Hi all!

After a long delay here is v3.

v3 is rebased on top of big refactoring of nbd connection code, and on
top of last portion of it, not yet merged:
Based-on: <20210902103805.25686-1-vsementsov@virtuozzo.com>
   "[PATCH v6 0/5] block/nbd: drop connection_co"

So, the core patch (02) is changed a lot. QAPI interface added.

Vladimir Sementsov-Ogievskiy (9):
  nbd/client-connection: nbd_co_establish_connection(): fix non set errp
  qapi: make blockdev-add a coroutine command
  nbd: allow reconnect on open, with corresponding new options
  nbd/client-connection: nbd_co_establish_connection(): return real
    error
  nbd/client-connection: improve error message of cancelled attempt
  iotests.py: add qemu_tool_popen()
  iotests.py: add and use qemu_io_wrap_args()
  iotests.py: add qemu_io_popen()
  iotests: add nbd-reconnect-on-open test

 qapi/block-core.json                          | 12 +++-
 block/nbd.c                                   | 45 +++++++++++-
 nbd/client-connection.c                       | 56 +++++++++++----
 tests/qemu-iotests/iotests.py                 | 39 ++++++----
 .../qemu-iotests/tests/nbd-reconnect-on-open  | 71 +++++++++++++++++++
 .../tests/nbd-reconnect-on-open.out           | 11 +++
 6 files changed, 203 insertions(+), 31 deletions(-)
 create mode 100755 tests/qemu-iotests/tests/nbd-reconnect-on-open
 create mode 100644 tests/qemu-iotests/tests/nbd-reconnect-on-open.out

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2.29.2