Hi all!

These series introduce backup-top driver. It's a filter-node, which
do copy-before-write operation. Mirror uses filter-node for handling
guest writes, let's move to filter-node (from write-notifiers) for
backup too.

v13 is queued in Max's branch, but I understand that new range locks
don't work in backup case. So, I've to resend.

v14: Drop range locks, keep old good in-flight requests waiting

12: new patch
14: use old request-waiting scheme instead of range locks

Vladimir Sementsov-Ogievskiy (14):
  block/backup: fix max_transfer handling for copy_range
  block/backup: fix backup_cow_with_offload for last cluster
  block/backup: split shareable copying part from backup_do_cow
  block/backup: improve comment about image fleecing
  block/backup: introduce BlockCopyState
  block/backup: fix block-comment style
  block: move block_copy from block/backup.c to separate file
  block: teach bdrv_debug_breakpoint skip filters with backing
  iotests: prepare 124 and 257 bitmap querying for backup-top filter
  iotests: 257: drop unused Drive.device field
  iotests: 257: drop device_add
  block: move in-flight requests handling from backup to block-copy
  block: introduce backup-top filter driver
  block/backup: use backup-top instead of write notifiers

 qapi/block-core.json          |   8 +-
 block/backup-top.h            |  37 ++
 include/block/block-copy.h    |  92 +++++
 include/block/block_int.h     |   1 +
 block.c                       |  34 +-
 block/backup-top.c            | 240 ++++++++++++
 block/backup.c                | 440 ++++-----------------
 block/block-copy.c            | 370 ++++++++++++++++++
 block/replication.c           |   2 +-
 blockdev.c                    |   1 +
 block/Makefile.objs           |   3 +
 block/trace-events            |  14 +-
 tests/qemu-iotests/056        |   8 +-
 tests/qemu-iotests/124        |  83 ++--
 tests/qemu-iotests/257        |  91 ++---
 tests/qemu-iotests/257.out    | 714 ++++++++++++++--------------------
 tests/qemu-iotests/iotests.py |  27 ++
 17 files changed, 1256 insertions(+), 909 deletions(-)
 create mode 100644 block/backup-top.h
 create mode 100644 include/block/block-copy.h
 create mode 100644 block/backup-top.c
 create mode 100644 block/block-copy.c

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2.21.0