Subject: Re: [PATCH v1 16/16] dma-mapping: Disallow .map_sg operations from returning zero on error

From: Christoph Hellwig <[email-masked]>
Date: Fri, 16 Jul 2021 08:33:32 +0200

On Thu, Jul 15, 2021 at 10:45:44AM -0600, Logan Gunthorpe wrote:
> @@ -194,6 +194,8 @@ static int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
>  	else
>  		ents = ops->map_sg(dev, sg, nents, dir, attrs);
>  
> +	WARN_ON_ONCE(ents == 0);

Turns this into a negative error code while we're at it, just to keep
the callers sane?