+
+/*
+ * For a given:
+ * - file or directory return the containing tree root id
+ * - subvolume return its own tree id
+ * - BTRFS_EMPTY_SUBVOL_DIR_OBJECTID (directory with ino == 2) the result is
+ * undefined and function returns -1
+ */
+int lookup_path_rootid(int fd, u64 *rootid)
+{
+ struct btrfs_ioctl_ino_lookup_args args;
+ int ret;
+
+ memset(&args, 0, sizeof(args));
+ args.treeid = 0;
+ args.objectid = BTRFS_FIRST_FREE_OBJECTID;
+
+ ret = ioctl(fd, BTRFS_IOC_INO_LOOKUP, &args);
+ if (ret < 0)
+ return -errno;
+
+ *rootid = args.treeid;
+
+ return 0;
+}
+