Re: [PATCH 1/2] mm/damon/core: Use only installed probe in damon_merge_two_regions()

[SJ Park <sj@kernel.org>]

Hello Suhaas,

On Wed,  7 Oct 2026 21:18:45 +0530 Suhaas Joshi <suhaas@s-joshi.in> wrote:

> While merging 2 regions, we iterate over the entire probe_hits[] array,
> whose size is determined by the DAMON_MAX_PROBES macro. It is possible,
> however, that we have fewer probes installed than DAMON_MAX_PROBES. In such
> cases, we end up making redundant iterations. Therefore, to remedy this,
> iterate over the list of installed probes instead of iterating over the
> entire array. For doing this, start accepting a struct damon_ctx in
> damon_merge_two_regions(), and update calling functions to pass this
> argument.
> 
> Update the damon_test_merge_two() test to use this new signature for
> damon_merge_two_regions() as well.

Thank you for this patch.

[...]
> --- a/mm/damon/tests/core-kunit.h
> +++ b/mm/damon/tests/core-kunit.h
> @@ -182,13 +182,27 @@ static void damon_test_merge_two(struct kunit *test)
>  {
>  	struct damon_target *t;
>  	struct damon_region *r, *r2, *r3;
> +	struct damon_probe *p;
> +	struct damon_ctx *ctx;
>  	int i;
>  
> +	p = damon_new_probe();
> +	if (!p)
> +		kunit_skip(test, "probe alloc fail");
> +	ctx = damon_new_ctx();
> +	if (!ctx) {
> +		damon_destroy_probe(p);
> +		kunit_skip(test, "context alloc fail");
> +	}
> +	damon_add_probe(ctx, p);
>  	t = damon_new_target();
> -	if (!t)
> +	if (!t) {
> +		damon_destroy_ctx(ctx);
>  		kunit_skip(test, "target alloc fail");
> +	}
>  	r = damon_new_region(0, 100);
>  	if (!r) {
> +		damon_destroy_ctx(ctx);
>  		damon_free_target(t);
>  		kunit_skip(test, "region alloc fail");
>  	}
> @@ -206,7 +220,7 @@ static void damon_test_merge_two(struct kunit *test)
>  	r2->age = 21;
>  	damon_add_region(r2, t);

As also found [1] by Sashiko, seems this patch mistakenly not calling
damon_destroy_ctx() for r2 allocation failure.  Could you please add that?

[1] https://lore.kernel.org/sashiko-outbox-163177@kernel.org


Thanks,
SJ