[libvirt] [PATCHv2 10/15] blockjob: support pivot operation on cancel

[Eric Blake]

On 04/06/2012 01:08 AM, Paolo Bonzini wrote:
> Il 06/04/2012 06:36, Eric Blake ha scritto:
>> If only qemu could get 'drive-reopen' inside 'transaction'...
> 
> Just a quick answer to this: if qemu could get 'drive-reopen' inside
> 'transaction', the standalone command could be made safe just as easily.
>  In fact, in QEMU 1.1 the blockdev-snapshot-sync command got a similar
> treatment: it became transactionable, _and_ the standalone command
> became a simple wrapper around a 1-command transaction.

Good point.  So unless we have a situation where we want to do
'drive-reopen' on multiple disks at once, we don't actually have to use
a transaction command to reopen a single disk.  Meanwhile, for
similarity with blockdev-snapshot-sync, it looks like I will someday be
adding a VIR_DOMAIN_BLOCK_JOB_ABORT_ATOMIC flag, which fails if qemu
lacks support for reopen within a transaction, and assuming that qemu
exposes a way to see which commands are transactionable.

-- 
Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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