Re: [RFC PATCH v2.2 01/17] mm/damon/core: introduce DAMON_FILTER_TYPE_PGIDLE_UNSET

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The newly introduced DAMON_FILTER_TYPE_PGIDLE_UNSET enum is unhandled in the filter matching logic and sysfs interface, leaving the promised functionality completely missing.
--

--- Patch [1]: [RFC PATCH v2.2 01/17] mm/damon/core: introduce DAMON_FILTER_TYPE_PGIDLE_UNSET ---
commit 1ede3c3f87a9caeeb7ad80090cbb84d20b477505
Author: SJ Park <sj@kernel.org>

mm/damon/core: introduce DAMON_FILTER_TYPE_PGIDLE_UNSET
    
Introduce a new DAMON filter type, pgidle_unset. It will match pages
that have their PG_Idle flag unset, or the page table accessed bit set.

> diff --git a/include/linux/damon.h b/include/linux/damon.h
> index 0c8b7ddef9abb..a8bb9ee6979e3 100644
> --- a/include/linux/damon.h
> +++ b/include/linux/damon.h
> @@ -742,12 +742,14 @@ struct damon_intervals_goal {
>  /**
>   * enum damon_filter_type - Type of &struct damon_filter
>   *
> - * @DAMON_FILTER_TYPE_ANON:	Anonymous pages.
> - * @DAMON_FILTER_TYPE_MEMCG:	Specific memcg's pages.
> + * @DAMON_FILTER_TYPE_ANON:		Anonymous pages.
> + * @DAMON_FILTER_TYPE_MEMCG:		Specific memcg's pages.
> + * @DAMON_FILTER_TYPE_PGIDLE_UNSET:	Pgidle is unset.
>   */
>  enum damon_filter_type {
>  	DAMON_FILTER_TYPE_ANON,
>  	DAMON_FILTER_TYPE_MEMCG,
> +	DAMON_FILTER_TYPE_PGIDLE_UNSET,

[Severity: Medium]
Is the implementation for this new filter type missing from this patch?

Looking at damon_pa_filter_match() in mm/damon/paddr.c, the switch
statement evaluating filter types does not appear to handle
DAMON_FILTER_TYPE_PGIDLE_UNSET. This means it will fall through to the
default case and fail to implement the promised page matching logic:

mm/damon/paddr.c:damon_pa_filter_match() {
    ...
    switch (filter->type) {
    case DAMON_FILTER_TYPE_ANON:
    ...
    }
}

Additionally, it looks like this new filter type is missing from the sysfs 
name mapping array, damon_sysfs_filter_type_names, in mm/damon/sysfs.c:

mm/damon/sysfs.c:damon_sysfs_filter_type_names {
    {
        .type = DAMON_FILTER_TYPE_ANON,
        .name = "anon",
    },
    ...
}

Without this mapping, type_store() will fail with -EINVAL, making it 
impossible for userspace to configure.

Will a follow-up patch add the handling logic and sysfs bindings, or should 
they be included directly in this commit?

>  };
>  
>  /**

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260728041242.187380-1-sj@kernel.org?part=1