BUILD_BUG_ON((void*)&old->file_on_disk !=
(void*)&old->staging_file_name);
new->staging_file_name = STRDUP(old->staging_file_name);
BUILD_BUG_ON((void*)&old->file_on_disk !=
(void*)&old->staging_file_name);
new->staging_file_name = STRDUP(old->staging_file_name);