[libvirt] [PATCHv2 4/3] snapshot: make offline qemu snapshots atomic

[Eric Blake]

On 03/19/2012 07:40 AM, Peter Krempa wrote:
> On 03/17/2012 05:33 PM, Eric Blake wrote:
>> Offline internal snapshots can be rolled back with just a little
>> bit of refactoring, meaning that we are now automatically atomic.
>>
>> * src/qemu/qemu_domain.c (qemuDomainSnapshotForEachQcow2): Move
>> guts...
>> (qemuDomainSnapshotForEachQcow2Raw): ...to new helper, to allow
>> rollbacks.
>> * src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Offline
>> snapshots are now atomic.
>> ---
> You rollback changes to disks if other disks are not snapshotable, but later on, 
> when the actual qemu-img command is run and fails the rollback is not performed. 

Good catch.

> 
> I's suggest squashing in:
> 

>              if (virRun(qemuimgarg, NULL) < 0) {
>                  if (try_all) {
>                      VIR_WARN("skipping snapshot action on %s",
>                               def->disks[i]->dst);
>                      skipped = true;
>                      continue;
> +                } else if (STREQ(op, "-c") && i) {
> +                    /* We must roll back partial creation by deleting
> +                     * all earlier snapshots.  */
> +                    qemuDomainSnapshotForEachQcow2Raw(driver, def, name,
> +                                                      "-d", false, i);
>                  }

Yep, that looks right.  Thanks for the test case.

> 
> Otherwise looks good. ACK with that suggested change.

Same story as for 3/3 - I'll wait to push this until I've run a few more
tests for the rest of my pending series, in case I find any more
last-minute issues.

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

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