Commit 25e8acbc authored by SeongJae Park's avatar SeongJae Park Committed by Andrew Morton
Browse files

mm/damon/tests/core-kunit: skip damon_test_nr_accesses_to_accesses_bp() if aggr_interval is zero 

The aggregation interval of test purpose damon_attrs for
damon_test_nr_accesses_to_accesses_bp() becomes zero on 32 bit
architecture, since size of int and long types are same.  As a result,
damon_nr_accesses_to_accesses_bp() call with the test data triggers
divide-by-zero exception.  damon_nr_accesses_to_accesses_bp() shouldn't
be called with such data, and the non-test code avoids that by checking
the case on damon_update_monitoring_results().  Skip the test code in
the case, and add an explicit caution of the case on the comment for the
test target function.

Link: https://lkml.kernel.org/r/20240905162423.74053-1-sj@kernel.org


Fixes: 5e06ad59 ("mm/damon/core-test: test max_nr_accesses overflow caused divide-by-zero")
Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Reported-by: default avatarGuenter Roeck <linux@roeck-us.net>
Closes: https://lore.kernel.org/c771b962-a58f-435b-89e4-1211a9323181@roeck-us.net


Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Gow <davidgow@google.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 08e28de1

mm/damon/core.c

+7 −1
Original line number Diff line number Diff line
@@ -552,7 +552,13 @@ static unsigned int damon_accesses_bp_to_nr_accesses( 
	return accesses_bp * damon_max_nr_accesses(attrs) / 10000;

}



/* convert nr_accesses to access ratio in bp (per 10,000) */

/*

 * Convert nr_accesses to access ratio in bp (per 10,000).

 *

 * Callers should ensure attrs.aggr_interval is not zero, like

 * damon_update_monitoring_results() does .  Otherwise, divide-by-zero would

 * happen.

 */

static unsigned int damon_nr_accesses_to_accesses_bp(

		unsigned int nr_accesses, struct damon_attrs *attrs)

{

mm/damon/tests/core-kunit.h

+12 −0
Original line number Diff line number Diff line
@@ -320,6 +320,18 @@ static void damon_test_nr_accesses_to_accesses_bp(struct kunit *test) 
		.aggr_interval = ((unsigned long)UINT_MAX + 1) * 10

	};



	/*

	 * In some cases such as 32bit architectures where UINT_MAX is

	 * ULONG_MAX, attrs.aggr_interval becomes zero.  Calling

	 * damon_nr_accesses_to_accesses_bp() in the case will cause

	 * divide-by-zero.  Such case is prohibited in normal execution since

	 * the caution is documented on the comment for the function, and

	 * damon_update_monitoring_results() does the check.  Skip the test in

	 * the case.

	 */

	if (!attrs.aggr_interval)

		kunit_skip(test, "aggr_interval is zero.");



	KUNIT_EXPECT_EQ(test, damon_nr_accesses_to_accesses_bp(123, &attrs), 0);

}