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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 B2A9CC433DB for ; Thu, 21 Jan 2021 10:53:31 +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 2EA5423602 for ; Thu, 21 Jan 2021 10:53:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2EA5423602 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]:46740 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l2Xak-00011T-4Q for qemu-devel@archiver.kernel.org; Thu, 21 Jan 2021 05:53:30 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:42926) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l2XZl-0008Ca-Lt for qemu-devel@nongnu.org; Thu, 21 Jan 2021 05:52:29 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:51686) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l2XZi-0008Rr-FG for qemu-devel@nongnu.org; Thu, 21 Jan 2021 05:52:29 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611226345; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Yn4zBVSTVT1GTDsWRie1gU481Kfn7/CJCNMVxfXsRxU=; b=fDLvGSNOcIg1SkBGbdbourQbm8qB9a4E1/0DDdy2vyQotifoB4lGEwv2B0kBwSFAmpXSoz +rKh+W3jUumLQ/wvPO2pBRKGC+FSl59NZjk9m9q5Y457ktd3icPb+4ADrEwqcUxuTV/3dw b8ndzQCl87Ukff7kUKMdq0aHM0Q3QJc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-353-Yktm-gylOwagmZQuphFKEA-1; Thu, 21 Jan 2021 05:52:21 -0500 X-MC-Unique: Yktm-gylOwagmZQuphFKEA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8C8571005586; Thu, 21 Jan 2021 10:52:20 +0000 (UTC) Received: from merkur.fritz.box (ovpn-113-104.ams2.redhat.com [10.36.113.104]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 00FBB70464; Thu, 21 Jan 2021 10:52:18 +0000 (UTC) Date: Thu, 21 Jan 2021 11:52:17 +0100 From: Kevin Wolf To: Vladimir Sementsov-Ogievskiy Subject: Re: [RFC PATCH 0/2] Allow changing bs->file on reopen Message-ID: <20210121105217.GA5466@merkur.fritz.box> References: MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.167, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action 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: Kashyap Chamarthy , Alberto Garcia , qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 18.01.2021 um 11:22 hat Vladimir Sementsov-Ogievskiy geschrieben: > 15.01.2021 16:02, Alberto Garcia wrote: > > Hi, > > > > during the past months we talked about making x-blockdev-reopen stable > > API, and one of the missing things was having support for changing > > bs->file. See here for the discusssion (I can't find the message from > > Kashyap that started the thread in the web archives): > > > > https://lists.gnu.org/archive/html/qemu-block/2020-10/msg00922.html > > > > I was testing this and one of the problems that I found was that > > removing a filter node using this command is tricky because of the > > permission system, see here for details: > > > > https://lists.gnu.org/archive/html/qemu-block/2020-12/msg00092.html > > > > The good news is that Vladimir posted a set of patches that changes > > the way that permissions are updated on reopen: > > > > https://lists.gnu.org/archive/html/qemu-block/2020-11/msg00745.html > > > > I was testing if this would be useful to solve the problem that I > > mentioned earlier and it seems to be the case so I wrote a patch to > > add support for changing bs->file, along with a couple of test cases. > > > > This is still an RFC but you can see the idea. > > Good idea and I glad to see that my patches help:) > > Hmm, still, removing a filter which want to unshare WRITE even when > doesn't have any parents will be a problem anyway, so we'll need a new > command to drop filter with a logic like in bdrv_drop_filter in my > series. > > Or, we can introduce multiple reopen.. So that x-blockdev-reopen will > take a list of BlockdevOptions, and do all modifications in one > transaction. Than we'll be able to drop filter by transactional update > of top node child and removing filter child link. Internally, we already have reopen queues anyway, so it would make sense to me to expose them externally and take a list of BlockdevOptions. This way we should be able to do even complex changes of the graph where adding some edges requires the removal of other edges in a single atomic operation. Kevin