FreeBSD 8.1 prerelease "security.jail.mount_allowed" is broken?

[Eugene Mitrofanov]

Hello

I try to do mount from a jail but it failed. Could you advise me where is my 
mistake?

root at ftp:eugene# uname -mrs
FreeBSD 8.1-PRERELEASE amd64
root at ftp:eugene# sysctl -a | grep -E '(jailed|mount)'
vfs.usermount: 1
vfs.ffs.compute_summary_at_mount: 0
security.jail.mount_allowed: 1
security.jail.jailed: 1
root at ftp:eugene# mount /dev/da2s2a /var/t
mount: /dev/da2s2a : Operation not permitted
root at ftp:eugene# mount /dev/md1 /var/t
mount: /dev/md1 : Operation not permitted
root at ftp:eugene# mount /dev/zvol/tank/ftp.journal /var/t
mount: /dev/zvol/tank/ftp.journal : Operation not permitted

Best regards
-- 
EMIT-RIPN, EVM7-RIPE