Some cleanup from the surprise direct-to-bio for O_DIRECT merge.

- Remove bits and pieces from the kiobuf implementation

- Replace the waitqueue in struct dio with just a task_struct pointer
  and use wake_up_process.  (Ben).

- Only take mmap_sem around the individual calls to get_user_pages().
   (It pins the vmas, yes?)

- Remove some debug code.

- Fix JFS.