rbd: add rbdVolume.open() to get access to an image

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

internal/rbd/rbd_util.go

@@ -200,6 +200,27 @@ func createImage(ctx context.Context, pOpts *rbdVolume, cr *util.Credentials) er
 	return nil
 }
 
+// open the rbdVolume after it has been connected.
+// ErrPoolNotFound or ErrImageNotFound are returned in case the pool or image
+// can not be found, other errors will contain more details about other issues
+// (permission denied, ...) and are expected to relate to configuration issues.
+func (rv *rbdVolume) open() (*librbd.Image, error) {
+	ioctx, err := rv.conn.GetIoctx(rv.Pool)
+	if err != nil {
+		// GetIoctx() can return util.ErrPoolNotFound
+		return nil, err
+	}
+
+	image, err := librbd.OpenImage(ioctx, rv.RbdImageName, librbd.NoSnapshot)
+	if err != nil {
+		if err == librbd.ErrNotFound {
+			err = ErrImageNotFound{rv.RbdImageName, err}
+		}
+		return nil, err
+	}
+	return image, nil
+}
+
 // rbdStatus checks if there is watcher on the image.
 // It returns true if there is a watcher on the image, otherwise returns false.
 func rbdStatus(ctx context.Context, pOpts *rbdVolume, cr *util.Credentials) (bool, string, error) {

internal/util/connection.go

@@ -71,7 +71,13 @@ func (cc *ClusterConnection) GetIoctx(pool string) (*rados.IOContext, error) {
 
 	ioctx, err := cc.conn.OpenIOContext(pool)
 	if err != nil {
-		return nil, errors.Wrapf(err, "failed to open IOContext for pool %s", pool)
+		// ErrNotFound indicates the Pool was not found
+		if err == rados.ErrNotFound {
+			err = ErrPoolNotFound{pool, err}
+		} else {
+			err = errors.Wrapf(err, "failed to open IOContext for pool %s", pool)
+		}
+		return nil, err
 	}
 
 	return ioctx, nil