MNT_FORCE
flags & (MNT_FORCE | MNT_DETACH))
if (flags & MNT_FORCE && sb->s_op->umount_begin) {
if (flags & MNT_FORCE && !ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))