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=-2.4 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT autolearn=ham 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 ECB22C4321D for ; Sat, 18 Aug 2018 01:22:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9825C219D2 for ; Sat, 18 Aug 2018 01:22:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Z8wXhcKJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9825C219D2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726202AbeHRE2A (ORCPT ); Sat, 18 Aug 2018 00:28:00 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:54546 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725763AbeHRE2A (ORCPT ); Sat, 18 Aug 2018 00:28:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=s9lr5/rBgfnFNqAAxR0xbQmN+jsipj97rBqkDfrabn4=; b=Z8wXhcKJoJ9YyjTOQsDC63Rn1 ik8aLgUyOR078ZkAkXiviZZtN+cZ9veJ0UKgw85OviJlSHhgpFfAqE7vOrgqW6vMNA0INOLgfgICs CCUB+G5jJXhhCfcdK3R8QS21TXjN6hqQ9srUxsa28d+WHeJjTB5E5a3DD6bRS2OWkglPoF2pK8X+N yDyud04Ua2KQWw34e40BCsRiBhpFwRwKxbUQgJpb0TgycNpM/tZbM9Q3CAU8GwrnWexJwA6ae5yVJ B3KHTrcZE6Zv28O6ADr/ZrQZhSqg+j2ZcmqAKiwmNbOfE5kectokJlGlgmj61XO1Adexoy0D+70ZR J/W+7IB2Q==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1fqpwU-0005xi-3d; Sat, 18 Aug 2018 01:22:14 +0000 Date: Fri, 17 Aug 2018 18:22:13 -0700 From: Matthew Wilcox To: Roman Gushchin Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Andrew Morton , Johannes Weiner , Michal Hocko , Tejun Heo , Rik van Riel , Konstantin Khlebnikov Subject: Re: [PATCH RFC] mm: don't miss the last page because of round-off error Message-ID: <20180818012213.GA14115@bombadil.infradead.org> References: <20180817231834.15959-1-guro@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180817231834.15959-1-guro@fb.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 17, 2018 at 04:18:34PM -0700, Roman Gushchin wrote: > - scan = div64_u64(scan * fraction[file], > - denominator); > + if (scan > 1) > + scan = div64_u64(scan * fraction[file], > + denominator); Wouldn't we be better off doing a div_round_up? ie: scan = div64_u64(scan * fraction[file] + denominator - 1, denominator); although i'd rather hide that in a new macro in math64.h than opencode it here.