Re: [RFC PATCH v2.1 05/17] mm/damon/core: introduce damon_prep struct

On Mon, 27 Jul 2026 14:48:42 +0000 [email protected] wrote:

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] damon_commit_probes() does not synchronize the newly added 'preps' list, leading to lost preparation actions during context updates.
> --
> 
> --- Patch [5]: [RFC PATCH v2.1 05/17] mm/damon/core: introduce damon_prep struct ---
> commit 560f806438365d13be862eb2266c647b1d981d0b
> Author: SJ Park <[email protected]>
> 
> mm/damon/core: introduce damon_prep struct
> 
> Some DAMON probe filter types require preparatory actions, like setting
> the PG_Idle flag at a specific time. This commit introduces a new data
> type called damon_prep to specify preparation actions for each probe.
> It also adds DAMON_PREP_SET_PGIDLE as the initial prep action.
> 
> > diff --git a/include/linux/damon.h b/include/linux/damon.h
> > index a8bb9ee6979e3..1a8de735f955b 100644
> > --- a/include/linux/damon.h
> > +++ b/include/linux/damon.h
> 
> [ ... ]
> 
> > @@ -780,6 +801,8 @@ struct damon_filter {
> >  struct damon_probe {
> >  	unsigned int weight;
> >  /* private: */
> > +	/* Preparation actions to apply to each probing memory. */
> > +	struct list_head preps;
> >  	/* Filters for assessing if a given region is for this probe. */
> >  	struct list_head filters;
> >  	/* Siblings list. */
> 
> [Severity: Medium]
> Does this change also require an update to damon_commit_probes() to copy the
> new preps list?
> 
> Currently, when updating a running context, damon_commit_probes() only copies
> the weight and filters from the source probe to the destination probe:
> 
> mm/damon/core.c:damon_commit_probes() {
>     ...
>     damon_for_each_probe_safe(dst_probe, next, dst) {
>         src_probe = damon_nth_probe(i++, src);
>         if (src_probe) {
>             dst_probe->weight = src_probe->weight;
>             err = damon_commit_filters(dst_probe, src_probe);
>     ...
> }
> 
> This applies both when synchronizing existing probes and when creating new
> ones to match the source context.
> 
> Without a corresponding damon_commit_preps() mechanism to synchronize these
> lists, it appears any preparation actions configured on a source context could
> be silently lost when committed to a running destination context.

A later patch in this series does that.

> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=5


Thanks,
SJ