Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Pull request

# gpg: Signature made Tue 27 Aug 2019 21:16:27 BST
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  block/qcow2: implement .bdrv_co_pwritev(_compressed)_part
  block/qcow2: implement .bdrv_co_preadv_part
  block/qcow2: refactor qcow2_co_preadv to use buffer-based io
  block/io: introduce bdrv_co_p{read, write}v_part
  block/io: bdrv_aligned_pwritev: use and support qiov_offset
  block/io: bdrv_aligned_preadv: use and support qiov_offset
  block/io: bdrv_co_do_copy_on_readv: lazy allocation
  block/io: bdrv_co_do_copy_on_readv: use and support qiov_offset
  block: define .*_part io handlers in BlockDriver
  block/io: refactor padding
  util/iov: improve qemu_iovec_is_zero
  util/iov: introduce qemu_iovec_init_extended

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