@@ -253,8 +253,9 @@ class TestYieldingAndTimers(iotests.QMPTestCase):
self.create_nbd_export()
# Simple VM with an NBD block device connected to the NBD export
- # provided by the QSD
+ # provided by the QSD, and an (initially unused) iothread
self.vm = iotests.VM()
+ self.vm.add_object('iothread,id=iothr')
self.vm.add_blockdev('nbd,node-name=nbd,server.type=unix,' +
f'server.path={self.sock},export=exp,' +
'reconnect-delay=1,open-timeout=1')
@@ -299,19 +300,40 @@ class TestYieldingAndTimers(iotests.QMPTestCase):
# thus not see the error, and so the test will pass.)
time.sleep(2)
+ def test_yield_in_iothread(self):
+ # Move the NBD node to the I/O thread; the NBD block driver should
+ # attach the connection's QIOChannel to that thread's AioContext, too
+ result = self.vm.qmp('x-blockdev-set-iothread',
+ node_name='nbd', iothread='iothr')
+ self.assert_qmp(result, 'return', {})
+
+ # Do some I/O that will be throttled by the QSD, so that the network
+ # connection hopefully will yield here. When it is resumed, it must
+ # then be resumed in the I/O thread's AioContext.
+ result = self.vm.qmp('human-monitor-command',
+ command_line='qemu-io nbd "read 0 128K"')
+ self.assert_qmp(result, 'return', '')
+
def create_nbd_export(self):
assert self.qsd is None
- # Simple NBD export of a null-co BDS
+ # Export a throttled null-co BDS: Reads are throttled (max 64 kB/s),
+ # writes are not.
self.qsd = QemuStorageDaemon(
+ '--object',
+ 'throttle-group,id=thrgr,x-bps-read=65536,x-bps-read-max=65536',
+
'--blockdev',
'null-co,node-name=null,read-zeroes=true',
+ '--blockdev',
+ 'throttle,node-name=thr,file=null,throttle-group=thrgr',
+
'--nbd-server',
f'addr.type=unix,addr.path={self.sock}',
'--export',
- 'nbd,id=exp,node-name=null,name=exp,writable=true'
+ 'nbd,id=exp,node-name=thr,name=exp,writable=true'
)
def stop_nbd_export(self):
@@ -1,5 +1,5 @@
-.....
+......
----------------------------------------------------------------------
-Ran 5 tests
+Ran 6 tests
OK
Put an NBD block device into an I/O thread, and then read data from it, hoping that the NBD connection will yield during that read. When it does, the coroutine must be reentered in the block device's I/O thread, which will only happen if the NBD block driver attaches the connection's QIOChannel to the new AioContext. It did not do that after 4ddb5d2fde ("block/nbd: drop connection_co") and prior to "block/nbd: Move s->ioc on AioContext change", which would cause an assertion failure. To improve our chances of yielding, the NBD server is throttled to reading 64 kB/s, and the NBD client reads 128 kB, so it should yield at some point. Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com> --- tests/qemu-iotests/281 | 28 +++++++++++++++++++++++++--- tests/qemu-iotests/281.out | 4 ++-- 2 files changed, 27 insertions(+), 5 deletions(-)