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

On Sat, 25 Jul 2026 21:11:56 +0000 [email protected] wrote:

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] The commit introduces `DAMON_FILTER_TYPE_PGIDLE_UNSET` but entirely omits its implementation in both the filter evaluation logic and the sysfs interface.
> --
> 
> --- Patch [1]: [RFC PATCH 01/17] mm/damon/core: introduce DAMON_FILTER_TYPE_PGIDLE_UNSET ---
> commit 227024f25ad71dec25a7b05a4270affaab5be023
> Author: SJ Park <[email protected]>
> 
> 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 the filter
> evaluation logic?
> 
> Looking at damon_pa_filter_match() in mm/damon/paddr.c, the switch
> statement evaluates filters but lacks a case to process the newly
> introduced type:
> 
> mm/damon/paddr.c:damon_pa_filter_match() {
>         ...
>         switch (filter->type) {
>         case DAMON_FILTER_TYPE_ANON:
>         ...
> }
> 
> Will this cause the evaluation to fall through to a default case and behave
> incorrectly rather than matching the PG_Idle or accessed bit as intended?
> 
> Also, does this new type need to be mapped in the sysfs interface so userspace
> can configure it? The damon_sysfs_filter_type_names array in mm/damon/sysfs.c
> doesn't seem to include the new mapping:
> 
> mm/damon/sysfs.c: {
>         ...
>         static const struct damon_sysfs_filter_type_name
>         damon_sysfs_filter_type_names[] = {
>         ...
> }

That will be introduced in a later patch of this series.

> 
> >  };
> >  
> >  /**
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=1


Thanks,
SJ