From: sashiko-bot@kernel.org
To: "Jaeyeon Lee" <jaeyeon.lee.dev@gmail.com>
Cc: damon@lists.linux.dev
Subject: Re: [PATCH] mm/damon/ops-common: fix age_in_sec overflow on 32-bit
Date: Wed, 30 Sep 2026 12:08:56 +0000 [thread overview]
Message-ID: <20260930120856.EBA021F000FF@smtp.kernel.org> (raw)
In-Reply-To: <20260930115812.138864-1-jaeyeon.lee.dev@gmail.com>
> damon_hot_score() calculates the age of a region by multiplying r->age
> and the aggregation interval. On 32-bit architectures, unsigned long
> is 32 bits, so the multiplication overflows once the age exceeds about
> 4295 seconds. Then old regions are scored as if they were young.
>
> Fix it by doing the calculation in 64-bit arithmetic using div_u64().
> Also make age_in_sec u64, so the result is not truncated back to 32
> bits.
>
> The issue was discovered [1] by Sashiko.
>
> [1] https://lore.kernel.org/20260623011652.1354-1-sj@kernel.org
>
> Fixes: 198f0f4c58b9 ("mm/damon/vaddr,paddr: support pageout prioritization")
> Assisted-by: LLM
> Signed-off-by: Jaeyeon Lee <jaeyeon.lee.dev@gmail.com>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260930115812.138864-1-jaeyeon.lee.dev@gmail.com?part=1
next prev parent reply other threads:[~2026-09-30 12:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-30 11:58 [PATCH] mm/damon/ops-common: fix age_in_sec overflow on 32-bit Jaeyeon Lee
2026-09-30 12:08 ` sashiko-bot [this message]
2026-09-30 19:10 ` SJ Park
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