From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C2E6C433E2 for ; Fri, 11 Sep 2020 17:12:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 225C4214F1 for ; Fri, 11 Sep 2020 17:12:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="dtr8rc1T" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726246AbgIKRML (ORCPT ); Fri, 11 Sep 2020 13:12:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50194 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726085AbgIKRLA (ORCPT ); Fri, 11 Sep 2020 13:11:00 -0400 Received: from mail-io1-xd43.google.com (mail-io1-xd43.google.com [IPv6:2607:f8b0:4864:20::d43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6F61C061757 for ; Fri, 11 Sep 2020 10:11:00 -0700 (PDT) Received: by mail-io1-xd43.google.com with SMTP id b6so11801750iof.6 for ; Fri, 11 Sep 2020 10:11:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=PjaHcTfFjzbLCw68IPxqcyo+o8vTrqFIU4LrLdQ6i4E=; b=dtr8rc1TFTdhuQX1JX6cpdjp7g5dPXot326EizN5cMg4FGGWCBF3SujtkOjH2g9AU8 VYooSex5NOHLaQmydJQvGP2ciPTbamrxy8e63sgmRcld3qe9CBysCiE7nkIJAWTrWWzD 5cPZyRl9Z1CgPdcCfFgCs0umR5vPyTmNsQ7ARuMaYYHRDmzXZ+nTUkdmdtXeWtLd5x6F HZeOjxlKX3IAgX2SHg4n37ycDB7odU4BCn88ZKZVTPuVXZ6SEHZ4H2WFRV979A/Iqjwg f8eUotxsYrCJSPi9GeB9lCE1tcTM+Wow6b+ZMYQyvCDgYzOgnphaaEjqYJOXrGsWBVEa ZVMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=PjaHcTfFjzbLCw68IPxqcyo+o8vTrqFIU4LrLdQ6i4E=; b=g2UUNmCH78jsYZAFdBLfwIDmCiiJ5yfolknCQsiKh0YYWkVuUE1o9VUEVRgnpBTHvz VhR4rXQmUwVQi83Co2fY3O3ziH6x8i7YxAG08ADXHYogtcMe/hslK5DD1w8fhxzgEWsw afvTmiCLajtpjwsZAPm0f9RDS/PVeUBBp9B6Oj/TGZM6UboiXBUY0mZv4UQNISEgs139 BlDre1ZukVaKoDVYKGcsS426PrAlMxVFSZuVmxzV7Tpw9ZFRTaYJC7alBEvdHmxQEiN4 UT+6XsvMevCIgJfLbW8tmtH6nT8EznRgYq00U77rESnsv3/gpQjoCfKyEsuhymQerclE NJHA== X-Gm-Message-State: AOAM532iY29jNYNTBRumzYf2QIYBTX6ybQKzSVxTn6RwdKWwItDsuGUZ gLt+yWHm08XxHT3pR5vaoDTVQQ== X-Google-Smtp-Source: ABdhPJya9L0YSSJEFVGJqL4QEUVLucOzZ18qlV1aPXjITgOpcqQR+btExvD6D25jNhpGgt8ZHCc9mw== X-Received: by 2002:a02:8805:: with SMTP id r5mr2931118jai.52.1599844260029; Fri, 11 Sep 2020 10:11:00 -0700 (PDT) Received: from [192.168.1.10] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id l14sm1509002ili.84.2020.09.11.10.10.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Sep 2020 10:10:59 -0700 (PDT) Subject: Re: [PATCH block/for-next] blk-iocost: fix divide-by-zero in transfer_surpluses() To: Tejun Heo Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, cgroups@vger.kernel.org References: <20200911170746.GG4295@mtj.thefacebook.com> From: Jens Axboe Message-ID: Date: Fri, 11 Sep 2020 11:10:58 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200911170746.GG4295@mtj.thefacebook.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/11/20 11:07 AM, Tejun Heo wrote: > Conceptually, root_iocg->hweight_donating must be less than WEIGHT_ONE but > all hweight calculations round up and thus it may end up >= WEIGHT_ONE > triggering divide-by-zero and other issues. Bound the value to avoid > surprises. Applied, thanks. -- Jens Axboe