For the ldiskfs backend, for a directory which parent resides on remote MDT, to satisfy the local e2fsck, we insert it into the /REMOTE_PARENT_DIR locally. On the other hand, to make the lookup(..) on the directory can return the real parent FID, we append the real parent FID after its ".." name entry in the /REMOTE_PARENT_DIR.

Unfortunately, such PFID-in-dirent cannot be preserved via file-level backup. So after the restore, we cannot get the right parent FID from its ".." name entry in the /REMOTE_PARENT_DIR. Under such case, since we have stored the real parent FID in the directory object's linkEA, we can parse the linkEA for the real parent FID.