Signed-off-by: Max Reitz <mre...@redhat.com>
---
tests/qemu-iotests/041 | 152 +++++++++++++++++++++++++++++++++++++
tests/qemu-iotests/041.out | 4 +-
2 files changed, 154 insertions(+), 2 deletions(-)
diff --git a/tests/qemu-iotests/041 b/tests/qemu-iotests/041
index e4cc829fe2..6ea4764ae8 100755
--- a/tests/qemu-iotests/041
+++ b/tests/qemu-iotests/041
@@ -1265,6 +1265,158 @@ class TestReplaces(iotests.QMPTestCase):
self.vm.assert_block_path('filter0/file', 'target')
+ '''
+ See what happens when the @sync/@replaces configuration dictates
+ creating a loop.
+ '''
+ def test_loop(self):
+ qemu_img('create', '-f', iotests.imgfmt, test_img, str(1 * 1024 *
1024))
+
+ # Dummy group so we can create a NOP filter
+ result = self.vm.qmp('object-add', qom_type='throttle-group', id='tg0')
+ self.assert_qmp(result, 'return', {})
+
+ result = self.vm.qmp('blockdev-add', **{
+ 'driver': 'throttle',
+ 'node-name': 'source',
+ 'throttle-group': 'tg0',
+ 'file': {
+ 'driver': iotests.imgfmt,
+ 'node-name': 'filtered',
+ 'file': {
+ 'driver': 'file',
+ 'filename': test_img
+ }
+ }
+ })
+ self.assert_qmp(result, 'return', {})
+
+ # Block graph is now:
+ # source[throttle] --file--> filtered[qcow2] --file--> ...
+
+ result = self.vm.qmp('drive-mirror', job_id='mirror', device='source',
+ target=target_img, format=iotests.imgfmt,
+ node_name='target', sync='none',
+ replaces='filtered')
+
+ '''
+ Block graph before mirror exits would be (ignoring mirror_top):
+ source[throttle] --file--> filtered[qcow2] --file--> ...
+ target[qcow2] --file--> ...
+
+ Then, because of sync=none and drive-mirror in absolute-paths mode,
+ the source is attached to the target:
+ source[throttle] --file--> filtered[qcow2] --file--> ...
+ ^
+ backing
+ |
+ target[qcow2] --file--> ...
+
+ Replacing filtered by target would yield:
+ source[throttle] --file--> target[qcow2] --file--> ...
+ ^ |
+ +------- backing --------+
+
+ I.e., a loop. bdrv_replace_node() detects this and simply
+ does not let source's file link point to target. However,
+ that means that target cannot really replace source.
+
+ drive-mirror should detect this and not allow this case.
+ '''
+
+ self.assert_qmp(result, 'error/desc',
+ "Replacing 'filtered' by 'target' with this sync " + \
+ "mode would result in a loop, because the former " + \
+ "would be a child of the latter's backing file " + \
+ "('source') after the mirror job")
+
+ '''
+ Test what happens when there would be no loop with the pre-mirror
+ configuration, but something changes during the mirror job that asks
+ for a loop to be created during completion.
+ '''
+ def test_loop_during_mirror(self):
+ qemu_img('create', '-f', iotests.imgfmt, test_img, str(1 * 1024 *
1024))
+
+ result = self.vm.qmp('blockdev-add', **{
+ 'driver': 'null-co',
+ 'node-name': 'common-base',
+ 'read-zeroes': True,
+ 'size': 1 * 1024 * 1024
+ })
+ self.assert_qmp(result, 'return', {})
+
+ result = self.vm.qmp('blockdev-add', **{
+ 'driver': 'copy-on-read',
+ 'node-name': 'source',
+ 'file': 'common-base'
+ })
+ self.assert_qmp(result, 'return', {})
+
+ '''
+ x-blockdev-change can only add children to a quorum node that
+ have no parent yet, so we need an intermediate node between
+ target and common-base that has no parents other than target.
+ We cannot use any parent that would forward the RESIZE
+ permission (because the job takes it, but unshares it on the
+ source), so we make it a backing child of a qcow2 node.
+ Unfortunately, we cannot add backing files to Quorum nodes
+ (because of an op blocker), so we put another raw node between
+ the qcow2 node and common-base.
+ '''
+ result = self.vm.qmp('blockdev-add', **{
+ 'driver': 'qcow2',
+ 'node-name': 'base-parent',
+ 'file': {
+ 'driver': 'file',
+ 'filename': test_img
+ },
+ 'backing': {
+ 'driver': 'raw',
+ 'file': 'common-base'
+ }
+ })
+
+ # Add a quorum node with a single child, we will add
+ # base-parent to prepare a loop later
+ result = self.vm.qmp('blockdev-add', **{
+ 'driver': 'quorum',
+ 'node-name': 'target',
+ 'vote-threshold': 1,
+ 'children': [
+ {
+ 'driver': 'null-co',
+ 'read-zeroes': True
+ }
+ ]
+ })
+ self.assert_qmp(result, 'return', {})
+
+ result = self.vm.qmp('blockdev-mirror', job_id='mirror',
+ device='source', target='target', sync='full',
+ replaces='common-base')
+ self.assert_qmp(result, 'return', {})
+
+ result = self.vm.qmp('x-blockdev-change',
+ parent='target', node='base-parent')
+ self.assert_qmp(result, 'return', {})
+
+ '''
+ This asks for this configuration post-mirror:
+
+ source -> target (replaced common-base) -> base-parent
+ ^ |
+ | v
+ +----------------- [raw]
+
+ bdrv_replace_node() would not allow such a configuration, but
+ we should not pretend we can create it, so the mirror job
+ should fail during completion.
+ '''
+
+ self.complete_and_wait('mirror',
+ completion_error='Operation not permitted')
+
if __name__ == '__main__':
iotests.main(supported_fmts=['qcow2', 'qed'],
supported_protocols=['file'])
diff --git a/tests/qemu-iotests/041.out b/tests/qemu-iotests/041.out
index 877b76fd31..20a8158b99 100644
--- a/tests/qemu-iotests/041.out
+++ b/tests/qemu-iotests/041.out
@@ -1,5 +1,5 @@
-..............................................................................................
+................................................................................................
----------------------------------------------------------------------
-Ran 94 tests
+Ran 96 tests
OK
--
2.21.0
