From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-99.freemail.mail.aliyun.com (out30-99.freemail.mail.aliyun.com [115.124.30.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4D5D43D64; Mon, 18 Dec 2023 03:29:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R961e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045176;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0Vye8VXv_1702870188; Received: from 30.221.145.126(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0Vye8VXv_1702870188) by smtp.aliyun-inc.com; Mon, 18 Dec 2023 11:29:49 +0800 Message-ID: <88cf7dcf-ec74-4176-9273-dbbc49dea271@linux.alibaba.com> Date: Mon, 18 Dec 2023 11:29:48 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: fix arithmetic for bdi min_ratio and max_ratio From: Jingbo Xu To: shr@devkernel.io, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, joseph.qi@linux.alibaba.com, "linux-fsdevel@vger.kernel.org" References: <20231218031640.77983-1-jefflexu@linux.alibaba.com> Content-Language: en-US In-Reply-To: <20231218031640.77983-1-jefflexu@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit +cc fsdevel On 12/18/23 11:16 AM, Jingbo Xu wrote: > bdi->[min|max]_ratio are both part per million. Fix the wrong > arithmetic when setting bdi's min_ratio and max_ratio. > > Fixes: efc3e6ad53ea ("mm: split off __bdi_set_max_ratio() function") > Fixes: 8021fb3232f2 ("mm: split off __bdi_set_min_ratio() function") > Reported-by: Joseph Qi > Signed-off-by: Jingbo Xu > --- > mm/page-writeback.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index ee2fd6a6af40..b393b3281ce9 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -692,7 +692,6 @@ static int __bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ra > > if (min_ratio > 100 * BDI_RATIO_SCALE) > return -EINVAL; > - min_ratio *= BDI_RATIO_SCALE; > > spin_lock_bh(&bdi_lock); > if (min_ratio > bdi->max_ratio) { > @@ -729,7 +728,8 @@ static int __bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ra > ret = -EINVAL; > } else { > bdi->max_ratio = max_ratio; > - bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100; > + bdi->max_prop_frac = div64_u64(FPROP_FRAC_BASE * max_ratio, > + 100UL * BDI_RATIO_SCALE); > } > spin_unlock_bh(&bdi_lock); > -- Thanks, Jingbo