PIDFD_NS_MNT
if (self->nsfds[PIDFD_NS_MNT] >= 0 && unshare(CLONE_NEWNS) < 0) {
if (self->nsfds[PIDFD_NS_MNT] >= 0 && unshare(CLONE_NEWNS) < 0) {
[PIDFD_NS_MNT] = { "mnt", CLONE_NEWNS, PIDFD_GET_MNT_NAMESPACE, },