rbd: add MakeVolumeGroupID() utility function

The Manager.MakeVolumeGroupID() function can be used to build a CSI
VolumeGroupID from the backend (pool and name of the RBD-group). This
will be used when checking if an RBD-image belongs to a group already.
It is also possible to resolve the VolumeGroup by passing the
VolumeGroupID to the existing Manager.GetVolumeGroupByID() function.

Signed-off-by: Niels de Vos <ndevos@ibm.com>

internal/journal/volumegroupjournal.go

@@ -20,6 +20,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"strings"
 	"time"
 
 	"github.com/ceph/ceph-csi/internal/util"
@@ -166,6 +167,28 @@ func generateVolumeGroupName(namePrefix, groupUUID string) string {
 	return namePrefix + groupUUID
 }
 
+// MakeVolumeGroupID is a utility function that takes details of a VolumeGroup
+// and creates the CSI VolumeGroupId out of those.
+func MakeVolumeGroupID(clusterID string, poolID int64, name, prefix string) (string, error) {
+	namePrefix := prefix
+	if prefix == "" {
+		namePrefix = defaultVolumeGroupNamingPrefix
+	}
+
+	id, found := strings.CutPrefix(name, namePrefix)
+	if !found {
+		return "", fmt.Errorf("volume group name %q does not start with %q", name, namePrefix)
+	}
+
+	handle := util.CSIIdentifier{
+		ClusterID:  clusterID,
+		LocationID: poolID,
+		ObjectUUID: id,
+	}
+
+	return handle.ComposeCSIID()
+}
+
 /*
 CheckReservation checks if given request name contains a valid reservation
   - If there is a valid reservation, then the corresponding VolumeGroupData for

internal/rbd/manager.go

@@ -238,6 +238,21 @@ func (mgr *rbdManager) GetVolumeGroupByID(ctx context.Context, id string) (types
 	return vg, nil
 }
 
+func (mgr *rbdManager) MakeVolumeGroupID(ctx context.Context, poolID int64, name string) (string, error) {
+	clusterID, err := util.GetClusterID(mgr.parameters)
+	if err != nil {
+		return "", fmt.Errorf("failed to get cluster-id: %w", err)
+	}
+
+	// convert the clusterid, poolid and name to an id/handle
+	id, err := journal.MakeVolumeGroupID(clusterID, poolID, name, mgr.getVolumeGroupNamePrefix())
+	if err != nil {
+		return "", fmt.Errorf("failed to convert name %q to a CSI-handle: %w", name, err)
+	}
+
+	return id, nil
+}
+
 func (mgr *rbdManager) CreateVolumeGroup(ctx context.Context, name string) (types.VolumeGroup, error) {
 	creds, err := mgr.getCredentials()
 	if err != nil {

internal/rbd/manager_test.go

@@ -0,0 +1,100 @@
+/*
+Copyright 2025 The Ceph-CSI Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package rbd
+
+import (
+	"context"
+	"testing"
+)
+
+func TestMakeVolumeGroupID(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+
+		// parameters for NewManager()
+		parameters map[string]string
+
+		// arguments for MakeVolumeGroupID()
+		poolID    int64
+		groupName string // should include the "volumeGroupNamePrefix"
+
+		// results
+		volumeGroupID string
+		expectError   bool
+	}{
+		{
+			name:          "no parameters set",
+			parameters:    nil,
+			volumeGroupID: "",
+			expectError:   true,
+		},
+		{
+			name: "missing 'clusterID' parameter",
+			parameters: map[string]string{
+				"pool":    "replicapool",
+				"missing": "clusterID",
+			},
+			poolID:        1,
+			groupName:     "csi-vol-group-my-volume-group",
+			volumeGroupID: "",
+			expectError:   true,
+		},
+		{
+			name: "good volume group with default prefix",
+			parameters: map[string]string{
+				"pool":      "replicapool",
+				"clusterID": "k8s-rook-ceph",
+			},
+			poolID:        1,
+			groupName:     "csi-vol-group-1fac1545-2d0f-4b42-8abb-066ebc39cba9",
+			volumeGroupID: "0001-000d-k8s-rook-ceph-0000000000000001-1fac1545-2d0f-4b42-8abb-066ebc39cba9",
+			expectError:   false,
+		},
+		{
+			name: "volume group with altervative prefix",
+			parameters: map[string]string{
+				"pool":                  "replicapool",
+				"clusterID":             "k8s-rook-ceph",
+				"volumeGroupNamePrefix": "its-a-group-",
+			},
+			poolID:        1,
+			groupName:     "its-a-group-df4a7204-6b06-4eb3-9547-036d845f0cd3",
+			volumeGroupID: "0001-000d-k8s-rook-ceph-0000000000000001-df4a7204-6b06-4eb3-9547-036d845f0cd3",
+			expectError:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			ctx := context.TODO()
+			mgr := NewManager("rbd.example.org", tt.parameters, nil)
+			defer mgr.Destroy(ctx)
+
+			id, err := mgr.MakeVolumeGroupID(ctx, tt.poolID, tt.groupName)
+			if (err != nil) != tt.expectError {
+				t.Logf("mgr: %+v", mgr)
+				t.Errorf("MakeVolumeGroupID failed unexpectedly: %v", err)
+			} else if id != tt.volumeGroupID {
+				t.Errorf("MakeVolumeGroupID returned %q, expected %q", id, tt.volumeGroupID)
+			}
+		})
+	}
+}

internal/rbd/types/manager.go

@@ -32,6 +32,16 @@ type SnapshotResolver interface {
 	GetSnapshotByID(ctx context.Context, id string) (Snapshot, error)
 }
 
+// VolumeGroupResolver can be used to construct a VolumeGroup from a CSI VolumeGroupId.
+type VolumeGroupResolver interface {
+	// MakeVolumeGroupID is called by Volume.GetVolumeGroupID to resolve
+	// the CSI VolumeGroupId of the VolumeGroup where the Volume belongs
+	// to.
+	// The poolID and name are details of the Ceph RBD-group for which the
+	// CSI VolumeGroupId should get constructed.
+	MakeVolumeGroupID(ctx context.Context, poolID int64, name string) (string, error)
+}
+
 // Manager provides a way for other packages to get Volumes and VolumeGroups.
 // It handles the operations on the backend, and makes sure the journal
 // reflects the expected state.
@@ -42,6 +52,9 @@ type Manager interface {
 	// SnapshotResolver is fully implemented by the Manager.
 	SnapshotResolver
 
+	// VolumeGroupResolver is fully implemented by the Manager.
+	VolumeGroupResolver
+
 	// Destroy frees all resources that the Manager allocated.
 	Destroy(ctx context.Context)