Re: [PATCH] swiotlb: Fix inversed DMA_ATTR_NO_WARN test

Michel Dänzer
2018-05-02T14:31:15Z

On 2018-05-02 02:41 PM, Christoph Hellwig wrote:
> On Wed, May 02, 2018 at 02:18:56PM +0200, Daniel Vetter wrote:
>> Other dma-api backends like cma just shut up when __GFP_NOWARN is
>> passed. And afaiui Christoph Hellwig has plans to nuke the DMA_ATTR
>> stuff (or at least clean it up) - should we just remove
>> DMA_ATTR_NO_WARN and instead only look at __GFP_NOWARN?
>
> No. __GFP_NOWARN (and gfp_t flags in general) are the wrong interface
> for dma allocations and just cause problems. I actually plan to
> get rid of the gfp_t argument in dma_alloc_attrs sooner, and only
> allow either GFP_KERNEL or GFP_DMA passed in dma_alloc_coherent.

How about GFP_TRANSHUGE_LIGHT? TTM uses that to opportunistically
allocate huge pages (GFP_TRANSHUGE can result in unacceptably long
delays with memory pressure).

--
Earthling Michel Dänzer | http://www.amd.com
Libre software enthusiast | Mesa and X developer