qemu-iotests: Test the x-blockdev-reopen QMP command

This patch adds several tests for the x-blockdev-reopen QMP command.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 991 insertions, 0 deletions

diff --git a/tests/qemu-iotests/245 b/tests/qemu-iotests/245
new file mode 100644
index 0000000..7891a21
--- /dev/null
+++ b/tests/qemu-iotests/245
@@ -0,0 +1,991 @@
+#!/usr/bin/env python
+#
+# Test cases for the QMP 'x-blockdev-reopen' command
+#
+# Copyright (C) 2018-2019 Igalia, S.L.
+# Author: Alberto Garcia <berto@igalia.com>
+#
+# 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
+import iotests
+import copy
+import json
+from iotests import qemu_img, qemu_io
+
+hd_path = [
+    os.path.join(iotests.test_dir, 'hd0.img'),
+    os.path.join(iotests.test_dir, 'hd1.img'),
+    os.path.join(iotests.test_dir, 'hd2.img')
+]
+
+def hd_opts(idx):
+    return {'driver': iotests.imgfmt,
+            'node-name': 'hd%d' % idx,
+            'file': {'driver': 'file',
+                     'node-name': 'hd%d-file' % idx,
+                     'filename':  hd_path[idx] } }
+
+class TestBlockdevReopen(iotests.QMPTestCase):
+    total_io_cmds = 0
+
+    def setUp(self):
+        qemu_img('create', '-f', iotests.imgfmt, hd_path[0], '3M')
+        qemu_img('create', '-f', iotests.imgfmt, '-b', hd_path[0], hd_path[1])
+        qemu_img('create', '-f', iotests.imgfmt, hd_path[2], '3M')
+        qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0xa0  0 1M', hd_path[0])
+        qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0xa1 1M 1M', hd_path[1])
+        qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0xa2 2M 1M', hd_path[2])
+        self.vm = iotests.VM()
+        self.vm.launch()
+
+    def tearDown(self):
+        self.vm.shutdown()
+        self.check_qemu_io_errors()
+        os.remove(hd_path[0])
+        os.remove(hd_path[1])
+        os.remove(hd_path[2])
+
+    # The output of qemu-io is not returned by vm.hmp_qemu_io() but
+    # it's stored in the log and can only be read when the VM has been
+    # shut down. This function runs qemu-io and keeps track of the
+    # number of times it's been called.
+    def run_qemu_io(self, img, cmd):
+        result = self.vm.hmp_qemu_io(img, cmd)
+        self.assert_qmp(result, 'return', '')
+        self.total_io_cmds += 1
+
+    # Once the VM is shut down we can parse the log and see if qemu-io
+    # ran without errors.
+    def check_qemu_io_errors(self):
+        self.assertFalse(self.vm.is_running())
+        found = 0
+        log = self.vm.get_log()
+        for line in log.split("\n"):
+            if line.startswith("Pattern verification failed"):
+                raise Exception("%s (command #%d)" % (line, found))
+            if re.match("read .*/.* bytes at offset", line):
+                found += 1
+        self.assertEqual(found, self.total_io_cmds,
+                         "Expected output of %d qemu-io commands, found %d" %
+                         (found, self.total_io_cmds))
+
+    # Run x-blockdev-reopen with 'opts' but applying 'newopts'
+    # on top of it. The original 'opts' dict is unmodified
+    def reopen(self, opts, newopts = {}, errmsg = None):
+        opts = copy.deepcopy(opts)
+
+        # Apply the changes from 'newopts' on top of 'opts'
+        for key in newopts:
+            value = newopts[key]
+            # If key has the form "foo.bar" then we need to do
+            # opts["foo"]["bar"] = value, not opts["foo.bar"] = value
+            subdict = opts
+            while key.find('.') != -1:
+                [prefix, key] = key.split('.', 1)
+                subdict = opts[prefix]
+            subdict[key] = value
+
+        result = self.vm.qmp('x-blockdev-reopen', conv_keys = False, **opts)
+        if errmsg:
+            self.assert_qmp(result, 'error/class', 'GenericError')
+            self.assert_qmp(result, 'error/desc', errmsg)
+        else:
+            self.assert_qmp(result, 'return', {})
+
+
+    # Run query-named-block-nodes and return the specified entry
+    def get_node(self, node_name):
+        result = self.vm.qmp('query-named-block-nodes')
+        for node in result['return']:
+            if node['node-name'] == node_name:
+                return node
+        return None
+
+    # Run 'query-named-block-nodes' and compare its output with the
+    # value passed by the user in 'graph'
+    def check_node_graph(self, graph):
+        result = self.vm.qmp('query-named-block-nodes')
+        self.assertEqual(json.dumps(graph,  sort_keys=True),
+                         json.dumps(result, sort_keys=True))
+
+    # This test opens one single disk image (without backing files)
+    # and tries to reopen it with illegal / incorrect parameters.
+    def test_incorrect_parameters_single_file(self):
+        # Open 'hd0' only (no backing files)
+        opts = hd_opts(0)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+        original_graph = self.vm.qmp('query-named-block-nodes')
+
+        # We can reopen the image passing the same options
+        self.reopen(opts)
+
+        # We can also reopen passing a child reference in 'file'
+        self.reopen(opts, {'file': 'hd0-file'})
+
+        # We cannot change any of these
+        self.reopen(opts, {'node-name': 'not-found'}, "Cannot find node named 'not-found'")
+        self.reopen(opts, {'node-name': ''}, "Cannot find node named ''")
+        self.reopen(opts, {'node-name': None}, "Invalid parameter type for 'node-name', expected: string")
+        self.reopen(opts, {'driver': 'raw'}, "Cannot change the option 'driver'")
+        self.reopen(opts, {'driver': ''}, "Invalid parameter ''")
+        self.reopen(opts, {'driver': None}, "Invalid parameter type for 'driver', expected: string")
+        self.reopen(opts, {'file': 'not-found'}, "Cannot change the option 'file'")
+        self.reopen(opts, {'file': ''}, "Cannot change the option 'file'")
+        self.reopen(opts, {'file': None}, "Invalid parameter type for 'file', expected: BlockdevRef")
+        self.reopen(opts, {'file.node-name': 'newname'}, "Cannot change the option 'node-name'")
+        self.reopen(opts, {'file.driver': 'host_device'}, "Cannot change the option 'driver'")
+        self.reopen(opts, {'file.filename': hd_path[1]}, "Cannot change the option 'filename'")
+        self.reopen(opts, {'file.aio': 'native'}, "Cannot change the option 'aio'")
+        self.reopen(opts, {'file.locking': 'off'}, "Cannot change the option 'locking'")
+        self.reopen(opts, {'file.filename': None}, "Invalid parameter type for 'file.filename', expected: string")
+
+        # node-name is optional in BlockdevOptions, but x-blockdev-reopen needs it
+        del opts['node-name']
+        self.reopen(opts, {}, "Node name not specified")
+
+        # Check that nothing has changed
+        self.check_node_graph(original_graph)
+
+        # Remove the node
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd0')
+        self.assert_qmp(result, 'return', {})
+
+    # This test opens an image with a backing file and tries to reopen
+    # it with illegal / incorrect parameters.
+    def test_incorrect_parameters_backing_file(self):
+        # Open hd1 omitting the backing options (hd0 will be opened
+        # with the default options)
+        opts = hd_opts(1)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+        original_graph = self.vm.qmp('query-named-block-nodes')
+
+        # We can't reopen the image passing the same options, 'backing' is mandatory
+        self.reopen(opts, {}, "backing is missing for 'hd1'")
+
+        # Everything works if we pass 'backing' using the existing node name
+        for node in original_graph['return']:
+            if node['drv'] == iotests.imgfmt and node['file'] == hd_path[0]:
+                backing_node_name = node['node-name']
+        self.reopen(opts, {'backing': backing_node_name})
+
+        # We can't use a non-existing or empty (non-NULL) node as the backing image
+        self.reopen(opts, {'backing': 'not-found'}, "Cannot find device= nor node_name=not-found")
+        self.reopen(opts, {'backing': ''}, "Cannot find device= nor node_name=")
+
+        # We can reopen the image just fine if we specify the backing options
+        opts['backing'] = {'driver': iotests.imgfmt,
+                           'file': {'driver': 'file',
+                                    'filename': hd_path[0]}}
+        self.reopen(opts)
+
+        # We cannot change any of these options
+        self.reopen(opts, {'backing.node-name': 'newname'}, "Cannot change the option 'node-name'")
+        self.reopen(opts, {'backing.driver': 'raw'}, "Cannot change the option 'driver'")
+        self.reopen(opts, {'backing.file.node-name': 'newname'}, "Cannot change the option 'node-name'")
+        self.reopen(opts, {'backing.file.driver': 'host_device'}, "Cannot change the option 'driver'")
+
+        # Check that nothing has changed since the beginning
+        self.check_node_graph(original_graph)
+
+        # Remove the node
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd1')
+        self.assert_qmp(result, 'return', {})
+
+    # Reopen an image several times changing some of its options
+    def test_reopen(self):
+        # Open the hd1 image passing all backing options
+        opts = hd_opts(1)
+        opts['backing'] = hd_opts(0)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+        original_graph = self.vm.qmp('query-named-block-nodes')
+
+        # We can reopen the image passing the same options
+        self.reopen(opts)
+
+        # Reopen in read-only mode
+        self.assert_qmp(self.get_node('hd1'), 'ro', False)
+
+        self.reopen(opts, {'read-only': True})
+        self.assert_qmp(self.get_node('hd1'), 'ro', True)
+        self.reopen(opts)
+        self.assert_qmp(self.get_node('hd1'), 'ro', False)
+
+        # Change the cache options
+        self.assert_qmp(self.get_node('hd1'), 'cache/writeback', True)
+        self.assert_qmp(self.get_node('hd1'), 'cache/direct', False)
+        self.assert_qmp(self.get_node('hd1'), 'cache/no-flush', False)
+        self.reopen(opts, {'cache': { 'direct': True, 'no-flush': True }})
+        self.assert_qmp(self.get_node('hd1'), 'cache/writeback', True)
+        self.assert_qmp(self.get_node('hd1'), 'cache/direct', True)
+        self.assert_qmp(self.get_node('hd1'), 'cache/no-flush', True)
+
+        # Reopen again with the original options
+        self.reopen(opts)
+        self.assert_qmp(self.get_node('hd1'), 'cache/writeback', True)
+        self.assert_qmp(self.get_node('hd1'), 'cache/direct', False)
+        self.assert_qmp(self.get_node('hd1'), 'cache/no-flush', False)
+
+        # Change 'detect-zeroes' and 'discard'
+        self.assert_qmp(self.get_node('hd1'), 'detect_zeroes', 'off')
+        self.reopen(opts, {'detect-zeroes': 'on'})
+        self.assert_qmp(self.get_node('hd1'), 'detect_zeroes', 'on')
+        self.reopen(opts, {'detect-zeroes': 'unmap'},
+                    "setting detect-zeroes to unmap is not allowed " +
+                    "without setting discard operation to unmap")
+        self.assert_qmp(self.get_node('hd1'), 'detect_zeroes', 'on')
+        self.reopen(opts, {'detect-zeroes': 'unmap', 'discard': 'unmap'})
+        self.assert_qmp(self.get_node('hd1'), 'detect_zeroes', 'unmap')
+        self.reopen(opts)
+        self.assert_qmp(self.get_node('hd1'), 'detect_zeroes', 'off')
+
+        # Changing 'force-share' is currently not supported
+        self.reopen(opts, {'force-share': True}, "Cannot change the option 'force-share'")
+
+        # Change some qcow2-specific options
+        # No way to test for success other than checking the return message
+        if iotests.imgfmt == 'qcow2':
+            self.reopen(opts, {'l2-cache-entry-size': 128 * 1024},
+                        "L2 cache entry size must be a power of two "+
+                        "between 512 and the cluster size (65536)")
+            self.reopen(opts, {'l2-cache-size': 1024 * 1024,
+                               'cache-size':     512 * 1024},
+                        "l2-cache-size may not exceed cache-size")
+            self.reopen(opts, {'l2-cache-size':        4 * 1024 * 1024,
+                               'refcount-cache-size':  4 * 1024 * 1024,
+                               'l2-cache-entry-size': 32 * 1024})
+            self.reopen(opts, {'pass-discard-request': True})
+
+        # Check that nothing has changed since the beginning
+        # (from the parameters that we can check)
+        self.check_node_graph(original_graph)
+
+        # Check that the node names (other than the top-level one) are optional
+        del opts['file']['node-name']
+        del opts['backing']['node-name']
+        del opts['backing']['file']['node-name']
+        self.reopen(opts)
+        self.check_node_graph(original_graph)
+
+        # Reopen setting backing = null, this removes the backing image from the chain
+        self.reopen(opts, {'backing': None})
+        self.assert_qmp_absent(self.get_node('hd1'), 'image/backing-image')
+
+        # Open the 'hd0' image
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **hd_opts(0))
+        self.assert_qmp(result, 'return', {})
+
+        # Reopen the hd1 image setting 'hd0' as its backing image
+        self.reopen(opts, {'backing': 'hd0'})
+        self.assert_qmp(self.get_node('hd1'), 'image/backing-image/filename', hd_path[0])
+
+        # Check that nothing has changed since the beginning
+        self.reopen(hd_opts(0), {'read-only': True})
+        self.check_node_graph(original_graph)
+
+        # The backing file (hd0) is now a reference, we cannot change backing.* anymore
+        self.reopen(opts, {}, "Cannot change the option 'backing.driver'")
+
+        # We can't remove 'hd0' while it's a backing image of 'hd1'
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd0')
+        self.assert_qmp(result, 'error/class', 'GenericError')
+        self.assert_qmp(result, 'error/desc', "Node 'hd0' is busy: node is used as backing hd of 'hd1'")
+
+        # But we can remove both nodes if done in the proper order
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd1')
+        self.assert_qmp(result, 'return', {})
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd0')
+        self.assert_qmp(result, 'return', {})
+
+    # Reopen a raw image and see the effect of changing the 'offset' option
+    def test_reopen_raw(self):
+        opts = {'driver': 'raw', 'node-name': 'hd0',
+                'file': { 'driver': 'file',
+                          'filename': hd_path[0],
+                          'node-name': 'hd0-file' } }
+
+        # First we create a 2MB raw file, and fill each half with a
+        # different value
+        qemu_img('create', '-f', 'raw', hd_path[0], '2M')
+        qemu_io('-f', 'raw', '-c', 'write -P 0xa0  0 1M', hd_path[0])
+        qemu_io('-f', 'raw', '-c', 'write -P 0xa1 1M 1M', hd_path[0])
+
+        # Open the raw file with QEMU
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Read 1MB from offset 0
+        self.run_qemu_io("hd0", "read -P 0xa0  0 1M")
+
+        # Reopen the image with a 1MB offset.
+        # Now the results are different
+        self.reopen(opts, {'offset': 1024*1024})
+        self.run_qemu_io("hd0", "read -P 0xa1  0 1M")
+
+        # Reopen again with the original options.
+        # We get the original results again
+        self.reopen(opts)
+        self.run_qemu_io("hd0", "read -P 0xa0  0 1M")
+
+        # Remove the block device
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd0')
+        self.assert_qmp(result, 'return', {})
+
+    # Omitting an option should reset it to the default value, but if
+    # an option cannot be changed it shouldn't be possible to reset it
+    # to its default value either
+    def test_reset_default_values(self):
+        opts = {'driver': 'qcow2', 'node-name': 'hd0',
+                'file': { 'driver': 'file',
+                          'filename': hd_path[0],
+                          'x-check-cache-dropped': True, # This one can be changed
+                          'locking': 'off',              # This one can NOT be changed
+                          'node-name': 'hd0-file' } }
+
+        # Open the file with QEMU
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # file.x-check-cache-dropped can be changed...
+        self.reopen(opts, { 'file.x-check-cache-dropped': False })
+        # ...and dropped completely (resetting to the default value)
+        del opts['file']['x-check-cache-dropped']
+        self.reopen(opts)
+
+        # file.locking cannot be changed nor reset to the default value
+        self.reopen(opts, { 'file.locking': 'on' }, "Cannot change the option 'locking'")
+        del opts['file']['locking']
+        self.reopen(opts, {}, "Option 'locking' cannot be reset to its default value")
+        # But we can reopen it if we maintain its previous value
+        self.reopen(opts, { 'file.locking': 'off' })
+
+        # Remove the block device
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd0')
+        self.assert_qmp(result, 'return', {})
+
+    # This test modifies the node graph a few times by changing the
+    # 'backing' option on reopen and verifies that the guest data that
+    # is read afterwards is consistent with the graph changes.
+    def test_io_with_graph_changes(self):
+        opts = []
+
+        # Open hd0, hd1 and hd2 without any backing image
+        for i in range(3):
+            opts.append(hd_opts(i))
+            opts[i]['backing'] = None
+            result = self.vm.qmp('blockdev-add', conv_keys = False, **opts[i])
+            self.assert_qmp(result, 'return', {})
+
+        # hd0
+        self.run_qemu_io("hd0", "read -P 0xa0  0 1M")
+        self.run_qemu_io("hd0", "read -P 0    1M 1M")
+        self.run_qemu_io("hd0", "read -P 0    2M 1M")
+
+        # hd1 <- hd0
+        self.reopen(opts[0], {'backing': 'hd1'})
+
+        self.run_qemu_io("hd0", "read -P 0xa0  0 1M")
+        self.run_qemu_io("hd0", "read -P 0xa1 1M 1M")
+        self.run_qemu_io("hd0", "read -P 0    2M 1M")
+
+        # hd1 <- hd0 , hd1 <- hd2
+        self.reopen(opts[2], {'backing': 'hd1'})
+
+        self.run_qemu_io("hd2", "read -P 0     0 1M")
+        self.run_qemu_io("hd2", "read -P 0xa1 1M 1M")
+        self.run_qemu_io("hd2", "read -P 0xa2 2M 1M")
+
+        # hd1 <- hd2 <- hd0
+        self.reopen(opts[0], {'backing': 'hd2'})
+
+        self.run_qemu_io("hd0", "read -P 0xa0  0 1M")
+        self.run_qemu_io("hd0", "read -P 0xa1 1M 1M")
+        self.run_qemu_io("hd0", "read -P 0xa2 2M 1M")
+
+        # hd2 <- hd0
+        self.reopen(opts[2], {'backing': None})
+
+        self.run_qemu_io("hd0", "read -P 0xa0  0 1M")
+        self.run_qemu_io("hd0", "read -P 0    1M 1M")
+        self.run_qemu_io("hd0", "read -P 0xa2 2M 1M")
+
+        # hd2 <- hd1 <- hd0
+        self.reopen(opts[1], {'backing': 'hd2'})
+        self.reopen(opts[0], {'backing': 'hd1'})
+
+        self.run_qemu_io("hd0", "read -P 0xa0  0 1M")
+        self.run_qemu_io("hd0", "read -P 0xa1 1M 1M")
+        self.run_qemu_io("hd0", "read -P 0xa2 2M 1M")
+
+        # Illegal operation: hd2 is a child of hd1
+        self.reopen(opts[2], {'backing': 'hd1'},
+                    "Making 'hd1' a backing file of 'hd2' would create a cycle")
+
+        # hd2 <- hd0, hd2 <- hd1
+        self.reopen(opts[0], {'backing': 'hd2'})
+
+        self.run_qemu_io("hd1", "read -P 0     0 1M")
+        self.run_qemu_io("hd1", "read -P 0xa1 1M 1M")
+        self.run_qemu_io("hd1", "read -P 0xa2 2M 1M")
+
+        # More illegal operations
+        self.reopen(opts[2], {'backing': 'hd1'},
+                    "Making 'hd1' a backing file of 'hd2' would create a cycle")
+        self.reopen(opts[2], {'file': 'hd0-file'}, "Cannot change the option 'file'")
+
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd2')
+        self.assert_qmp(result, 'error/class', 'GenericError')
+        self.assert_qmp(result, 'error/desc', "Node 'hd2' is busy: node is used as backing hd of 'hd0'")
+
+        # hd1 doesn't have a backing file now
+        self.reopen(opts[1], {'backing': None})
+
+        self.run_qemu_io("hd1", "read -P 0     0 1M")
+        self.run_qemu_io("hd1", "read -P 0xa1 1M 1M")
+        self.run_qemu_io("hd1", "read -P 0    2M 1M")
+
+        # We can't remove the 'backing' option if the image has a
+        # default backing file
+        del opts[1]['backing']
+        self.reopen(opts[1], {}, "backing is missing for 'hd1'")
+
+        self.run_qemu_io("hd1", "read -P 0     0 1M")
+        self.run_qemu_io("hd1", "read -P 0xa1 1M 1M")
+        self.run_qemu_io("hd1", "read -P 0    2M 1M")
+
+    # This test verifies that we can't change the children of a block
+    # device during a reopen operation in a way that would create
+    # cycles in the node graph
+    def test_graph_cycles(self):
+        opts = []
+
+        # Open all three images without backing file
+        for i in range(3):
+            opts.append(hd_opts(i))
+            opts[i]['backing'] = None
+            result = self.vm.qmp('blockdev-add', conv_keys = False, **opts[i])
+            self.assert_qmp(result, 'return', {})
+
+        # hd1 <- hd0, hd1 <- hd2
+        self.reopen(opts[0], {'backing': 'hd1'})
+        self.reopen(opts[2], {'backing': 'hd1'})
+
+        # Illegal: hd2 is backed by hd1
+        self.reopen(opts[1], {'backing': 'hd2'},
+                    "Making 'hd2' a backing file of 'hd1' would create a cycle")
+
+        # hd1 <- hd0 <- hd2
+        self.reopen(opts[2], {'backing': 'hd0'})
+
+        # Illegal: hd2 is backed by hd0, which is backed by hd1
+        self.reopen(opts[1], {'backing': 'hd2'},
+                    "Making 'hd2' a backing file of 'hd1' would create a cycle")
+
+        # Illegal: hd1 cannot point to itself
+        self.reopen(opts[1], {'backing': 'hd1'},
+                    "Making 'hd1' a backing file of 'hd1' would create a cycle")
+
+        # Remove all backing files
+        self.reopen(opts[0])
+        self.reopen(opts[2])
+
+        ##########################################
+        # Add a blkverify node using hd0 and hd1 #
+        ##########################################
+        bvopts = {'driver': 'blkverify',
+                  'node-name': 'bv',
+                  'test': 'hd0',
+                  'raw': 'hd1'}
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **bvopts)
+        self.assert_qmp(result, 'return', {})
+
+        # blkverify doesn't currently allow reopening. TODO: implement this
+        self.reopen(bvopts, {}, "Block format 'blkverify' used by node 'bv'" +
+                    " does not support reopening files")
+
+        # Illegal: hd0 is a child of the blkverify node
+        self.reopen(opts[0], {'backing': 'bv'},
+                    "Making 'bv' a backing file of 'hd0' would create a cycle")
+
+        # Delete the blkverify node
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'bv')
+        self.assert_qmp(result, 'return', {})
+
+    # Misc reopen tests with different block drivers
+    def test_misc_drivers(self):
+        ####################
+        ###### quorum ######
+        ####################
+        for i in range(3):
+            opts = hd_opts(i)
+            # Open all three images without backing file
+            opts['backing'] = None
+            result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+            self.assert_qmp(result, 'return', {})
+
+        opts = {'driver': 'quorum',
+                'node-name': 'quorum0',
+                'children': ['hd0', 'hd1', 'hd2'],
+                'vote-threshold': 2}
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Quorum doesn't currently allow reopening. TODO: implement this
+        self.reopen(opts, {}, "Block format 'quorum' used by node 'quorum0'" +
+                    " does not support reopening files")
+
+        # You can't make quorum0 a backing file of hd0:
+        # hd0 is already a child of quorum0.
+        self.reopen(hd_opts(0), {'backing': 'quorum0'},
+                    "Making 'quorum0' a backing file of 'hd0' would create a cycle")
+
+        # Delete quorum0
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'quorum0')
+        self.assert_qmp(result, 'return', {})
+
+        # Delete hd0, hd1 and hd2
+        for i in range(3):
+            result = self.vm.qmp('blockdev-del', conv_keys = True,
+                                 node_name = 'hd%d' % i)
+            self.assert_qmp(result, 'return', {})
+
+        ######################
+        ###### blkdebug ######
+        ######################
+        opts = {'driver': 'blkdebug',
+                'node-name': 'bd',
+                'config': '/dev/null',
+                'image': hd_opts(0)}
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # blkdebug allows reopening if we keep the same options
+        self.reopen(opts)
+
+        # but it currently does not allow changes
+        self.reopen(opts, {'image': 'hd1'}, "Cannot change the option 'image'")
+        self.reopen(opts, {'align': 33554432}, "Cannot change the option 'align'")
+        self.reopen(opts, {'config': '/non/existent'}, "Cannot change the option 'config'")
+        del opts['config']
+        self.reopen(opts, {}, "Option 'config' cannot be reset to its default value")
+
+        # Delete the blkdebug node
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'bd')
+        self.assert_qmp(result, 'return', {})
+
+        ##################
+        ###### null ######
+        ##################
+        opts = {'driver': 'null-aio', 'node-name': 'root', 'size': 1024}
+
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # 1 << 30 is the default value, but we cannot change it explicitly
+        self.reopen(opts, {'size': (1 << 30)}, "Cannot change the option 'size'")
+
+        # We cannot change 'size' back to its default value either
+        del opts['size']
+        self.reopen(opts, {}, "Option 'size' cannot be reset to its default value")
+
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'root')
+        self.assert_qmp(result, 'return', {})
+
+        ##################
+        ###### file ######
+        ##################
+        opts = hd_opts(0)
+        opts['file']['locking'] = 'on'
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # 'locking' cannot be changed
+        del opts['file']['locking']
+        self.reopen(opts, {'file.locking': 'on'})
+        self.reopen(opts, {'file.locking': 'off'}, "Cannot change the option 'locking'")
+        self.reopen(opts, {}, "Option 'locking' cannot be reset to its default value")
+
+        # Trying to reopen the 'file' node directly does not make a difference
+        opts = opts['file']
+        self.reopen(opts, {'locking': 'on'})
+        self.reopen(opts, {'locking': 'off'}, "Cannot change the option 'locking'")
+        self.reopen(opts, {}, "Option 'locking' cannot be reset to its default value")
+
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd0')
+        self.assert_qmp(result, 'return', {})
+
+        ######################
+        ###### throttle ######
+        ######################
+        opts = { 'qom-type': 'throttle-group', 'id': 'group0',
+                 'props': { 'limits': { 'iops-total': 1000 } } }
+        result = self.vm.qmp('object-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        opts = { 'qom-type': 'throttle-group', 'id': 'group1',
+                 'props': { 'limits': { 'iops-total': 2000 } } }
+        result = self.vm.qmp('object-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Add a throttle filter with group = group0
+        opts = { 'driver': 'throttle', 'node-name': 'throttle0',
+                 'throttle-group': 'group0', 'file': hd_opts(0) }
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # We can reopen it if we keep the same options
+        self.reopen(opts)
+
+        # We can also reopen if 'file' is a reference to the child
+        self.reopen(opts, {'file': 'hd0'})
+
+        # This is illegal
+        self.reopen(opts, {'throttle-group': 'notfound'}, "Throttle group 'notfound' does not exist")
+
+        # But it's possible to change the group to group1
+        self.reopen(opts, {'throttle-group': 'group1'})
+
+        # Now group1 is in use, it cannot be deleted
+        result = self.vm.qmp('object-del', id = 'group1')
+        self.assert_qmp(result, 'error/class', 'GenericError')
+        self.assert_qmp(result, 'error/desc', "object 'group1' is in use, can not be deleted")
+
+        # Default options, this switches the group back to group0
+        self.reopen(opts)
+
+        # So now we cannot delete group0
+        result = self.vm.qmp('object-del', id = 'group0')
+        self.assert_qmp(result, 'error/class', 'GenericError')
+        self.assert_qmp(result, 'error/desc', "object 'group0' is in use, can not be deleted")
+
+        # But group1 is free this time, and it can be deleted
+        result = self.vm.qmp('object-del', id = 'group1')
+        self.assert_qmp(result, 'return', {})
+
+        # Let's delete the filter node
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'throttle0')
+        self.assert_qmp(result, 'return', {})
+
+        # And we can finally get rid of group0
+        result = self.vm.qmp('object-del', id = 'group0')
+        self.assert_qmp(result, 'return', {})
+
+    # If an image has a backing file then the 'backing' option must be
+    # passed on reopen. We don't allow leaving the option out in this
+    # case because it's unclear what the correct semantics would be.
+    def test_missing_backing_options_1(self):
+        # hd2
+        opts = hd_opts(2)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # hd0
+        opts = hd_opts(0)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # hd0 has no backing file: we can omit the 'backing' option
+        self.reopen(opts)
+
+        # hd2 <- hd0
+        self.reopen(opts, {'backing': 'hd2'})
+
+        # hd0 has a backing file: we must set the 'backing' option
+        self.reopen(opts, {}, "backing is missing for 'hd0'")
+
+        # hd2 can't be removed because it's the backing file of hd0
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd2')
+        self.assert_qmp(result, 'error/class', 'GenericError')
+        self.assert_qmp(result, 'error/desc', "Node 'hd2' is busy: node is used as backing hd of 'hd0'")
+
+        # Detach hd2 from hd0.
+        self.reopen(opts, {'backing': None})
+        self.reopen(opts, {}, "backing is missing for 'hd0'")
+
+        # Remove both hd0 and hd2
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd0')
+        self.assert_qmp(result, 'return', {})
+
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd2')
+        self.assert_qmp(result, 'return', {})
+
+    # If an image has default backing file (as part of its metadata)
+    # then the 'backing' option must be passed on reopen. We don't
+    # allow leaving the option out in this case because it's unclear
+    # what the correct semantics would be.
+    def test_missing_backing_options_2(self):
+        # hd0 <- hd1
+        # (hd0 is hd1's default backing file)
+        opts = hd_opts(1)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # hd1 has a backing file: we can't omit the 'backing' option
+        self.reopen(opts, {}, "backing is missing for 'hd1'")
+
+        # Let's detach the backing file
+        self.reopen(opts, {'backing': None})
+
+        # No backing file attached to hd1 now, but we still can't omit the 'backing' option
+        self.reopen(opts, {}, "backing is missing for 'hd1'")
+
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd1')
+        self.assert_qmp(result, 'return', {})
+
+    # Test that making 'backing' a reference to an existing child
+    # keeps its current options
+    def test_backing_reference(self):
+        # hd2 <- hd1 <- hd0
+        opts = hd_opts(0)
+        opts['backing'] = hd_opts(1)
+        opts['backing']['backing'] = hd_opts(2)
+        # Enable 'detect-zeroes' on all three nodes
+        opts['detect-zeroes'] = 'on'
+        opts['backing']['detect-zeroes'] = 'on'
+        opts['backing']['backing']['detect-zeroes'] = 'on'
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Reopen the chain passing the minimum amount of required options.
+        # By making 'backing' a reference to hd1 (instead of a sub-dict)
+        # we tell QEMU to keep its current set of options.
+        opts = {'driver': iotests.imgfmt,
+                'node-name': 'hd0',
+                'file': 'hd0-file',
+                'backing': 'hd1' }
+        self.reopen(opts)
+
+        # This has reset 'detect-zeroes' on hd0, but not on hd1 and hd2.
+        self.assert_qmp(self.get_node('hd0'), 'detect_zeroes', 'off')
+        self.assert_qmp(self.get_node('hd1'), 'detect_zeroes', 'on')
+        self.assert_qmp(self.get_node('hd2'), 'detect_zeroes', 'on')
+
+    # Test what happens if the graph changes due to other operations
+    # such as block-stream
+    def test_block_stream_1(self):
+        # hd1 <- hd0
+        opts = hd_opts(0)
+        opts['backing'] = hd_opts(1)
+        opts['backing']['backing'] = None
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Stream hd1 into hd0 and wait until it's done
+        result = self.vm.qmp('block-stream', conv_keys = True, job_id = 'stream0', device = 'hd0')
+        self.assert_qmp(result, 'return', {})
+        self.wait_until_completed(drive = 'stream0')
+
+        # Now we have only hd0
+        self.assertEqual(self.get_node('hd1'), None)
+
+        # We have backing.* options but there's no backing file anymore
+        self.reopen(opts, {}, "Cannot change the option 'backing.driver'")
+
+        # If we remove the 'backing' option then we can reopen hd0 just fine
+        del opts['backing']
+        self.reopen(opts)
+
+        # We can also reopen hd0 if we set 'backing' to null
+        self.reopen(opts, {'backing': None})
+
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd0')
+        self.assert_qmp(result, 'return', {})
+
+    # Another block_stream test
+    def test_block_stream_2(self):
+        # hd2 <- hd1 <- hd0
+        opts = hd_opts(0)
+        opts['backing'] = hd_opts(1)
+        opts['backing']['backing'] = hd_opts(2)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Stream hd1 into hd0 and wait until it's done
+        result = self.vm.qmp('block-stream', conv_keys = True, job_id = 'stream0',
+                             device = 'hd0', base_node = 'hd2')
+        self.assert_qmp(result, 'return', {})
+        self.wait_until_completed(drive = 'stream0')
+
+        # The chain is hd2 <- hd0 now. hd1 is missing
+        self.assertEqual(self.get_node('hd1'), None)
+
+        # The backing options in the dict were meant for hd1, but we cannot
+        # use them with hd2 because hd1 had a backing file while hd2 does not.
+        self.reopen(opts, {}, "Cannot change the option 'backing.driver'")
+
+        # If we remove hd1's options from the dict then things work fine
+        opts['backing'] = opts['backing']['backing']
+        self.reopen(opts)
+
+        # We can also reopen hd0 if we use a reference to the backing file
+        self.reopen(opts, {'backing': 'hd2'})
+
+        # But we cannot leave the option out
+        del opts['backing']
+        self.reopen(opts, {}, "backing is missing for 'hd0'")
+
+        # Now we can delete hd0 (and hd2)
+        result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd0')
+        self.assert_qmp(result, 'return', {})
+        self.assertEqual(self.get_node('hd2'), None)
+
+    # Reopen the chain during a block-stream job (from hd1 to hd0)
+    def test_block_stream_3(self):
+        # hd2 <- hd1 <- hd0
+        opts = hd_opts(0)
+        opts['backing'] = hd_opts(1)
+        opts['backing']['backing'] = hd_opts(2)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # hd2 <- hd0
+        result = self.vm.qmp('block-stream', conv_keys = True, job_id = 'stream0',
+                             device = 'hd0', base_node = 'hd2', speed = 512 * 1024)
+        self.assert_qmp(result, 'return', {})
+
+        # We can't remove hd2 while the stream job is ongoing
+        opts['backing']['backing'] = None
+        self.reopen(opts, {}, "Cannot change 'backing' link from 'hd1' to 'hd2'")
+
+        # We can't remove hd1 while the stream job is ongoing
+        opts['backing'] = None
+        self.reopen(opts, {}, "Cannot change 'backing' link from 'hd0' to 'hd1'")
+
+        self.wait_until_completed(drive = 'stream0')
+
+    # Reopen the chain during a block-stream job (from hd2 to hd1)
+    def test_block_stream_4(self):
+        # hd2 <- hd1 <- hd0
+        opts = hd_opts(0)
+        opts['backing'] = hd_opts(1)
+        opts['backing']['backing'] = hd_opts(2)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # hd1 <- hd0
+        result = self.vm.qmp('block-stream', conv_keys = True, job_id = 'stream0',
+                             device = 'hd1', speed = 512 * 1024)
+        self.assert_qmp(result, 'return', {})
+
+        # We can't reopen with the original options because that would
+        # make hd1 read-only and block-stream requires it to be read-write
+        self.reopen(opts, {}, "Can't set node 'hd1' to r/o with copy-on-read enabled")
+
+        # We can't remove hd2 while the stream job is ongoing
+        opts['backing']['backing'] = None
+        self.reopen(opts, {'backing.read-only': False}, "Cannot change 'backing' link from 'hd1' to 'hd2'")
+
+        # We can detach hd1 from hd0 because it doesn't affect the stream job
+        opts['backing'] = None
+        self.reopen(opts)
+
+        self.wait_until_completed(drive = 'stream0')
+
+    # Reopen the chain during a block-commit job (from hd0 to hd2)
+    def test_block_commit_1(self):
+        # hd2 <- hd1 <- hd0
+        opts = hd_opts(0)
+        opts['backing'] = hd_opts(1)
+        opts['backing']['backing'] = hd_opts(2)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        result = self.vm.qmp('block-commit', conv_keys = True, job_id = 'commit0',
+                             device = 'hd0', speed = 1024 * 1024)
+        self.assert_qmp(result, 'return', {})
+
+        # We can't remove hd2 while the commit job is ongoing
+        opts['backing']['backing'] = None
+        self.reopen(opts, {}, "Cannot change 'backing' link from 'hd1' to 'hd2'")
+
+        # We can't remove hd1 while the commit job is ongoing
+        opts['backing'] = None
+        self.reopen(opts, {}, "Cannot change 'backing' link from 'hd0' to 'hd1'")
+
+        event = self.vm.event_wait(name='BLOCK_JOB_READY')
+        self.assert_qmp(event, 'data/device', 'commit0')
+        self.assert_qmp(event, 'data/type', 'commit')
+        self.assert_qmp_absent(event, 'data/error')
+
+        result = self.vm.qmp('block-job-complete', device='commit0')
+        self.assert_qmp(result, 'return', {})
+
+        self.wait_until_completed(drive = 'commit0')
+
+    # Reopen the chain during a block-commit job (from hd1 to hd2)
+    def test_block_commit_2(self):
+        # hd2 <- hd1 <- hd0
+        opts = hd_opts(0)
+        opts['backing'] = hd_opts(1)
+        opts['backing']['backing'] = hd_opts(2)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        result = self.vm.qmp('block-commit', conv_keys = True, job_id = 'commit0',
+                             device = 'hd0', top_node = 'hd1', speed = 1024 * 1024)
+        self.assert_qmp(result, 'return', {})
+
+        # We can't remove hd2 while the commit job is ongoing
+        opts['backing']['backing'] = None
+        self.reopen(opts, {}, "Cannot change the option 'backing.driver'")
+
+        # We can't remove hd1 while the commit job is ongoing
+        opts['backing'] = None
+        self.reopen(opts, {}, "Cannot change backing link if 'hd0' has an implicit backing file")
+
+        # hd2 <- hd0
+        self.wait_until_completed(drive = 'commit0')
+
+        self.assert_qmp(self.get_node('hd0'), 'ro', False)
+        self.assertEqual(self.get_node('hd1'), None)
+        self.assert_qmp(self.get_node('hd2'), 'ro', True)
+
+    # We don't allow setting a backing file that uses a different AioContext
+    def test_iothreads(self):
+        opts = hd_opts(0)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        opts2 = hd_opts(2)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts2)
+        self.assert_qmp(result, 'return', {})
+
+        result = self.vm.qmp('object-add', qom_type='iothread', id='iothread0')
+        self.assert_qmp(result, 'return', {})
+
+        result = self.vm.qmp('object-add', qom_type='iothread', id='iothread1')
+        self.assert_qmp(result, 'return', {})
+
+        result = self.vm.qmp('x-blockdev-set-iothread', node_name='hd0', iothread='iothread0')
+        self.assert_qmp(result, 'return', {})
+
+        self.reopen(opts, {'backing': 'hd2'}, "Cannot use a new backing file with a different AioContext")
+
+        result = self.vm.qmp('x-blockdev-set-iothread', node_name='hd2', iothread='iothread1')
+        self.assert_qmp(result, 'return', {})
+
+        self.reopen(opts, {'backing': 'hd2'}, "Cannot use a new backing file with a different AioContext")
+
+        result = self.vm.qmp('x-blockdev-set-iothread', node_name='hd2', iothread='iothread0')
+        self.assert_qmp(result, 'return', {})
+
+        self.reopen(opts, {'backing': 'hd2'})
+
+if __name__ == '__main__':
+    iotests.main(supported_fmts=["qcow2"])