rbd: introduce functions for comparing Volumes in a VolumeGroup

CompareVolumesInGroup() verifies that all the volumes are part of the
given VolumeGroup. It does so by obtaining the VolumeGroupID for each
volume with GetVolumeGroupByID().

The helper VolumesInSameGroup() verifies that all volumes belong to the
same (or no) VolumeGroup. It can be called by CSI(-Addons) procedures
before acting on a VolumeGroup.

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

internal/rbd/group.go

@@ -22,6 +22,7 @@ import (
 
 	librbd "github.com/ceph/go-ceph/rbd"
 
+	rbderrors "github.com/ceph/ceph-csi/internal/rbd/errors"
 	"github.com/ceph/ceph-csi/internal/rbd/types"
 )
 
@@ -79,6 +80,28 @@ func (rv *rbdVolume) RemoveFromGroup(ctx context.Context, vg types.VolumeGroup)
 	return librbd.GroupImageRemove(ioctx, name, rv.ioctx, rv.RbdImageName)
 }
 
+// GetVolumeGroupID returns the ID of the VolumeGroup where this rbdVolume
+// belongs to. If the rbdVolume does not belong to a VolumeGroup, a
+// rbderrors.ErrGroupNotFound is returned.
+func (rv *rbdVolume) GetVolumeGroupID(ctx context.Context, resolver types.VolumeGroupResolver) (string, error) {
+	image, err := rv.open()
+	if err != nil {
+		return "", fmt.Errorf("failed to open image %q: %w", rv, err)
+	}
+	defer image.Close()
+
+	info, err := image.GetGroup()
+	if err != nil {
+		return "", fmt.Errorf("could not get group information for image %q: %w", rv, err)
+	}
+
+	if info.Name == "" {
+		return "", fmt.Errorf("%w: image %q is not part of a volume group", rbderrors.ErrGroupNotFound, rv)
+	}
+
+	return resolver.MakeVolumeGroupID(ctx, info.PoolID, info.Name)
+}
+
 func (rv *rbdVolume) ToMirror() (types.Mirror, error) {
 	return rv, nil
 }