Fix some pointer issues and type changes

Grabbed a copy of your branch and just fixed the compile errors.

Look's like you've come a long way, hello world to kernel/zfs hacking, nice one!

Only had time for a quick run but is looking quite good... Ran some dd's against it for a while and it gradually assigned more io's to the ram drive till it stopped using the slow disk altogether leaving the ram drive to deliver reads at 700MB/sec ( which is about its peak on this vm )

I'll be quite interested in how it goes on your setup.