snapshot: add flag for requesting disk snapshot

Prior to this patch, <domainsnapshot>/<disks> was ignored.  This
changes it to be an error unless an explicit disk snapshot is
requested (a future patch may relax things if it turns out to
be useful to have a <disks> specification alongside a system
checkpoint).

* include/libvirt/libvirt.h.in
(VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY): New flag.
* src/libvirt.c (virDomainSnapshotCreateXML): Document it.
* src/esx/esx_driver.c (esxDomainSnapshotCreateXML): Disk
snapshots not supported yet.
* src/vbox/vbox_tmpl.c (vboxDomainSnapshotCreateXML): Likewise.
* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Likewise.

include/libvirt/libvirt.h.in

@@ -2581,6 +2581,8 @@ typedef enum {
                                                           remembering it */
     VIR_DOMAIN_SNAPSHOT_CREATE_HALT        = (1 << 3), /* Stop running guest
                                                           after snapshot */
+    VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY   = (1 << 4), /* disk snapshot, not
+                                                          system checkpoint */
 } virDomainSnapshotCreateFlags;
 
 /* Take a snapshot of the current VM state */

src/esx/esx_driver.c

@@ -4226,6 +4226,12 @@ esxDomainSnapshotCreateXML(virDomainPtr domain, const char *xmlDesc,
         return NULL;
     }
 
+    if (def->ndisks) {
+        ESX_ERROR(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                  _("disk snapshots not supported yet"));
+        return NULL;
+    }
+
     if (esxVI_LookupVirtualMachineByUuidAndPrepareForTask
           (priv->primary, domain->uuid, NULL, &virtualMachine,
            priv->parsedUri->autoAnswer) < 0 ||

src/libvirt.c

@@ -15643,6 +15643,12 @@ error:
  * running after the snapshot.  This flag is invalid on transient domains,
  * and is incompatible with VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE.
  *
+ * If @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY, then the
+ * snapshot will be limited to the disks described in @xmlDesc, and no
+ * VM state will be saved.  For an active guest, the disk image may be
+ * inconsistent (as if power had been pulled), and specifying this
+ * with the VIR_DOMAIN_SNAPSHOT_CREATE_HALT flag risks data loss.
+ *
  * Returns an (opaque) virDomainSnapshotPtr on success, NULL on failure.
  */
 virDomainSnapshotPtr

src/qemu/qemu_driver.c

@@ -8899,6 +8899,12 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain,
     if (!qemuDomainSnapshotIsAllowed(vm))
         goto cleanup;
 
+    if (def->ndisks) {
+        qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                        _("disk snapshots not supported yet"));
+        goto cleanup;
+    }
+
     if (!(snap = virDomainSnapshotAssignDef(&vm->snapshots, def)))
         goto cleanup;
     def = NULL;

src/vbox/vbox_tmpl.c

@@ -5661,6 +5661,12 @@ vboxDomainSnapshotCreateXML(virDomainPtr dom,
     if (!(def = virDomainSnapshotDefParseString(xmlDesc, NULL, 0, 0)))
         goto cleanup;
 
+    if (def->ndisks) {
+        vboxError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                  _("disk snapshots not supported yet"));
+        goto cleanup;
+    }
+
     vboxIIDFromUUID(&domiid, dom->uuid);
     rc = VBOX_OBJECT_GET_MACHINE(domiid.value, &machine);
     if (NS_FAILED(rc)) {