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

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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



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