iotests: Refactor blockdev-reopen test for iothreads

We'll want to test more than one successful case in the future, so
prepare the test for that by a refactoring that runs each scenario in a
separate VM.

test_iothreads_switch_{backing,overlay} currently produce errors, but
these are cases that should actually work, by switching either the
backing file node or the overlay node to the AioContext of the other
node.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Message-Id: <20200306141413.30705-2-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

2 files changed, 39 insertions, 12 deletions

diff --git a/tests/qemu-iotests/245 b/tests/qemu-iotests/245
index 489bf78bd0..7d9eb6285c 100755
--- a/tests/qemu-iotests/245
+++ b/tests/qemu-iotests/245
@@ -970,8 +970,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
         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):
+    def run_test_iothreads(self, iothread_a, iothread_b, errmsg = None):
         opts = hd_opts(0)
         result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
         self.assert_qmp(result, 'return', {})
@@ -986,20 +985,48 @@ class TestBlockdevReopen(iotests.QMPTestCase):
         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')
+        result = self.vm.qmp('device_add', driver='virtio-scsi', id='scsi0',
+                             iothread=iothread_a)
         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')
+        result = self.vm.qmp('device_add', driver='virtio-scsi', id='scsi1',
+                             iothread=iothread_b)
         self.assert_qmp(result, 'return', {})
 
-        self.reopen(opts, {'backing': 'hd2'}, "Cannot use a new backing file with a different AioContext")
+        if iothread_a:
+            result = self.vm.qmp('device_add', driver='scsi-hd', drive='hd0',
+                                 share_rw=True, bus="scsi0.0")
+            self.assert_qmp(result, 'return', {})
 
-        result = self.vm.qmp('x-blockdev-set-iothread', node_name='hd2', iothread='iothread0')
-        self.assert_qmp(result, 'return', {})
+        if iothread_b:
+            result = self.vm.qmp('device_add', driver='scsi-hd', drive='hd2',
+                                 share_rw=True, bus="scsi1.0")
+            self.assert_qmp(result, 'return', {})
 
-        self.reopen(opts, {'backing': 'hd2'})
+        # Attaching the backing file may or may not work
+        self.reopen(opts, {'backing': 'hd2'}, errmsg)
+
+        # But removing the backing file should always work
+        self.reopen(opts, {'backing': None})
+
+        self.vm.shutdown()
+
+    # We don't allow setting a backing file that uses a different AioContext if
+    # neither of them can switch to the other AioContext
+    def test_iothreads_error(self):
+        self.run_test_iothreads('iothread0', 'iothread1',
+                                "Cannot use a new backing file with a different AioContext")
+
+    def test_iothreads_compatible_users(self):
+        self.run_test_iothreads('iothread0', 'iothread0')
+
+    def test_iothreads_switch_backing(self):
+        self.run_test_iothreads('iothread0', None,
+                                "Cannot use a new backing file with a different AioContext")
+
+    def test_iothreads_switch_overlay(self):
+        self.run_test_iothreads(None, 'iothread0',
+                                "Cannot use a new backing file with a different AioContext")
 
 if __name__ == '__main__':
     iotests.main(supported_fmts=["qcow2"],
diff --git a/tests/qemu-iotests/245.out b/tests/qemu-iotests/245.out
index a19de5214d..682b93394d 100644
--- a/tests/qemu-iotests/245.out
+++ b/tests/qemu-iotests/245.out
@@ -1,6 +1,6 @@
-..................
+.....................
 ----------------------------------------------------------------------
-Ran 18 tests
+Ran 21 tests
 
 OK
 {"execute": "job-finalize", "arguments": {"id": "commit0"}}