On 03/06/2018 02:48 PM, Stefan Hajnoczi wrote:
The blockdev-snapshot-sync command uses bdrv_append() to update all parents to
point at the external snapshot node.  This breaks BlockBackend's
blk_add/remove_aio_context_notifier(), which doesn't expect a BDS change.

Patch 1 fixes this by tracking AioContext notifiers in BlockBackend.

See the test case in Patch 2 for a reproducer.

Stefan Hajnoczi (2):
   block: let blk_add/remove_aio_context_notifier() tolerate BDS changes
   iotests: add 208 nbd-server + blockdev-snapshot-sync test case

  block/block-backend.c      | 63 ++++++++++++++++++++++++++++++++++++++++++++++
  block/trace-events         |  2 ++
  tests/qemu-iotests/208     | 55 ++++++++++++++++++++++++++++++++++++++++
  tests/qemu-iotests/208.out |  9 +++++++
  tests/qemu-iotests/group   |  1 +
  5 files changed, 130 insertions(+)
  create mode 100755 tests/qemu-iotests/208
  create mode 100644 tests/qemu-iotests/208.out

Whose tree should this series go through? MAINTAINERS didn't flag it as directly touching any files that normally affect my NBD queue, but given that the iotest that reproduces the problem uses NBD, I'm fine if you want it to go through me.

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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