed as if setup succeeded, leading to false
positive passes or confusing downstream errors?

[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=6