Re: [PATCH v1 10/16] s390/pci: return error code from s390_dma_map_sg()

[Niklas Schnelle <schnelle@xxxxxxxxxxxxx>]

On Thu, 2021-07-15 at 10:45 -0600, Logan Gunthorpe wrote:
> From: Martin Oliveira <martin.oliveira@xxxxxxxxxxxxx>
> 
> The .map_sg() op now expects an error code instead of zero on failure.
> 
> So propagate the error from __s390_dma_map_sg() up.
> 
> Signed-off-by: Martin Oliveira <martin.oliveira@xxxxxxxxxxxxx>
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> Cc: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
> Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
> Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> ---
>  arch/s390/pci/pci_dma.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
> index ebc9a49523aa..c78b02012764 100644
> --- a/arch/s390/pci/pci_dma.c
> +++ b/arch/s390/pci/pci_dma.c
> @@ -487,7 +487,7 @@ static int s390_dma_map_sg(struct device *dev, struct 
> scatterlist *sg,
>       unsigned int max = dma_get_max_seg_size(dev);
>       unsigned int size = s->offset + s->length;
>       unsigned int offset = s->offset;
> -     int count = 0, i;
> +     int count = 0, i, ret;
>  
>       for (i = 1; i < nr_elements; i++) {
>               s = sg_next(s);
> @@ -497,8 +497,9 @@ static int s390_dma_map_sg(struct device *dev, struct 
> scatterlist *sg,
>  
>               if (s->offset || (size & ~PAGE_MASK) ||
>                   size + s->length > max) {
> -                     if (__s390_dma_map_sg(dev, start, size,
> -                                           &dma->dma_address, dir))
> +                     ret = __s390_dma_map_sg(dev, start, size,
> +                                             &dma->dma_address, dir);
> +                     if (ret)
>                               goto unmap;
>  
>                       dma->dma_address += offset;
> @@ -511,7 +512,8 @@ static int s390_dma_map_sg(struct device *dev, struct 
> scatterlist *sg,
>               }
>               size += s->length;
>       }
> -     if (__s390_dma_map_sg(dev, start, size, &dma->dma_address, dir))
> +     ret = __s390_dma_map_sg(dev, start, size, &dma->dma_address, dir);
> +     if (ret)
>               goto unmap;
>  
>       dma->dma_address += offset;
> @@ -523,7 +525,7 @@ static int s390_dma_map_sg(struct device *dev, struct 
> scatterlist *sg,
>               s390_dma_unmap_pages(dev, sg_dma_address(s), sg_dma_len(s),
>                                    dir, attrs);
>  
> -     return 0;
> +     return ret;
>  }
>  
>  static void s390_dma_unmap_sg(struct device *dev, struct scatterlist *sg,

So the error codes we return are -ENOMEM if allocating a DMA
translation entry fails and -EINVAL if the DMA translation table hasn't
been initialized or the caller tries to map 0 sized memory. Are these
error codes that you would expect? If yes then this change looks good
to me.

Acked-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>