Userspace should fail over to dropping all logs on the floor. Not useful but it should work.
We're still getting back online after the kernel.org downtime, so I don't have a handy URL for browseable source. Before kernel.org went down the ION kernel side sources were being developed in the open in the kernel repositories at android.git.kernel.org.
Hopefully it'll all be sorted out in the near future alongside the ICS userspace source release.