Re: [PATCH] selftests/damon: prevent remaining cross-object state pollution

[sashiko-bot@kernel.org]

> From: zhaozhengzhuo <zhaozhengzhuo@uniontech.com>
> 
> _damon_sysfs.py defines constructors with mutable default arguments,
> including DamosAccessPattern(), DamosQuota(), DamosWatermarks(),
> DamosDests(), IntervalsGoal(), and empty lists.
> 
> Default arguments are evaluated once at function definition time.
> Damos() instances created without explicit arguments therefore share
> the same DamosQuota(), and the other default-constructed sub-objects
> and lists are shared in the same way.  The sub-objects keep
> back-pointers to their owner scheme, so constructing the second Damos()
> rebinds the shared quota's scheme pointer to the second object.  An
> item appended to one object's default contexts or filters list is also
> visible from other default-constructed objects.
> 
> The shared state can corrupt test configurations.  DamosQuota.sysfs_dir()
> derives the sysfs directory from its scheme pointer, so operating on
> the first scheme's default quota may write to the second scheme's
> directory.  The wrong values often match the defaults, so tests still
> pass, but the behavior depends on object creation order.
> 
> Commit 8319dadcbd81 ("selftests/damon: prevent cross-context state
> pollution in DamonCtx") fixed the same pattern in DamonCtx only.  Fix
> the remaining constructors by defaulting to None and creating fresh
> objects or lists inside each constructor.  Explicit arguments keep
> their previous behavior.
> 
> Signed-off-by: zhaozhengzhuo <zhaozhengzhuo@uniontech.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/38E4AAAAEDFCC283+20260827021515.1316838-1-zhaozhengzhuo@uniontech.com?part=1