rbd: check parent image while mirroring of child

This commit adds code to check parent image while enabling
mirroring on child image. It errors out if the parent is in
trash or not mirror enabled.
This enables better communication with the user on why mirroring
cannot be enabled on the child image.

Signed-off-by: Rakshith R <[email protected]>

internal/rbd/mirror.go

@@ -33,6 +33,39 @@ func (ri *rbdImage) EnableImageMirroring(mode librbd.ImageMirrorMode) error {
 	}
 	defer image.Close()
 
+	parentInfo, err := image.GetParent()
+	if err != nil {
+		return fmt.Errorf("failed to get parent info of image %q: %w",
+			ri, err)
+	}
+
+	if parentInfo.Image.Trash {
+		return fmt.Errorf("failed to enable mirroring on image %q:"+
+			" parent %q is in trash",
+			parentInfo.Image.ImageID, ri)
+	}
+
+	parent, err := ri.getParent()
+	if err != nil {
+		return fmt.Errorf("failed to enable mirroring on image %q:"+
+			" failed to get parent: %w", ri, err)
+	}
+
+	if parent != nil {
+		parentMirroringInfo, err := parent.GetImageMirroringInfo()
+		if err != nil {
+			return fmt.Errorf("failed to enable mirroring on image %q:"+
+				" failed to get mirroring info of parent %q: %w",
+				ri, parent, err)
+		}
+
+		if parentMirroringInfo.State != librbd.MirrorImageEnabled {
+			return fmt.Errorf("failed to enable mirroring on image %q:"+
+				"parent image %q is not enabled for mirroring",
+				ri, parent)
+		}
+	}
+
 	err = image.MirrorEnable(mode)
 	if err != nil {
 		return fmt.Errorf("failed to enable mirroring on %q with error: %w", ri, err)