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

[Fam Zheng <famz@redhat.com>]

On Mon, 03/10 06:13, Benoît Canet wrote:
> 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 ?
> 

No, I used qemu.git master. I see some conflicts, I will rebase and send to
list.  But I think you meant kevin/block, since kevin/block-next looks very
old, right?

Fam