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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 41420C33CB1 for ; Thu, 16 Jan 2020 14:15:05 +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 07BA32077B for ; Thu, 16 Jan 2020 14:15:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Q8WiRhfk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 07BA32077B 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]:42614 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1is5vL-0007n8-Uw for qemu-devel@archiver.kernel.org; Thu, 16 Jan 2020 09:15:03 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:49781) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1is5uO-0006lG-Jd for qemu-devel@nongnu.org; Thu, 16 Jan 2020 09:14:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1is5uL-0005dv-1y for qemu-devel@nongnu.org; Thu, 16 Jan 2020 09:14:04 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:55449 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1is5uK-0005cK-Ua for qemu-devel@nongnu.org; Thu, 16 Jan 2020 09:14:01 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579184038; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=ZveQj1LFTWiYdGDJswQVsZyoOvvwQTRsf7Ry6Olo5j0=; b=Q8WiRhfkJqkLVnPSwZODDtqSeJwWGCXXgopyxNokju8P8OJuRLgDN5f4ywsl6+IeTq/LhZ RgpGEVyhL3pxUB8HTDnCeBO8pj3EpUqnra/UeQAwE3j6nY6ae6DJgsOxU1G85uBPSoLX95 7KtWaCAhWPKbUKbBXzA+lLHLH4uRKGc= 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-288-A-sqFkd3P-eeZb-1wsiK3A-1; Thu, 16 Jan 2020 09:13:54 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DC7181800D48; Thu, 16 Jan 2020 14:13:53 +0000 (UTC) Received: from localhost (ovpn-117-237.ams2.redhat.com [10.36.117.237]) by smtp.corp.redhat.com (Postfix) with ESMTP id 66C6B5DA32; Thu, 16 Jan 2020 14:13:53 +0000 (UTC) Date: Thu, 16 Jan 2020 14:13:52 +0000 From: "Richard W.M. Jones" To: qemu-devel@nongnu.org, qemu-block@nongnu.org, mreitz@redhat.com, mlevitsk@redhat.com, sgarzare@redhat.com Subject: Bug? qemu-img convert to preallocated image makes it sparse Message-ID: <20200116141352.GA32053@redhat.com> MIME-Version: 1.0 User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-MC-Unique: A-sqFkd3P-eeZb-1wsiK3A-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.61 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" I'm not necessarily saying this is a bug, but a change in behaviour in qemu has caused virt-v2v to fail. The reproducer is quite simple. Create sparse and preallocated qcow2 files of the same size: $ qemu-img create -f qcow2 sparse.qcow2 50M Formatting 'sparse.qcow2', fmt=3Dqcow2 size=3D52428800 cluster_size=3D655= 36 lazy_refcounts=3Doff refcount_bits=3D16 $ qemu-img create -f qcow2 prealloc.qcow2 50M -o preallocation=3Dfalloc,c= ompat=3D1.1 Formatting 'prealloc.qcow2', fmt=3Dqcow2 size=3D52428800 compat=3D1.1 clu= ster_size=3D65536 preallocation=3Dfalloc lazy_refcounts=3Doff refcount_bits= =3D16 $ du -m sparse.qcow2 prealloc.qcow2=20 1 sparse.qcow2 51=09prealloc.qcow2 Now copy the sparse file into the preallocated file using the -n option so qemu-img doesn't create the target: $ qemu-img convert -p -n -f qcow2 -O qcow2 sparse.qcow2 prealloc.qcow2 (100.00/100%) In new qemu that makes the target file sparse: $ du -m sparse.qcow2 prealloc.qcow2=20 1 sparse.qcow2 1 prealloc.qcow2 <-- should still be 51 In old qemu the target file remained preallocated, which is what I and virt-v2v are expecting. I bisected this to the following commit: 4d7c487eac1652dfe4498fe84f32900ad461d61b is the first bad commit commit 4d7c487eac1652dfe4498fe84f32900ad461d61b Author: Max Reitz Date: Wed Jul 24 19:12:29 2019 +0200 qemu-img: Fix bdrv_has_zero_init() use in convert =20 bdrv_has_zero_init() only has meaning for newly created images or image areas. If qemu-img convert did not create the image itself, it cannot rely on bdrv_has_zero_init()'s result to carry any meaning. =20 Signed-off-by: Max Reitz Message-id: 20190724171239.8764-2-mreitz@redhat.com Reviewed-by: Maxim Levitsky Reviewed-by: Stefano Garzarella Signed-off-by: Max Reitz qemu-img.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) Reverting this commit on the current master branch restores the expected behaviour. Thoughts? Rich. --=20 Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjon= es Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org