iotests: Test two stream jobs in a single iothread

This tests two parallel stream jobs that will complete around the same
time and run on two different disks in the same iothreads. It is loosely
based on the bug report at https://issues.redhat.com/browse/RHEL-1761.

For me, this test hangs reliably with the originally reported bug in
blk_remove_bs(). After fixing it, it intermittently hangs for the bugs
fixed after it, missing AioContext unlocking in bdrv_graph_wrunlock()
and in stream_prepare(). The deadlocks seem to happen more frequently
when the test directory is on tmpfs.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231115172012.112727-5-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/tests/iothreads-stream

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+# group: rw quick auto
+#
+# Copyright (C) 2023 Red Hat, Inc.
+#
+# 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/>.
+#
+# Creator/Owner: Kevin Wolf <kwolf@redhat.com>
+
+import iotests
+
+iotests.script_initialize(supported_fmts=['qcow2'],
+                          supported_platforms=['linux'])
+iotests.verify_virtio_scsi_pci_or_ccw()
+
+with iotests.FilePath('disk1.img') as base1_path, \
+     iotests.FilePath('disk1-snap.img') as snap1_path, \
+     iotests.FilePath('disk2.img') as base2_path, \
+     iotests.FilePath('disk2-snap.img') as snap2_path, \
+     iotests.VM() as vm:
+
+    img_size = '10M'
+
+    # Only one iothread for both disks
+    vm.add_object('iothread,id=iothread0')
+    vm.add_device('virtio-scsi,iothread=iothread0')
+
+    iotests.log('Preparing disks...')
+    for i, base_path, snap_path in ((0, base1_path, snap1_path),
+                                    (1, base2_path, snap2_path)):
+        iotests.qemu_img_create('-f', iotests.imgfmt, base_path, img_size)
+        iotests.qemu_img_create('-f', iotests.imgfmt, '-b', base_path,
+                                '-F', iotests.imgfmt, snap_path)
+
+        iotests.qemu_io_log('-c', f'write 0 {img_size}', base_path)
+
+        vm.add_blockdev(f'file,node-name=disk{i}-base-file,'
+                        f'filename={base_path}')
+        vm.add_blockdev(f'qcow2,node-name=disk{i}-base,file=disk{i}-base-file')
+        vm.add_blockdev(f'file,node-name=disk{i}-file,filename={snap_path}')
+        vm.add_blockdev(f'qcow2,node-name=disk{i},file=disk{i}-file,'
+                        f'backing=disk{i}-base')
+        vm.add_device(f'scsi-hd,drive=disk{i}')
+
+    iotests.log('Launching VM...')
+    vm.launch()
+
+    iotests.log('Starting stream jobs...')
+    iotests.log(vm.qmp('block-stream', device='disk0', job_id='job0'))
+    iotests.log(vm.qmp('block-stream', device='disk1', job_id='job1'))
+
+    finished = 0
+    while True:
+        try:
+            ev = vm.event_wait('JOB_STATUS_CHANGE', timeout=0.1)
+            if ev is not None and ev['data']['status'] == 'null':
+                finished += 1
+                # The test is done once both jobs are gone
+                if finished == 2:
+                    break
+        except TimeoutError:
+            pass
+        vm.cmd('query-jobs')

tests/qemu-iotests/tests/iothreads-stream.out

@@ -0,0 +1,11 @@
+Preparing disks...
+wrote 10485760/10485760 bytes at offset 0
+10 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+wrote 10485760/10485760 bytes at offset 0
+10 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+Launching VM...
+Starting stream jobs...
+{"return": {}}
+{"return": {}}