From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8E6F3ECE587 for ; Tue, 1 Oct 2019 16:41:47 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6837D21855 for ; Tue, 1 Oct 2019 16:41:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6837D21855 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:44736 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iFLDd-0006aA-N3 for qemu-devel@archiver.kernel.org; Tue, 01 Oct 2019 12:41:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53691) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iFKp3-0007jC-90 for qemu-devel@nongnu.org; Tue, 01 Oct 2019 12:16:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iFKp1-00045c-3a for qemu-devel@nongnu.org; Tue, 01 Oct 2019 12:16:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54254) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iFKoy-00043g-QI; Tue, 01 Oct 2019 12:16:16 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 10C1F30917EF; Tue, 1 Oct 2019 16:16:16 +0000 (UTC) Received: from linux.fritz.box (ovpn-117-215.ams2.redhat.com [10.36.117.215]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2957B5D712; Tue, 1 Oct 2019 16:16:12 +0000 (UTC) Date: Tue, 1 Oct 2019 18:16:10 +0200 From: Kevin Wolf To: Vladimir Sementsov-Ogievskiy Subject: Re: bitmap migration bug with -drive while block mirror runs Message-ID: <20191001161610.GG4688@linux.fritz.box> References: <315cff78-dcdb-a3ce-2742-da3cc9f0ca97@redhat.com> <4bc910ef-0bec-cfd6-89f6-a93d35367218@redhat.com> <9431d242-bfe1-b9db-17d0-6c1a280a05da@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9431d242-bfe1-b9db-17d0-6c1a280a05da@virtuozzo.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Tue, 01 Oct 2019 16:16:16 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: John Snow , qemu-devel , Qemu-block , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 01.10.2019 um 17:57 hat Vladimir Sementsov-Ogievskiy geschrieben: > 01.10.2019 17:10, John Snow wrote: > > > > > > On 10/1/19 10:00 AM, Vladimir Sementsov-Ogievskiy wrote: > >>> Otherwise: I have a lot of cloudy ideas on how to solve this, but > >>> ultimately what we want is to be able to find the "addressable" name for > >>> the node the bitmap is attached to, which would be the name of the first > >>> ancestor node that isn't a filter. (OR, the name of the block-backend > >>> above that node.) > >> Not the name of ancestor node, it will break mapping: it must be name of the > >> node itself or name of parent (may be through several filters) block-backend > >> > > > > Ah, you are right of course -- because block-backends are the only > > "nodes" for which we actually descend the graph and add the bitmap to > > its child. > > > > So the real back-resolution mechanism is: > > > > - Find the first non-filter ancestor, A > > - if A is not a block-backend, we must use our node-local name. > > - if A's name is empty, we must use our node-local name. > > - If the name we have chosen is not id_wellformed, we have no > > migration-stable addressable name for this bitmap and the migration must > > fail! > > > > > > For resolving bitmap addresses via QMP (node, name) pairs; the > > resolution method would be this: > > > > - if the node-name N is a block-backend, descend the tree until we find > > the first non-filter node V. > > - if the node-name N is a BlockDriverState, use this node directly. > > > > Looks good for me. > > I also think if on destination we have both block-backend with name N and > block-node with name N and the latter is not (filtered) child of the former, > we should fail migration of at least that bitmap. (Hope, nobody reuse > block-backend names as node-names in practice.. (should we restrict it > explicitly ?)) You can't have a node and a BlockBackend of the same name, they share a single namespace. If you try to do so, you get an error. Kevin