v2 was here:
https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg10926.html

Since then:
rebase to master
patches 1-3/5 of v2 are in pull request
patch 4/5 in v2 (1/6 here) includes improvements from Vladimir
patches 3-6/6 here are new (and I hope to have public patches to
libnbd's 'nbdinfo --map' to take advantage of it posted soon...)

Based-on: <20201008185951.1026052-1-eblake@redhat.com>
([PULL 0/8] NBD patches through 2020-10-08)

Also available at:
https://repo.or.cz/qemu/ericb.git/shortlog/refs/tags/nbd-alloc-depth-v3

001/6:[0056] [FC] 'nbd: Add new qemu:allocation-depth metacontext'
002/6:[0002] [FC] 'nbd: Add 'qemu-nbd -A' to expose allocation depth'
003/6:[down] 'nbd: Update qapi to support multiple bitmaps'
004/6:[down] 'nbd: Simplify qemu bitmap context name'
005/6:[down] 'nbd: Refactor counting of meta contexts'
006/6:[down] 'nbd: Allow export of multiple bitmaps for one device'

Eric Blake (6):
  nbd: Add new qemu:allocation-depth metacontext
  nbd: Add 'qemu-nbd -A' to expose allocation depth
  nbd: Update qapi to support multiple bitmaps
  nbd: Simplify qemu bitmap context name
  nbd: Refactor counting of meta contexts
  nbd: Allow export of multiple bitmaps for one device

 docs/interop/nbd.txt       |  23 +++-
 docs/tools/qemu-nbd.rst    |   6 ++
 qapi/block-core.json       |   7 +-
 qapi/block-export.json     |  20 +++-
 include/block/nbd.h        |   8 +-
 blockdev-nbd.c             |  20 +++-
 nbd/server.c               | 210 +++++++++++++++++++++++++++++--------
 qemu-nbd.c                 |  25 +++--
 tests/qemu-iotests/291     |   6 +-
 tests/qemu-iotests/309     |  73 +++++++++++++
 tests/qemu-iotests/309.out |  22 ++++
 tests/qemu-iotests/group   |   1 +
 12 files changed, 350 insertions(+), 71 deletions(-)
 create mode 100755 tests/qemu-iotests/309
 create mode 100644 tests/qemu-iotests/309.out

-- 
2.28.0