Allow full clone volumes with thin provisioning in KVM (#11177)

It adds a configuration called create.full.clone to the agent.properties file. When set to true, all QCOW2 volumes created will be full-clone. If false (default), the current behavior remains, where only FAT and SPARSE volumes are full-clone and THIN volumes are linked-clone.

Author: JoaoJandre

agent/conf/agent.properties

@@ -447,3 +447,6 @@ iscsi.session.cleanup.enabled=false
 
 # Timeout (in seconds) to wait for the incremental snapshot to complete.
 # incremental.snapshot.timeout=10800
+
+# If set to true, creates VMs as full clones of their templates on KVM hypervisor. Creates as linked clones otherwise.
+# create.full.clone=false

agent/src/main/java/com/cloud/agent/properties/AgentProperties.java

@@ -863,6 +863,14 @@ public Property<Integer> getWorkers() {
      * */
     public static final Property<Integer> REVERT_SNAPSHOT_TIMEOUT = new Property<>("revert.snapshot.timeout", 10800);
 
+    /**
+     *  If set to true, creates VMs as full clones of their templates on KVM hypervisor. Creates as linked clones otherwise. <br>
+     * Data type: Boolean. <br>
+     * Default value: <code>false</code>
+     */
+    public static final Property<Boolean> CREATE_FULL_CLONE = new Property<>("create.full.clone", false);
+
+
     public static class Property <T>{
         private String name;
         private T defaultValue;

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

@@ -32,6 +32,8 @@
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Collectors;
 
+import com.cloud.agent.properties.AgentProperties;
+import com.cloud.agent.properties.AgentPropertiesFileHandler;
 import org.apache.cloudstack.api.ApiConstants;
 import org.apache.cloudstack.utils.cryptsetup.KeyFile;
 import org.apache.cloudstack.utils.qemu.QemuImageOptions;
@@ -1315,14 +1317,22 @@ public KVMPhysicalDisk createDiskFromTemplate(KVMPhysicalDisk template,
                         passphraseObjects.add(QemuObject.prepareSecretForQemuImg(format, QemuObject.EncryptFormat.LUKS, keyFile.toString(), "sec0", options));
                         disk.setQemuEncryptFormat(QemuObject.EncryptFormat.LUKS);
                     }
+
+                    QemuImgFile srcFile = new QemuImgFile(template.getPath(), template.getFormat());
+                    Boolean createFullClone = AgentPropertiesFileHandler.getPropertyValue(AgentProperties.CREATE_FULL_CLONE);
                     switch(provisioningType){
                     case THIN:
-                        QemuImgFile backingFile = new QemuImgFile(template.getPath(), template.getFormat());
-                        qemu.create(destFile, backingFile, options, passphraseObjects);
+                        logger.info("Creating volume [{}] {} backing file [{}] as the property [{}] is [{}].", destFile.getFileName(), createFullClone ? "without" : "with",
+                                template.getPath(), AgentProperties.CREATE_FULL_CLONE.getName(), createFullClone);
+                        if (createFullClone) {
+                            qemu.convert(srcFile, destFile, options, passphraseObjects, null, false);
+                        } else {
+                            qemu.create(destFile, srcFile, options, passphraseObjects);
+                        }
                         break;
                     case SPARSE:
                     case FAT:
-                        QemuImgFile srcFile = new QemuImgFile(template.getPath(), template.getFormat());
+                        srcFile = new QemuImgFile(template.getPath(), template.getFormat());
                         qemu.convert(srcFile, destFile, options, passphraseObjects, null, false);
                         break;
                     }