Re: [PATCH] swiotlb: suppress warning when __GFP_NOWARN is set v4

[Christian KÃnig]

Am 04.01.2018 um 10:53 schrieb Christoph Hellwig:
> This seems to collide with my dma direct/swiotlb series posted recently.
>
> > +++ b/lib/swiotlb.c
> > @@ -490,11 +490,11 @@ static void swiotlb_bounce(phys_addr_t orig_addr, phys_addr_t tlb_addr,
> >   	}
> >   }
> >   
> > -phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
> > -				   dma_addr_t tbl_dma_addr,
> > -				   phys_addr_t orig_addr, size_t size,
> > -				   enum dma_data_direction dir,
> > -				   unsigned long attrs)
> > +static phys_addr_t tbl_map_single(struct device *hwdev,
> > +				  dma_addr_t tbl_dma_addr,
> > +				  phys_addr_t orig_addr, size_t size,
> > +				  enum dma_data_direction dir,
> > +				  unsigned long attrs, bool warn)
> We already have DMA_ATTR_NO_WARN which can be passed in attrs.  Please
> use it instead of reinventing it.
>
> >   swiotlb_alloc_coherent(struct device *hwdev, size_t size,
> >   		       dma_addr_t *dma_handle, gfp_t flags)
> >   {
> > +	bool warn = !(flags & __GFP_NOWARN);
> >   	dma_addr_t dev_addr;
> >   	void *ret;
> >   	int order = get_order(size);
> > @@ -739,7 +750,7 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
> >   		 * will grab memory from the lowest available address range.
> >   		 */
> >   		phys_addr_t paddr = map_single(hwdev, 0, size,
> > -					       DMA_FROM_DEVICE, 0);
> > +					       DMA_FROM_DEVICE, 0, warn);
> Note: in my above series swiotlb_alloc_coherent is going away, and
> replaced with a swiotlb_alloc that takes a dma_attrs argument.

That's what I thought about as well, but this is a bug fix for stable 
kernels. So the changes should be as small as possible.

But using DMA_ATTR_NO_WARN is a good point, going to send a v5 which 
uses this instead.

Regards,
Christian.

> Using that for passing the nowarn flag is the right way to go instead
> of using __GFP_NOWARN.