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 <[email protected]> Reviewed-by: Keith Busch <[email protected]> Reviewed-by: Sagi Grimberg <[email protected]> Reviewed-by: Chaitanya Kulkarni <[email protected]>
josf · Apr 5, 2019 · 2979105 · 2979105
1 parent dff824b
commit 2979105
Showing 1 changed file with 22 additions and 0 deletions.
diff --git 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);
 		}
 	}