Re: [RFC PATCH v3 1/4] mm/damon/sysfs: set goal_tuner after scheme creation

[Ravi Jonnalagadda]

On Mon, Feb 23, 2026 at 5:40 PM SeongJae Park <sj@xxxxxxxxxx> wrote:
>
> On Mon, 23 Feb 2026 12:32:29 +0000 Ravi Jonnalagadda <ravis.opensrc@xxxxxxxxx> wrote:
>
> > damon_new_scheme() always sets quota.goal_tuner to CONSIST (the default)
> > regardless of what was passed in the quota struct. This caused the sysfs
> > goal_tuner setting to be ignored.
> >
> > The comment in damon_new_scheme() says "quota.goals and .goal_tuner
> > should be separately set by caller", but the sysfs code wasn't doing
> > this. Add explicit assignment of goal_tuner after damon_new_scheme()
> > returns to properly apply the user's setting.
> >
> > Without this fix, setting goal_tuner to "temporal" via sysfs has no
> > effect - the scheme always uses the CONSIST (feed loop) tuner, causing
> > overshoot when the goal is reached instead of immediate stop.
>
> Thank you for catching this, Ravi!  So, this is a fix for the RFC patch series
> [1] that not yet merged, right?  I think this fix is better to be carried with
> the series, and squashed into the broken commit to not introduce unnecessary
> regression.
>
> So, if you don't mind, I will squash this into the sysfs-schemes part change on
> my tree, with your Co-developed-by: tag.

Yes. Please go ahead and squash it into your series.

>
> [1] https://lore.kernel.org/20260212062314.69961-1-sj@xxxxxxxxxx
> [2] https://lore.kernel.org/20260212062314.69961-4-sj@xxxxxxxxxx
>
> >
> > Signed-off-by: Ravi Jonnalagadda <ravis.opensrc@xxxxxxxxx>
>
> Reviewed-by: SeongJae Park <sj@xxxxxxxxxx>
>
> > ---
> >  mm/damon/sysfs-schemes.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
> > index bbea908074bb..fe2e3b2db9e1 100644
> > --- a/mm/damon/sysfs-schemes.c
> > +++ b/mm/damon/sysfs-schemes.c
> > @@ -2809,6 +2809,9 @@ static struct damos *damon_sysfs_mk_scheme(
> >       if (!scheme)
> >               return NULL;
> >
> > +     /* Set goal_tuner after damon_new_scheme() as it defaults to CONSIST */
> > +     scheme->quota.goal_tuner = sysfs_quotas->goal_tuner;
> > +
> >       err = damos_sysfs_add_quota_score(sysfs_quotas->goals, &scheme->quota);
> >       if (err) {
> >               damon_destroy_scheme(scheme);
>
> To follow the order on the comment ("quota.goals and .goal_tuner should be
> separately set by caller"), I'd prefer setting the goal_tuner after
> damos_sysfs_add_quota_Score() call here, if you don't mind.  Let me know if you
> prefer keeping the current order.  If not, I will just make the change when I
> apply this to damon/next.
>

Agreed. Please make that change when you apply it.

>
> Thanks,
> SJ
>
> [...]