nvme-pci: don't allocate dma_vec for IOVA mappings

Not only do IOVA mappings no need the separate dma_vec tracking, it
also won't free it and thus leak the allocations.

Fixes: b8b7570 ("nvme-pci: fix dma unmapping when using PRPs and not using the IOVA mapping")
Reported-by: Klara Modin <klarasmodin@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Klara Modin <klarasmodin@gmail.com>
Link: https://lore.kernel.org/r/20250711112250.633269-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Christoph Hellwig

drivers/nvme/host/pci.c

@@ -745,7 +745,7 @@ static bool nvme_pci_prp_iter_next(struct request *req, struct device *dma_dev,
 		return true;
 	if (!blk_rq_dma_map_iter_next(req, dma_dev, &iod->dma_state, iter))
 		return false;
-	if (dma_need_unmap(dma_dev)) {
+	if (!dma_use_iova(&iod->dma_state) && dma_need_unmap(dma_dev)) {
 		iod->dma_vecs[iod->nr_dma_vecs].addr = iter->addr;
 		iod->dma_vecs[iod->nr_dma_vecs].len = iter->len;
 		iod->nr_dma_vecs++;
@@ -763,7 +763,7 @@ static blk_status_t nvme_pci_setup_data_prp(struct request *req,
 	unsigned int prp_len, i;
 	__le64 *prp_list;
 
-	if (dma_need_unmap(nvmeq->dev->dev)) {
+	if (!dma_use_iova(&iod->dma_state) && dma_need_unmap(nvmeq->dev->dev)) {
 		iod->dma_vecs = mempool_alloc(nvmeq->dev->dmavec_mempool,
 				GFP_ATOMIC);
 		if (!iod->dma_vecs)