Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- qemu-img create: Fail gracefully when backing file is an empty string
- Fixes related to filter block nodes ("Deal with filters" series)
- block/nvme: Various cleanups required to use multiple queues
- block/nvme: Use NvmeBar structure from "block/nvme.h"
- file-win32: Fix "locking" option
- iotests: Allow running from different directory

# gpg: Signature made Thu 10 Sep 2020 10:11:19 BST
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (65 commits)
  block/qcow2-cluster: Add missing "fallthrough" annotation
  block/nvme: Pair doorbell registers
  block/nvme: Use generic NvmeBar structure
  block/nvme: Group controller registers in NVMeRegs structure
  file-win32: Fix "locking" option
  iotests: Allow running from different directory
  iotests: Test committing to overridden backing
  iotests: Add test for commit in sub directory
  iotests: Add filter mirror test cases
  iotests: Add filter commit test cases
  iotests: Let complete_and_wait() work with commit
  iotests: Test that qcow2's data-file is flushed
  block: Leave BDS.backing_{file,format} constant
  block: Inline bdrv_co_block_status_from_*()
  blockdev: Fix active commit choice
  block: Drop backing_bs()
  qemu-img: Use child access functions
  nbd: Use CAF when looking for dirty bitmap
  commit: Deal with filters
  backup: Deal with filters
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --cc qapi/block-core.json
Simple merge