Re: [RFC PATCH 4/6] mm/damon/sysfs-schemes: setup range_{min,max} for probe_hits_wsum filter

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Incorrect union member assignment for PROBE_HITS_WSUM filter type risks silent corruption if struct layout changes.
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commit 67e5bf0750883cfdf7b8857b78d72c17c2de406e
Author: SJ Park <sj@kernel.org>

mm/damon/sysfs-schemes: setup range_{min,max} for probe_hits_wsum filter

This commit extends the DAMON sysfs interface to support probe_hits_wsum
input. It updates the sysfs input based scheme build logic to set up the
min/max probe hits weighted sum range provided by the user.

> diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
> index 4d9147d2a269e..e297a20c0af03 100644
> --- a/mm/damon/sysfs-schemes.c
> +++ b/mm/damon/sysfs-schemes.c

[ ... ]

> @@ -2844,6 +2847,14 @@ static int damon_sysfs_add_scheme_filters(struct damos *scheme,
>  			}
>  			filter->sz_range.min = sysfs_filter->range_min;
>  			filter->sz_range.max = sysfs_filter->range_max;
> +		} else if (filter->type == DAMOS_FILTER_TYPE_PROBE_HITS_WSUM) {
> +			if (sysfs_filter->range_min >
> +					sysfs_filter->range_max) {
> +				damos_destroy_filter(filter);
> +				return -EINVAL;
> +			}
> +			filter->sz_range.min = sysfs_filter->range_min;
> +			filter->sz_range.max = sysfs_filter->range_max;

[Severity: Low]
Is this assigning to the wrong union member? Since the filter type is
DAMOS_FILTER_TYPE_PROBE_HITS_WSUM, should this be assigning directly to
filter->range_min and filter->range_max instead of filter->sz_range?

While struct damon_size_range and the anonymous { unsigned long range_min;
unsigned long range_max; } struct currently share the exact same memory layout
in the struct damos_filter union, using sz_range here appears to be a
copy-paste error from the DAMOS_FILTER_TYPE_HUGEPAGE_SIZE block.

This seems to bypass the earlier refactoring that explicitly introduced
the anonymous struct to avoid reusing sz_range for non-size fields. If
struct damon_size_range is modified in the future, assigning via sz_range
while the core logic consumes range_min could lead to silent data corruption
when building a PROBE_HITS_WSUM scheme filter.

>  		}
>  
>  		damos_add_filter(scheme, filter);

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Sashiko AI review · https://sashiko.dev/#/patchset/20260906210513.106895-1-sj@kernel.org?part=4