btrfs: use libbtrfsutil for get/set default subvolume

libbtrfsutil provides it's own error enum for libbtrfsutil functions and
as we no longer parse output this introduces a BD_BTRFS_ERROR_NOT_FOUND
error type. As the mount point not being found is the most likely
failure scenario.

Author: jelly

src/plugins/btrfs.c

@@ -18,10 +18,12 @@
  */
 
 #include <glib.h>
+#include <stdio.h>
 #include <string.h>
 #include <unistd.h>
 #include <blockdev/utils.h>
 #include <bs_size.h>
+#include <btrfsutil.h>
 
 #include "btrfs.h"
 #include "check_deps.h"
@@ -258,6 +260,10 @@ static BDBtrfsFilesystemInfo* get_filesystem_info_from_match (GMatchInfo *match_
     return ret;
 }
 
+static const char* format_btrfs_error (enum btrfs_util_error err) {
+    return g_strdup_printf ("%s: %m", btrfs_util_strerror (err));
+}
+
 /**
  * bd_btrfs_create_volume:
  * @devices: (array zero-terminated=1): list of devices to create btrfs volume from
@@ -454,75 +460,37 @@ gboolean bd_btrfs_delete_subvolume (const gchar *mountpoint, const gchar *name,
  * Tech category: %BD_BTRFS_TECH_SUBVOL-%BD_BTRFS_TECH_MODE_QUERY
  */
 guint64 bd_btrfs_get_default_subvolume_id (const gchar *mountpoint, GError **error) {
-    GRegex *regex = NULL;
-    GMatchInfo *match_info = NULL;
-    gboolean success = FALSE;
-    gchar *output = NULL;
-    gchar *match = NULL;
+    enum btrfs_util_error err;
     guint64 ret = 0;
-    const gchar *argv[5] = {"btrfs", "subvol", "get-default", mountpoint, NULL};
 
-    if (!check_deps (&avail_deps, DEPS_BTRFS_MASK, deps, DEPS_LAST, &deps_check_lock, error) ||
-        !check_module_deps (&avail_module_deps, MODULE_DEPS_BTRFS_MASK, module_deps, MODULE_DEPS_LAST, &deps_check_lock, error))
-        return 0;
-
-    regex = g_regex_new ("ID (\\d+) .*", 0, 0, error);
-    if (!regex) {
-        bd_utils_log_format (BD_UTILS_LOG_WARNING, "Failed to create new GRegex");
-        /* error is already populated */
-        return 0;
+    err = btrfs_util_get_default_subvolume (mountpoint, &ret);
+    if (err) {
+        g_set_error (error, BD_BTRFS_ERROR, BD_BTRFS_ERROR_NOT_FOUND, format_btrfs_error (err));
     }
 
-    success = bd_utils_exec_and_capture_output (argv, NULL, &output, error);
-    if (!success) {
-        g_regex_unref (regex);
-        return 0;
-    }
-
-    success = g_regex_match (regex, output, 0, &match_info);
-    if (!success) {
-        g_set_error (error, BD_BTRFS_ERROR, BD_BTRFS_ERROR_PARSE, "Failed to parse subvolume's ID");
-        g_regex_unref (regex);
-        g_match_info_free (match_info);
-        g_free (output);
-        return 0;
-    }
-
-    match = g_match_info_fetch (match_info, 1);
-    ret = g_ascii_strtoull (match, NULL, 0);
-
-    g_free (match);
-    g_match_info_free (match_info);
-    g_regex_unref (regex);
-    g_free (output);
-
     return ret;
 }
 
 /**
  * bd_btrfs_set_default_subvolume:
  * @mountpoint: mountpoint of the volume to set the default subvolume ID of
  * @subvol_id: ID of the subvolume to be set as the default subvolume
- * @extra: (nullable) (array zero-terminated=1): extra options for the setting (right now
- *                                                 passed to the 'btrfs' utility)
  * @error: (out) (optional): place to store error (if any)
  *
  * Returns: whether the @mountpoint volume's default subvolume was correctly set
  * to @subvol_id or not
  *
  * Tech category: %BD_BTRFS_TECH_SUBVOL-%BD_BTRFS_TECH_MODE_MODIFY
  */
-gboolean bd_btrfs_set_default_subvolume (const gchar *mountpoint, guint64 subvol_id, const BDExtraArg **extra, GError **error) {
-    const gchar *argv[6] = {"btrfs", "subvol", "set-default", NULL, mountpoint, NULL};
+gboolean bd_btrfs_set_default_subvolume (const gchar *mountpoint, guint64 subvol_id, GError **error) {
+    enum btrfs_util_error err;
     gboolean ret = FALSE;
 
-    if (!check_deps (&avail_deps, DEPS_BTRFS_MASK, deps, DEPS_LAST, &deps_check_lock, error) ||
-        !check_module_deps (&avail_module_deps, MODULE_DEPS_BTRFS_MASK, module_deps, MODULE_DEPS_LAST, &deps_check_lock, error))
-        return FALSE;
-
-    argv[3] = g_strdup_printf ("%"G_GUINT64_FORMAT, subvol_id);
-    ret = bd_utils_exec_and_report_error (argv, extra, error);
-    g_free ((gchar *) argv[3]);
+    err = btrfs_util_set_default_subvolume (mountpoint, subvol_id);
+    if (err)
+        g_set_error (error, BD_BTRFS_ERROR, BD_BTRFS_ERROR_NOT_FOUND, format_btrfs_error (err));
+    else
+        ret = TRUE;
 
     return ret;
 }

src/plugins/btrfs.h

@@ -14,6 +14,7 @@ typedef enum {
     BD_BTRFS_ERROR_TECH_UNAVAIL,
     BD_BTRFS_ERROR_DEVICE,
     BD_BTRFS_ERROR_PARSE,
+    BD_BTRFS_ERROR_NOT_FOUND,
 } BDBtrfsError;
 
 typedef struct BDBtrfsDeviceInfo {
@@ -79,7 +80,7 @@ gboolean bd_btrfs_remove_device (const gchar *mountpoint, const gchar *device, c
 gboolean bd_btrfs_create_subvolume (const gchar *mountpoint, const gchar *name, const BDExtraArg **extra, GError **error);
 gboolean bd_btrfs_delete_subvolume (const gchar *mountpoint, const gchar *name, const BDExtraArg **extra, GError **error);
 guint64 bd_btrfs_get_default_subvolume_id (const gchar *mountpoint, GError **error);
-gboolean bd_btrfs_set_default_subvolume (const gchar *mountpoint, guint64 subvol_id, const BDExtraArg **extra, GError **error);
+gboolean bd_btrfs_set_default_subvolume (const gchar *mountpoint, guint64 subvol_id, GError **error);
 gboolean bd_btrfs_create_snapshot (const gchar *source, const gchar *dest, gboolean ro, const BDExtraArg **extra, GError **error);
 BDBtrfsDeviceInfo** bd_btrfs_list_devices (const gchar *device, GError **error);
 BDBtrfsSubvolumeInfo** bd_btrfs_list_subvolumes (const gchar *mountpoint, gboolean snapshots_only, GError **error);

tests/btrfs_test.py

@@ -277,7 +277,7 @@ def test_get_default_subvolume_id(self):
         self.assertTrue(succ)
 
         # not mounted yet, should fail
-        with self.assertRaisesRegex(GLib.GError, r".*(can't|cannot) access.*"):
+        with self.assertRaisesRegex(GLib.GError, r".*Could not open: No such file or directory.*"):
             ret = BlockDev.btrfs_get_default_subvolume_id(TEST_MNT)
 
         mount(self.loop_dev, TEST_MNT)
@@ -292,6 +292,10 @@ def test_set_default_subvolume(self):
         succ = BlockDev.btrfs_create_volume([self.loop_dev], "myShinyBtrfs", None, None, None)
         self.assertTrue(succ)
 
+        # not mounted yet, should fail
+        with self.assertRaisesRegex(GLib.GError, r".*Could not open: No such file or directory.*"):
+            ret = BlockDev.btrfs_get_default_subvolume_id(TEST_MNT)
+
         mount(self.loop_dev, TEST_MNT)
 
         ret = BlockDev.btrfs_get_default_subvolume_id(TEST_MNT)