From nobody Wed Dec 17 13:02:43 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0EDE1CDB482 for ; Thu, 19 Oct 2023 19:49:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346539AbjJSTth (ORCPT ); Thu, 19 Oct 2023 15:49:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48248 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346503AbjJSTte (ORCPT ); Thu, 19 Oct 2023 15:49:34 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6876311B; Thu, 19 Oct 2023 12:49:32 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F662C433C8; Thu, 19 Oct 2023 19:49:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697744972; bh=mpZ0rzQnlOTIrrYJTnG5fwff80O37UKmtsf+aHi2YNo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OOgE1jz3lvMQfVP7TQZSOyc2aRshLkRxLJ6fzn2xEUat6kCKF9dHCXjOeqKgMRUkn JciYs/7W2GFKrLW8hHfKWb7PqfogevqMt/W8HSQOH0D+82UwlpAdZ4kkAZlACm/7Yd lD6zHpOrNamlwYL1JvFr3UqFSKsZRQ1C83Lu4MTrb569Z96fQBnp9j01s7w6xZ9Yus L+XY6w6H9dDlGykT60OConZ8snDx2JZCuR0vhKoLc74v3VmzIH7s8RZFN1aRYiH6OY +7tcNIopiD0jvwS2tVxbGdb8rayh09UhaZvj0Vg1VvBTo7/44eLy16O3BQ4MwcSBs7 FXMYu/8h+hHrw== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 3/5] mm/damon/ops-common: avoid divide-by-zero during region hotness calculation Date: Thu, 19 Oct 2023 19:49:22 +0000 Message-Id: <20231019194924.100347-4-sj@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231019194924.100347-1-sj@kernel.org> References: <20231019194924.100347-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When calculating the hotness of each region for the under-quota regions prioritization, 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. Fixes: 198f0f4c58b9 ("mm/damon/vaddr,paddr: support pageout prioritization") Cc: # 5.16.x Signed-off-by: SeongJae Park --- mm/damon/ops-common.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c index ac1c3fa80f98..d25d99cb5f2b 100644 --- a/mm/damon/ops-common.c +++ b/mm/damon/ops-common.c @@ -73,7 +73,6 @@ void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *= vma, unsigned long addr int damon_hot_score(struct damon_ctx *c, struct damon_region *r, struct damos *s) { - unsigned int max_nr_accesses; int freq_subscore; unsigned int age_in_sec; int age_in_log, age_subscore; @@ -81,8 +80,8 @@ int damon_hot_score(struct damon_ctx *c, struct damon_reg= ion *r, unsigned int age_weight =3D s->quota.weight_age; int hotness; =20 - max_nr_accesses =3D c->attrs.aggr_interval / c->attrs.sample_interval; - freq_subscore =3D r->nr_accesses * DAMON_MAX_SUBSCORE / max_nr_accesses; + freq_subscore =3D r->nr_accesses * DAMON_MAX_SUBSCORE / + damon_max_nr_accesses(&c->attrs); =20 age_in_sec =3D (unsigned long)r->age * c->attrs.aggr_interval / 1000000; for (age_in_log =3D 0; age_in_log < DAMON_MAX_AGE_IN_LOG && age_in_sec; --=20 2.34.1