Swapfile on ZFS & Deadlock

[Benjamin Close]

Hi All,
    Whilst running out of memory compiling Xorg (scanPCI is a killer) I 
discovered a quick way to deadlock the system:

dd if=/dev/zero of=somefileonzfs bs=something count=something
mdconfig -a -f something
swapon /dev/md0

Then do something that needs swap.. instant deadlock. The system is 
still responsive but all disk access become hung.

Known issue? If so is there a way we can warn users/prevent users from 
doing it?

Cheers,
    Benjamin