iotests: add copy-before-write: on-cbw-error tests

Add tests for new option of copy-before-write filter: on-cbw-error.

Note that we use QEMUMachine instead of VM class, because in further
commit we'll want to use throttling which doesn't work with -accel
qtest used by VM.

We also touch pylintrc to not break iotest 297.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
  [vsementsov: add arguments to QEMUMachine constructor]
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

tests/qemu-iotests/pylintrc

@@ -51,3 +51,8 @@ notes=FIXME,
 
 # Maximum number of characters on a single line.
 max-line-length=79
+
+
+[SIMILARITIES]
+
+min-similarity-lines=6

tests/qemu-iotests/tests/copy-before-write

@@ -0,0 +1,135 @@
+#!/usr/bin/env python3
+# group: auto backup
+#
+# Copyright (c) 2022 Virtuozzo International GmbH
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import os
+import re
+
+from qemu.machine import QEMUMachine
+
+import iotests
+from iotests import qemu_img_create, qemu_io
+
+
+temp_img = os.path.join(iotests.test_dir, 'temp')
+source_img = os.path.join(iotests.test_dir, 'source')
+size = '1M'
+
+
+class TestCbwError(iotests.QMPTestCase):
+    def tearDown(self):
+        self.vm.shutdown()
+        os.remove(temp_img)
+        os.remove(source_img)
+
+    def setUp(self):
+        qemu_img_create('-f', iotests.imgfmt, source_img, size)
+        qemu_img_create('-f', iotests.imgfmt, temp_img, size)
+        qemu_io('-c', 'write 0 1M', source_img)
+
+        opts = ['-nodefaults', '-display', 'none', '-machine', 'none']
+        self.vm = QEMUMachine(iotests.qemu_prog, opts,
+                              base_temp_dir=iotests.test_dir,
+                              sock_dir=iotests.sock_dir)
+        self.vm.launch()
+
+    def do_cbw_error(self, on_cbw_error):
+        result = self.vm.qmp('blockdev-add', {
+            'node-name': 'cbw',
+            'driver': 'copy-before-write',
+            'on-cbw-error': on_cbw_error,
+            'file': {
+                'driver': iotests.imgfmt,
+                'file': {
+                    'driver': 'file',
+                    'filename': source_img,
+                }
+            },
+            'target': {
+                'driver': iotests.imgfmt,
+                'file': {
+                    'driver': 'blkdebug',
+                    'image': {
+                        'driver': 'file',
+                        'filename': temp_img
+                    },
+                    'inject-error': [
+                        {
+                            'event': 'write_aio',
+                            'errno': 5,
+                            'immediately': False,
+                            'once': True
+                        }
+                    ]
+                }
+            }
+        })
+        self.assert_qmp(result, 'return', {})
+
+        result = self.vm.qmp('blockdev-add', {
+            'node-name': 'access',
+            'driver': 'snapshot-access',
+            'file': 'cbw'
+        })
+        self.assert_qmp(result, 'return', {})
+
+        result = self.vm.qmp('human-monitor-command',
+                             command_line='qemu-io cbw "write 0 1M"')
+        self.assert_qmp(result, 'return', '')
+
+        result = self.vm.qmp('human-monitor-command',
+                             command_line='qemu-io access "read 0 1M"')
+        self.assert_qmp(result, 'return', '')
+
+        self.vm.shutdown()
+        log = self.vm.get_log()
+        log = re.sub(r'^\[I \d+\.\d+\] OPENED\n', '', log)
+        log = re.sub(r'\[I \+\d+\.\d+\] CLOSED\n?$', '', log)
+        log = iotests.filter_qemu_io(log)
+        return log
+
+    def test_break_snapshot_on_cbw_error(self):
+        """break-snapshot behavior:
+        Guest write succeed, but further snapshot-read fails, as snapshot is
+        broken.
+        """
+        log = self.do_cbw_error('break-snapshot')
+
+        self.assertEqual(log, """\
+wrote 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read failed: Permission denied
+""")
+
+    def test_break_guest_write_on_cbw_error(self):
+        """break-guest-write behavior:
+        Guest write fails, but snapshot-access continues working and further
+        snapshot-read succeeds.
+        """
+        log = self.do_cbw_error('break-guest-write')
+
+        self.assertEqual(log, """\
+write failed: Input/output error
+read 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+""")
+
+
+if __name__ == '__main__':
+    iotests.main(supported_fmts=['qcow2'],
+                 supported_protocols=['file'])

tests/qemu-iotests/tests/copy-before-write.out

@@ -0,0 +1,5 @@
+..
+----------------------------------------------------------------------
+Ran 2 tests
+
+OK