blockcopy: add a way to parse disk source

The new blockcopy API wants to reuse only a subset of the disk
hotplug parser - namely, we only care about the embedded
virStorageSourcePtr inside a <disk> XML.  Strange as it may
seem, it was easier to just parse an entire disk definition,
then throw away everything but the embedded source, than it
was to disentangle the source parsing code from the rest of
the overall disk parsing function.  All that I needed was a
couple of tweaks and a new internal flag that determines
whether the normally-mandatory target element can be
gracefully skipped, since everything else was already optional.

* src/conf/domain_conf.h (virDomainDiskSourceParse): New
prototype.
* src/conf/domain_conf.c (VIR_DOMAIN_XML_INTERNAL_DISK_SOURCE):
New flag.
(virDomainDiskDefParseXML): Honor flag to make target optional.
(virDomainDiskSourceParse): New function.
Signed-off-by: NEric Blake <eblake@redhat.com>

src/conf/domain_conf.c

@@ -100,6 +100,8 @@ typedef enum {
    VIR_DOMAIN_XML_INTERNAL_ALLOW_ROM       = 1 << 19,
    VIR_DOMAIN_XML_INTERNAL_ALLOW_BOOT      = 1 << 20,
    VIR_DOMAIN_XML_INTERNAL_CLOCK_ADJUST    = 1 << 21,
+   /* parse only source half of <disk> */
+   VIR_DOMAIN_XML_INTERNAL_DISK_SOURCE     = 1 << 22,
 } virDomainXMLInternalFlags;
 
 #define DUMPXML_FLAGS                           \
@@ -113,7 +115,8 @@ verify(((VIR_DOMAIN_XML_INTERNAL_STATUS |
          VIR_DOMAIN_XML_INTERNAL_PCI_ORIG_STATES |
          VIR_DOMAIN_XML_INTERNAL_ALLOW_ROM |
          VIR_DOMAIN_XML_INTERNAL_ALLOW_BOOT |
-         VIR_DOMAIN_XML_INTERNAL_CLOCK_ADJUST)
+         VIR_DOMAIN_XML_INTERNAL_CLOCK_ADJUST |
+         VIR_DOMAIN_XML_INTERNAL_DISK_SOURCE)
         & DUMPXML_FLAGS) == 0);
 
 VIR_ENUM_IMPL(virDomainTaint, VIR_DOMAIN_TAINT_LAST,
@@ -5847,9 +5850,8 @@ virDomainDiskDefParseXML(virDomainXMLOptionPtr xmlopt,
      * to indicate no media present. LUN is for raw access CD-ROMs
      * that are not attached to a physical device presently */
     if (source == NULL && def->src->hosts == NULL && !def->src->srcpool &&
-        def->device != VIR_DOMAIN_DISK_DEVICE_CDROM &&
-        def->device != VIR_DOMAIN_DISK_DEVICE_LUN &&
-        def->device != VIR_DOMAIN_DISK_DEVICE_FLOPPY) {
+        (def->device == VIR_DOMAIN_DISK_DEVICE_DISK ||
+         (flags & VIR_DOMAIN_XML_INTERNAL_DISK_SOURCE))) {
         virReportError(VIR_ERR_NO_SOURCE,
                        target ? "%s" : NULL, target);
         goto error;
@@ -5869,7 +5871,7 @@ virDomainDiskDefParseXML(virDomainXMLOptionPtr xmlopt,
         ctxt->node = saved_node;
     }
 
-    if (target == NULL) {
+    if (!target && !(flags & VIR_DOMAIN_XML_INTERNAL_DISK_SOURCE)) {
         if (def->src->srcpool) {
             char *tmp;
             if (virAsprintf(&tmp, "pool = '%s', volume = '%s'",
@@ -5884,27 +5886,29 @@ virDomainDiskDefParseXML(virDomainXMLOptionPtr xmlopt,
         goto error;
     }
 
-    if (def->device == VIR_DOMAIN_DISK_DEVICE_FLOPPY &&
-        !STRPREFIX(target, "fd")) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("Invalid floppy device name: %s"), target);
-        goto error;
-    }
+    if (!(flags & VIR_DOMAIN_XML_INTERNAL_DISK_SOURCE)) {
+        if (def->device == VIR_DOMAIN_DISK_DEVICE_FLOPPY &&
+            !STRPREFIX(target, "fd")) {
+            virReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("Invalid floppy device name: %s"), target);
+            goto error;
+        }
 
-    /* Force CDROM to be listed as read only */
-    if (def->device == VIR_DOMAIN_DISK_DEVICE_CDROM)
-        def->src->readonly = true;
+        /* Force CDROM to be listed as read only */
+        if (def->device == VIR_DOMAIN_DISK_DEVICE_CDROM)
+            def->src->readonly = true;
 
-    if ((def->device == VIR_DOMAIN_DISK_DEVICE_DISK ||
-         def->device == VIR_DOMAIN_DISK_DEVICE_LUN) &&
-        !STRPREFIX((const char *)target, "hd") &&
-        !STRPREFIX((const char *)target, "sd") &&
-        !STRPREFIX((const char *)target, "vd") &&
-        !STRPREFIX((const char *)target, "xvd") &&
-        !STRPREFIX((const char *)target, "ubd")) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("Invalid harddisk device name: %s"), target);
-        goto error;
+        if ((def->device == VIR_DOMAIN_DISK_DEVICE_DISK ||
+             def->device == VIR_DOMAIN_DISK_DEVICE_LUN) &&
+            !STRPREFIX((const char *)target, "hd") &&
+            !STRPREFIX((const char *)target, "sd") &&
+            !STRPREFIX((const char *)target, "vd") &&
+            !STRPREFIX((const char *)target, "xvd") &&
+            !STRPREFIX((const char *)target, "ubd")) {
+            virReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("Invalid harddisk device name: %s"), target);
+            goto error;
+        }
     }
 
     if (snapshot) {
@@ -5958,7 +5962,7 @@ virDomainDiskDefParseXML(virDomainXMLOptionPtr xmlopt,
     } else {
         if (def->device == VIR_DOMAIN_DISK_DEVICE_FLOPPY) {
             def->bus = VIR_DOMAIN_DISK_BUS_FDC;
-        } else {
+        } else if (!(flags & VIR_DOMAIN_XML_INTERNAL_DISK_SOURCE)) {
             if (STRPREFIX(target, "hd"))
                 def->bus = VIR_DOMAIN_DISK_BUS_IDE;
             else if (STRPREFIX(target, "sd"))
@@ -6193,12 +6197,14 @@ virDomainDiskDefParseXML(virDomainXMLOptionPtr xmlopt,
         }
     }
 
-    if (def->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_NONE
-        && virDomainDiskDefAssignAddress(xmlopt, def) < 0)
-        goto error;
+    if (!(flags & VIR_DOMAIN_XML_INTERNAL_DISK_SOURCE)) {
+        if (def->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_NONE
+            && virDomainDiskDefAssignAddress(xmlopt, def) < 0)
+            goto error;
 
-    if (virDomainDiskBackingStoreParse(ctxt, def->src) < 0)
-        goto error;
+        if (virDomainDiskBackingStoreParse(ctxt, def->src) < 0)
+            goto error;
+    }
 
  cleanup:
     VIR_FREE(bus);
@@ -10412,6 +10418,47 @@ virDomainDeviceDefParse(const char *xmlStr,
 }
 
 
+virStorageSourcePtr
+virDomainDiskDefSourceParse(const char *xmlStr,
+                            const virDomainDef *def,
+                            virDomainXMLOptionPtr xmlopt,
+                            unsigned int flags)
+{
+    xmlDocPtr xml;
+    xmlNodePtr node;
+    xmlXPathContextPtr ctxt = NULL;
+    virDomainDiskDefPtr disk = NULL;
+    virStorageSourcePtr ret = NULL;
+
+    if (!(xml = virXMLParseStringCtxt(xmlStr, _("(disk_definition)"), &ctxt)))
+        goto cleanup;
+    node = ctxt->node;
+
+    if (!xmlStrEqual(node->name, BAD_CAST "disk")) {
+        virReportError(VIR_ERR_XML_ERROR,
+                       _("expecting root element of 'disk', not '%s'"),
+                       node->name);
+        goto cleanup;
+    }
+
+    flags |= VIR_DOMAIN_XML_INTERNAL_DISK_SOURCE;
+    if (!(disk = virDomainDiskDefParseXML(xmlopt, node, ctxt,
+                                          NULL, def->seclabels,
+                                          def->nseclabels,
+                                          flags)))
+        goto cleanup;
+
+    ret = disk->src;
+    disk->src = NULL;
+
+ cleanup:
+    virDomainDiskDefFree(disk);
+    xmlFreeDoc(xml);
+    xmlXPathFreeContext(ctxt);
+    return ret;
+}
+
+
 static const char *
 virDomainChrTargetTypeToString(int deviceType,
                                int targetType)

src/conf/domain_conf.h

@@ -2297,6 +2297,10 @@ virDomainDeviceDefPtr virDomainDeviceDefParse(const char *xmlStr,
                                               virCapsPtr caps,
                                               virDomainXMLOptionPtr xmlopt,
                                               unsigned int flags);
+virStorageSourcePtr virDomainDiskDefSourceParse(const char *xmlStr,
+                                                const virDomainDef *def,
+                                                virDomainXMLOptionPtr xmlopt,
+                                                unsigned int flags);
 virDomainDefPtr virDomainDefParseString(const char *xmlStr,
                                         virCapsPtr caps,
                                         virDomainXMLOptionPtr xmlopt,

src/libvirt_private.syms

@@ -222,6 +222,7 @@ virDomainDiskDefAssignAddress;
 virDomainDiskDefForeachPath;
 virDomainDiskDefFree;
 virDomainDiskDefNew;
+virDomainDiskDefSourceParse;
 virDomainDiskDeviceTypeToString;
 virDomainDiskDiscardTypeToString;
 virDomainDiskErrorPolicyTypeFromString;