From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932254Ab0HCSZM (ORCPT ); Tue, 3 Aug 2010 14:25:12 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:57336 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757392Ab0HCSZK (ORCPT ); Tue, 3 Aug 2010 14:25:10 -0400 Date: Tue, 3 Aug 2010 11:23:54 -0700 From: Randy Dunlap To: Eric Paris Cc: linux-kernel@vger.kernel.org, selinux@tycho.nsa.gov, akpm@linux-foundation.org, sds@tycho.nsa.gov, jmorris@namei.org Subject: Re: [PATCH] kernel: rounddown helper function Message-Id: <20100803112354.8761e49d.randy.dunlap@oracle.com> In-Reply-To: <20100803181607.30614.36916.stgit@paris.rdu.redhat.com> References: <20100803181607.30614.36916.stgit@paris.rdu.redhat.com> Organization: Oracle Linux Eng. X-Mailer: Sylpheed 2.7.1 (GTK+ 2.16.6; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Source-IP: acsmt355.oracle.com [141.146.40.155] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090204.4C585ED3.028D:SCFMA4539814,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 03 Aug 2010 14:16:07 -0400 Eric Paris wrote: > The roundup() helper function will round a given value up to a multiple of > another given value. aka roundup(11, 7) would give 14 = 7 * 2. This new > function does the opposite. It will round a given number down to the > nearest multiple of the second number: rounddown(11, 7) would give 7. > > I need this in some future SELinux code and can carry the macro myself, but > figured I would put it in the core kernel so others might find and use it > if need be. > > Signed-off-by: Eric Paris > --- > > include/linux/kernel.h | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index 7d5b10f..d6092fd 100644 > --- a/include/linux/kernel.h > +++ b/include/linux/kernel.h > @@ -59,6 +59,7 @@ extern const char linux_proc_banner[]; > #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f)) > #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d)) > #define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y)) > +#define rounddown(x, y) ((x) - ((x) % (y))) > #define DIV_ROUND_CLOSEST(x, divisor)( \ > { \ > typeof(divisor) __divisor = divisor; \ > > -- I'm more used to seeing it like #define DIV_ROUND_DOWN(n, d) (((n) / (d)) * (d)) but since multiply/divide/modulus are usually slower, your (SELinux) way is better, I suppose. and the usual caveats apply: don't use these macros with expressions (nor with y or d == 0). --- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code ***