Comment 2 for bug 837143

Given this code in os0file.c:

if (srv_file_per_table) {
 retry = os_file_handle_error_no_exit(name,
   create_mode == OS_FILE_CREATE ?
   "create" : "open");
} else {
 retry = os_file_handle_error(name,
   create_mode == OS_FILE_CREATE ?
   "create" : "open");
}

I can confirm that you cannot work around by simply giving xtrabackup binary --innodb_file_per_table=1 on the command line. The only work around is actually creating the tmpdir you need.