From 33d2271cd62a634bbd6f31d797e0d2347284ec44 Mon Sep 17 00:00:00 2001
From: Jelle van der Waa <jvanderwaa@redhat.com>
Date: Wed, 22 Nov 2023 19:24:17 +0100
Subject: [PATCH] modules/btrfs: add SetDefaultSubvolumeID

libblockdev provides a method to set the default subvolume id since
2014. This method does requires administrative privileges as it changes
the default mount target subvolume of a btrfs volume.
---
 .../data/org.freedesktop.UDisks2.btrfs.xml    | 15 +++++
 modules/btrfs/udiskslinuxfilesystembtrfs.c    | 56 +++++++++++++++++++
 src/tests/dbus-tests/test_btrfs.py            |  9 ++-
 3 files changed, 79 insertions(+), 1 deletion(-)

diff --git a/modules/btrfs/data/org.freedesktop.UDisks2.btrfs.xml b/modules/btrfs/data/org.freedesktop.UDisks2.btrfs.xml
index 385886863..7e03c7ce9 100644
--- a/modules/btrfs/data/org.freedesktop.UDisks2.btrfs.xml
+++ b/modules/btrfs/data/org.freedesktop.UDisks2.btrfs.xml
@@ -233,6 +233,21 @@
       <arg name="options" type="a{sv}" direction="in"/>
     </method>
 
+    <!--
+        SetDefaultSubvolumeID:
+        @id: New default subvolume id.
+        @options: Additional options.
+        @since: 2.11.0
+
+        Sets the default subvolume id.
+
+        No additional options are currently defined.
+    -->
+    <method name="SetDefaultSubvolumeID">
+      <arg name="id" direction="in" type="u"/>
+      <arg name="options" type="a{sv}" direction="in"/>
+    </method>
+
     <property name="label" type="s" access="read"/>
     <property name="uuid" type="s" access="read"/>
     <property name="num_devices" type="t" access="read"/>
diff --git a/modules/btrfs/udiskslinuxfilesystembtrfs.c b/modules/btrfs/udiskslinuxfilesystembtrfs.c
index 82e404f55..7a7e354b9 100644
--- a/modules/btrfs/udiskslinuxfilesystembtrfs.c
+++ b/modules/btrfs/udiskslinuxfilesystembtrfs.c
@@ -705,6 +705,61 @@ handle_get_default_subvolume_id (UDisksFilesystemBTRFS *fs_btrfs,
   return TRUE;
 }
 
+static gboolean
+handle_set_default_subvolume_id (UDisksFilesystemBTRFS *fs_btrfs,
+                       GDBusMethodInvocation *invocation,
+                       guint arg_id,
+                       GVariant              *arg_options)
+{
+  UDisksLinuxFilesystemBTRFS *l_fs_btrfs = UDISKS_LINUX_FILESYSTEM_BTRFS (fs_btrfs);
+  UDisksLinuxBlockObject *object = NULL;
+  GError *error = NULL;
+  UDisksDaemon *daemon;
+  gchar *mount_point = NULL;
+
+  object = udisks_daemon_util_dup_object (l_fs_btrfs, &error);
+  if (! object)
+    {
+      g_dbus_method_invocation_take_error (invocation, error);
+      goto out;
+    }
+
+  daemon = udisks_module_get_daemon (UDISKS_MODULE (l_fs_btrfs->module));
+
+  /* Policy check. */
+  UDISKS_DAEMON_CHECK_AUTHORIZATION (daemon,
+                                     UDISKS_OBJECT (object),
+                                     BTRFS_POLICY_ACTION_ID,
+                                     arg_options,
+                                     N_("Authentication is required to set the default BTRFS subvolume"),
+                                     invocation);
+
+  /* Get the mount point for this volume. */
+  mount_point = udisks_filesystem_btrfs_get_first_mount_point (fs_btrfs, &error);
+  if (! mount_point)
+    {
+      g_dbus_method_invocation_take_error (invocation, error);
+      goto out;
+    }
+
+  if (! bd_btrfs_set_default_subvolume (mount_point, arg_id, NULL, &error))
+    {
+      g_dbus_method_invocation_take_error (invocation, error);
+      goto out;
+    }
+
+  /* Complete DBus call. */
+  udisks_filesystem_btrfs_complete_set_default_subvolume_id (fs_btrfs, invocation);
+
+out:
+  /* Release the resources */
+  g_clear_object (&object);
+  g_free (mount_point);
+
+  /* Indicate that we handled the method invocation */
+  return TRUE;
+}
+
 static gboolean
 handle_create_snapshot (UDisksFilesystemBTRFS  *fs_btrfs,
                         GDBusMethodInvocation  *invocation,
@@ -895,6 +950,7 @@ udisks_linux_filesystem_btrfs_iface_init (UDisksFilesystemBTRFSIface *iface)
   iface->handle_remove_subvolume = handle_remove_subvolume;
   iface->handle_get_subvolumes = handle_get_subvolumes;
   iface->handle_get_default_subvolume_id = handle_get_default_subvolume_id;
+  iface->handle_set_default_subvolume_id = handle_set_default_subvolume_id;
   iface->handle_create_snapshot = handle_create_snapshot;
   iface->handle_repair = handle_repair;
   iface->handle_resize = handle_resize;
diff --git a/src/tests/dbus-tests/test_btrfs.py b/src/tests/dbus-tests/test_btrfs.py
index 5e179c82f..be781ef06 100644
--- a/src/tests/dbus-tests/test_btrfs.py
+++ b/src/tests/dbus-tests/test_btrfs.py
@@ -382,7 +382,7 @@ def test_subvolume_mount(self):
         dbus_mnt = self.ay_to_str(dbus_mounts.value[0])  # mountpoints are arrays of bytes
         self.assertEqual(dbus_mnt, mnt_path)
 
-    def test_get_default_subvolume_id(self):
+    def test_default_subvolume_id(self):
         dev = self._get_devices(1)[0]
         self.addCleanup(self._clean_format, dev.obj)
 
@@ -399,3 +399,10 @@ def test_get_default_subvolume_id(self):
             default_id = dev.obj.GetDefaultSubvolumeID(self.no_options,
                              dbus_interface=self.iface_prefix + '.Filesystem.BTRFS')
             self.assertEqual(default_id, 5)
+
+            dev.obj.SetDefaultSubvolumeID(dbus.UInt32(5), self.no_options,
+                                          dbus_interface=self.iface_prefix + '.Filesystem.BTRFS')
+
+            default_id = dev.obj.GetDefaultSubvolumeID(self.no_options,
+                             dbus_interface=self.iface_prefix + '.Filesystem.BTRFS')
+            self.assertEqual(default_id, 5)