I'm going to bring block-status driven, async copying process to
block-copy, to make it fast. The first step is to limit memory usage of
backup, here is it.

v2: [mostly by Max's comments]
Now based on master (Thank you Max!)
01: add Max's r-b
02: add Max's r-b
03: - refactor block_copy_do_copy goto/return
    - add small comment to block_copy_do_copy
04: - a lot of renaming and wording fixes
    - refactor to use "available" instead of "taken"
    - refactor co_get_from_shres
05: rebase on 04 changes
06: drop extra things from max_transfer calculation

Vladimir Sementsov-Ogievskiy (6):
  block/block-copy: allocate buffer in block_copy_with_bounce_buffer
  block/block-copy: limit copy_range_size to 16 MiB
  block/block-copy: refactor copying
  util: introduce SharedResource
  block/block-copy: add memory limit
  block/block-copy: increase buffered copy request

 include/block/block-copy.h        |   5 +-
 include/qemu/co-shared-resource.h |  71 ++++++++++++
 block/block-copy.c                | 182 +++++++++++++++---------------
 util/qemu-co-shared-resource.c    |  76 +++++++++++++
 block/trace-events                |   6 +-
 util/Makefile.objs                |   1 +
 6 files changed, 249 insertions(+), 92 deletions(-)
 create mode 100644 include/qemu/co-shared-resource.h
 create mode 100644 util/qemu-co-shared-resource.c

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2.21.0