[Bug 1881231] Re: colo: Can not recover colo after svm failover twice

[Thomas Huth]

QEMU v5.2 has been released now and should contain the fix

** Changed in: qemu
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1881231

Title:
  colo: Can not  recover colo after svm failover twice

Status in QEMU:
  Fix Released

Bug description:
  Hi Expert,
  x-blockdev-change met some error, during testing colo

  Host os:
  CentOS Linux release 7.6.1810 (Core)

  Reproduce steps:
  1. create colo vm following 
https://github.com/qemu/qemu/blob/master/docs/COLO-FT.txt
  2. kill secondary vm and remove the nbd child from the quorum to wait for 
recover
    type those commands on primary vm console:
    { 'execute': 'x-blockdev-change', 'arguments': {'parent': 'colo-disk0', 
'child': 'children.1'}}
    { 'execute': 'human-monitor-command','arguments': {'command-line': 
'drive_del replication0'}}
    { 'execute': 'x-colo-lost-heartbeat'}
  3. recover colo
  4. kill secondary vm again after recover colo and type same commands as step 
2:
    { 'execute': 'x-blockdev-change', 'arguments': {'parent': 'colo-disk0', 
'child': 'children.1'}}
    { 'execute': 'human-monitor-command','arguments': {'command-line': 
'drive_del replication0'}}
    { 'execute': 'x-colo-lost-heartbeat'}
    but the first command got error
    { 'execute': 'x-blockdev-change', 'arguments': {'parent': 'colo-disk0', 
'child': 'children.1'}}
  {"error": {"class": "GenericError", "desc": "Node 'colo-disk0' does not have 
child 'children.1'"}}

  according to https://www.qemu.org/docs/master/qemu-qmp-ref.html
  Command: x-blockdev-change
  Dynamically reconfigure the block driver state graph. It can be used to add, 
remove, insert or replace a graph node. Currently only the Quorum driver 
implements this feature to add or remove its child. This is useful to fix a 
broken quorum child.

  It seems x-blockdev-change not worked as expected.

  Thanks.

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