- The CPU must not touch the buffer after it was DMA-mapped.
  - The size argument of dma_unmap_single(...page_table...) was bogus.
  - Move a comment closer to the code to which it refers to.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: NKristian Høgsberg <krh@redhat.com>