The patch titled
Subject: mm/damon/core: avoid divide-by-zero from pseudo-moving window length calculation
has been added to the -mm mm-unstable branch. Its filename is
mm-damon-core-avoid-divide-by-zero-from-pseudo-moving-window-length-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-core-avoid-divide-by-zero-from-pseudo-moving-window-length-calculation.patch
This patch will later appear in the mm-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/core: avoid divide-by-zero from pseudo-moving window length calculation
Date: Thu, 19 Oct 2023 19:49:24 +0000
When calculating the pseudo-moving access rate, DAMON 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.
Note that this is a fix for a commit that not in the mainline but mm
tree.
Link: https://lkml.kernel.org/r/20231019194924.100347-6-sj@xxxxxxxxxx
Fixes: ace30fb21af5 ("mm/damon/core: use pseudo-moving sum for nr_accesses_bp")
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/damon/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/damon/core.c~mm-damon-core-avoid-divide-by-zero-from-pseudo-moving-window-length-calculation
+++ a/mm/damon/core.c
@@ -1665,7 +1665,7 @@ void damon_update_region_access_rate(str
* aggr_interval, owing to validation of damon_set_attrs().
*/
if (attrs->sample_interval)
- len_window = attrs->aggr_interval / attrs->sample_interval;
+ len_window = damon_max_nr_accesses(attrs);
r->nr_accesses_bp = damon_moving_sum(r->nr_accesses_bp,
r->last_nr_accesses * 10000, len_window,
accessed ? 10000 : 0);
_
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
mm-damon-core-avoid-divide-by-zero-from-pseudo-moving-window-length-calculation.patch
