[Intel-gfx] [PATCH 3/6] drm/i915: use vmap in shmem_pin_map

[Christoph Hellwig]

On Tue, Sep 22, 2020 at 12:21:44PM +0100, Matthew Wilcox wrote:
> Actually, vfree() will work today; I cc'd you on a documentation update
> to make it clear that this is permitted.

vfree calls __free_pages, the i915 and a lot of other code calls
put_page.  They are mostly the same, but not quite and everytime I
look into that mess I'm more confused than before.

Can someone in the know write sensible documentation on when to use
__free_page(s) vs put_page?