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 8BF0BC2BA1A for ; Fri, 24 Apr 2020 10:41:50 +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 576292071E for ; Fri, 24 Apr 2020 10:41:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="O3QTNBPC" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 576292071E 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]:59742 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jRvmH-0002La-CU for qemu-devel@archiver.kernel.org; Fri, 24 Apr 2020 06:41:49 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41032) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jRvlL-0001YH-SB for qemu-devel@nongnu.org; Fri, 24 Apr 2020 06:40:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.90_1) (envelope-from ) id 1jRvlK-0001Hu-Jm for qemu-devel@nongnu.org; Fri, 24 Apr 2020 06:40:51 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:38202 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jRvlK-0001EN-4g for qemu-devel@nongnu.org; Fri, 24 Apr 2020 06:40:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587724848; 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:autocrypt:autocrypt; bh=ue0z5EgI8Fzg/uVdVMdVCDoYtm3/AjUSmAzKK9UEDYU=; b=O3QTNBPC/x8Tegr+zT6nPXcIGCkhcV+iLr5ea5jqG81/lfQK3sdCYNcnxHL0DyFamW2MA/ 4elZLLh887lYLd7L30IX8FnLUuLWgWKW552wLz/MgCsAiSJtfdeWr4Oj2k8fUba+bFAvER wgjxSb0ViCtJ8g+wvTb6DVvp+1uadmc= 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-193-Z6bGdK3ZM1W2i3N2OB2vRg-1; Fri, 24 Apr 2020 06:40:46 -0400 X-MC-Unique: Z6bGdK3ZM1W2i3N2OB2vRg-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 3D772800580; Fri, 24 Apr 2020 10:40:45 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-113-192.ams2.redhat.com [10.36.113.192]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F31BC60CD0; Fri, 24 Apr 2020 10:40:43 +0000 (UTC) Subject: Re: [PATCH v2 2/3] qcow2: Allow resize of images with internal snapshots To: Eric Blake , qemu-devel@nongnu.org References: <20200423221707.477404-1-eblake@redhat.com> <20200423221707.477404-3-eblake@redhat.com> From: Max Reitz Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: Date: Fri, 24 Apr 2020 12:40:42 +0200 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: <20200423221707.477404-3-eblake@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="jNDKCuQbJ55jxz5q1ihll6i9Iz2b4QVeS" Received-SPF: pass client-ip=207.211.31.81; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/24 03:11:53 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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: kwolf@redhat.com, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --jNDKCuQbJ55jxz5q1ihll6i9Iz2b4QVeS Content-Type: multipart/mixed; boundary="yPTa7I1YflnW0vjJvfet7v0txY8Lb6cUk" --yPTa7I1YflnW0vjJvfet7v0txY8Lb6cUk Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 24.04.20 00:17, Eric Blake wrote: > We originally refused to allow resize of images with internal > snapshots because the v2 image format did not require the tracking of > snapshot size, making it impossible to safely revert to a snapshot > with a different size than the current view of the image. But the > snapshot size tracking was rectified in v3, and our recent fixes to > qemu-img amend (see 0a85af35) guarantee that we always have a valid > snapshot size. Thus, we no longer need to artificially limit image > resizes, but it does become one more thing that would prevent a > downgrade back to v2. And now that we support different-sized > snapshots, it's also easy to fix reverting to a snapshot to apply the > new size. >=20 > Upgrade iotest 61 to cover this (we previously had NO coverage of > refusal to resize while snapshots exist). Note that the amend process > can fail but still have effects: in particular, since we break things > into upgrade, resize, downgrade, a failure during resize does not roll > back changes made during upgrade, nor does failure in downgrade roll > back a resize. But this situation is pre-existing even without this > patch; and without journaling, the best we could do is minimize the > chance of partial failure by collecting all changes prior to doing any > writes - which adds a lot of complexity but could still fail with EIO. > On the other hand, we are careful that even if we have partial > modification but then fail, the image is left viable (that is, we are > careful to sequence things so that after each successful cluster > write, there may be transient leaked clusters but no corrupt > metadata). And complicating the code to make it more transaction-like > is not worth the effort: a user can always request multiple 'qemu-img > amend' changing one thing each, if they need finer-grained control > over detecting the first failure than what they get by letting qemu > decide how to sequence multiple changes. >=20 > Signed-off-by: Eric Blake > --- > block/qcow2-snapshot.c | 20 ++++++++++++++++---- > block/qcow2.c | 25 ++++++++++++++++++++++--- > tests/qemu-iotests/061 | 35 +++++++++++++++++++++++++++++++++++ > tests/qemu-iotests/061.out | 28 ++++++++++++++++++++++++++++ > 4 files changed, 101 insertions(+), 7 deletions(-) Reviewed-by: Max Reitz --yPTa7I1YflnW0vjJvfet7v0txY8Lb6cUk-- --jNDKCuQbJ55jxz5q1ihll6i9Iz2b4QVeS Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl6iwioACgkQ9AfbAGHV z0Av2Qf+LIZQktE/zbtOeLLgf0vEJyCIqMIqi9AlxMlEVi3wTCGzYc6QzRh5hSCb vt3T6Q2RWSagmp0Q8+prZOQT2B85sdYgJrQ6MJP2rY8LGEfrCvGhbQ9/nEE3KTuO NKVw6fKeI3RKzhqVDbQDdrDXftszoG45zU+TEoYF89mzSAtygS9dL8XYaRh1C5WK 8LKwA3xQ7l+DqyVFXBm/Ap3TLWpKayO7xOtbm3j1dyzpCLJW9VzdFgGsX/2Q4Ikt Ou4Z/kjzsMFVESrj/r39xYE3yrlxxXv/DW6lt7KXuEYLAx522wOmPxK4mk5ZJRPw ign4Epj3w/RqP6TiEoWwNS7es1eREA== =k9s0 -----END PGP SIGNATURE----- --jNDKCuQbJ55jxz5q1ihll6i9Iz2b4QVeS--