Allow creating snapshot from VM snapshot (#4739)

If `kvm.snapshot.enabled` is set to false then we cant create snapshot from
VM snapshot. With this change, its possible to create snapshot from VM
snapshot even when the global setting is set to false.
Note that you still cant directly create a snapshot from volume though

Author: ravening

api/src/main/java/com/cloud/storage/snapshot/SnapshotApiService.java

@@ -88,6 +88,10 @@ public interface SnapshotApiService {
 
     Snapshot allocSnapshot(Long volumeId, Long policyId, String snapshotName, Snapshot.LocationType locationType) throws ResourceAllocationException;
 
+    Snapshot allocSnapshot(Long volumeId, Long policyId, String snapshotName, Snapshot.LocationType locationType, Boolean isFromVmSnapshot)
+            throws ResourceAllocationException;
+
+
     /**
      * Create a snapshot of a volume
      *

server/src/main/java/com/cloud/storage/VolumeApiServiceImpl.java

@@ -3302,7 +3302,7 @@ public Snapshot allocSnapshot(Long volumeId, Long policyId, String snapshotName,
             throw new InvalidParameterValueException("VolumeId: " + volumeId + " please attach this volume to a VM before create snapshot for it");
         }
 
-        return snapshotMgr.allocSnapshot(volumeId, policyId, snapshotName, locationType);
+        return snapshotMgr.allocSnapshot(volumeId, policyId, snapshotName, locationType, false);
     }
 
     @Override
@@ -3358,7 +3358,7 @@ public Snapshot allocSnapshotForVm(Long vmId, Long volumeId, String snapshotName
             throw new InvalidParameterValueException("Cannot perform this operation, unsupported on storage pool type " + storagePool.getPoolType());
         }
 
-        return snapshotMgr.allocSnapshot(volumeId, Snapshot.MANUAL_POLICY_ID, snapshotName, null);
+        return snapshotMgr.allocSnapshot(volumeId, Snapshot.MANUAL_POLICY_ID, snapshotName, null, true);
     }
 
     @Override

server/src/main/java/com/cloud/storage/snapshot/SnapshotManagerImpl.java

@@ -1126,7 +1126,7 @@ private Type getSnapshotType(IntervalType intvType) {
         return null;
     }
 
-    private boolean hostSupportSnapsthotForVolume(HostVO host, VolumeInfo volume) {
+    private boolean hostSupportsSnapsthotForVolume(HostVO host, VolumeInfo volume, boolean isFromVmSnapshot) {
         if (host.getHypervisorType() != HypervisorType.KVM) {
             return true;
         }
@@ -1138,7 +1138,7 @@ private boolean hostSupportSnapsthotForVolume(HostVO host, VolumeInfo volume) {
             VMInstanceVO vm = _vmDao.findById(vmId);
             if (vm.getState() != VirtualMachine.State.Stopped && vm.getState() != VirtualMachine.State.Destroyed) {
                 boolean snapshotEnabled = Boolean.parseBoolean(_configDao.getValue("kvm.snapshot.enabled"));
-                if (!snapshotEnabled) {
+                if (!snapshotEnabled && !isFromVmSnapshot) {
                     s_logger.debug("Snapshot is not supported on host " + host + " for the volume " + volume + " attached to the vm " + vm);
                     return false;
                 }
@@ -1159,7 +1159,7 @@ private boolean hostSupportSnapsthotForVolume(HostVO host, VolumeInfo volume) {
         return false;
     }
 
-    private boolean supportedByHypervisor(VolumeInfo volume) {
+    private boolean supportedByHypervisor(VolumeInfo volume, boolean isFromVmSnapshot) {
         HypervisorType hypervisorType;
         StoragePoolVO storagePool = _storagePoolDao.findById(volume.getDataStore().getId());
         ScopeType scope = storagePool.getScope();
@@ -1183,7 +1183,7 @@ private boolean supportedByHypervisor(VolumeInfo volume) {
             }
             if (hosts != null && !hosts.isEmpty()) {
                 HostVO host = hosts.get(0);
-                if (!hostSupportSnapsthotForVolume(host, volume)) {
+                if (!hostSupportsSnapsthotForVolume(host, volume, isFromVmSnapshot)) {
                     throw new CloudRuntimeException(
                             "KVM Snapshot is not supported for Running VMs. It is disabled by default due to a possible volume corruption in certain cases. To enable it set global settings kvm.snapshot.enabled to True. See the documentation for more details.");
                 }
@@ -1460,9 +1460,14 @@ public void cleanupSnapshotsByVolume(Long volumeId) {
 
     @Override
     public Snapshot allocSnapshot(Long volumeId, Long policyId, String snapshotName, Snapshot.LocationType locationType) throws ResourceAllocationException {
+        return allocSnapshot(volumeId, policyId, snapshotName, locationType, false);
+    }
+
+    @Override
+    public Snapshot allocSnapshot(Long volumeId, Long policyId, String snapshotName, Snapshot.LocationType locationType, Boolean isFromVmSnapshot) throws ResourceAllocationException {
         Account caller = CallContext.current().getCallingAccount();
         VolumeInfo volume = volFactory.getVolume(volumeId);
-        supportedByHypervisor(volume);
+        supportedByHypervisor(volume, isFromVmSnapshot);
 
         // Verify permissions
         _accountMgr.checkAccess(caller, null, true, volume);