[<prev] [next>] [day] [month] [year] [list]
Message-Id: <20240905162423.74053-1-sj@kernel.org>
Date: Thu, 5 Sep 2024 09:24:23 -0700
From: SeongJae Park <sj@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: SeongJae Park <sj@...nel.org>,
Brendan Higgins <brendanhiggins@...gle.com>,
David Gow <davidgow@...gle.com>,
Guenter Roeck <linux@...ck-us.net>,
damon@...ts.linux.dev,
linux-mm@...ck.org,
kunit-dev@...glegroups.com,
linux-kselftest@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] 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.
Reported-by: Guenter Roeck <linux@...ck-us.net>
Closes: https://lore.kernel.org/c771b962-a58f-435b-89e4-1211a9323181@roeck-us.net
Fixes: 5e06ad590096 ("mm/damon/core-test: test max_nr_accesses overflow caused divide-by-zero")
Signed-off-by: SeongJae Park <sj@...nel.org>
---
mm/damon/core.c | 8 +++++++-
mm/damon/tests/core-kunit.h | 12 ++++++++++++
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 8b99c5a99c38..a83f3b736d51 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -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)
{
diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index ae03df71737e..cf22e09a3507 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -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);
}
--
2.39.2
Powered by blists - more mailing lists