[PATCH V2 3/3] Adding device_dma_parameters->offset_preserve_mask to NVMe driver.

[Jianxiong Gao]

NVMe driver relies on the address offset to function properly.
This patch adds the offset preserve mask to NVMe driver when mapping
via dma_map_sg_attrs and unmapping via nvme_unmap_sg. The mask
depends on the page size defined by CC.MPS register of NVMe
controller.

Signed-off-by: Jianxiong Gao <jxgao at google.com>
---
 drivers/nvme/host/pci.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 81e6389b2042..30e45f7e0f75 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -580,12 +580,15 @@ 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 (dma_set_min_align_mask(dev->dev, NVME_CTRL_PAGE_SIZE - 1))
+		dev_warn(dev->dev, "dma_set_min_align_mask failed to set offset\n");
 	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));
+	if (dma_set_min_align_mask(dev->dev, 0))
+		dev_warn(dev->dev, "dma_set_min_align_mask failed to reset offset\n");
 }
 
 static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
@@ -842,7 +845,7 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
 {
 	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
 	blk_status_t ret = BLK_STS_RESOURCE;
-	int nr_mapped;
+	int nr_mapped, offset_ret;
 
 	if (blk_rq_nr_phys_segments(req) == 1) {
 		struct bio_vec bv = req_bvec(req);
@@ -868,12 +871,24 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
 	if (!iod->nents)
 		goto out_free_sg;
 
+	offset_ret = dma_set_min_align_mask(dev->dev, NVME_CTRL_PAGE_SIZE - 1);
+	if (offset_ret) {
+		dev_warn(dev->dev, "dma_set_min_align_mask failed to set offset\n");
+		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);
+
+	offset_ret = dma_set_min_align_mask(dev->dev, 0);
+	if (offset_ret) {
+		dev_warn(dev->dev, "dma_set_min_align_mask failed to reset offset\n");
+		goto out_free_sg;
+	}
 	if (!nr_mapped)
 		goto out_free_sg;
 
-- 
2.27.0