[sheepdog] [PATCH v4] sheepdog: fix loadvm operation

[Stefan Hajnoczi]

On Fri, Apr 26, 2013 at 05:04:06PM +0800, Liu Yuan wrote:
> On 04/25/2013 09:06 PM, MORITA Kazutaka wrote:
> > At Thu, 25 Apr 2013 20:49:39 +0800,
> > Liu Yuan wrote:
> >>
> >> From: Liu Yuan <tailai.ly at taobao.com>
> >>
> >> Currently the 'loadvm' opertaion works as following:
> >> 1. switch to the snapshot
> >> 2. mark current working VDI as a snapshot
> >> 3. rely on sd_create_branch to create a new working VDI based on the snapshot
> >>
> >> This works not the same as other format as QCOW2. For e.g,
> >>
> >> qemu > savevm # get a live snapshot snap1
> >> qemu > savevm # snap2
> >> qemu > loadvm 1 # This will steally create snap3 of the working VDI
> >>
> >> Which will result in following snapshot chain:
> >>
> >> base <-- snap1 <-- snap2 <-- snap3
> >>           ^
> >>           |
> >>       working VDI
> >>
> >> snap3 was unnecessarily created and might be annoying users.
> >>
> >> This patch discard the unnecessary 'snap3' creation. and implement
> >> rollback(loadvm) operation to the specified snapshot by
> >> 1. switch to the snapshot
> >> 2. delete working VDI
> >> 3. rely on sd_create_branch to create a new working VDI based on the snapshot
> >>
> >> The snapshot chain for above example will be:
> >>
> >> base <-- snap1 <-- snap2
> >>           ^
> >>           |
> >>       working VDI
> >>
> >> Cc: qemu-devel at nongnu.org
> >> Cc: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>
> >> Cc: Kevin Wolf <kwolf at redhat.com>
> >> Cc: Stefan Hajnoczi <stefanha at redhat.com>
> >> Signed-off-by: Liu Yuan <tailai.ly at taobao.com>
> >> ---
> >> v4:
> >>  - print an error message when NO_VDI found
> >>
> >> v3:
> >>  - let boot from snapshot behave like 'loadvm'
> >>
> >> v2:
> >>  - use do_req() because sd_delete isn't in coroutine
> >>  - don't break old behavior if we boot up on the snapshot by using s->reverted
> >>    to indicate if we delete working VDI successfully
> >>  - fix a subtle case that sd_create_branch() isn't called yet while another
> >>    'loadvm' is executed
> >>
> >>  block/sheepdog.c |   54 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
> >>  1 file changed, 53 insertions(+), 1 deletion(-)
> > 
> > Reviewed-by: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>
> 
> Missed this one, Stefan?

Please send patches as top-level email threads instead of replies so
that they get noticed.

Thanks,
Stefan