The patch titled
Subject: mm/damon/lru_sort: avoid divide-by-zero in hot threshold calculation
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-damon-lru_sort-avoid-divide-by-zero-in-hot-threshold-calculation.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-lru_sort-avoid-divide-by-zero-in-hot-threshold-calculation.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: SeongJae Park <sj@xxxxxxxxxx>
Subject: mm/damon/lru_sort: avoid divide-by-zero in hot threshold calculation
Date: Thu, 19 Oct 2023 19:49:23 +0000
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@xxxxxxxxxx
Fixes: 40e983cca927 ("mm/damon: introduce DAMON-based LRU-lists Sorting")
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [6.0+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/damon/lru_sort.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
--- a/mm/damon/lru_sort.c~mm-damon-lru_sort-avoid-divide-by-zero-in-hot-threshold-calculation
+++ a/mm/damon/lru_sort.c
@@ -193,9 +193,7 @@ static int damon_lru_sort_apply_paramete
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)
_
Patches currently in -mm which might be from sj@xxxxxxxxxx are
mm-damon-implement-a-function-for-max-nr_accesses-safe-calculation.patch
mm-damon-core-avoid-divide-by-zero-during-monitoring-results-update.patch
mm-damon-ops-common-avoid-divide-by-zero-during-region-hotness-calculation.patch
mm-damon-lru_sort-avoid-divide-by-zero-in-hot-threshold-calculation.patch
