Merge branch 'writeback' of git://git.kernel.dk/linux-2.6-block

* 'writeback' of git://git.kernel.dk/linux-2.6-block:
  nfs: initialize the backing_dev_info when creating the server
  writeback: make balance_dirty_pages() gradually back more off
  writeback: don't use schedule_timeout() without setting runstate
  nfs: nfs_kill_super() should call bdi_unregister() after killing super