btrfs: add option to not set subvolumes as default

When we want to create a subvolume and set is as default, we can
use the set_default parameter. The current code will check, for
already created subvolumes, if it is actually marked as default,
and if not it will be set inside the state.

For composability with other states, we sometimes want to avoid
the re-set of the default flag for already present subvolumes, as
can be that this was change in a later action by another state.

salt/states/btrfs.py

@@ -129,7 +129,8 @@ def wrapper(*args, **kwargs):
 
 @__mount_device
 def subvolume_created(name, device, qgroupids=None, set_default=False,
-                      copy_on_write=True, __dest=None):
+                      copy_on_write=True, force_set_default=True,
+                      __dest=None):
     '''
     Makes sure that a btrfs subvolume is present.
 
@@ -150,6 +151,10 @@ def subvolume_created(name, device, qgroupids=None, set_default=False,
     copy_on_write
         If false, set the subvolume with chattr +C
 
+    force_set_default
+        If false and the subvolume is already present, it will not
+        force it as default if ``set_default`` is True
+
     '''
     ret = {
         'name': name,
@@ -190,7 +195,10 @@ def subvolume_created(name, device, qgroupids=None, set_default=False,
 
         ret['changes'][name] = 'Created subvolume {}'.format(name)
 
-    if set_default and not _is_default(path, __dest, name):
+    # If the volume was already present, we can opt-out the check for
+    # default subvolume.
+    if (not exists or (exists and force_set_default)) and \
+       set_default and not _is_default(path, __dest, name):
         ret['changes'][name + '_default'] = _set_default(path, __dest, name)
 
     if not copy_on_write and _is_cow(path):

tests/unit/states/test_btrfs.py

@@ -316,6 +316,42 @@ def test_subvolume_created_exists_set_default(self, mount, umount,
             mount.assert_called_once()
             umount.assert_called_once()
 
+    @patch('salt.states.btrfs._set_default')
+    @patch('salt.states.btrfs._is_default')
+    @patch('salt.states.btrfs._umount')
+    @patch('salt.states.btrfs._mount')
+    def test_subvolume_created_exists_set_default_no_force(self,
+                                                           mount,
+                                                           umount,
+                                                           is_default,
+                                                           set_default):
+        '''
+        Test creating a subvolume.
+        '''
+        mount.return_value = '/tmp/xxx'
+        is_default.return_value = False
+        set_default.return_value = True
+        salt_mock = {
+            'btrfs.subvolume_exists': MagicMock(return_value=True),
+        }
+        opts_mock = {
+            'test': False,
+        }
+        with patch.dict(btrfs.__salt__, salt_mock), \
+                patch.dict(btrfs.__opts__, opts_mock):
+            assert btrfs.subvolume_created(name='@/var',
+                                           device='/dev/sda1',
+                                           set_default=True,
+                                           force_set_default=False) == {
+                'name': '@/var',
+                'result': True,
+                'changes': {},
+                'comment': ['Subvolume @/var already present'],
+            }
+            salt_mock['btrfs.subvolume_exists'].assert_called_with('/tmp/xxx/@/var')
+            mount.assert_called_once()
+            umount.assert_called_once()
+
     @patch('salt.states.btrfs._is_cow')
     @patch('salt.states.btrfs._umount')
     @patch('salt.states.btrfs._mount')