Re: [PATCH] MIPS: Fix `dma_alloc_coherent' returning a non-coherent allocation

[Christoph Hellwig]

On Thu, Nov 01, 2018 at 07:54:24AM +0000, Maciej W. Rozycki wrote:
> Fix a MIPS `dma_alloc_coherent' regression from commit bc3ec75de545 
> ("dma-mapping: merge direct and noncoherent ops") that causes a cached 
> allocation to be returned on noncoherent cache systems.
> 
> This is due to an inverted check now used in the MIPS implementation of 
> `arch_dma_alloc' on the result from `dma_direct_alloc_pages' before 
> doing the cached-to-uncached mapping of the allocation address obtained.  
> The mapping has to be done for a non-NULL rather than NULL result, 
> because a NULL result means the allocation has failed.
> 
> Invert the check for correct operation then.
> 
> Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxxxxx>
> Fixes: bc3ec75de545 ("dma-mapping: merge direct and noncoherent ops")
> Cc: stable@xxxxxxxxxxxxxxx # 4.19+

Oops, yes this looks good:

Reviewed-by: Christoph Hellwig <hch@xxxxxx>