From: SeongJae Park <sj@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: SeongJae Park <sj@kernel.org>,
damon@lists.linux.dev, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 5/5] mm/damon/core: avoid divide-by-zero from pseudo-moving window length calculation
Date: Fri, 20 Oct 2023 17:23:17 +0000 [thread overview]
Message-ID: <20231020172317.64192-6-sj@kernel.org> (raw)
In-Reply-To: <20231020172317.64192-1-sj@kernel.org>
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.
Fixes: ace30fb21af5 ("mm/damon/core: use pseudo-moving sum for nr_accesses_bp")
Signed-off-by: SeongJae Park <sj@kernel.org>
---
Note that this is for a patch in mm-stable that not yet merged into the
mainline.
mm/damon/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/damon/core.c b/mm/damon/core.c
index e194c8075235..aa2dc7087cd9 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1665,7 +1665,7 @@ void damon_update_region_access_rate(struct damon_region *r, bool accessed,
* 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);
--
2.34.1
next prev parent reply other threads:[~2023-10-20 17:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-20 17:23 [PATCH v2 0/5] avoid divide-by-zero due to max_nr_accesses overflow SeongJae Park
2023-10-20 17:23 ` [PATCH v2 1/5] mm/damon: implement a function for max nr_accesses safe calculation SeongJae Park
2023-10-20 17:23 ` [PATCH v2 2/5] mm/damon/core: avoid divide-by-zero during monitoring results update SeongJae Park
2023-10-20 17:23 ` [PATCH v2 3/5] mm/damon/ops-common: avoid divide-by-zero during region hotness calculation SeongJae Park
2023-10-20 17:23 ` [PATCH v2 4/5] mm/damon/lru_sort: avoid divide-by-zero in hot threshold calculation SeongJae Park
2023-10-20 17:23 ` SeongJae Park [this message]
-- strict thread matches above, loose matches on Subject: below --
2023-10-19 19:49 [PATCH 0/5] avoid divide-by-zero due to max_nr_accesses overflow SeongJae Park
2023-10-19 19:49 ` [PATCH 5/5] mm/damon/core: avoid divide-by-zero from pseudo-moving window length calculation SeongJae Park
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