MNTK_UPPER_WAITER
if ((mp->mnt_kern_flag & MNTK_UPPER_WAITER) != 0 &&
mp->mnt_kern_flag &= ~MNTK_UPPER_WAITER;
mp->mnt_kern_flag |= MNTK_UPPER_WAITER;
if ((mp->mnt_kern_flag & MNTK_UPPER_WAITER) != 0 &&
mp->mnt_kern_flag &= ~MNTK_UPPER_WAITER;
MNT_KERN_FLAG(MNTK_UPPER_WAITER);