From 2ed48247fd39ade97164dee3c65162b96a116f14 Mon Sep 17 00:00:00 2001 From: Hanna Reitz Date: Fri, 4 Feb 2022 12:10:12 +0100 Subject: [PATCH 6/6] iotests/281: Let NBD connection yield in iothread RH-Author: Hanna Reitz RH-MergeRequest: 117: block/nbd: Handle AioContext changes RH-Commit: [6/6] a23706f34022d301eb7ffc84fc0d0a77d72b9844 RH-Bugzilla: 2035185 RH-Acked-by: Kevin Wolf RH-Acked-by: Eric Blake RH-Acked-by: Stefan Hajnoczi 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 Signed-off-by: Hanna Reitz Signed-off-by: Vladimir Sementsov-Ogievskiy (cherry picked from commit 8cfbe929e8c26050f0a4580a1606a370a947d4ce) Signed-off-by: Hanna Reitz --- tests/qemu-iotests/281 | 28 +++++++++++++++++++++++++--- tests/qemu-iotests/281.out | 4 ++-- 2 files changed, 27 insertions(+), 5 deletions(-) diff --git a/tests/qemu-iotests/281 b/tests/qemu-iotests/281 index 13c588be75..b2ead7f388 100755 --- a/tests/qemu-iotests/281 +++ b/tests/qemu-iotests/281 @@ -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') @@ -293,19 +294,40 @@ 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): diff --git a/tests/qemu-iotests/281.out b/tests/qemu-iotests/281.out index 914e3737bd..3f8a935a08 100644 --- a/tests/qemu-iotests/281.out +++ b/tests/qemu-iotests/281.out @@ -1,5 +1,5 @@ -..... +...... ---------------------------------------------------------------------- -Ran 5 tests +Ran 6 tests OK -- 2.27.0