linstor: use sparse/discard qemu-img convert on thin devices (apache#11787)

Author: rp-

plugins/storage/volume/linstor/CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to Linstor CloudStack plugin will be documented in this file
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2025-10-03]
+
+### Changed
+
+- Revert qcow2 snapshot now use sparse/discard options to convert on thin devices.
+
 ## [2025-08-05]
 
 ### Fixed

plugins/storage/volume/linstor/src/main/java/org/apache/cloudstack/storage/datastore/util/LinstorUtil.java

@@ -42,6 +42,7 @@
 import java.util.Optional;
 import java.util.stream.Collectors;
 
+import com.cloud.hypervisor.kvm.storage.KVMStoragePool;
 import com.cloud.utils.Pair;
 import com.cloud.utils.exception.CloudRuntimeException;
 import org.apache.logging.log4j.Logger;
@@ -431,4 +432,37 @@ public static ResourceDefinition findResourceDefinition(DevelopersApi api, Strin
     public static boolean isRscDiskless(ResourceWithVolumes rsc) {
         return rsc.getFlags() != null && rsc.getFlags().contains(ApiConsts.FLAG_DISKLESS);
     }
+
+    /**
+     * Checks if all diskful resource are on a zeroed block device.
+     * @param pool Linstor pool to use
+     * @param resName Linstor resource name
+     * @return true if all resources are on a provider with zeroed blocks.
+     */
+    public static boolean resourceSupportZeroBlocks(KVMStoragePool pool, String resName) {
+        final DevelopersApi api = getLinstorAPI(pool.getSourceHost());
+        try {
+            List<ResourceWithVolumes> resWithVols = api.viewResources(
+                    Collections.emptyList(),
+                    Collections.singletonList(resName),
+                    Collections.emptyList(),
+                    Collections.emptyList(),
+                    null,
+                    null);
+
+            if (resWithVols != null) {
+                return resWithVols.stream()
+                        .allMatch(res -> {
+                            Volume vol0 = res.getVolumes().get(0);
+                            return vol0 != null && (vol0.getProviderKind() == ProviderKind.LVM_THIN ||
+                                    vol0.getProviderKind() == ProviderKind.ZFS ||
+                                    vol0.getProviderKind() == ProviderKind.ZFS_THIN ||
+                                    vol0.getProviderKind() == ProviderKind.DISKLESS);
+                        } );
+            }
+        } catch (ApiException apiExc) {
+            s_logger.error(apiExc.getMessage());
+        }
+        return false;
+    }
 }