Second pull request of 2014-03-12. The first one was requested to be canceled.

Rob's fix for oops on invalidate_caches() and a fix for a
performance regression.

* tag 'ttm-fixes-3.14-2014-03-12' of git://people.freedesktop.org/~thomash/linux:
  drm/ttm: don't oops if no invalidate_caches()
  drm/ttm: Work around performance regression with VM_PFNMAP