fix bootloader device by label for disks (bsc#1009493)

src/lib/bootloader/udev_mapping.rb

@@ -56,6 +56,12 @@ def to_mountby_device(dev)
       # explicit request to mount by kernel device
       return kernel_dev if mount_by == :device
 
+      disk = Yast::Storage.GetTargetMap.key?(kernel_dev)
+      if disk && mount_by == :label
+        log.info "mount be label for disk, so using kernel device as fallback"
+        return kernel_dev
+      end
+
       udev_data_key = MOUNT_BY_MAPPING_TO_UDEV[mount_by]
       raise "Internal error unknown mountby #{mount_by}" unless udev_data_key
       udev_pair = map_device_to_udev_devices(

test/udev_mapping_test.rb

@@ -100,6 +100,13 @@
       expect(subject.to_mountby_device("/dev/vda1")).to eq "/dev/vda1"
     end
 
+    it "returns kernel device if mount by is used by label" do
+      target_map_stub("storage_dm.yaml")
+      expect(Yast::Storage).to receive(:GetDefaultMountBy).and_return(:label)
+
+      expect(subject.to_mountby_device("/dev/sda")).to eq "/dev/sda"
+    end
+
     it "returns its name if partition do not exists" do
       target_map_stub("storage_lvm.yaml")
       allow(Yast::Storage).to receive(:GetDefaultMountBy).and_return(:uuid)