From c1c6adb8dc3b1fc2fb034afc930ba4f7aa012932 Mon Sep 17 00:00:00 2001
From: Jelle van der Waa <jvanderwaa@redhat.com>
Date: Fri, 17 Nov 2023 18:21:10 +0100
Subject: [PATCH] modules/btrfs: add GetDefaultSubvolumeID

libblockdev provides a method to get the default subvolume id since
2014, with no way to change it. This method does not require any
administrative privileges but requires it for setting.
---
 .../data/org.freedesktop.UDisks2.btrfs.xml    | 14 ++++++
 modules/btrfs/udiskslinuxfilesystembtrfs.c    | 46 +++++++++++++++++++
 src/tests/dbus-tests/test_btrfs.py            | 18 ++++++++
 3 files changed, 78 insertions(+)

diff --git a/modules/btrfs/data/org.freedesktop.UDisks2.btrfs.xml b/modules/btrfs/data/org.freedesktop.UDisks2.btrfs.xml
index e2b01e21cf..3858868635 100644
--- a/modules/btrfs/data/org.freedesktop.UDisks2.btrfs.xml
+++ b/modules/btrfs/data/org.freedesktop.UDisks2.btrfs.xml
@@ -219,6 +219,20 @@
       <arg name="options" type="a{sv}" direction="in"/>
     </method>
 
+    <!--
+        GetDefaultSubvolumeID:
+        @options: Additional options.
+        @since: 2.11.0
+
+        Returns the default subvolume id.
+
+        No additional options are currently defined.
+    -->
+    <method name="GetDefaultSubvolumeID">
+      <arg name="id" direction="out" 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 ba3e4f105c..82e404f553 100644
--- a/modules/btrfs/udiskslinuxfilesystembtrfs.c
+++ b/modules/btrfs/udiskslinuxfilesystembtrfs.c
@@ -660,6 +660,51 @@ handle_get_subvolumes (UDisksFilesystemBTRFS *fs_btrfs,
   return TRUE;
 }
 
+static gboolean
+handle_get_default_subvolume_id (UDisksFilesystemBTRFS *fs_btrfs,
+                       GDBusMethodInvocation *invocation,
+                       GVariant              *arg_options)
+{
+  UDisksLinuxFilesystemBTRFS *l_fs_btrfs = UDISKS_LINUX_FILESYSTEM_BTRFS (fs_btrfs);
+  UDisksLinuxBlockObject *object = NULL;
+  GError *error = NULL;
+  gchar *mount_point = NULL;
+  guint64 default_id;
+
+  object = udisks_daemon_util_dup_object (l_fs_btrfs, &error);
+  if (! object)
+    {
+      g_dbus_method_invocation_take_error (invocation, error);
+      goto out;
+    }
+
+  /* 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;
+    }
+
+  default_id = bd_btrfs_get_default_subvolume_id (mount_point, &error);
+  if (! default_id && error)
+    {
+      g_dbus_method_invocation_take_error (invocation, error);
+      goto out;
+    }
+
+  /* Complete DBus call. */
+  udisks_filesystem_btrfs_complete_get_default_subvolume_id (fs_btrfs, invocation, default_id);
+
+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,
@@ -849,6 +894,7 @@ udisks_linux_filesystem_btrfs_iface_init (UDisksFilesystemBTRFSIface *iface)
   iface->handle_create_subvolume = handle_create_subvolume;
   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_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 af991202a7..5e179c82fb 100644
--- a/src/tests/dbus-tests/test_btrfs.py
+++ b/src/tests/dbus-tests/test_btrfs.py
@@ -381,3 +381,21 @@ def test_subvolume_mount(self):
         dbus_mounts.assertLen(1)  # just one mountpoint
         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):
+        dev = self._get_devices(1)[0]
+        self.addCleanup(self._clean_format, dev.obj)
+
+        manager = self.get_object('/Manager')
+        manager.CreateVolume([dev.obj_path],
+                             'test_subvolume_id', 'single', 'single',
+                             self.no_options,
+                             dbus_interface=self.iface_prefix + '.Manager.BTRFS')
+
+        fstype = self.get_property(dev.obj, '.Block', 'IdType')
+        fstype.assertEqual('btrfs')
+
+        with self._temp_mount(dev.path):
+            default_id = dev.obj.GetDefaultSubvolumeID(self.no_options,
+                             dbus_interface=self.iface_prefix + '.Filesystem.BTRFS')
+            self.assertEqual(default_id, 5)