conf: Properly parse <backingStore/>

The terminator would not be parsed properly since the XPath selector was
looking for an populated element, and also the code did not bother
assigning the terminating virStorageSourcePtr to the backingStore
property of the parent.

Some tests would catch it if there wasn't bigger fallout from the change
to backing store termination in a693fdba. Fix them properly now.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1509110

src/conf/domain_conf.c

@@ -8545,23 +8545,21 @@ virDomainDiskBackingStoreParse(xmlXPathContextPtr ctxt,
     char *idx = NULL;
     int ret = -1;
 
-    if (!(ctxt->node = virXPathNode("./backingStore[*]", ctxt))) {
+    if (!(ctxt->node = virXPathNode("./backingStore", ctxt))) {
         ret = 0;
         goto cleanup;
     }
 
-    if (!(type = virXMLPropString(ctxt->node, "type"))) {
-        /* terminator does not have a type */
     if (VIR_ALLOC(backingStore) < 0)
         goto cleanup;
 
+    /* terminator does not have a type */
+    if (!(type = virXMLPropString(ctxt->node, "type"))) {
+        VIR_STEAL_PTR(src->backingStore, backingStore);
         ret = 0;
         goto cleanup;
     }
 
-    if (VIR_ALLOC(backingStore) < 0)
-        goto cleanup;
-
     if (!(flags & VIR_DOMAIN_DEF_PARSE_INACTIVE) &&
         (idx = virXMLPropString(ctxt->node, "index")) &&
         virStrToLong_uip(idx, NULL, 10, &backingStore->id) < 0) {

tests/qemuhotplugtestdomains/qemuhotplug-base-live+disk-scsi-wwn+disk-scsi-duplicate-wwn.xml

@@ -22,6 +22,7 @@
     <disk type='file' device='disk'>
       <driver name='qemu' type='raw' cache='none'/>
       <source file='/dev/null'/>
+      <backingStore/>
       <target dev='sdf' bus='scsi'/>
       <readonly/>
       <shareable/>

tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-active-commit.xml

@@ -20,6 +20,7 @@
       <backingStore type='block' index='1'>
         <format type='raw'/>
         <source dev='/dev/HostVG/QEMUGuest1'/>
+        <backingStore/>
       </backingStore>
       <mirror type='block' job='active-commit'>
         <format type='raw'/>

tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-backing-chains-active.xml

@@ -49,6 +49,7 @@
                 <backingStore type='file' index='6'>
                   <format type='raw'/>
                   <source file='/tmp/Fedora-17-x86_64-Live-KDE.iso'/>
+                  <backingStore/>
                 </backingStore>
               </backingStore>
             </backingStore>
@@ -63,6 +64,7 @@
       <source protocol='gluster' name='Volume1/Image'>
         <host name='example.org' port='6000'/>
       </source>
+      <backingStore/>
       <target dev='vdc' bus='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
     </disk>
@@ -79,6 +81,7 @@
       <backingStore type='file' index='1'>
         <format type='qcow2'/>
         <source file='/tmp/image.qcow'/>
+        <backingStore/>
       </backingStore>
       <target dev='vdd' bus='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>

tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-mirror-active.xml

@@ -16,6 +16,7 @@
     <emulator>/usr/bin/qemu-system-i686</emulator>
     <disk type='block' device='disk'>
       <source dev='/dev/HostVG/QEMUGuest1'/>
+      <backingStore/>
       <mirror type='block' job='copy' ready='yes'>
         <source dev='/dev/HostVG/QEMUGuest1Copy'/>
       </mirror>
@@ -24,12 +25,14 @@
     </disk>
     <disk type='block' device='cdrom'>
       <source dev='/dev/HostVG/QEMUGuest2'/>
+      <backingStore/>
       <target dev='hdc' bus='ide'/>
       <readonly/>
       <address type='drive' controller='0' bus='1' target='0' unit='0'/>
     </disk>
     <disk type='file' device='disk'>
       <source file='/tmp/data.img'/>
+      <backingStore/>
       <mirror type='file' file='/tmp/copy.img' format='qcow2' job='copy'>
         <format type='qcow2'/>
         <source file='/tmp/copy.img'/>
@@ -39,6 +42,7 @@
     </disk>
     <disk type='file' device='disk'>
       <source file='/tmp/logs.img'/>
+      <backingStore/>
       <mirror type='file' file='/tmp/logcopy.img' format='qcow2' job='copy' ready='abort'>
         <format type='qcow2'/>
         <source file='/tmp/logcopy.img'/>

tests/qemuxml2xmloutdata/qemuxml2xmlout-disk-mirror-old.xml

@@ -16,6 +16,7 @@
     <emulator>/usr/bin/qemu-system-i686</emulator>
     <disk type='block' device='disk'>
       <source dev='/dev/HostVG/QEMUGuest1'/>
+      <backingStore/>
       <mirror type='file' file='/dev/HostVG/QEMUGuest1Copy' job='copy' ready='yes'>
         <source file='/dev/HostVG/QEMUGuest1Copy'/>
       </mirror>
@@ -24,12 +25,14 @@
     </disk>
     <disk type='block' device='cdrom'>
       <source dev='/dev/HostVG/QEMUGuest2'/>
+      <backingStore/>
       <target dev='hdc' bus='ide'/>
       <readonly/>
       <address type='drive' controller='0' bus='1' target='0' unit='0'/>
     </disk>
     <disk type='file' device='disk'>
       <source file='/tmp/data.img'/>
+      <backingStore/>
       <mirror type='file' file='/tmp/copy.img' format='qcow2' job='copy'>
         <format type='qcow2'/>
         <source file='/tmp/copy.img'/>
@@ -39,6 +42,7 @@
     </disk>
     <disk type='file' device='disk'>
       <source file='/tmp/logs.img'/>
+      <backingStore/>
       <target dev='vdb' bus='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
     </disk>

tests/qemuxml2xmloutdata/qemuxml2xmlout-seclabel-static-labelskip.xml

@@ -18,6 +18,7 @@
       <source dev='/dev/HostVG/QEMUGuest1'>
         <seclabel model='selinux' labelskip='yes'/>
       </source>
+      <backingStore/>
       <target dev='hda' bus='ide'/>
       <address type='drive' controller='0' bus='0' target='0' unit='0'/>
     </disk>