From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263050AbVGNQCi (ORCPT ); Thu, 14 Jul 2005 12:02:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263053AbVGNQCi (ORCPT ); Thu, 14 Jul 2005 12:02:38 -0400 Received: from smtp.osdl.org ([65.172.181.4]:21165 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S263050AbVGNQCh (ORCPT ); Thu, 14 Jul 2005 12:02:37 -0400 Subject: Re: [rfc patch 2/2] direct-io: remove address alignment check From: Daniel McNeil To: Andi Kleen Cc: Linux Kernel Mailing List In-Reply-To: References: <1121298112.6025.21.camel@ibm-c.pdx.osdl.net.suse.lists.linux.kernel> Content-Type: text/plain Message-Id: <1121356952.6025.33.camel@ibm-c.pdx.osdl.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Thu, 14 Jul 2005 09:02:32 -0700 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2005-07-14 at 06:18, Andi Kleen wrote: > Daniel McNeil writes: > > > This patch relaxes the direct i/o alignment check so that user addresses > > do not have to be a multiple of the device block size. > > The original reason for this limit was that lots of drivers > (not only IDE) explode when you give them odd sizes. Sometimes > it is even worse. > > I doubt all of them have been fixed. > > Very risky change. > That is exactly why I made this a separate patch, so that we can test and find out where the problems are and work to fix them. Are there problems only with odd sizes, or do drivers have problems with non-512 sizes? Allowing 4-byte aligned user addresses would be a good step forward, since it looks like malloc() returns 4-byte aligned addresses. Daniel