Re: [Qemu-devel] [PATCH v13 00/14] Drop in_use from BlockDriverState and enable point-in-time snapshot exporting over NBD

["Richard W.M. Jones" <rjones@redhat.com>]

On Wed, Feb 12, 2014 at 09:22:29AM -0800, Ian Main wrote:
> On Wed, Jan 29, 2014 at 01:07:27PM +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
> > 
> > v12 -> v13: Address comments from Stefan.
> > 
> >     [05/15] block: Add bdrv_set_backing_hd()
> >             Remove duplicated assignments.
> >             
> >     [10/15] qmp: Add command 'blockdev-backup'
> >             Add check for source == target.
> >             
> >     [13/15] block: Add blockdev-backup to transaction
> >             New.
> >             
> >     [14/15] qemu-iotests: Test blockdev-backup in 055
> >             New.
> >             
> >     [15/15] qemu-iotests: Image fleecing test case 081
> >             New. Hope this number has no conflict. I have a 080 on my
> >             iothrottling test branch.
> > 
> > v11 -> v12: Rebase to qemu.git.
> >      Call bdrv_refresh_limits() in bdrv_set_backing_hd().
> 
> I've been using this patch and testing it for the last few weeks and it
> all seems to be working very well.  Kevin is waiting on more reviewers for
> this rev before it can go in.  Can someone else look through this please?
> 
> Tested-by: Ian Main <imain@redhat.com>

Adding Pino Toscano to this thread, since he is working on libguestfs.

Pino, I believe the latest patch series is this:

https://lists.gnu.org/archive/html/qemu-devel/2014-01/threads.html#03904

Rich.

> > 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 081
> > 
> >  block-migration.c               |   7 +-
> >  block.c                         | 306 ++++++++++++++++++++++++++--------------
> >  block/backup.c                  |  26 ++++
> >  block/commit.c                  |   1 +
> >  block/stream.c                  |  30 +---
> >  blockdev.c                      | 118 ++++++++++++++--
> >  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/081          |  99 +++++++++++++
> >  tests/qemu-iotests/081.out      |   5 +
> >  tests/qemu-iotests/group        |   1 +
> >  18 files changed, 836 insertions(+), 204 deletions(-)
> >  create mode 100755 tests/qemu-iotests/081
> >  create mode 100644 tests/qemu-iotests/081.out
> > 
> > -- 
> > 1.8.5.3
> > 

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Fedora Windows cross-compiler. Compile Windows programs, test, and
build Windows installers. Over 100 libraries supported.
http://fedoraproject.org/wiki/MinGW