Re: [PATCH 15/19] mm/damon/core: implement damon_has_probe_weight()

[SJ Park <sj@kernel.org>]

On Fri, 10 Jul 2026 14:11:00 +0000 sashiko-bot@kernel.org wrote:

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [High] Setting probe weights unconditionally disables access checks without validating if the active operation set supports data attribute probes (`apply_probes`), silently breaking monitoring.
> --
> 
> --- Patch [15]: [PATCH 15/19] mm/damon/core: implement damon_has_probe_weight() ---
> commit 7b3dfd9b2d27b35cdf18598b48bc4927675cb47a
> Author: SJ Park <sj@kernel.org>
> 
> mm/damon/core: implement damon_has_probe_weight()
> 
> This commit updates damon_has_probe_weights() to properly iterate over the
> probes and return true if any probe has a weight configured. This enables the
> data attribute monitoring mode that previously returned false intentionally
> during incremental development.
> 
> > diff --git a/mm/damon/core.c b/mm/damon/core.c
> > index 91964336ce31e..806a67d02a6e9 100644
> > --- a/mm/damon/core.c
> > +++ b/mm/damon/core.c
> > @@ -211,6 +211,12 @@ static struct damon_probe *damon_nth_probe(int n, struct damon_ctx *ctx)
> >  
> >  static bool damon_has_probe_weights(struct damon_ctx *c)
> >  {
> > +	struct damon_probe *p;
> > +
> > +	damon_for_each_probe(p, c) {
> > +		if (p->weight)
> > +			return true;
> > +	}
> 
> [Severity: High]
> If a user configures a DAMON context with an operation set that does not
> implement apply_probes (e.g. vaddr operations) and adds a probe with a
> non-zero weight, will this silently break monitoring?
> 
> With this change, damon_has_probe_weights() returning true will skip
> standard access monitoring in kdamond_fn():
> 
> mm/damon/core.c:kdamond_fn() {
> ...
> 	bool access_check_disabled = damon_has_probe_weights(ctx);
> 	unsigned int max_merge_score = 0;
> ...
> 	if (!access_check_disabled && ctx->ops.check_accesses)
> 		max_merge_score = ctx->ops.check_accesses(ctx);
> 
> 	if (ctx->ops.apply_probes) {
> 		/* bypassed if apply_probes is not implemented */
> 		...
> 	}
> ...
> 	/* max_merge_score remains 0 */
> 	if (time_after_eq(ctx->passed_sample_intervals,
> 				next_aggregation_sis)) {
> 		kdamond_merge_regions(ctx, max_merge_score / 10, sz_limit);
> ...
> }
> 
> Should damon_valid_probe_params() or damon_has_probe_weights() also verify
> that ctx->ops.apply_probes is implemented before allowing this mode, to
> prevent kdamond_merge_regions() from unconditionally merging regions with
> a threshold of 0?

No issue.  This is an intentional behavior.

> 
> >  	return false;
> >  }
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20260710134651.18084-1-sj@kernel.org?part=15


Thanks,
SJ