On Mon, Oct 08, 2018 at 10:02:42AM +0200, Christoph Hellwig wrote:
> No need to duplicate the code - map_sg is equivalent to map_page
> for each page in the scatterlist.
> 
> Signed-off-by: Christoph Hellwig <h...@lst.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>

Thank you!
> ---
>  kernel/dma/swiotlb.c | 34 ++++++++++++----------------------
>  1 file changed, 12 insertions(+), 22 deletions(-)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 15335f3a1bf3..15755d7a5242 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -845,37 +845,27 @@ swiotlb_sync_single_for_device(struct device *hwdev, 
> dma_addr_t dev_addr,
>   * same here.
>   */
>  int
> -swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int 
> nelems,
> +swiotlb_map_sg_attrs(struct device *dev, struct scatterlist *sgl, int nelems,
>                    enum dma_data_direction dir, unsigned long attrs)
>  {
>       struct scatterlist *sg;
>       int i;
>  
> -     BUG_ON(dir == DMA_NONE);
> -
>       for_each_sg(sgl, sg, nelems, i) {
> -             phys_addr_t paddr = sg_phys(sg);
> -             dma_addr_t dev_addr = phys_to_dma(hwdev, paddr);
> -
> -             if (swiotlb_force == SWIOTLB_FORCE ||
> -                 !dma_capable(hwdev, dev_addr, sg->length)) {
> -                     phys_addr_t map = map_single(hwdev, sg_phys(sg),
> -                                                  sg->length, dir, attrs);
> -                     if (map == SWIOTLB_MAP_ERROR) {
> -                             /* Don't panic here, we expect map_sg users
> -                                to do proper error handling. */
> -                             attrs |= DMA_ATTR_SKIP_CPU_SYNC;
> -                             swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
> -                                                    attrs);
> -                             sg_dma_len(sgl) = 0;
> -                             return 0;
> -                     }
> -                     sg->dma_address = __phys_to_dma(hwdev, map);
> -             } else
> -                     sg->dma_address = dev_addr;
> +             sg->dma_address = swiotlb_map_page(dev, sg_page(sg), sg->offset,
> +                             sg->length, dir, attrs);
> +             if (sg->dma_address == DIRECT_MAPPING_ERROR)
> +                     goto out_error;
>               sg_dma_len(sg) = sg->length;
>       }
> +
>       return nelems;
> +
> +out_error:
> +     swiotlb_unmap_sg_attrs(dev, sgl, i, dir,
> +                     attrs | DMA_ATTR_SKIP_CPU_SYNC);
> +     sg_dma_len(sgl) = 0;
> +     return 0;
>  }
>  
>  /*
> -- 
> 2.19.0
> 
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