From nobody Sun May 10 22:40:32 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 0F8C5C433FE for ; Fri, 22 Apr 2022 09:34:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1446073AbiDVJhL (ORCPT ); Fri, 22 Apr 2022 05:37:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352701AbiDVJhJ (ORCPT ); Fri, 22 Apr 2022 05:37:09 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E463527EE for ; Fri, 22 Apr 2022 02:34:16 -0700 (PDT) Received: from dggpemm500021.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Kl8P74l4kzhY7q; Fri, 22 Apr 2022 17:34:03 +0800 (CST) Received: from dggpemm500002.china.huawei.com (7.185.36.229) by dggpemm500021.china.huawei.com (7.185.36.109) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 22 Apr 2022 17:34:14 +0800 Received: from localhost.localdomain (10.175.112.125) by dggpemm500002.china.huawei.com (7.185.36.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 22 Apr 2022 17:34:14 +0800 From: Chen Wandun To: , , Subject: [PATCH] mm: rework calculation of bdi_min_ratio in bdi_set_min_ratio Date: Fri, 22 Apr 2022 17:51:59 +0800 Message-ID: <20220422095159.2858305-1-chenwandun@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.112.125] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500002.china.huawei.com (7.185.36.229) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" In function bdi_set_min_ratio, min_ratio is unsigned int, it will result underflow when setting min_ratio below bdi->min_ratio, it is confusing. Rework it, no functional change. Signed-off-by: Chen Wandun --- mm/page-writeback.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 438762173a59..d4291de77097 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -655,18 +655,25 @@ static unsigned int bdi_min_ratio; =20 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio) { + unsigned int delta; int ret =3D 0; =20 spin_lock_bh(&bdi_lock); if (min_ratio > bdi->max_ratio) { ret =3D -EINVAL; } else { - min_ratio -=3D bdi->min_ratio; - if (bdi_min_ratio + min_ratio < 100) { - bdi_min_ratio +=3D min_ratio; - bdi->min_ratio +=3D min_ratio; + if (min_ratio < bdi->min_ratio) { + delta =3D bdi->min_ratio - min_ratio; + bdi_min_ratio -=3D delta; + bdi->min_ratio =3D min_ratio; } else { - ret =3D -EINVAL; + delta =3D min_ratio - bdi->min_ratio; + if (bdi_min_ratio + delta < 100) { + bdi_min_ratio +=3D delta; + bdi->min_ratio =3D min_ratio; + } else { + ret =3D -EINVAL; + } } } spin_unlock_bh(&bdi_lock); --=20 2.25.1