Re: [Qemu-devel] [PATCH v16 00/14] Drop in_use from BlockDriverState and enable point-in-time snapshot exporting over NBD

[Benoît Canet]

The Friday 07 Mar 2014 à 16:20:42 (+0800), Fam Zheng wrote :
> 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-cancel device=source-drive
> 
>  2. (HMP) drive_del target0
> 
>  3. (SHELL) rm BACKUP.qcow2
> 
> v16: Address review comments from Jeff and Markus (thanks for reviewing!)
>      (A side-by-side diff of v15 -> v16: http://goo.gl/1goc6S)
> 
>     [03/14] block: Replace in_use with operation blocker
>             Improve error message. (Markus)
> 
>     [05/14] block: Add bdrv_set_backing_hd()
>             in bdrv_set_backing_hd:
>             * Don't call bdrv_ref and bdrv_unref. (Jeff)
>             * Add "bs->open_flags &= ~BDRV_O_NO_BACKING". (Jeff)
>             in bdrv_open_backing_file:
>             * Remove unnecessary "bs->backing_hd = NULL;". (Jeff)
>             * Don't get wrong refcnt on backing_hd. (Jeff)
>             in bdrv_append:
>             * Remove unnessary backing_file and backing_format copy, it's 
> taken
>               care of in bdrv_set_backing_hd(). (Jeff)
> 
>     [06/14] block: Add backing_blocker in BlockDriverState
>             Add call to bdrv_ref() since bdrv_set_backing_hd() doesn't do it
>             now.
> 
>     [08/14] block: Support dropping active in bdrv_drop_intermediate
>             Verify active, top, base are in the same backing chain. (Jeff)
>             Remember to change backing file when base != NULL. (Jeff)
>             
>     [09/14] stream: Use bdrv_drop_intermediate and drop close_unused_images
>             Drop more unnecessary code. (Jeff)
> 
> Thanks,
> Fam
> 
> 
> Fam Zheng (14):
>   block: Add BlockOpType enum
>   block: Introduce op_blockers to BlockDriverState
>   block: Replace in_use with operation blocker
>   block: Move op_blocker check from block_job_create to its caller
>   block: Add bdrv_set_backing_hd()
>   block: Add backing_blocker in 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
>   qmp: Add command 'blockdev-backup'
>   block: Allow backup on referenced named BlockDriverState
>   block: Add blockdev-backup to transaction
>   qemu-iotests: Test blockdev-backup in 055
>   qemu-iotests: Image fleecing test case 083
> 
>  block-migration.c               |   7 +-
>  block.c                         | 314 
> +++++++++++++++++++++++++++-------------
>  block/backup.c                  |  26 ++++
>  block/commit.c                  |   2 +-
>  block/mirror.c                  |   1 +
>  block/stream.c                  |  42 +-----
>  blockdev.c                      | 122 ++++++++++++++--
>  blockjob.c                      |  14 +-
>  hw/block/dataplane/virtio-blk.c |  19 ++-
>  include/block/block.h           |  29 +++-
>  include/block/block_int.h       |   9 +-
>  include/block/blockjob.h        |   3 +
>  qapi-schema.json                |  50 +++++++
>  qmp-commands.hx                 |  44 ++++++
>  tests/qemu-iotests/055          | 275 +++++++++++++++++++++++++++++------
>  tests/qemu-iotests/055.out      |   4 +-
>  tests/qemu-iotests/083          |  99 +++++++++++++
>  tests/qemu-iotests/083.out      |   5 +
>  tests/qemu-iotests/group        |   1 +
>  19 files changed, 854 insertions(+), 212 deletions(-)
>  create mode 100755 tests/qemu-iotests/083
>  create mode 100644 tests/qemu-iotests/083.out
> 
> -- 
> 1.9.0
> 

Hi Fam,

I want to rebase my patches on top of yours but I have trouble applying your
series to kevin/block-next. Is it based on it ?

Best regards

Benoît