Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754516AbXJVNrh (ORCPT ); Mon, 22 Oct 2007 09:47:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752593AbXJVNra (ORCPT ); Mon, 22 Oct 2007 09:47:30 -0400 Received: from ns1.suse.de ([195.135.220.2]:45184 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752490AbXJVNr3 (ORCPT ); Mon, 22 Oct 2007 09:47:29 -0400 To: Jeremy Fitzhardinge Cc: dean gaudet , Nick Piggin , Xen-devel , Morten@suse.de, David Chinner , Linux Kernel Mailing List , =?iso-8859-1?Q?B=F8geskov?= , xfs@oss.sgi.com, xfs-masters@oss.sgi.com, Mark Williamson Subject: Re: Interaction between Xen and XFS: stray RW mappings From: Andi Kleen References: <470FA7C3.90404@goop.org> <20071014225618.GN23367404@sgi.com> <4712A254.4090604@goop.org> <200710151415.07248.nickpiggin@yahoo.com.au> <471C1A61.1010001@goop.org> Date: Mon, 22 Oct 2007 15:47:27 +0200 In-Reply-To: <471C1A61.1010001@goop.org> (Jeremy Fitzhardinge's message of "Sun\, 21 Oct 2007 20\:34\:57 -0700") Message-ID: User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1027 Lines: 24 Jeremy Fitzhardinge writes: > > Yes, that's precisely the problem. xfs does delay the unmap, leaving > stray mappings, which upsets Xen. Again it not just upsets Xen, keeping mappings to freed pages is wrong generally and violates the x86 (and likely others like PPC) architecture because it can cause illegal caching attribute aliases. The patch that went into the tree was really not correct -- this bogus optimization should have been unconditionally removed or if you really wanted an ifdef made dependent on !CONFIG_XEN && !CONFIG_AGP (and likely && !CONFIG_DRM && !CONFIG_anything else that uses uncached mappings in memory). You just worked around the obvious failure and leave the non obvious rare corruptions in, which isn't a good strategy. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/