Create bottles as btrfs subvolumes

bottles/backend/managers/btrfssubvolume.py

@@ -2,6 +2,11 @@
 import os.path
 import btrfsutil
 
+# Internal subvolumes created at initialization time:
+_internal_subvolumes = [
+    "cache",
+    ]
+
 class BtrfsSubvolumeManager:
     """
     Manager to handle bottles created as btrfs subvolume.
@@ -11,4 +16,26 @@ def __init__(
         self,
         manager,
     ):
-        self.manager = manager
+        self._manager = manager
+
+    @staticmethod
+    def create_bottle_as_subvolume(bottle_path) -> bool:
+        """Create bottle as btrfs subvolume.
+
+        Creates the directory 'bottle_path' as btrfs subvolume and internal
+        subvolumes inside of it. Returns True on success and False on failure.
+        In particular it fails, if the filesystem is not btrfs.
+        """
+
+        os.makedirs(os.path.dirname(bottle_path), exist_ok=True)
+        try:
+            btrfsutil.create_subvolume(bottle_path)
+            for internal_subvolume in _internal_subvolumes:
+                path = os.path.join(bottle_path, internal_subvolume)
+                btrfsutil.create_subvolume(path)
+        except btrfsutil.BtrfsUtilError as error:
+            if not error.btrfsutilerror == btrfsutil.ERROR_NOT_BTRFS:
+                raise
+            return False
+        else:
+            return True

bottles/backend/managers/manager.py

@@ -1069,7 +1069,8 @@ def create_bottle_from_config(self, config: BottleConfig) -> bool:
             config.Name = f"{config.Name}__{rnd}"
             config.Path = f"{config.Path}__{rnd}"
 
-        os.makedirs(bottle_path)
+        if not self.btrfs_subvolume_manager.create_bottle_as_subvolume(bottle_path):
+            os.makedirs(bottle_path)
 
         # Pre-create drive_c directory and set the case-fold flag
         bottle_drive_c = os.path.join(bottle_path, "drive_c")
@@ -1232,14 +1233,15 @@ def components_check():
 
         # create the bottle directory
         try:
-            os.makedirs(bottle_complete_path)
+            if not self.btrfs_subvolume_manager.create_bottle_as_subvolume(bottle_complete_path):
+                os.makedirs(bottle_complete_path)
             # Pre-create drive_c directory and set the case-fold flag
             bottle_drive_c = os.path.join(bottle_complete_path, "drive_c")
             os.makedirs(bottle_drive_c)
             FileUtils.chattr_f(bottle_drive_c)
-        except:
+        except RuntimeError as e:
             logging.error(
-                f"Failed to create bottle directory: {bottle_complete_path}", jn=True
+                f"Failed to create bottle directory '{bottle_complete_path}' {e}", jn=True
             )
             log_update(_("Failed to create bottle directory."))
             return Result(False)