Currently, you can define a logical storage pool with something like:

<pool type='logical'>
	<source>
		<name>MyVG</name>
		<device name='/dev/sdb'/>
...

However, dumping out the XML for this same storage pool (with, say, virsh
pool-dumpxml), gives:

<pool type='logical'>
	<source>
		<name>MyVG</name>
		<device name='/dev/sdb'>
		</device>


To make this more idempotent, do the <device name='/dev/sdb'/> form by default,
and only do the <device>...</device> form if .nfreeExtent is defined for the
storage pool.
Signed-off-by: NChris Lalancette <clalance@redhat.com>

ChangeLog

+Tue Oct 21 19:22:00 CEST 2008 Chris Lalancette <clalance@redhat.com>
+	* src/storage_conf.c: Make logical pool dumpXML more idempotent with
+	  defineXML by outputting <device name='/dev/sdb' /> when we are
+	  dumping XML.  We only use the longer <device
+	  name='/dev/sdb'>foo</device> when a pool has .nfreeExtent defined.
+
 Tue Oct 21 19:18:00 CEST 2008 Chris Lalancette <clalance@redhat.com>
 	* src/storage_conf.c: Make sure to set errors on paths where
 	  ->formatToString() or ->formatFromString() fail.

src/storage_conf.c

@@ -466,7 +466,7 @@ virStoragePoolDefFormat(virConnectPtr conn,
     virBuffer buf = VIR_BUFFER_INITIALIZER;
     const char *type;
     char uuid[VIR_UUID_STRING_BUFLEN];
-    int i;
+    int i, j;
 
     options = virStorageBackendPoolOptionsForType(def->type);
     if (options == NULL)
@@ -499,17 +499,20 @@ virStoragePoolDefFormat(virConnectPtr conn,
     if ((options->flags & VIR_STORAGE_BACKEND_POOL_SOURCE_DEVICE) &&
         def->source.ndevice) {
         for (i = 0 ; i < def->source.ndevice ; i++) {
-            virBufferVSprintf(&buf,"    <device path='%s'>\n", def->source.devices[i].path);
             if (def->source.devices[i].nfreeExtent) {
-                int j;
+                virBufferVSprintf(&buf,"    <device path='%s'>\n",
+                                  def->source.devices[i].path);
                 for (j = 0 ; j < def->source.devices[i].nfreeExtent ; j++) {
                     virBufferVSprintf(&buf, "    <freeExtent start='%llu' end='%llu'/>\n",
                                       def->source.devices[i].freeExtents[j].start,
                                       def->source.devices[i].freeExtents[j].end);
                 }
-            }
                 virBufferAddLit(&buf,"    </device>\n");
             }
+            else
+                virBufferVSprintf(&buf, "    <device path='%s'/>\n",
+                                  def->source.devices[i].path);
+        }
     }
     if ((options->flags & VIR_STORAGE_BACKEND_POOL_SOURCE_DIR) &&
         def->source.dir)