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

From: Niklas Schnelle <schnelle@linux.ibm.com>
To: Logan Gunthorpe <logang@deltatee.com>,
	linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
	linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org, sparclinux@vger.kernel.org,
	iommu@lists.linux-foundation.org, linux-parisc@vger.kernel.org,
	xen-devel@lists.xenproject.org
Cc: Vasily Gorbik <gor@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Martin Oliveira <martin.oliveira@eideticom.com>,
	Stephen Bates <sbates@raithlin.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Christoph Hellwig <hch@lst.de>,
	Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH v1 10/16] s390/pci: return error code from s390_dma_map_sg()
Date: Fri, 16 Jul 2021 10:24:08 +0200	[thread overview]
Message-ID: <352f2a35d62399fce1dca0ce1158974ecda3904c.camel@linux.ibm.com> (raw)
In-Reply-To: <20210715164544.6827-11-logang@deltatee.com>

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