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Tue, 21 Jan 2020 14:01:13 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-117-116.ams2.redhat.com [10.36.117.116]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0CCCF1001DE1; Tue, 21 Jan 2020 14:01:11 +0000 (UTC) Subject: Re: [PATCH 2/2] iotests: add test for backup-top failure on permission activation To: Vladimir Sementsov-Ogievskiy , "qemu-block@nongnu.org" References: <20200116155452.30972-1-vsementsov@virtuozzo.com> <20200116155452.30972-3-vsementsov@virtuozzo.com> <0e865df2-7d21-b18f-b73c-2948577b9dcb@virtuozzo.com> <1313e55e-0eb1-890a-4e8e-2517f1e80d38@redhat.com> <04a32d71-31da-a3e3-5c5f-cc6465fc9402@virtuozzo.com> <6923bc19-d203-63af-b206-8fe18e4a01c6@redhat.com> <6e0c4e88-6745-a668-6946-237032fdbedd@virtuozzo.com> <29434a72-d2cc-5976-cbd7-ceac714d4d65@redhat.com> <08bc201e-b40c-a79c-6388-bd17a3a8316c@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: Date: Tue, 21 Jan 2020 15:01:10 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <08bc201e-b40c-a79c-6388-bd17a3a8316c@virtuozzo.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="e2nuHTFvzX5XZGAvRfGeOwebI40A4q42k" X-detected-operating-system: by eggs.gnu.org: GNU/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-devel@nongnu.org" , "qemu-stable@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) --e2nuHTFvzX5XZGAvRfGeOwebI40A4q42k Content-Type: multipart/mixed; boundary="DUcNDpWZKEle0czoYsuP8srpBcwGUwOEv" --DUcNDpWZKEle0czoYsuP8srpBcwGUwOEv Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 21.01.20 14:55, Vladimir Sementsov-Ogievskiy wrote: > 21.01.2020 16:51, Max Reitz wrote: >> On 21.01.20 14:48, Vladimir Sementsov-Ogievskiy wrote: >>> 21.01.2020 15:39, Max Reitz wrote: >>>> On 21.01.20 11:40, Vladimir Sementsov-Ogievskiy wrote: >>>>> 21.01.2020 12:41, Max Reitz wrote: >>>>>> On 21.01.20 10:23, Vladimir Sementsov-Ogievskiy wrote: >>>>>>> 21.01.2020 12:14, Max Reitz wrote: >>>>>>>> On 20.01.20 18:20, Vladimir Sementsov-Ogievskiy wrote: >>>>>>>>> 20.01.2020 20:04, Max Reitz wrote: >>>>>>>>>> On 16.01.20 16:54, Vladimir Sementsov-Ogievskiy wrote: >>>>>>>>>>> This test checks that bug is really fixed by previous commit. >>>>>>>>>>> >>>>>>>>>>> Cc: qemu-stable@nongnu.org # v4.2.0 >>>>>>>>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy >>>>>>>>>>> --- >>>>>>>>>>> tests/qemu-iotests/283 | 75 +++++++++++++++++++++++++= +++++++++++++ >>>>>>>>>>> tests/qemu-iotests/283.out | 8 ++++ >>>>>>>>>>> tests/qemu-iotests/group | 1 + >>>>>>>>>>> 3 files changed, 84 insertions(+) >>>>>>>>>>> create mode 100644 tests/qemu-iotests/283 >>>>>>>>>>> create mode 100644 tests/qemu-iotests/283.out >>>>>>>>>> >>>>>>>>>> The test looks good to me, I just have a comment nit and a note = on the >>>>>>>>>> fact that this should probably be queued only after Thomas=E2=80= =99s =E2=80=9CEnable >>>>>>>>>> more iotests during "make check-block"=E2=80=9D series. >>>>>>>>>> >>>>>>>>>>> diff --git a/tests/qemu-iotests/283 b/tests/qemu-iotests/283 >>>>>>>>>>> new file mode 100644 >>>>>>>>>>> index 0000000000..f0f216d109 >>>>>>>>>>> --- /dev/null >>>>>>>>>>> +++ b/tests/qemu-iotests/283 >>>>>>>>>>> @@ -0,0 +1,75 @@ >>>>>>>>>>> +#!/usr/bin/env python >>>>>>>>>>> +# >>>>>>>>>>> +# Test for backup-top filter permission activation failure >>>>>>>>>>> +# >>>>>>>>>>> +# Copyright (c) 2019 Virtuozzo International GmbH. >>>>>>>>>>> +# >>>>>>>>>>> +# This program is free software; you can redistribute it and/o= r modify >>>>>>>>>>> +# it under the terms of the GNU General Public License as publ= ished by >>>>>>>>>>> +# the Free Software Foundation; either version 2 of the Licens= e, or >>>>>>>>>>> +# (at your option) any later version. >>>>>>>>>>> +# >>>>>>>>>>> +# This program is distributed in the hope that it will be usef= ul, >>>>>>>>>>> +# but WITHOUT ANY WARRANTY; without even the implied warranty = of >>>>>>>>>>> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See th= e >>>>>>>>>>> +# GNU General Public License for more details. >>>>>>>>>>> +# >>>>>>>>>>> +# You should have received a copy of the GNU General Public Li= cense >>>>>>>>>>> +# along with this program. If not, see . >>>>>>>>>>> +# >>>>>>>>>>> + >>>>>>>>>>> +import iotests >>>>>>>>>>> + >>>>>>>>>>> +# The test is unrelated to formats, restrict it to qcow2 to av= oid extra runs >>>>>>>>>>> +iotests.verify_image_format(supported_fmts=3D['qcow2']) >>>>>>>>>>> + >>>>>>>>>>> +size =3D 1024 * 1024 >>>>>>>>>>> + >>>>>>>>>>> +""" >>>>>>>>>>> +On activation, backup-top is going to unshare write permission= on its >>>>>>>>>>> +source child. It will be impossible for the following configur= ation: >>>>>>>>>> >>>>>>>>>> =E2=80=9CThe following configuration will become impossible=E2= =80=9D? >>>>>>>>> >>>>>>>>> Hmm, no, the configuration is possible. But "it", i.e. "unshare w= rite permission", >>>>>>>>> is impossible with such configuration.. >>>>>>>> >>>>>>>> But backup_top always unshares the write permission on the source. >>>>>>> >>>>>>> Yes, and I just try to say, that this action will fail. And the tes= t checks that it >>>>>>> fails (and it crashes with current master instead of fail). >>>>>> >>>>>> OK. So what I was trying to say is that the comment currently only >>>>>> states that this will fail. I=E2=80=99d prefer it to also reassure = me that it=E2=80=99s >>>>>> correct that this fails (because all writes on the backup source mus= t go >>>>>> through backup_top), and that this is exactly what we want to test h= ere. >>>>>> >>>>>> On first reading, I was wondering why exactly this comment would tel= l me >>>>>> all these things, because I didn=E2=80=99t know what the test wants = to test in >>>>>> the first place. >>>>>> >>>>>> Max >>>>> >>>>> Hmm, something like: >>>>> >>>>> Backup wants to copy a point-in-time state of the source node. So, it= catches all writes >>>>> to the source node by appending backup-top filter above it. So we han= dle all changes which >>>>> comes from source node parents. To prevent appearing of new writing p= arents during the >>>>> progress, backup-top unshares write permission on its source child. T= his has additional >>>>> implication: as this "unsharing" is propagated by default by backing/= file children, >>>>> backup-top conflicts with any side parents of source sub-tree with wr= ite permission. >>>>> And this is in good relation with the general idea: with such parents= we can't guarantee >>>>> point-in-time backup. >>>> >>>> Works for me (thanks :-)), but a shorter =E2=80=9CWhen performing a ba= ckup, all >>>> writes on the source subtree must go through the backup-top filter so = it >>>> can copy all data to the target before it is changed. Therefore, >>>> backup-top cannot allow other nodes to change data on its source child= .=E2=80=9D >>>> would work for me just as well. >>>> >>>>> So, trying to backup the configuration with writing side parents of >>>>> source sub-tree nodes should fail. Let's test it. >>> >>> But than, we need somehow link part about appending backup-top and so-o= n... >>> >>> When performing a backup, all writes on the source subtree must go thro= ugh the backup-top filter so it can copy all data to the target before it i= s changed. >>> backup-top filter is appended above source node, to achieve this thing,= so all parents of source node are handled. >>> A configuration with side parents of source sub-tree with write permiss= ion is unsupported (we'd have append several backup-top filter like nodes t= o handle such parents). >>> The test create an example of such configuration and checks that backup= fails. >> >> Sounds good! >> >> (Except maybe s/that backup fails/that a backup is then not allowed/? >> =E2=80=9Cbackup fails=E2=80=9D might also mean that the job just produce= s garbage.) >=20 > OK for me. May be "backup is then not allowed (blockdev-backup command sh= ould fail)". >=20 > Should I resend? I think it's better drop "auto" mark and not create extr= a dependency on other series. I=E2=80=99d prefer a resend so I don=E2=80=99t modify the comment in a way = you don=E2=80=99t want. You can keep the test in auto, as I=E2=80=99ve just merged Thomas=E2=80=99s= series (which was the dependency). Max --DUcNDpWZKEle0czoYsuP8srpBcwGUwOEv-- --e2nuHTFvzX5XZGAvRfGeOwebI40A4q42k Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl4nBCYACgkQ9AfbAGHV z0Cm2ggAjqK4jZpJkVQKtY3HFyT6nNVE+p/vChWoCiWFbQgCoIJEadr5p5yPnbkE zop+UIZxycxY0dB/sPWry2uk06JGNFxXQDJdz1vAPQVvCD95Xstp1SRKBAFtzL3f sNyHteJdSGd+f0q3rGrAHOPvvDuxz6ldwr9q1vA/5OFrSl1Pwh5Iq2GTS0UV1obt bHklFS14jgSqBLa2soUWYXAliI5Db0emeVcIvyVXcSedRRmoQ5j2TbNOf1Xk0LvY eoMLol57N6BeK1HSGvTfgSYgd9U5RMO7rzcs14c0toXl8AnVVX2lefFFGGCNvT6X nFBpBPp0zQa7XkCoCWLinMieW+OpXg== =w2rh -----END PGP SIGNATURE----- --e2nuHTFvzX5XZGAvRfGeOwebI40A4q42k--