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=-8.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 5D0FDC4363D for ; Thu, 24 Sep 2020 12:47:02 +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 C4B6220708 for ; Thu, 24 Sep 2020 12:47:01 +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="JmCXm0M+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C4B6220708 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]:41604 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kLQeK-000291-Nf for qemu-devel@archiver.kernel.org; Thu, 24 Sep 2020 08:47:00 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58866) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kLQda-0001ex-7X for qemu-devel@nongnu.org; Thu, 24 Sep 2020 08:46:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:43149) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kLQdX-0006jA-FD for qemu-devel@nongnu.org; Thu, 24 Sep 2020 08:46:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600951569; 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=CGgdG9jGEf6N66KLx/ZohEMslHeSAn+QkcSOMzuO/vg=; b=JmCXm0M+my2CKAThrtf3hkJ3Es07O43P5TcEqsN6xTqvjHVvGw+p9IOLbWQjk1WmfErgAU d2rNPp0gvQ+IyVThtvDpZ1tK1yftnZOVHfIHFDCXivdqXCEQjUkx7x7+XmARcOuj1KjgxM /dVBJvJrgOKPoqXyRI1bRxl69VNLUIA= 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-216-4dw7UmddPTCcaR4vUP8hYw-1; Thu, 24 Sep 2020 08:46:07 -0400 X-MC-Unique: 4dw7UmddPTCcaR4vUP8hYw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C2101AD502; Thu, 24 Sep 2020 12:46:04 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-114-153.ams2.redhat.com [10.36.114.153]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F41B55C1C7; Thu, 24 Sep 2020 12:46:01 +0000 (UTC) Subject: Re: [PATCH v8 6/7] block-stream: freeze link to base node during stream job To: Vladimir Sementsov-Ogievskiy , Andrey Shinkevich , qemu-block@nongnu.org References: <1598633579-221780-1-git-send-email-andrey.shinkevich@virtuozzo.com> <1598633579-221780-7-git-send-email-andrey.shinkevich@virtuozzo.com> <9739719d-0681-d839-cf8d-398b78b6d323@redhat.com> <3a52e54e-22fe-6eee-439a-dc1db0a1bf63@virtuozzo.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: <0f478f6e-77fe-476e-584f-7b4d4262dca0@redhat.com> Date: Thu, 24 Sep 2020 14:46:00 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="aG8NwhZrel2elzQSH3oIYfvg3lfcgiZtG" Received-SPF: pass client-ip=63.128.21.124; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/24 01:10:00 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.199, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.214, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=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: kwolf@redhat.com, jsnow@redhat.com, qemu-devel@nongnu.org, armbru@redhat.com, den@openvz.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) --aG8NwhZrel2elzQSH3oIYfvg3lfcgiZtG Content-Type: multipart/mixed; boundary="r9uZMevWPNOMdeTtkB9BORSNj0JWntqQJ" --r9uZMevWPNOMdeTtkB9BORSNj0JWntqQJ Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 07.09.20 14:17, Vladimir Sementsov-Ogievskiy wrote: > 07.09.2020 14:44, Max Reitz wrote: >> On 04.09.20 15:48, Vladimir Sementsov-Ogievskiy wrote: >>> 04.09.2020 16:21, Max Reitz wrote: >>>> On 28.08.20 18:52, Andrey Shinkevich wrote: >>>>> To keep the base node unchanged during the block-stream operation, >>>>> freeze it as the other part of the backing chain with the intermediat= e >>>>> nodes related to the job. >>>>> This patch revers the change made with the commit c624b015bf as the >>>>> correct base file name and its format have to be written down to the >>>>> QCOW2 header on the disk when the backing file is being changed after >>>>> the stream job completes. >>>>> This reversion incurs changes in the tests 030, 245 and discards the >>>>> test 258 where concurrent stream/commit jobs are tested. When the lin= k >>>>> to a base node is frozen, the concurrent job cannot change the common >>>>> backing chain. >>>>> >>>>> Signed-off-by: Andrey Shinkevich >>>>> --- >>>>> =C2=A0=C2=A0 block/stream.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0 29 ++------ >>>>> =C2=A0=C2=A0 tests/qemu-iotests/030=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0 1= 0 +-- >>>>> =C2=A0=C2=A0 tests/qemu-iotests/245=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0= =C2=A0 2 +- >>>>> =C2=A0=C2=A0 tests/qemu-iotests/258=C2=A0=C2=A0=C2=A0=C2=A0 | 161 >>>>> --------------------------------------------- >>>>> =C2=A0=C2=A0 tests/qemu-iotests/258.out |=C2=A0 33 ---------- >>>>> =C2=A0=C2=A0 5 files changed, 14 insertions(+), 221 deletions(-) >>>>> =C2=A0=C2=A0 delete mode 100755 tests/qemu-iotests/258 >>>>> =C2=A0=C2=A0 delete mode 100644 tests/qemu-iotests/258.out >>>> >>>> Does this need to be in this series?=C2=A0 (I=E2=80=99m not entirely s= ure, based on >>>> what I can see in patch 7.) >>>> >>>> When doing this, should we introduce a @bottom-node option >>>> alongside, so >>>> that we can make all the tests that are deleted here pass still, just >>>> with changes? >>>> >>> >>> That's a question to discuss, and I asked Andrey to make this patch >>> in this >>> simple way to see, how much damage we have with this change. >>> >>> Honestly, I doubt that we need the new option. Previously, we decided >>> that >>> we can make this change without a deprecation. If we still going to >>> do it, >>> we shouldn't care about these use cases. So, if we freeze base again >>> wituhout >>> a depreaction and: >>> >>> 1. add bottom-node >>> >>> =C2=A0=C2=A0- we keep the iotests >>> =C2=A0=C2=A0- If (unlikely) someone will came and say: hey, you've brok= en my >>> working scenario, we will say "use bottom-node option, sorry" >>> =C2=A0=C2=A0- Most likely we'll have unused option and corresponding un= used logic, >>> making code more complex for nothing (and we'll have to say "sorry" >>> anyway) >>> >>> 2. without option >>> >>> =C2=A0=C2=A0- we loose the iotests. this looks scary, but it is honest:= we drop >>> use-cases and corresponding iotests >>> =C2=A0=C2=A0- If (unlikely) someone will came and say: hey, you've brok= en my >>> working scenario, he will have to wait for next release / package >>> version / or update the downstream himself >>> =C2=A0=C2=A0- Most likely all will be OK. >> >> Well, yes, we=E2=80=99ll disrupt either way, but it is a difference whet= her we >> can tell people immediately that there=E2=80=99s an alternative now, or = whether >> we=E2=80=99ll have to make them wait for the next release. >> >> Basically, the whole argument hinges on the question of whether anyone >> uses this right now or not, and we just don=E2=80=99t know. >> >> The question remains whether this patch is necessary for this series. >=20 > Otherwise iotests fail :) >=20 >> We also have the option of introducing @bottom-node, leaving @base=E2=80= =99s >> behavior as-is >=20 > You mean not make it freeze base again, but just don't care? Yes. I think the only problem with that would be that it=E2=80=99s unintui= tive in case the graph is modified while the job is running, but I can=E2=80=99t= find that worse than forbidding that case completely. (And I think it would be easier to explain if we introduced @bottom-node.) >> and explaining it as a legacy option from which >> @bottom-node is inferred.=C2=A0 Then specifying @base just becomes weird= and >> problem-prone when the graph is reconfigured while the job is active, >> but you can get around that by simply using the non-legacy option. >=20 > Hmm. Last time, I thought that bottom-node was a bad idea, as we have a > lot of problems with it, Hm, did we? Off the top of my head, I can=E2=80=99t remember any. Besides= the fact that it would require users to use a different parameter and us to support two parameters unless we decide to deprecate @base. > but you think it should be kept as preferred > behavior? But this sounds as working idea. >=20 > Then, we'll probably want to set skip_filters(bottom->backing) as > backing of top in qcow2 metadata, and direct bottom->backing as new > backing of top in block node graph. I=E2=80=99m not sure whether I agree with skipping filters for the qcow2 metadata, just because then it=E2=80=99s different from the runtime state. = But OTOH I would expect that any application that seriously cares about filters would override the qcow2 metadata anyway, so I think I do agree after all. Yeah, I think skipping filters for the backing file name in the qcow2 header is right. > Anyway, I like the idea to deprecate filename-based interfaces wherever > we can. Who doesn=E2=80=99t... Max --r9uZMevWPNOMdeTtkB9BORSNj0JWntqQJ-- --aG8NwhZrel2elzQSH3oIYfvg3lfcgiZtG Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl9slQgACgkQ9AfbAGHV z0DtBQf/csyYmpJNkS4uRYTqa/L74f0KYXjBTcYlZIoQN+yXZqBFslJlcPbcDS12 8jk1RLx9iutwsb9wVy1/nLuJG0HZnvjbrlE7cfRA1yP1c6BRHZVPKVaaDQllZP78 0QsT9JYLeQoeEdLCGwglHMZ3MJmwxP+Xxxc8l+Hm9vDdd0zyAqyNoUygqz6nfmUe gwJmU/e7y0axz6/FLQSvKn3FiwgVewDYpGTnSQtYLPLNCBixLPGJG3RKUjkrsVO+ jzVPDXnEVST0/+CMsdKCU4v7kW0koEBuelWZng0dqfuvdWdnLvYfOumO5DgfpuBD Thp5J5gDL6M+IvxtvaVmYLqoq0KRxA== =7FTm -----END PGP SIGNATURE----- --aG8NwhZrel2elzQSH3oIYfvg3lfcgiZtG--