The snapshot-create operation of running guests saves the live
XML and uses it to replace the active and inactive domain in
case of revert. So, the config XML is ignored by the snapshot
process. This commit changes it and adds the config XML in the
snapshot XML as the <inactiveDomain> entry.

In case of offline guest, the behavior remains the same and the
config XML is saved in the snapshot XML as <domain> entry. The
behavior of older snapshots of running guests, that don't have
the new <inactiveDomain>, remains the same too. The revert, in
this case, overrides both active and inactive domain with the
<domain> entry. So, the <inactiveDomain> in the snapshot XML is
not required to snapshot work, but it's useful to preserve the
config XML of running guests.

Signed-off-by: Maxiwell S. Garcia <maxiwell@linux.ibm.com>
---
 src/conf/moment_conf.c   |  1 +
 src/conf/moment_conf.h   | 11 +++++++++
 src/conf/snapshot_conf.c | 48 +++++++++++++++++++++++++++++++++++-----
 src/qemu/qemu_driver.c   | 27 +++++++++++++++++-----
 src/util/virxml.c        | 45 +++++++++++++++++++++++++++++++++++++
 src/util/virxml.h        |  8 +++++++
 6 files changed, 130 insertions(+), 10 deletions(-)

diff --git a/src/conf/moment_conf.c b/src/conf/moment_conf.c
index fea13f0f97..f54a44b33e 100644
--- a/src/conf/moment_conf.c
+++ b/src/conf/moment_conf.c
@@ -66,6 +66,7 @@ virDomainMomentDefDispose(void *obj)
     VIR_FREE(def->description);
     VIR_FREE(def->parent_name);
     virDomainDefFree(def->dom);
+    virDomainDefFree(def->inactiveDom);
 }
 
 /* Provide defaults for creation time and moment name after parsing XML */
diff --git a/src/conf/moment_conf.h b/src/conf/moment_conf.h
index 9fdbef2172..70cc47bd70 100644
--- a/src/conf/moment_conf.h
+++ b/src/conf/moment_conf.h
@@ -36,7 +36,18 @@ struct _virDomainMomentDef {
     char *parent_name;
     long long creationTime; /* in seconds */
 
+    /*
+     * Store the active domain definition in case of online
+     * guest and the inactive domain definition in case of
+     * offline guest
+     */
     virDomainDefPtr dom;
+
+    /*
+     * Store the inactive domain definition in case of online
+     * guest and leave NULL in case of offline guest
+     */
+    virDomainDefPtr inactiveDom;
 };
 
 virClassPtr virClassForDomainMomentDef(void);
diff --git a/src/conf/snapshot_conf.c b/src/conf/snapshot_conf.c
index 324901a560..8aeac9ab20 100644
--- a/src/conf/snapshot_conf.c
+++ b/src/conf/snapshot_conf.c
@@ -243,6 +243,8 @@ virDomainSnapshotDefParse(xmlXPathContextPtr ctxt,
     char *memoryFile = NULL;
     bool offline = !!(flags & VIR_DOMAIN_SNAPSHOT_PARSE_OFFLINE);
     virSaveCookieCallbacksPtr saveCookie = virDomainXMLOptionGetSaveCookie(xmlopt);
+    int domainflags = VIR_DOMAIN_DEF_PARSE_INACTIVE |
+                      VIR_DOMAIN_DEF_PARSE_SKIP_VALIDATE;
 
     if (!(def = virDomainSnapshotDefNew()))
         return NULL;
@@ -292,8 +294,6 @@ virDomainSnapshotDefParse(xmlXPathContextPtr ctxt,
          * clients will have to decide between best effort
          * initialization or outright failure.  */
         if ((tmp = virXPathString("string(./domain/@type)", ctxt))) {
-            int domainflags = VIR_DOMAIN_DEF_PARSE_INACTIVE |
-                              VIR_DOMAIN_DEF_PARSE_SKIP_VALIDATE;
             xmlNodePtr domainNode = virXPathNode("./domain", ctxt);
 
             VIR_FREE(tmp);
@@ -309,6 +309,20 @@ virDomainSnapshotDefParse(xmlXPathContextPtr ctxt,
         } else {
             VIR_WARN("parsing older snapshot that lacks domain");
         }
+
+        /* /inactiveDomain entry saves the config XML present in a running
+         * VM. In case of absent, leave parent.inactiveDom NULL and use
+         * parent.dom for config and live XML. */
+        if (virXPathString("string(./inactiveDomain/@type)", ctxt)) {
+            xmlNodePtr domainNode = virXPathNode("./inactiveDomain", ctxt);
+
+            if (domainNode) {
+                def->parent.inactiveDom = virDomainDefParseNode(ctxt->node->doc, domainNode,
+                                                                caps, xmlopt, NULL, domainflags);
+                if (!def->parent.inactiveDom)
+                    goto cleanup;
+            }
+        }
     } else if (virDomainXMLOptionRunMomentPostParse(xmlopt, &def->parent) < 0) {
         goto cleanup;
     }
@@ -845,6 +859,10 @@ virDomainSnapshotDefFormatInternal(virBufferPtr buf,
 {
     size_t i;
     int domainflags = VIR_DOMAIN_DEF_FORMAT_INACTIVE;
+    virBuffer inactivedom_buf = VIR_BUFFER_INITIALIZER;
+    xmlXPathContextPtr inactivedom_ctxt = NULL;
+    char *inactivedom_str = NULL;
+    int ret = -1;
 
     if (flags & VIR_DOMAIN_SNAPSHOT_FORMAT_SECURE)
         domainflags |= VIR_DOMAIN_DEF_FORMAT_SECURE;
@@ -903,6 +921,20 @@ virDomainSnapshotDefFormatInternal(virBufferPtr buf,
         virBufferAddLit(buf, "</domain>\n");
     }
 
+    if (def->parent.inactiveDom) {
+        if (virDomainDefFormatInternal(def->parent.inactiveDom, caps,
+                                       domainflags, &inactivedom_buf, xmlopt) < 0)
+            goto error;
+
+        inactivedom_ctxt = virXPathBuildContext(&inactivedom_buf);
+        if (!(inactivedom_str = virXPathRenameNode("/domain", "inactiveDomain",
+                                                   inactivedom_ctxt)))
+            goto error;
+
+        virBufferAddStr(buf, inactivedom_str);
+        virBufferAddLit(buf, "\n");
+    }
+
     if (virSaveCookieFormatBuf(buf, def->cookie,
                                virDomainXMLOptionGetSaveCookie(xmlopt)) < 0)
         goto error;
@@ -917,11 +949,17 @@ virDomainSnapshotDefFormatInternal(virBufferPtr buf,
     if (virBufferCheckError(buf) < 0)
         goto error;
 
-    return 0;
+    ret = 0;
 
  error:
-    virBufferFreeAndReset(buf);
-    return -1;
+    VIR_FREE(inactivedom_str);
+    xmlXPathFreeContext(inactivedom_ctxt);
+    virBufferFreeAndReset(&inactivedom_buf);
+
+    if (ret < 0)
+        virBufferFreeAndReset(buf);
+
+    return ret;
 }
 
 
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 482f915b67..9b95e9b766 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -15697,6 +15697,13 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain,
                                                         VIR_DOMAIN_DEF_PARSE_SKIP_VALIDATE)))
             goto endjob;
 
+        if (vm->newDef) {
+            def->parent.inactiveDom = virDomainDefCopy(vm->newDef, caps,
+                                                       driver->xmlopt, NULL, true);
+            if (!def->parent.inactiveDom)
+                goto endjob;
+        }
+
         if (flags & VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY) {
             align_location = VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL;
             align_match = false;
@@ -16231,6 +16238,7 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
     qemuDomainObjPrivatePtr priv;
     int rc;
     virDomainDefPtr config = NULL;
+    virDomainDefPtr inactiveConfig = NULL;
     virQEMUDriverConfigPtr cfg = NULL;
     virCapsPtr caps = NULL;
     bool was_stopped = false;
@@ -16331,17 +16339,22 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
          * in the failure cases where we know there was no change?  */
     }
 
-    /* Prepare to copy the snapshot inactive xml as the config of this
-     * domain.
-     *
-     * XXX Should domain snapshots track live xml rather
-     * than inactive xml?  */
+    /* Prepare to copy the snapshot inactive domain as the config XML
+     * and the snapshot domain as the live XML. In case of inactive domain
+     * NULL, both config and live XML will be copied from snapshot domain.
+     */
     if (snap->def->dom) {
         config = virDomainDefCopy(snap->def->dom, caps,
                                   driver->xmlopt, NULL, true);
         if (!config)
             goto endjob;
     }
+    if (snap->def->inactiveDom) {
+        inactiveConfig = virDomainDefCopy(snap->def->inactiveDom, caps,
+                                          driver->xmlopt, NULL, true);
+        if (!inactiveConfig)
+            goto endjob;
+    }
 
     cookie = (qemuDomainSaveCookiePtr) snapdef->cookie;
 
@@ -16592,6 +16605,10 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
         goto endjob;
     }
 
+    if (inactiveConfig) {
+        virDomainDefFree(vm->newDef);
+        VIR_STEAL_PTR(vm->newDef, inactiveConfig);
+    }
     ret = 0;
 
  endjob:
diff --git a/src/util/virxml.c b/src/util/virxml.c
index f55b9a362c..756c0eedbc 100644
--- a/src/util/virxml.c
+++ b/src/util/virxml.c
@@ -1408,3 +1408,48 @@ virXPathContextNodeRestore(virXPathContextNodeSavePtr save)
 
     save->ctxt->node = save->node;
 }
+
+
+/**
+ * virXPathBuildContext: convert an parent buffer to an
+ * XPath context ptr. The caller has to free the ptr.
+ */
+xmlXPathContextPtr
+virXPathBuildContext(virBufferPtr root)
+{
+    xmlDocPtr doc;
+
+    if (!root)
+        return NULL;
+
+    doc = virXMLParseString(virBufferCurrentContent(root), NULL);
+    if (!doc)
+        return NULL;
+
+    return xmlXPathNewContext(doc);
+}
+
+
+/**
+ * virXPathRenameNode: get the XML node using the 'xpath' and
+ * rename it with the 'newname' string.
+ *
+ * Returns the XML string of the node found by 'xpath' or NULL
+ * on error. The caller has to free the string.
+ */
+char *
+virXPathRenameNode(const char *xpath,
+                   const char *newname,
+                   xmlXPathContextPtr ctxt)
+{
+    xmlNodePtr node;
+
+    if (!xpath || !newname || !ctxt)
+        return NULL;
+
+    if (!(node = virXPathNode(xpath, ctxt)))
+        return NULL;
+
+    xmlNodeSetName(node, (xmlChar *) newname);
+    return virXMLNodeToString(node->doc, node);
+}
diff --git a/src/util/virxml.h b/src/util/virxml.h
index 6208977dd1..48a507c3c1 100644
--- a/src/util/virxml.h
+++ b/src/util/virxml.h
@@ -220,6 +220,14 @@ virXMLFormatElement(virBufferPtr buf,
                     virBufferPtr childBuf)
     ATTRIBUTE_RETURN_CHECK;
 
+xmlXPathContextPtr
+virXPathBuildContext(virBufferPtr root);
+
+char *
+virXPathRenameNode(const char *xpath,
+                   const char *newname,
+                   xmlXPathContextPtr ctxt);
+
 struct _virXPathContextNodeSave {
     xmlXPathContextPtr ctxt;
     xmlNodePtr node;