nvme-pci: do not build a scatterlist to map metadata

fix #29327388

commit 783b94bd9250478154904fa782d2cfc46336cdf6 upstream

We always have exactly one segment, so we can simply call dma_map_bvec.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NKeith Busch <keith.busch@intel.com>
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Reviewed-by: NChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: NBaolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

drivers/nvme/host/pci.c

@@ -224,7 +224,7 @@ struct nvme_iod {
 	int npages;		/* In the PRP list. 0 means small pool in use */
 	int nents;		/* Used in scatterlist */
 	dma_addr_t first_dma;
-	struct scatterlist meta_sg; /* metadata requires single contiguous buffer */
+	dma_addr_t meta_dma;
 	struct scatterlist *sg;
 	struct scatterlist inline_sg[0];
 };
@@ -600,13 +600,14 @@ static void nvme_unmap_data(struct nvme_dev *dev, struct request *req)
 	dma_addr_t dma_addr = iod->first_dma, next_dma_addr;
 	int i;
 
-	if (iod->nents) {
-		dma_unmap_sg(dev->dev, iod->sg, iod->nents, dma_dir);
-
-		if (blk_integrity_rq(req))
-			dma_unmap_sg(dev->dev, &iod->meta_sg, 1, dma_dir);
+	if (blk_integrity_rq(req)) {
+		dma_unmap_page(dev->dev, iod->meta_dma,
+				rq_integrity_vec(req)->bv_len, dma_dir);
 	}
 
+	if (iod->nents)
+		dma_unmap_sg(dev->dev, iod->sg, iod->nents, dma_dir);
+
 	if (iod->npages == 0)
 		dma_pool_free(dev->prp_small_pool, nvme_pci_iod_list(req)[0],
 			dma_addr);
@@ -862,19 +863,14 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
 
 	ret = BLK_STS_IOERR;
 	if (blk_integrity_rq(req)) {
-		if (blk_rq_count_integrity_sg(q, req->bio) != 1)
-			goto out;
-
-		sg_init_table(&iod->meta_sg, 1);
-		if (blk_rq_map_integrity_sg(q, req->bio, &iod->meta_sg) != 1)
+		iod->meta_dma = dma_map_bvec(dev->dev, rq_integrity_vec(req),
+				dma_dir, 0);
+		if (dma_mapping_error(dev->dev, iod->meta_dma))
 			goto out;
 
-		if (!dma_map_sg(dev->dev, &iod->meta_sg, 1, dma_dir))
-			goto out;
+		cmnd->rw.metadata = cpu_to_le64(iod->meta_dma);
 	}
 
-	if (blk_integrity_rq(req))
-		cmnd->rw.metadata = cpu_to_le64(sg_dma_address(&iod->meta_sg));
 	return BLK_STS_OK;
 
 out: