FDEFER
(oflags | FSCAN) & ~(FMARK|FDEFER));
if ((fp->f_flag & FDEFER) != 0) {
atomic_and_uint(&fp->f_flag, ~FDEFER);
if (fp->f_flag & (FMARK | FDEFER)) {
atomic_or_uint(&fp->f_flag, FDEFER);