linux-kernel - Re: [PATCH v1 10/16] s390/pci: return error code from s390_dma_map

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Message-ID: <352f2a35d62399fce1dca0ce1158974ecda3904c.camel@linux.ibm.com>
Date:   Fri, 16 Jul 2021 10:24:08 +0200
From:   Niklas Schnelle <schnelle@...ux.ibm.com>
To:     Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org, linux-alpha@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, sparclinux@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-parisc@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Cc:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Stephen Bates <sbates@...thlin.com>,
        Martin Oliveira <martin.oliveira@...eticom.com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>
Subject: Re: [PATCH v1 10/16] s390/pci: return error code from
 s390_dma_map_sg()

On Thu, 2021-07-15 at 10:45 -0600, Logan Gunthorpe wrote:
> From: Martin Oliveira <martin.oliveira@...eticom.com>
> 
> 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@...eticom.com>
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> Cc: Niklas Schnelle <schnelle@...ux.ibm.com>
> Cc: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>
> Cc: Heiko Carstens <hca@...ux.ibm.com>
> Cc: Vasily Gorbik <gor@...ux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@...ibm.com>
> ---
>  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@...ux.ibm.com>