use exact allocation for dma coherent memory

[Christoph Hellwig]

On Tue, Jul 02, 2019 at 11:48:44AM +0200, Arend Van Spriel wrote:
> You made me look ;-) Actually not touching my drivers so I'm off the hook. 
> However, I was wondering if drivers could know so I decided to look into 
> the DMA-API.txt documentation which currently states:
>
> """
> The flag parameter (dma_alloc_coherent() only) allows the caller to
> specify the ``GFP_`` flags (see kmalloc()) for the allocation (the
> implementation may choose to ignore flags that affect the location of
> the returned memory, like GFP_DMA).
> """
>
> I do expect you are going to change that description as well now that you 
> are going to issue a warning on __GFP_COMP. Maybe include that in patch 
> 15/16 where you introduce that warning.

Yes, that description needs an updated, even without this series.
I'll make sure it is more clear.