From 297910571f08f1d7e398793df6e606ebb375a3f1 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 5 Mar 2019 05:54:18 -0700 Subject: [PATCH] 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: Christoph Hellwig Reviewed-by: Keith Busch Reviewed-by: Sagi Grimberg Reviewed-by: Chaitanya Kulkarni --- drivers/nvme/host/pci.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c index 59731264b052..82aa5cb21828 100644 --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -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); } }