Fix the calculation of a volume's physical size

Author: Gean Jair Silva

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/LibvirtStorageVolumeDef.java

@@ -83,6 +83,10 @@ public VolumeFormat getFormat() {
         return this._volFormat;
     }
 
+    public Long getVolSize() {
+        return _volSize;
+    }
+
     @Override
     public String toString() {
         StringBuilder storageVolBuilder = new StringBuilder();

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/resource/LibvirtStorageVolumeXMLParser.java

@@ -22,6 +22,7 @@
 import javax.xml.parsers.DocumentBuilder;
 import javax.xml.parsers.ParserConfigurationException;
 
+import com.cloud.utils.StringUtils;
 import org.apache.cloudstack.utils.security.ParserUtils;
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.LogManager;
@@ -35,6 +36,35 @@
 public class LibvirtStorageVolumeXMLParser {
     protected Logger logger = LogManager.getLogger(getClass());
 
+    public String getBackingFileNameIfExists(String volXML) {
+        try {
+            DocumentBuilder builder = ParserUtils.getSaferDocumentBuilderFactory().newDocumentBuilder();
+
+            InputSource is = new InputSource();
+            is.setCharacterStream(new StringReader(volXML));
+            Document doc = builder.parse(is);
+
+            Element rootElement = doc.getDocumentElement();
+            NodeList backingStores = rootElement.getElementsByTagName("backingStore");
+            if (backingStores.getLength() > 0) {
+                Element backingStore = (Element) backingStores.item(0);
+                NodeList pathNodes = backingStore.getElementsByTagName("path");
+                if (pathNodes.getLength() > 0) {
+                    String path = pathNodes.item(0).getTextContent();
+                    if (StringUtils.isBlank(path)) {
+                        return null;
+                    }
+                    path = path.trim();
+                    int lastSlash = path.lastIndexOf('/');
+                    return lastSlash >= 0 ? path.substring(lastSlash + 1) : path;
+                }
+            }
+        } catch (ParserConfigurationException | SAXException | IOException e) {
+            logger.error(e.toString(), e);
+        }
+        return null;
+    }
+
     public LibvirtStorageVolumeDef parseStorageVolumeXML(String volXML) {
         DocumentBuilder builder;
         try {
@@ -50,6 +80,7 @@ public LibvirtStorageVolumeDef parseStorageVolumeXML(String volXML) {
             Element target = (Element)rootElement.getElementsByTagName("target").item(0);
             String format = getAttrValue("type", "format", target);
             Long capacity = Long.parseLong(getTagValue("capacity", rootElement));
+
             return new LibvirtStorageVolumeDef(VolName, capacity, LibvirtStorageVolumeDef.VolumeFormat.getFormat(format), null, null);
         } catch (ParserConfigurationException e) {
             logger.debug(e.toString());

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/storage/LibvirtStorageAdaptor.java

@@ -505,6 +505,12 @@ public LibvirtStoragePoolDef getStoragePoolDef(Connect conn, StoragePool pool) t
         return parser.parseStoragePoolXML(poolDefXML);
     }
 
+    private String getBackingFileOfVolumeIfExists(StorageVol vol) throws LibvirtException {
+        String volDefXML = vol.getXMLDesc(0);
+        LibvirtStorageVolumeXMLParser parser = new LibvirtStorageVolumeXMLParser();
+        return parser.getBackingFileNameIfExists(volDefXML);
+    }
+
     public LibvirtStorageVolumeDef getStorageVolumeDef(Connect conn, StorageVol vol) throws LibvirtException {
         String volDefXML = vol.getXMLDesc(0);
         LibvirtStorageVolumeXMLParser parser = new LibvirtStorageVolumeXMLParser();
@@ -655,6 +661,28 @@ public KVMStoragePool getStoragePool(String uuid, boolean refreshInfo) {
         }
     }
 
+    private Long getBackingFileSizes(StoragePool pool, StorageVol vol) throws LibvirtException {
+        long total = 0L;
+        Set<String> visited = new HashSet<>();
+        StorageVol current = vol;
+
+        while (current != null) {
+            total += current.getInfo().allocation;
+            String backingName = getBackingFileOfVolumeIfExists(current);
+            if (StringUtils.isBlank(backingName) || !visited.add(backingName)) {
+                break;
+            }
+            try {
+                current = getVolume(pool, backingName);
+            } catch (CloudRuntimeException e) {
+                logger.error("Unable to resolve backing volume {} in pool {}: {}", backingName, pool.getName(), e.getMessage());
+                break;
+            }
+        }
+
+        return total;
+    }
+
     @Override
     public KVMPhysicalDisk getPhysicalDisk(String volumeUuid, KVMStoragePool pool) {
         LibvirtStoragePool libvirtPool = (LibvirtStoragePool)pool;
@@ -663,8 +691,9 @@ public KVMPhysicalDisk getPhysicalDisk(String volumeUuid, KVMStoragePool pool) {
             StorageVol vol = getVolume(libvirtPool.getPool(), volumeUuid);
             KVMPhysicalDisk disk;
             LibvirtStorageVolumeDef voldef = getStorageVolumeDef(libvirtPool.getPool().getConnect(), vol);
+            Long allSizes = getBackingFileSizes(libvirtPool.getPool(), vol);
             disk = new KVMPhysicalDisk(vol.getPath(), vol.getName(), pool);
-            disk.setSize(vol.getInfo().allocation);
+            disk.setSize(allSizes);
             disk.setVirtualSize(vol.getInfo().capacity);
 
             /**