Re: [PATCH 13/16] nvme-pci: Convert to using dma_map_sg_p2pdma for p2pdma pages

[John Hubbard]

On 5/3/21 10:19 AM, Logan Gunthorpe wrote:
...
> > > +	nr_mapped = dma_map_sg_p2pdma_attrs(dev->dev, iod->sg, iod->nents,
> > > +				     rq_dma_dir(req), DMA_ATTR_NO_WARN);
> > > +	if (nr_mapped < 0) {
> > > +		if (nr_mapped != -ENOMEM)
> > > +			ret = BLK_STS_TARGET;
> > >    		goto out_free_sg;
> > > +	}
> >
> > But now the "nr_mapped == 0" case is no longer doing an early out_free_sg.
> > Is that OK?
>
> dma_map_sg_p2pdma_attrs() never returns zero. It will return -ENOMEM in
> the same situation and results in the same goto out_free_sg.

OK...that's true, it doesn't return zero. A comment or WARN or something
might be nice, to show that the zero case hasn't been overlooked. It's
true that the dma_map_sg_p2pdma_attrs() documentation sort of says
that (although not quite out loud).

thanks,
--
John Hubbard
NVIDIA