T_MARKED
m->mnt_t_flags &= ~(T_MARKED | T_UMOUNT_CANDIDATE);
#define IS_MNT_MARKED(m) ((m)->mnt_t_flags & T_MARKED)
#define SET_MNT_MARK(m) ((m)->mnt_t_flags |= T_MARKED)
#define CLEAR_MNT_MARK(m) ((m)->mnt_t_flags &= ~T_MARKED)