at http://www.leidinger.net/FreeBSD/current-patches/jail.diff I have a patch to switch the jail rc script to the new jail (8-current) syntax. This includes new config options for a jail (see etc/defaults/rc.conf after patching). The patch also contains my X-in-a-jail stuff (feel free to ignore this part, it's disabled by default).

If you do not make any config change, you will be able to see all mounted filesystems of the entire machine. To get back to the previous behavior, you have to add a config option: jail_XXX_startparams="enforce_statfs=2"

This config option can also take other jail parameters like allow.sysvipc and other ones described in the jail man-page (additional parameters need to be space separated).

Feedback welcome.