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

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Message-ID: <82c0f8d8-9050-dcf7-d68d-93691878a6dd@deltatee.com>
Date:   Fri, 16 Jul 2021 10:17:58 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Christoph Hellwig <hch@....de>
Cc:     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,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Stephen Bates <sbates@...thlin.com>,
        Martin Oliveira <martin.oliveira@...eticom.com>
Subject: Re: [PATCH v1 16/16] dma-mapping: Disallow .map_sg operations from
 returning zero on error



On 2021-07-16 12:33 a.m., Christoph Hellwig wrote:
> 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?
> 

Sure thing. All the feedback makes sense, we'll fix it up and send a v2
in due course.

Thanks,

Logan