[fstab] fix btrfs with LUKS and systemd

- see also #730
- credit goes to @abucodonosor

src/modules/fstab/main.py

@@ -226,6 +226,7 @@ class FstabGenerator(object):
     def generate_fstab_line_info(self, partition):
         """ Generates information for each fstab entry. """
         filesystem = partition["fs"].lower()
+        has_luks = "luksMapperName" in partition
         mount_point = partition["mountPoint"]
         disk_name = disk_name_for_partition(partition)
         is_ssd = disk_name in self.ssd_disks
@@ -253,6 +254,17 @@ class FstabGenerator(object):
             self.root_is_ssd = is_ssd
 
         if filesystem == "btrfs" and "subvol" in partition:
+            if has_luks:
+                return dict(
+                    device="/dev/mapper/" + partition["luksMapperName"],
+                    mount_point=mount_point,
+                    fs=filesystem,
+                    options=",".join(
+                        ["subvol={}".format(partition["subvol"]), options]
+                        ),
+                    check=check,
+                    )
+            else:
                 return dict(
                     device="UUID=" + partition["uuid"],
                     mount_point=mount_point,
@@ -263,7 +275,7 @@ class FstabGenerator(object):
                     check=check,
                     )
 
-        if "luksMapperName" in partition:
+        if has_luks:
             return dict(device="/dev/mapper/" + partition["luksMapperName"],
                         mount_point=mount_point or "swap",
                         fs=filesystem,