Re: [PATCH 6.18.y] mm/damon/tests/core-kunit: catch test failure in test_merge_regions_of()

[SJ Park <sj@kernel.org>]

On Wed, 09 Sep 2026 03:45:27 +0000 sashiko-bot@kernel.org wrote:

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] Typo in the early exit condition causes the unit test to silently skip validation on successful execution.
> --
> 
> commit 8cca227124d565ed51f4791e649f908f0754a67f
> Author: SJ Park <sj@kernel.org>
> 
> mm/damon/tests/core-kunit: catch test failure in test_merge_regions_of()
> 
> This commit adds an early exit to the damon_test_merge_regions_of() unit test
> to catch when the region merge expectation is not met. By skipping the
> per-region test loop on failure, it prevents potential NULL pointer
> dereferences.
> 
> Link: https://lore.kernel.org/20260715031002.108504-3-sj@kernel.org
> Link: https://lore.kernel.org/20260710144937.26981-1-sj@kernel.org [1]
> 
> > diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
> > index 6687778752728..c1f0be6746abd 100644
> > --- a/mm/damon/tests/core-kunit.h
> > +++ b/mm/damon/tests/core-kunit.h
> > @@ -264,11 +264,14 @@ static void damon_test_merge_regions_of(struct kunit *test)
> >  	damon_merge_regions_of(t, 9, 9999);
> >  	/* 0-112, 114-130, 130-156, 156-170 */
> >  	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 5u);
> > +	if (damon_nr_regions(t) != 6)
> > +		goto out;
> 
> [Severity: Medium]
> Should this check compare against 5 instead of 6?
> 
> When damon_merge_regions_of() works correctly, it merges the target into
> exactly 5 regions, matching the KUNIT_EXPECT_EQ check immediately above. 
> 
> Because 5 != 6 evaluates to true, a successful test execution will jump out 
> and silently bypass the per-region validation loop. The validations will only 
> execute if exactly 6 regions are produced, which would indicate a test failure.

Nice catch.  I will fix.

> 
> >  	for (i = 0; i < 5; i++) {
> >  		r = __nth_region_of(t, i);
> >  		KUNIT_EXPECT_EQ(test, r->ar.start, saddrs[i]);
> >  		KUNIT_EXPECT_EQ(test, r->ar.end, eaddrs[i]);
> >  	}
> > +out:
> >  	damon_free_target(t);
> >  }
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20260909033832.132107-1-sj@kernel.org?part=1
> 


Thanks,
SJ