snapshot_conf: introduce <revertDisks> metadata element

This new element will hold the new disk overlay created when reverting
to non-leaf snapshot in order to remember the files libvirt created.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>

src/conf/schemas/domainsnapshot.rng

@@ -60,6 +60,13 @@
             </zeroOrMore>
           </element>
         </optional>
+        <optional>
+          <element name="revertDisks">
+            <zeroOrMore>
+              <ref name="disksnapshot"/>
+            </zeroOrMore>
+          </element>
+        </optional>
         <optional>
           <element name="active">
             <choice>

src/conf/snapshot_conf.c

@@ -112,6 +112,9 @@ virDomainSnapshotDefDispose(void *obj)
     for (i = 0; i < def->ndisks; i++)
         virDomainSnapshotDiskDefClear(&def->disks[i]);
     g_free(def->disks);
+    for (i = 0; i < def->nrevertdisks; i++)
+        virDomainSnapshotDiskDefClear(&def->revertdisks[i]);
+    g_free(def->revertdisks);
     virObjectUnref(def->cookie);
 }
 
@@ -376,6 +379,22 @@ virDomainSnapshotDefParse(xmlXPathContextPtr ctxt,
             return NULL;
     }
 
+    if (flags & VIR_DOMAIN_SNAPSHOT_PARSE_REDEFINE) {
+        g_autofree xmlNodePtr *revertDiskNodes = NULL;
+
+        if ((n = virXPathNodeSet("./revertDisks/*", ctxt, &revertDiskNodes)) < 0)
+            return NULL;
+        if (n)
+            def->revertdisks = g_new0(virDomainSnapshotDiskDef, n);
+        def->nrevertdisks = n;
+        for (i = 0; i < def->nrevertdisks; i++) {
+            if (virDomainSnapshotDiskDefParseXML(revertDiskNodes[i], ctxt,
+                                                 &def->revertdisks[i],
+                                                 flags, xmlopt) < 0)
+                return NULL;
+        }
+    }
+
     if (flags & VIR_DOMAIN_SNAPSHOT_PARSE_INTERNAL) {
         int active;
 
@@ -834,6 +853,17 @@ virDomainSnapshotDefFormatInternal(virBuffer *buf,
         virBufferAddLit(buf, "</disks>\n");
     }
 
+    if (def->nrevertdisks > 0) {
+        g_auto(virBuffer) childBuf = VIR_BUFFER_INIT_CHILD(buf);
+
+        for (i = 0; i < def->nrevertdisks; i++) {
+            if (virDomainSnapshotDiskDefFormat(&childBuf, &def->revertdisks[i], xmlopt) < 0)
+                return -1;
+        }
+
+        virXMLFormatElement(buf, "revertDisks", NULL, &childBuf);
+    }
+
     if (def->parent.dom) {
         if (virDomainDefFormatInternal(def->parent.dom, xmlopt,
                                        buf, domainflags) < 0)

src/conf/snapshot_conf.h

@@ -80,6 +80,11 @@ struct _virDomainSnapshotDef {
     size_t ndisks; /* should not exceed dom->ndisks */
     virDomainSnapshotDiskDef *disks;
 
+    /* When we revert to non-leaf snapshot we need to
+     * store the new overlay disks. */
+    size_t nrevertdisks;
+    virDomainSnapshotDiskDef *revertdisks;
+
     virObject *cookie;
 };