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

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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: 5e06ad5900 ("mm/damon/core-test: test max_nr_accesses overflow caused divide-by-zero")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Guenter 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SeongJae Park 2024-09-05 09:24:23 -07:00 committed by Andrew Morton
parent 08e28de116
commit 25e8acbcf1
2 changed files with 19 additions and 1 deletions
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8
mm/damon/core.c
View File

@ -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)
{

12
mm/damon/tests/core-kunit.h
View File

@ -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);
}