pin_user_pages*() APIs are clearly distinct from the get_user_pages*() APIs, so
that's a natural dividing line, and a good point to make separate wrapper calls.
In other words, use pin_user_pages*() for DMA-pinned pages, and
-get_user_pages*() for other cases. There are four cases described later on in
+get_user_pages*() for other cases. There are five cases described later on in
this document, to further clarify that concept.
FOLL_PIN and FOLL_GET are mutually exclusive for a given gup call. However,