Excerpts from Li Zefan's message of 2011-02-16 01:06:41 -0500:

When decompressing a chunk of data, we'll copy the data out to
a working buffer if the data is stored in more than one page,
otherwise we'll use the mapped page directly to avoid memory
copy.

In the latter case, we'll end up accessing the kernel address
after we've unmapped the page in a corner case.

Great, thanks I've got this running here now.

-chris