From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751203AbWFEPs0 (ORCPT ); Mon, 5 Jun 2006 11:48:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751201AbWFEPs0 (ORCPT ); Mon, 5 Jun 2006 11:48:26 -0400 Received: from stat9.steeleye.com ([209.192.50.41]:17575 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S1751193AbWFEPsZ (ORCPT ); Mon, 5 Jun 2006 11:48:25 -0400 Subject: Re: [PATCHSET] block: fix PIO cache coherency bug, take 2 From: James Bottomley To: Russell King Cc: Tejun Heo , Jens Axboe , Dave Miller , bzolnier@gmail.com, jgarzik@pobox.com, mattjreimer@gmail.com, Guennadi Liakhovetski , lkml , linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org In-Reply-To: <20060605153420.GB26666@flint.arm.linux.org.uk> References: <1149392479501-git-send-email-htejun@gmail.com> <20060604204444.GF4484@flint.arm.linux.org.uk> <20060604222347.GG4484@flint.arm.linux.org.uk> <1149517656.3489.15.camel@mulgrave.il.steeleye.com> <20060605144456.GA26666@flint.arm.linux.org.uk> <1149521085.3489.24.camel@mulgrave.il.steeleye.com> <20060605153420.GB26666@flint.arm.linux.org.uk> Content-Type: text/plain Date: Mon, 05 Jun 2006 10:47:40 -0500 Message-Id: <1149522460.3489.26.camel@mulgrave.il.steeleye.com> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-4.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2006-06-05 at 16:34 +0100, Russell King wrote: > What has zero copy (your reply) got to do with faulting pages into > userspace (my message). I'm sorry, I don't understand why you've > brought this up. The zero copy case is the case where we end up with user and kernel mappings simultaneously on the page. The nopage (or fault) case is where we end up with them sequentially. Both cases actually require the same cache treatment, but it's easiest to understand in the zero copy case. James