0b877d09df
Parts of the block layer treat BDS.backing_file as if it were whatever the image header says (i.e., if it is a relative path, it is relative to the overlay), other parts treat it like a cache for bs->backing->bs->filename (relative paths are relative to the CWD). Considering bs->backing->bs->filename exists, let us make it mean the former. Among other things, this now allows the user to specify a base when using qemu-img to commit an image file in a directory that is not the CWD (assuming, everything uses relative filenames). Before this patch: $ ./qemu-img create -f qcow2 foo/bot.qcow2 1M $ ./qemu-img create -f qcow2 -b bot.qcow2 foo/mid.qcow2 $ ./qemu-img create -f qcow2 -b mid.qcow2 foo/top.qcow2 $ ./qemu-img commit -b mid.qcow2 foo/top.qcow2 qemu-img: Did not find 'mid.qcow2' in the backing chain of 'foo/top.qcow2' $ ./qemu-img commit -b foo/mid.qcow2 foo/top.qcow2 qemu-img: Did not find 'foo/mid.qcow2' in the backing chain of 'foo/top.qcow2' $ ./qemu-img commit -b $PWD/foo/mid.qcow2 foo/top.qcow2 qemu-img: Did not find '[...]/foo/mid.qcow2' in the backing chain of 'foo/top.qcow2' After this patch: $ ./qemu-img commit -b mid.qcow2 foo/top.qcow2 Image committed. $ ./qemu-img commit -b foo/mid.qcow2 foo/top.qcow2 qemu-img: Did not find 'foo/mid.qcow2' in the backing chain of 'foo/top.qcow2' $ ./qemu-img commit -b $PWD/foo/mid.qcow2 foo/top.qcow2 Image committed. With this change, bdrv_find_backing_image() must look at whether the user has overridden a BDS's backing file. If so, it can no longer use bs->backing_file, but must instead compare the given filename against the backing node's filename directly. Note that this changes the QAPI output for a node's backing_file. We had very inconsistent output there (sometimes what the image header said, sometimes the actual filename of the backing image). This inconsistent output was effectively useless, so we have to decide one way or the other. Considering that bs->backing_file usually at runtime contained the path to the image relative to qemu's CWD (or absolute), this patch changes QAPI's backing_file to always report the bs->backing->bs->filename from now on. If you want to receive the image header information, you have to refer to full-backing-filename. This necessitates a change to iotest 228. The interesting information it really wanted is the image header, and it can get that now, but it has to use full-backing-filename instead of backing_file. Because of this patch's changes to bs->backing_file's behavior, we also need some reference output changes. Along with the changes to bs->backing_file, stop updating BDS.backing_format in bdrv_backing_attach() as well. This way, ImageInfo's backing-filename and backing-filename-format fields will represent what the image header says and nothing else. iotest 245 changes in behavior: With the backing node no longer overriding the parent node's backing_file string, you can now omit the @backing option when reopening a node with neither a default nor a current backing file even if it used to have a backing node at some point. 273 also changes: The base image is opened without a format layer, so ImageInfo.backing-filename-format used to report "file" for the base image's overlay after blockdev-snapshot. However, the image header never says "file" anywhere, so it now reports $IMGFMT. Signed-off-by: Max Reitz <mreitz@redhat.com>
243 lines
7.8 KiB
Python
Executable File
243 lines
7.8 KiB
Python
Executable File
#!/usr/bin/env python3
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#
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# Test for when a backing file is considered overridden (thus, a
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# json:{} filename is generated for the overlay) and when it is not
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#
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# Copyright (C) 2018 Red Hat, Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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# Creator/Owner: Max Reitz <mreitz@redhat.com>
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import iotests
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from iotests import log, qemu_img, filter_testfiles, filter_imgfmt, \
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filter_qmp_testfiles, filter_qmp_imgfmt
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# Need backing file and change-backing-file support
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iotests.script_initialize(
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supported_fmts=['qcow2', 'qed'],
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supported_platforms=['linux'],
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)
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def log_node_info(node):
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log('')
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log('bs->filename: ' + node['image']['filename'],
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filters=[filter_testfiles, filter_imgfmt])
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log('bs->backing_file: ' + node['image']['full-backing-filename'],
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filters=[filter_testfiles, filter_imgfmt])
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if 'backing-image' in node['image']:
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log('bs->backing->bs->filename: ' +
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node['image']['backing-image']['filename'],
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filters=[filter_testfiles, filter_imgfmt])
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else:
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log('bs->backing: (none)')
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log('')
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with iotests.FilePath('base.img') as base_img_path, \
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iotests.FilePath('top.img') as top_img_path, \
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iotests.VM() as vm:
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assert qemu_img('create', '-f', iotests.imgfmt, base_img_path, '64M') == 0
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# Choose a funny way to describe the backing filename
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assert qemu_img('create', '-f', iotests.imgfmt, '-b',
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'file:' + base_img_path, '-F', iotests.imgfmt,
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top_img_path) == 0
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vm.launch()
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log('--- Implicit backing file ---')
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log('')
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vm.qmp_log('blockdev-add',
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node_name='node0',
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driver=iotests.imgfmt,
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file={
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'driver': 'file',
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'filename': top_img_path
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},
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filters=[filter_qmp_testfiles, filter_qmp_imgfmt])
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# Filename should be plain, and the backing node filename should
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# not contain the "file:" prefix
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log_node_info(vm.node_info('node0'))
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vm.qmp_log('blockdev-del', node_name='node0')
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log('')
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log('--- change-backing-file ---')
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log('')
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vm.qmp_log('blockdev-add',
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node_name='node0',
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driver=iotests.imgfmt,
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file={
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'driver': 'file',
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'filename': top_img_path
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},
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filters=[filter_qmp_testfiles, filter_qmp_imgfmt])
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# Changing the backing file to a qemu-reported filename should
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# result in qemu accepting the corresponding BDS as the implicit
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# backing BDS (and thus not generate a json:{} filename).
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# So, first, query the backing filename.
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backing_filename = \
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vm.node_info('node0')['image']['backing-image']['filename']
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# Next, change the backing file to something different
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vm.qmp_log('change-backing-file',
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image_node_name='node0',
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device='node0',
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backing_file='null-co://',
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filters=[filter_qmp_testfiles])
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# Now, verify that we get a json:{} filename
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# (Image header says "null-co://", actual backing file still is
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# base_img_path)
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log_node_info(vm.node_info('node0'))
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# Change it back
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# (To get header and backing file in sync)
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vm.qmp_log('change-backing-file',
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image_node_name='node0',
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device='node0',
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backing_file=backing_filename,
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filters=[filter_qmp_testfiles])
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# And verify that we get our original results
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log_node_info(vm.node_info('node0'))
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# Finally, try a "file:" prefix. While this is actually what we
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# originally had in the image header, qemu will not reopen the
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# backing file here, so it cannot verify that this filename
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# "resolves" to the actual backing BDS's filename and will thus
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# consider both to be different.
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# (This may be fixed in the future.)
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vm.qmp_log('change-backing-file',
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image_node_name='node0',
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device='node0',
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backing_file=('file:' + backing_filename),
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filters=[filter_qmp_testfiles])
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# So now we should get a json:{} filename
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log_node_info(vm.node_info('node0'))
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# Remove and re-attach so we can see that (as in our first try),
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# opening the image anew helps qemu resolve the header backing
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# filename.
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vm.qmp_log('blockdev-del', node_name='node0')
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vm.qmp_log('blockdev-add',
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node_name='node0',
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driver=iotests.imgfmt,
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file={
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'driver': 'file',
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'filename': top_img_path
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},
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filters=[filter_qmp_testfiles, filter_qmp_imgfmt])
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log_node_info(vm.node_info('node0'))
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vm.qmp_log('blockdev-del', node_name='node0')
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log('')
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log('--- Override backing file ---')
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log('')
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# For this test, we need the plain filename in the image header
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# (because qemu cannot "canonicalize"/"resolve" the backing
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# filename unless the backing file is opened implicitly with the
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# overlay)
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assert qemu_img('create', '-f', iotests.imgfmt, '-b', base_img_path,
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'-F', iotests.imgfmt, top_img_path) == 0
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# You can only reliably override backing options by using a node
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# reference (or by specifying file.filename, but, well...)
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vm.qmp_log('blockdev-add', node_name='null', driver='null-co')
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vm.qmp_log('blockdev-add',
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node_name='node0',
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driver=iotests.imgfmt,
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file={
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'driver': 'file',
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'filename': top_img_path
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},
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backing='null',
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filters=[filter_qmp_testfiles, filter_qmp_imgfmt])
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# Should get a json:{} filename (and bs->backing_file is
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# null-co://, because that field actually has not much to do
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# with the header backing filename (except that it is changed by
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# change-backing-file))
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log_node_info(vm.node_info('node0'))
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# Detach the backing file by reopening the whole thing
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vm.qmp_log('blockdev-del', node_name='node0')
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vm.qmp_log('blockdev-del', node_name='null')
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vm.qmp_log('blockdev-add',
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node_name='node0',
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driver=iotests.imgfmt,
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file={
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'driver': 'file',
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'filename': top_img_path
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},
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backing=None,
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filters=[filter_qmp_testfiles, filter_qmp_imgfmt])
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# Should get a json:{} filename (because we overrode the backing
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# file to not be there)
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log_node_info(vm.node_info('node0'))
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# Open the original backing file
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vm.qmp_log('blockdev-add',
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node_name='original-backing',
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driver=iotests.imgfmt,
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file={
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'driver': 'file',
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'filename': base_img_path
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},
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filters=[filter_qmp_testfiles, filter_qmp_imgfmt])
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# Attach the original backing file to its overlay
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vm.qmp_log('blockdev-snapshot',
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node='original-backing',
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overlay='node0')
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# This should give us the original plain result
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log_node_info(vm.node_info('node0'))
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vm.qmp_log('blockdev-del', node_name='node0')
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vm.qmp_log('blockdev-del', node_name='original-backing')
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vm.shutdown()
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