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From b56684f6c1bef4fb5bf87ac5a1106d3830c05ad0 Mon Sep 17 00:00:00 2001
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From: Hanna Reitz <hreitz@redhat.com>
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Date: Fri, 4 Feb 2022 12:10:10 +0100
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Subject: [PATCH 4/6] iotests/281: Test lingering timers
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RH-Author: Hanna Reitz <hreitz@redhat.com>
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RH-MergeRequest: 117: block/nbd: Handle AioContext changes
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RH-Commit: [4/6] aaad466941637a34224dc037bbea37d128b5676b
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RH-Bugzilla: 2035185
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Eric Blake <eblake@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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Prior to "block/nbd: Delete reconnect delay timer when done" and
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"block/nbd: Delete open timer when done", both of those timers would
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remain scheduled even after successfully (re-)connecting to the server,
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and they would not even be deleted when the BDS is deleted.
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This test constructs exactly this situation:
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(1) Configure an @open-timeout, so the open timer is armed, and
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(2) Configure a @reconnect-delay and trigger a reconnect situation
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    (which succeeds immediately), so the reconnect delay timer is armed.
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Then we immediately delete the BDS, and sleep for longer than the
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@open-timeout and @reconnect-delay.  Prior to said patches, this caused
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one (or both) of the timer CBs to access already-freed data.
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Accessing freed data may or may not crash, so this test can produce
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false successes, but I do not know how to show the problem in a better
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or more reliable way.  If you run this test on "block/nbd: Assert there
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are no timers when closed" and without the fix patches mentioned above,
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you should reliably see an assertion failure.
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(But all other tests that use the reconnect delay timer (264 and 277)
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will fail in that configuration, too; as will nbd-reconnect-on-open,
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which uses the open timer.)
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Remove this test from the quick group because of the two second sleep
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this patch introduces.
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(I decided to put this test case into 281, because the main bug this
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series addresses is in the interaction of the NBD block driver and I/O
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threads, which is precisely the scope of 281.  The test case for that
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other bug will also be put into the test class added here.
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Also, excuse the test class's name, I couldn't come up with anything
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better.  The "yield" part will make sense two patches from now.)
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Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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Signed-off-by: Hanna Reitz <hreitz@redhat.com>
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Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
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(cherry picked from commit eaf1e85d4ddefdbd197f393fa9c5acc7ba8133b0)
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Conflict:
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- @open-timeout was introduced after the 6.2 release, and has not been
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  backported.  Consequently, there is no open_timer, and we can (and
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  must) drop the respective parts of the test here.
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Signed-off-by: Hanna Reitz <hreitz@redhat.com>
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---
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 tests/qemu-iotests/281     | 73 ++++++++++++++++++++++++++++++++++++--
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 tests/qemu-iotests/281.out |  4 +--
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 2 files changed, 73 insertions(+), 4 deletions(-)
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diff --git a/tests/qemu-iotests/281 b/tests/qemu-iotests/281
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index 956698083f..13c588be75 100755
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--- a/tests/qemu-iotests/281
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+++ b/tests/qemu-iotests/281
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@@ -1,5 +1,5 @@
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 #!/usr/bin/env python3
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-# group: rw quick
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+# group: rw
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 #
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 # Test cases for blockdev + IOThread interactions
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 #
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@@ -20,8 +20,9 @@
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 #
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 import os
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+import time
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 import iotests
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-from iotests import qemu_img
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+from iotests import qemu_img, QemuStorageDaemon
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 image_len = 64 * 1024 * 1024
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@@ -243,6 +244,74 @@ class TestBlockdevBackupAbort(iotests.QMPTestCase):
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         # Hangs on failure, we expect this error.
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         self.assert_qmp(result, 'error/class', 'GenericError')
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+# Test for RHBZ#2033626
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+class TestYieldingAndTimers(iotests.QMPTestCase):
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+    sock = os.path.join(iotests.sock_dir, 'nbd.sock')
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+    qsd = None
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+
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+    def setUp(self):
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+        self.create_nbd_export()
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+
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+        # Simple VM with an NBD block device connected to the NBD export
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+        # provided by the QSD
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+        self.vm = iotests.VM()
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+        self.vm.add_blockdev('nbd,node-name=nbd,server.type=unix,' +
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+                             f'server.path={self.sock},export=exp,' +
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+                             'reconnect-delay=1')
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+
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+        self.vm.launch()
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+
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+    def tearDown(self):
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+        self.stop_nbd_export()
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+        self.vm.shutdown()
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+
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+    def test_timers_with_blockdev_del(self):
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+        # Stop and restart the NBD server, and do some I/O on the client to
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+        # trigger a reconnect and start the reconnect delay timer
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+        self.stop_nbd_export()
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+        self.create_nbd_export()
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+
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+        result = self.vm.qmp('human-monitor-command',
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+                             command_line='qemu-io nbd "write 0 512"')
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+        self.assert_qmp(result, 'return', '')
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+
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+        # Reconnect is done, so the reconnect delay timer should be gone.
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+        # (But there used to be a bug where it remained active, for which this
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+        # is a regression test.)
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+
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+        # Delete the BDS to see whether the timer is gone.  If it is not,
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+        # it will remain active, fire later, and then access freed data.
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+        # (Or, with "block/nbd: Assert there are no timers when closed"
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+        # applied, the assertion added in that patch will fail.)
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+        result = self.vm.qmp('blockdev-del', node_name='nbd')
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+        self.assert_qmp(result, 'return', {})
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+
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+        # Give the timer some time to fire (it has a timeout of 1 s).
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+        # (Sleeping in an iotest may ring some alarm bells, but note that if
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+        # the timing is off here, the test will just always pass.  If we kill
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+        # the VM too early, then we just kill the timer before it can fire,
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+        # thus not see the error, and so the test will pass.)
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+        time.sleep(2)
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+
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+    def create_nbd_export(self):
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+        assert self.qsd is None
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+
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+        # Simple NBD export of a null-co BDS
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+        self.qsd = QemuStorageDaemon(
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+            '--blockdev',
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+            'null-co,node-name=null,read-zeroes=true',
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+
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+            '--nbd-server',
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+            f'addr.type=unix,addr.path={self.sock}',
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+
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+            '--export',
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+            'nbd,id=exp,node-name=null,name=exp,writable=true'
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+        )
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+
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+    def stop_nbd_export(self):
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+        self.qsd.stop()
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+        self.qsd = None
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+
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 if __name__ == '__main__':
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     iotests.main(supported_fmts=['qcow2'],
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                  supported_protocols=['file'])
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diff --git a/tests/qemu-iotests/281.out b/tests/qemu-iotests/281.out
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index 89968f35d7..914e3737bd 100644
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--- a/tests/qemu-iotests/281.out
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+++ b/tests/qemu-iotests/281.out
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@@ -1,5 +1,5 @@
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-....
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+.....
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 ----------------------------------------------------------------------
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-Ran 4 tests
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+Ran 5 tests
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 OK
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-- 
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2.27.0
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