[libvirt] [PATCHv4 34/51] snapshot: store qemu domain details in xml

[Eric Blake]

On 09/01/2011 10:25 PM, Eric Blake wrote:
> When reverting to a snapshot, the inactive domain configuration
> has to be rolled back to what it was at the time of the snapshot.
> Additionally, if the VM is active and the snapshot was active,
> this now adds a failure if the two configurations are ABI
> incompatible, rather than risking qemu confusion.
>
> A future patch will add a VIR_DOMAIN_SNAPSHOT_FORCE flag, which
> will be required for two risky code paths - reverting to an
> older snapshot that lacked full domain information, and reverting
> from running to a live snapshot that requires starting a new qemu
> process.  Any reverting that stops a running vm is also a form
> of data loss (discarding the current running state to go back in
> time), but as that is what reversion usually implies, it is
> probably not worth requiring a force flag.
>
> * src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Copy out
> domain.
> (qemuDomainRevertToSnapshot): Perform ABI compatibility checks.
> ---
>   src/qemu/qemu_driver.c |   77 +++++++++++++++++++++++++++++++++++++++--------
>   1 files changed, 64 insertions(+), 13 deletions(-)

I'm squashing in these additional safety checks, now that domain 
snapshot redefine is also a place where ABI compatibility matters.

diff --git i/src/qemu/qemu_driver.c w/src/qemu/qemu_driver.c
index ea11d0b..7028d72 100644
--- i/src/qemu/qemu_driver.c
+++ w/src/qemu/qemu_driver.c
@@ -8826,6 +8826,13 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain,
          }

          /* Check that any replacement is compatible */
+        if (def->dom &&
+            memcmp(def->dom->uuid, domain->uuid, VIR_UUID_BUFLEN)) {
+            qemuReportError(VIR_ERR_INVALID_ARG,
+                            _("definition for snapshot %s must use uuid 
%s"),
+                            def->name, uuidstr);
+            goto cleanup;
+        }
          other = virDomainSnapshotFindByName(&vm->snapshots, def->name);
          if (other) {
              if ((other->def->state == VIR_DOMAIN_RUNNING ||
@@ -8838,7 +8845,17 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain,
                                  def->name);
                  goto cleanup;
              }
-            /* XXX Ensure ABI compatibility before replacing anything.  */
+            if (other->def->dom) {
+                if (def->dom) {
+                    if (!virDomainDefCheckABIStability(other->def->dom,
+                                                       def->dom))
+                        goto cleanup;
+                } else {
+                    /* Transfer the domain def */
+                    def->dom = other->def->dom;
+                    other->def->dom = NULL;
+                }
+            }
              if (other == vm->current_snapshot) {
                  update_current = true;
                  vm->current_snapshot = NULL;


-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org