mm/damon/lru_sort: avoid divide-by-zero in hot threshold calculation

When calculating the hotness threshold for lru_prio scheme of
DAMON_LRU_SORT, the module divides some values by the maximum nr_accesses.
However, due to the type of the related variables, simple division-based
calculation of the divisor can return zero.  As a result, divide-by-zero
is possible.  Fix it by using damon_max_nr_accesses(), which handles the
case.

Link: https://lkml.kernel.org/r/20231019194924.100347-5-sj@kernel.org
Fixes: 40e983cca927 ("mm/damon: introduce DAMON-based LRU-lists Sorting")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: Jakub Acs <acsjakub@amazon.de>
Cc: <stable@vger.kernel.org>	[6.0+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
index 3ecdcc02944387a05098be7a80154a46846ab28c..f2e5f9431892eb207bec1da87224282e3de27371 100644 (file)
--- a/mm/damon/lru_sort.c
+++ b/mm/damon/lru_sort.c
@@ -195,9 +195,7 @@ static int damon_lru_sort_apply_parameters(void)
        if (err)
                return err;
 
-       /* aggr_interval / sample_interval is the maximum nr_accesses */
-       hot_thres = damon_lru_sort_mon_attrs.aggr_interval /
-               damon_lru_sort_mon_attrs.sample_interval *
+       hot_thres = damon_max_nr_accesses(&damon_lru_sort_mon_attrs) *
                hot_thres_access_freq / 1000;
        scheme = damon_lru_sort_new_hot_scheme(hot_thres);
        if (!scheme)