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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 2DAD0C43331 for ; Fri, 27 Mar 2020 18:53:01 +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 F26C5206F2 for ; Fri, 27 Mar 2020 18:53:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="D10NS/tl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F26C5206F2 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]:45748 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jHu6G-00030i-4m for qemu-devel@archiver.kernel.org; Fri, 27 Mar 2020 14:53:00 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:47239) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jHu5g-0002c0-8X for qemu-devel@nongnu.org; Fri, 27 Mar 2020 14:52:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jHu5e-0001HL-44 for qemu-devel@nongnu.org; Fri, 27 Mar 2020 14:52:23 -0400 Received: from us-smtp-delivery-74.mimecast.com ([63.128.21.74]:29039) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jHu5c-00016W-CR for qemu-devel@nongnu.org; Fri, 27 Mar 2020 14:52:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585335139; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=cSHrU53WNenHfU0CEVdVpegT4l+i/SSx8bONTKGRtZ8=; b=D10NS/tlwEcAOfN1KKYn573yescn3zCwPF4uo9EYNvzAKiUGFxJCp0CC9jw7PbPmtXRCoC otdPzkaqVIcFNoY5ijkuGy9Hvz0QK4gte9O1rq8efCpSWunhskESQ5ahVuVT+JYofsGZDw S1GGTuRO2+IP0QXxR62pSf1E/dpx5mc= 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-164-g7Fd8XqPPEKjXpllSOJKBg-1; Fri, 27 Mar 2020 14:52:17 -0400 X-MC-Unique: g7Fd8XqPPEKjXpllSOJKBg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 59EA2800D4E; Fri, 27 Mar 2020 18:52:16 +0000 (UTC) Received: from [10.3.113.103] (ovpn-113-103.phx2.redhat.com [10.3.113.103]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 84D0B60BF4; Fri, 27 Mar 2020 18:52:15 +0000 (UTC) Subject: Re: [PATCH v3] qcow2: Forbid discard in qcow2 v2 images with backing files To: Alberto Garcia , qemu-devel@nongnu.org References: <20200327164857.31415-1-berto@igalia.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <6b561422-e3f5-eca2-8b11-e23081cb7ec2@redhat.com> Date: Fri, 27 Mar 2020 13:52:14 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 63.128.21.74 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: Kevin Wolf , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/27/20 1:43 PM, Alberto Garcia wrote: > On Fri 27 Mar 2020 07:13:04 PM CET, Eric Blake wrote: >>> +for qcow2_compat in 0.10 1.1; do >>> + echo "# Create an image with compat=$qcow2_compat without a backing file" >>> + _make_test_img -o "compat=$qcow2_compat" 128k >>> + >>> + echo "# Fill all clusters with data and then discard them" >>> + $QEMU_IO -c 'write -P 0x01 0 128k' "$TEST_IMG" | _filter_qemu_io >>> + $QEMU_IO -c 'discard 0 128k' "$TEST_IMG" | _filter_qemu_io >>> + >>> + echo "# Read the data from the discarded clusters" >>> + $QEMU_IO -c 'read -P 0x00 0 128k' "$TEST_IMG" | _filter_qemu_io >>> +done >> >> Should this loop also inspect qemu-img map output? > > I guess we can, although here the image is completely unallocated in > both cases. Which shows that even for v2 images, discard DOES do something when there is no backing file (even if it is now a no-op when there is a backing file after this patch). -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org