fleecing-hook driver for backup

v2 was "[RFC v2] new, node-graph-based fleecing and backup"

Hi all!

These series introduce fleecing-hook 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 (patch 18)

Proposed filter driver is complete and separate: it can be used standalone, as fleecing provider (instead of backup(sync=none)). (old-style fleecing based on backup(sync=none) is supported too), look at patch 16.

There a lot of other ideas and improvements which can be achieved basing on these series which were discussed on v2 thread, for the beginning I want to concentrate on the following:

done in these series:
1. use filter node instead of write notifiers in backup
2. filter-based fleecing scheme, without a job

near to be done (a test is needed and may be tiny adjustment)
3. backup scheme for push backup with fleecing, to no disturb the guest with long handling of its writes (if target is far from remote NBD): just start fleecing to local qcow2 temp node and start a backup job (or mirror, why not?) from temp node to remote target. These series provide a possibility to share dirty bitmap between fleecing-hook and backup job to create efficient scenarios.

These series are based on
[PATCH v4 0/8] dirty-bitmap: rewrite bdrv_dirty_iter_next_area
and
[PATCH 0/2] replication: drop extra sync

Based-on: <[email protected]>
Based-on: <[email protected]>

Vladimir Sementsov-Ogievskiy (18):
block/dirty-bitmap: allow set/reset bits in disabled bitmaps block/io: allow BDRV_REQ_SERIALISING for read block/backup: simplify backup_incremental_init_copy_bitmap block/backup: move from HBitmap to BdrvDirtyBitmap util/id: add block-bitmap subsystem
block/backup: give a name to copy-bitmap block/backup: allow use existent copy-bitmap
block: allow serialized reads to intersect
block: improve should_update_child
iotests: handle -f argument correctly for qemu_io_silent
iotests: allow resume_drive by node name
iotests: prepare 055 to graph changes during backup job
block: introduce new filter driver: fleecing-hook block/fleecing-hook: internal api
qapi: add x-drop-fleecing qmp command
iotests: test new fleecing-hook driver in context of 222 iotest block/backup: tiny refactor backup_job_create block/backup: use fleecing-hook instead of write notifiers

 qapi/block-core.json          |  57 +++++-
 include/block/block.h         |   9 +
 include/block/block_int.h     |   2 +-
 include/qemu/id.h             |   1 +
 block.c                       |  32 +++-
 block/backup.c                | 320 ++++++++++++++-----------------
 block/dirty-bitmap.c          |   2 -
 block/fleecing-hook.c         | 349 ++++++++++++++++++++++++++++++++++
 block/io.c                    |  16 +-
 block/replication.c           |   2 +-
 blockdev.c                    |  49 ++++-
 util/id.c                     |   1 +
 block/Makefile.objs           |   2 +
 tests/qemu-iotests/055        |  23 ++-
 tests/qemu-iotests/222        |  59 ++++--
 tests/qemu-iotests/222.out    |  66 +++++++
 tests/qemu-iotests/iotests.py |  16 +-
 17 files changed, 778 insertions(+), 228 deletions(-)
 create mode 100644 block/fleecing-hook.c

2.18.0