Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2020-12-18' into staging

Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2020-12-18' into staging

Block patches:
- New block filter: preallocate (which, on writes beyond an image file's
  end, allocates big chunks of data so that such post-EOF writes will
  occur less frequently)
- write-zeroes and block-status support for Quorum
- Implementation of truncate for the nvme block driver similarly to the
  existing implementations for host block devices and iscsi devices
- Block layer refactoring: Drop the tighten_restrictions concept in the
  block permission functions
- iotest fixes

# gpg: Signature made Fri 18 Dec 2020 14:45:30 GMT
# gpg:                using RSA key 91BEB60A30DB3E8857D11829F407DB0061D5CF40
# gpg:                issuer "mreitz@redhat.com"
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2020-12-18: (30 commits)
  iotests: Fix _send_qemu_cmd with bash 5.1
  iotests/102: Pass $QEMU_HANDLE to _send_qemu_cmd
  block/nvme: Implement fake truncate() coroutine
  quorum: Implement bdrv_co_pwrite_zeroes()
  quorum: Implement bdrv_co_block_status()
  scripts/simplebench: add bench_prealloc.py
  simplebench/results_to_text: make executable
  simplebench/results_to_text: add difference line to the table
  simplebench/results_to_text: improve view of the table
  simplebench: move results_to_text() into separate file
  simplebench: rename ascii() to results_to_text()
  scripts/simplebench: use standard deviation for +- error
  scripts/simplebench: support iops
  scripts/simplebench: fix grammar: s/successed/succeeded/
  iotests: add 298 to test new preallocate filter driver
  iotests.py: execute_setup_common(): add required_fmts argument
  iotests: qemu_io_silent: support --image-opts
  qemu-io: add preallocate mode parameter for truncate command
  block: introduce preallocate filter
  block: bdrv_check_perm(): process children anyway
  ...

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