The semantics of the backup operation don't strictly require that all
disks being backed up are part of the same incremental part (when a disk
was checkpointed/backed up separately or in a different VM), or even
they may not have a previous checkpoint at all (e.g. when the disk
was freshly hotplugged to the vm).
In such cases we can still create a common checkpoint for all of them
and backup differences according to configuration.
This patch adds a per-disk configuration of the checkpoint to do the
incremental backup from via the 'incremental' attribute and allows
perform full backups via the 'backupmode' attribute.
Note that no changes to the qemu driver are necessary to take advantage
of this as we already obey the per-disk 'incremental' field.
https://bugzilla.redhat.com/show_bug.cgi?id=1829829
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Prepare for new backup APIs by describing the XML that will represent
a backup. The XML resembles snapshots and checkpoints in being able
to select actions for a set of disks, but has other differences. It
can support both push model (the hypervisor does the backup directly
into the destination file) and pull model (the hypervisor exposes an
access port for a third party to grab what is necessary). Add
testsuite coverage for some minimal uses of the XML.
The <disk> element within <domainbackup> tries to model the same
elements as a <disk> under <domain>, but sharing the RNG grammar
proved to be hairy. That is in part because while <domain> use
<source> to describe a host resource in use by the guest, a backup job
is using a host resource that is not visible to the guest: a push
backup action is instead describing a <target> (which ultimately could
be a remote network resource, but for simplicity the RNG just
validates a local file for now), and a pull backup action is instead
describing a temporary local file <scratch> (which probably should not
be a remote resource). A future refactoring may thus introduce some
way to parameterize RNG to accept <disk type='FOO'>...</disk> so that
the name of the subelement can be <source> for domain, or <target> or
<scratch> as needed for backups. Future patches may improve this area
of code.
Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
