Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755964AbZKDNhZ (ORCPT ); Wed, 4 Nov 2009 08:37:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755694AbZKDNhZ (ORCPT ); Wed, 4 Nov 2009 08:37:25 -0500 Received: from one.firstfloor.org ([213.235.205.2]:47243 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755259AbZKDNhY (ORCPT ); Wed, 4 Nov 2009 08:37:24 -0500 Date: Wed, 4 Nov 2009 14:37:28 +0100 From: Andi Kleen To: "Michael S. Tsirkin" Cc: Andi Kleen , netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@elte.hu, linux-mm@kvack.org, akpm@linux-foundation.org Subject: Re: [PATCHv7 3/3] vhost_net: a kernel-level virtio server Message-ID: <20091104133728.GN31511@one.firstfloor.org> References: <20091103172422.GD5591@redhat.com> <878wema6o0.fsf@basil.nowhere.org> <20091104121009.GF8398@redhat.com> <20091104125957.GL31511@one.firstfloor.org> <20091104130828.GC8920@redhat.com> <20091104131533.GM31511@one.firstfloor.org> <20091104131735.GD8920@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091104131735.GD8920@redhat.com> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1357 Lines: 37 On Wed, Nov 04, 2009 at 03:17:36PM +0200, Michael S. Tsirkin wrote: > On Wed, Nov 04, 2009 at 02:15:33PM +0100, Andi Kleen wrote: > > On Wed, Nov 04, 2009 at 03:08:28PM +0200, Michael S. Tsirkin wrote: > > > On Wed, Nov 04, 2009 at 01:59:57PM +0100, Andi Kleen wrote: > > > > > Fine? > > > > > > > > I cannot say -- are there paths that could drop the device beforehand? > > > > > > Do you mean drop the mm reference? > > > > No the reference to the device, which owns the mm for you. > > The device is created when file is open and destroyed > when file is closed. So I think the fs code handles the > reference counting for me: it won't call file cleanup > callback while some userspace process has the file open. > Right? Yes. But the semantics when someone inherits such a fd through exec or through file descriptor passing would be surely "interesting" You would still do IO on the old VM. I guess it would be a good way to confuse memory accounting schemes or administrators @) It would be all saner if this was all a single atomic step. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- 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/