xref: /qemu/tests/qemu-iotests/283 (revision 5086c997) 
1#!/usr/bin/env python3
2# group: auto quick
3#
4# Test for backup-top filter permission activation failure
5#
6# Copyright (c) 2019 Virtuozzo International GmbH.
7#
8# This program is free software; you can redistribute it and/or modify
9# it under the terms of the GNU General Public License as published by
10# the Free Software Foundation; either version 2 of the License, or
11# (at your option) any later version.
12#
13# This program is distributed in the hope that it will be useful,
14# but WITHOUT ANY WARRANTY; without even the implied warranty of
15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16# GNU General Public License for more details.
17#
18# You should have received a copy of the GNU General Public License
19# along with this program.  If not, see <http://www.gnu.org/licenses/>.
20#
21
22import iotests
23
24# The test is unrelated to formats, restrict it to qcow2 to avoid extra runs
25iotests.script_initialize(
26    supported_fmts=['qcow2'],
27)
28
29size = 1024 * 1024
30
31""" Test description
32
33When performing a backup, all writes on the source subtree must go through the
34backup-top filter so it can copy all data to the target before it is changed.
35backup-top filter is appended above source node, to achieve this thing, so all
36parents of source node are handled. A configuration with side parents of source
37sub-tree with write permission is unsupported (we'd have append several
38backup-top filter like nodes to handle such parents). The test create an
39example of such configuration and checks that a backup is then not allowed
40(blockdev-backup command should fail).
41
42The configuration:
43
44    ┌────────┐  target  ┌─────────────┐
45    │ target │ ◀─────── │ backup_top  │
46    └────────┘          └─────────────┘
47                            │
48                            │ backing
49                            ▼
50                        ┌─────────────┐
51                        │   source    │
52                        └─────────────┘
53                            │
54                            │ file
55                            ▼
56                        ┌─────────────┐  write perm   ┌───────┐
57                        │    base     │ ◀──────────── │ other │
58                        └─────────────┘               └───────┘
59
60On activation (see .active field of backup-top state in block/backup-top.c),
61backup-top is going to unshare write permission on its source child. Write
62unsharing will be propagated to the "source->base" link and will conflict with
63other node write permission. So permission update will fail and backup job will
64not be started.
65
66Note, that the only thing which prevents backup of running on such
67configuration is default permission propagation scheme. It may be altered by
68different block drivers, so backup will run in invalid configuration. But
69something is better than nothing. Also, before the previous commit (commit
70preceding this test creation), starting backup on such configuration led to
71crash, so current "something" is a lot better, and this test actual goal is
72to check that crash is fixed :)
73"""
74
75vm = iotests.VM()
76vm.launch()
77
78vm.qmp_log('blockdev-add', **{
79    'node-name': 'target',
80    'driver': 'null-co',
81    'size': size,
82})
83
84vm.qmp_log('blockdev-add', **{
85    'node-name': 'source',
86    'driver': 'blkdebug',
87    'image': {'node-name': 'base', 'driver': 'null-co', 'size': size}
88})
89
90vm.qmp_log('blockdev-add', **{
91    'node-name': 'other',
92    'driver': 'blkdebug',
93    'image': 'base',
94    'take-child-perms': ['write']
95})
96
97vm.qmp_log('blockdev-backup', sync='full', device='source', target='target')
98
99vm.shutdown()
100