From nobody Sun Feb 8 05:14:46 2026 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 B3B1DC25B41 for ; Fri, 20 Oct 2023 17:23:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377941AbjJTRXc (ORCPT ); Fri, 20 Oct 2023 13:23:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37020 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377927AbjJTRX1 (ORCPT ); Fri, 20 Oct 2023 13:23:27 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D512A3; Fri, 20 Oct 2023 10:23:26 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78EB3C433CA; Fri, 20 Oct 2023 17:23:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697822606; bh=GfglrsOk5qGjGnmruIH7Op0UcLOq5YxxSRcQby/wYY8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=t9O9pz8w8PavHtJRAmDjnfs+pzDqdv3x4tnFpqQpQW1CJed83FYVNs8li7TGn1UA+ inQgRhjia22JOeOI1IOX/SU72zUdILTB4zjucts/LRz4x26P/X2PpEbbKFOOvzENqP dKo+VdyORmHfwzLfarroponzPoeHT8djRKCvqTMW1WtHdE0g6GJD957y+s2jxH4Urs QFIzBdNY3ViZk53G1vYRSdwpxAlC/HrSaZug/ZAIIXroUlMmTWB8Z61PD7o6nsbsBr aDrtNJE0Qkr2Z/vqvRHNvfNu3zG7BvnrJYEkW94xpTpAp0LOz/mKWk9XUqXVvox+lk GpfvMq1vSBR6w== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , Jakub Acs , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v2 3/5] mm/damon/ops-common: avoid divide-by-zero during region hotness calculation Date: Fri, 20 Oct 2023 17:23:15 +0000 Message-Id: <20231020172317.64192-4-sj@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231020172317.64192-1-sj@kernel.org> References: <20231020172317.64192-1-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. Reported-by: Jakub Acs 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