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

Block layer patches:

- file-posix: Make auto-read-only dynamic
- Add x-blockdev-reopen QMP command
- Finalize block-latency-histogram QMP command
- gluster: Build fixes for newer lib version

# gpg: Signature made Tue 12 Mar 2019 19:30:31 GMT
# gpg:                using RSA key 7F09B272C88F2FD6
# 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: (28 commits)
  qemu-iotests: Test the x-blockdev-reopen QMP command
  block: Add an 'x-blockdev-reopen' QMP command
  block: Remove the AioContext parameter from bdrv_reopen_multiple()
  block: Add bdrv_reset_options_allowed()
  block: Add a 'mutable_opts' field to BlockDriver
  block: Allow changing the backing file on reopen
  block: Allow omitting the 'backing' option in certain cases
  block: Handle child references in bdrv_reopen_queue()
  block: Add 'keep_old_opts' parameter to bdrv_reopen_queue()
  block: Freeze the backing chain for the duration of the stream job
  block: Freeze the backing chain for the duration of the mirror job
  block: Freeze the backing chain for the duration of the commit job
  block: Allow freezing BdrvChild links
  nvme: fix write zeroes offset and count
  file-posix: Make auto-read-only dynamic
  file-posix: Prepare permission code for fd switching
  file-posix: Lock new fd in raw_reopen_prepare()
  file-posix: Store BDRVRawState.reopen_state during reopen
  file-posix: Factor out raw_reconfigure_getfd()
  file-posix: Fix bdrv_open_flags() for snapshot=on
  ...

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