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 source-drive 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=source-drive 2. (HMP) drive_del target0 3. (SHELL) rm BACKUP.qcow2 v7: Fix typo in cover letter "ide0-hd0". (Markus) Rebase to current qemu.git. (Resolved a few trivial contextual conflict) 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 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 | 7 +- 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, 519 insertions(+), 190 deletions(-) -- 1.8.5.1