This series adds for point-in-time snapshot NBD exporting based on
blockdev-backup (variant of drive-backup with existing device as target).
We get a thin point-in-time snapshot by COW mechanism of drive-backup, and
export it through built in NBD server. The steps are as below:
1. (SHELL) qemu-img create -f qcow2 BACKUP.qcow2 <source size here>
(Alternatively we can use -o backing_file=RUNNING-VM.img to omit explicitly
providing the size by ourselves, but it's risky because RUNNING-VM.qcow2 is
used r/w by guest. Whether or not setting backing file in the image file
doesn't matter, as we are going to override the backing hd in the next
step)
2. (QMP) blockdev-add backing=source-drive file.driver=file
file.filename=BACKUP.qcow2 id=target0 if=none driver=qcow2
(where ide0-hd0 is the running BlockDriverState name for
RUNNING-VM.img. This patch implements "backing=" option to override
backing_hd for added drive)
3. (QMP) blockdev-backup device=source-drive sync=none target=target0
(this is the QMP command introduced by this series, which use a named
device as target of drive-backup)
4. (QMP) nbd-server-add device=target0
When image fleecing done:
1. (QMP) block-job-complete device=ide0-hd0
2. (HMP) drive_del target0
3. (SHELL) rm BACKUP.qcow2
v6: Address Paolo's comments, (except for bitmask):
- Add blocker for all backing_hd references, a relatively big change, some
patches are reordered.
- Introduce a few other necessary patches.
- Move two snapshot checks into bdrv_snapshot_*.
The interface is unchanged.
Fam
Fam Zheng (10):
qapi: Add BlockOperationType enum
block: Introduce op_blockers to BlockDriverState
block: Parse "backing" option to reference existing BDS
block: support dropping active in bdrv_drop_intermediate
stream: Use bdrv_drop_intermediate and drop close_unused_images
block: Replace in_use with operation blocker
block: Pass error in bdrv_snapshot_create
block: Add checks of blocker in block operations
qmp: add command 'blockdev-backup'
block: Allow backup on referenced named BlockDriverState
block-migration.c | 8 +-
block.c | 348 +++++++++++++++++++++++++---------------
block/backup.c | 21 +++
block/commit.c | 1 +
block/mirror.c | 2 +-
block/snapshot.c | 16 +-
block/stream.c | 28 +---
blockdev.c | 86 ++++++++--
blockjob.c | 12 +-
hw/block/dataplane/virtio-blk.c | 16 +-
include/block/block.h | 11 +-
include/block/block_int.h | 9 +-
include/block/blockjob.h | 3 +
include/block/snapshot.h | 3 +-
qapi-schema.json | 98 +++++++++++
qemu-img.c | 2 +-
qmp-commands.hx | 44 +++++
savevm.c | 2 +-
18 files changed, 520 insertions(+), 190 deletions(-)
--
1.8.4.2
