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

[John Hubbard]

On 4/8/21 10:01 AM, Logan Gunthorpe wrote:
> Convert to using dma_map_sg_p2pdma() for PCI p2pdma pages.
>
> This should be equivalent but allows for heterogeneous scatterlists
> with both P2PDMA and regular pages. However, P2PDMA support will be
> slightly more restricted (only dma-direct and dma-iommu are currently
> supported).
>
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> ---
>   drivers/nvme/host/pci.c | 28 ++++++++--------------------
>   1 file changed, 8 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 14f092973792..a1ed07ff38b7 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -577,17 +577,6 @@ static void nvme_free_sgls(struct nvme_dev *dev, struct request *req)
>   
>   }
>   
> -static void nvme_unmap_sg(struct nvme_dev *dev, struct request *req)
> -{
> -	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
> -
> -	if (is_pci_p2pdma_page(sg_page(iod->sg)))
> -		pci_p2pdma_unmap_sg(dev->dev, iod->sg, iod->nents,
> -				    rq_dma_dir(req));
> -	else
> -		dma_unmap_sg(dev->dev, iod->sg, iod->nents, rq_dma_dir(req));
> -}
> -
>   static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
>   {
>   	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
> @@ -600,7 +589,7 @@ static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
>   
>   	WARN_ON_ONCE(!iod->nents);
>   
> -	nvme_unmap_sg(dev, req);
> +	dma_unmap_sg(dev->dev, iod->sg, iod->nents, rq_dma_dir(req));


Nice simplification!


>   	if (iod->npages == 0)
>   		dma_pool_free(dev->prp_small_pool, nvme_pci_iod_list(req)[0],
>   			      iod->first_dma);
> @@ -868,14 +857,13 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
>   	if (!iod->nents)
>   		goto out_free_sg;
>   
> -	if (is_pci_p2pdma_page(sg_page(iod->sg)))
> -		nr_mapped = pci_p2pdma_map_sg_attrs(dev->dev, iod->sg,
> -				iod->nents, rq_dma_dir(req), DMA_ATTR_NO_WARN);
> -	else
> -		nr_mapped = dma_map_sg_attrs(dev->dev, iod->sg, iod->nents,
> -					     rq_dma_dir(req), DMA_ATTR_NO_WARN);
> -	if (!nr_mapped)
> +	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?

>   
>   	iod->use_sgl = nvme_pci_use_sgls(dev, req);
>   	if (iod->use_sgl)
> @@ -887,7 +875,7 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
>   	return BLK_STS_OK;
>   
>   out_unmap_sg:
> -	nvme_unmap_sg(dev, req);
> +	dma_unmap_sg(dev->dev, iod->sg, iod->nents, rq_dma_dir(req));
>   out_free_sg:
>   	mempool_free(iod->sg, dev->iod_mempool);
>   	return ret;

thanks,
--
John Hubbard
NVIDIA