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Commit 29791057 authored by Christoph Hellwig's avatar Christoph Hellwig
Browse files

nvme-pci: optimize mapping single segment requests using SGLs 



If the controller supports SGLs we can take another short cut for single
segment request, given that we can always map those without another
indirection structure, and thus don't need to create a scatterlist
structure.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarKeith Busch <keith.busch@intel.com>
Reviewed-by: default avatarSagi Grimberg <sagi@grimberg.me>
Reviewed-by: default avatarChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
parent dff824b2

drivers/nvme/host/pci.c

+22 −0
Original line number Diff line number Diff line
@@ -819,6 +819,23 @@ static blk_status_t nvme_setup_prp_simple(struct nvme_dev *dev, 
	return 0;

}



static blk_status_t nvme_setup_sgl_simple(struct nvme_dev *dev,

		struct request *req, struct nvme_rw_command *cmnd,

		struct bio_vec *bv)

{

	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);



	iod->first_dma = dma_map_bvec(dev->dev, bv, rq_dma_dir(req), 0);

	if (dma_mapping_error(dev->dev, iod->first_dma))

		return BLK_STS_RESOURCE;

	iod->dma_len = bv->bv_len;



	cmnd->dptr.sgl.addr = cpu_to_le64(iod->first_dma);

	cmnd->dptr.sgl.length = cpu_to_le32(iod->dma_len);

	cmnd->dptr.sgl.type = NVME_SGL_FMT_DATA_DESC << 4;

	return 0;

}



static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,

		struct nvme_command *cmnd)

{
@@ -836,6 +853,11 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req, 
			if (bv.bv_offset + bv.bv_len <= dev->ctrl.page_size * 2)

				return nvme_setup_prp_simple(dev, req,

							     &cmnd->rw, &bv);



			if (iod->nvmeq->qid &&

			    dev->ctrl.sgls & ((1 << 0) | (1 << 1)))

				return nvme_setup_sgl_simple(dev, req,

							     &cmnd->rw, &bv);

		}

	}