Allow /boot to be a btrfs subvolume

In a btrfs based design, allow to put /boot as subvolume.
This required a small fix in the mount order in a way that
boot/efi gets mounted after the subvolume mounts are done.
The respective integration test has been updated to test
this functionality. This Fixes #2824

Author: schaefi

build-tests/x86/fedora/test-image-live-disk/appliance.kiwi

@@ -30,9 +30,10 @@
         </type>
     </preferences>
     <preferences profiles="Virtual">
-        <type image="oem" filesystem="btrfs" kernelcmdline="console=ttyS0" firmware="uefi" format="qcow2" btrfs_root_is_subvolume="true" btrfs_set_default_volume="false" rootfs_label="fedora" bootpartition="true" bootfilesystem="ext4">
+        <type image="oem" filesystem="btrfs" kernelcmdline="console=ttyS0" firmware="uefi" format="qcow2" btrfs_root_is_subvolume="true" btrfs_set_default_volume="false" rootfs_label="fedora" bootpartition="false">
             <systemdisk name="fedora">
                 <volume name="@root=root"/>
+                <volume name="boot" parent="/"/>
                 <volume name="home" parent="/"/>
                 <volume name="var" parent="/"/>
             </systemdisk>

kiwi/bootloader/config/base.py

@@ -397,21 +397,21 @@ def get_boot_path(self, target='disk'):
                     # according to the mount path.
                     bootpath = '/'
 
-        if target == 'disk':
-            if not need_boot_partition:
-                filesystem = self.xml_state.build_type.get_filesystem()
-                volumes = self.xml_state.get_volumes()
-                if filesystem == 'btrfs' and volumes:
-                    # grub boot data paths must not be in a subvolume
-                    # otherwise grub won't be able to find its config file
-                    grub2_boot_data_paths = ['boot', 'boot/grub', 'boot/grub2']
-                    for volume in volumes:
-                        if volume.name in grub2_boot_data_paths:
-                            raise KiwiBootLoaderTargetError(
-                                '{0} must not be a subvolume'.format(
-                                    volume.name
-                                )
-                            )
+#        if target == 'disk':
+#            if not need_boot_partition:
+#                filesystem = self.xml_state.build_type.get_filesystem()
+#                volumes = self.xml_state.get_volumes()
+#                if filesystem == 'btrfs' and volumes:
+#                    # grub boot data paths must not be in a subvolume
+#                    # otherwise grub won't be able to find its config file
+#                    grub2_boot_data_paths = ['boot', 'boot/grub', 'boot/grub2']
+#                    for volume in volumes:
+#                        if volume.name in grub2_boot_data_paths:
+#                            raise KiwiBootLoaderTargetError(
+#                                '{0} must not be a subvolume'.format(
+#                                    volume.name
+#                                )
+#                            )
 
         if target == 'iso':
             bootpath = '/boot/' + self.arch + '/loader'
@@ -541,9 +541,6 @@ def _mount_system(
         if not self.root_mount.device == self.boot_mount.device:
             self.boot_mount.mount()
 
-        if efi_device:
-            self.efi_mount.mount()
-
         if volumes:
             for volume_path in Path.sort_by_hierarchy(
                 sorted(volumes.keys())
@@ -557,6 +554,9 @@ def _mount_system(
                     options=[volumes[volume_path]['volume_options']]
                 )
 
+        if efi_device:
+            self.efi_mount.mount()
+
         if self.root_filesystem_is_overlay:
             # In case of an overlay root system all parts of the rootfs
             # are read-only. However tools like grub's mkconfig creates
@@ -600,6 +600,10 @@ def _umount_system(self):
             setup = SystemSetup(self.xml_state, self.root_mount.mountpoint)
             setup.setup_selinux_file_contexts()
             # Umount system
+            if self.efi_mount:
+                self.efi_mount.umount()
+            if self.boot_mount:
+                self.boot_mount.umount()
             for volume_mount in reversed(self.volumes_mount):
                 volume_mount.umount()
             if self.device_mount:
@@ -608,14 +612,10 @@ def _umount_system(self):
                 self.proc_mount.umount()
             if self.sys_mount:
                 self.sys_mount.umount()
-            if self.efi_mount:
-                self.efi_mount.umount()
             if self.tmp_mount:
                 self.tmp_mount.umount()
             if self.etc_kernel_mount:
                 self.etc_kernel_mount.umount()
-            if self.boot_mount:
-                self.boot_mount.umount()
             if self.root_mount:
                 self.root_mount.umount()
             self.system_is_mounted = False

test/unit/bootloader/config/base_test.py

@@ -247,24 +247,6 @@ def test_get_boot_path_raises(self):
         with raises(KiwiBootLoaderTargetError):
             self.bootloader.get_boot_path('foo')
 
-    @patch('kiwi.bootloader.config.base.DiskSetup')
-    @patch('kiwi.xml_parse.type_.get_filesystem')
-    @patch('kiwi.xml_state.XMLState.get_volumes')
-    def test_get_boot_path_btrfs_boot_is_a_volume_error(
-        self, mock_volumes, mock_fs, mock_disk_setup
-    ):
-        volume = Mock()
-        volume.name = 'boot'
-        mock_volumes.return_value = [volume]
-        mock_fs.return_value = 'btrfs'
-        disk_setup = Mock()
-        disk_setup.need_boot_partition = Mock(
-            return_value=False
-        )
-        mock_disk_setup.return_value = disk_setup
-        with raises(KiwiBootLoaderTargetError):
-            self.bootloader.get_boot_path()
-
     @patch('kiwi.bootloader.config.base.DiskSetup')
     @patch('kiwi.xml_parse.type_.get_filesystem')
     @patch('kiwi.xml_parse.type_.get_btrfs_root_is_snapper_snapshot')