nvme-pci: allocate nvme_command within driver pdu

Except for pci, all the nvme transport drivers allocate a command within
the driver's pdu. Align pci with everyone else by allocating the nvme
command within pci's pdu and replace the .queue_rq() stack variable with
this.
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/pci.c

@@ -224,6 +224,7 @@ struct nvme_queue {
  */
 struct nvme_iod {
 	struct nvme_request req;
+	struct nvme_command cmd;
 	struct nvme_queue *nvmeq;
 	bool use_sgl;
 	int aborted;
@@ -917,7 +918,7 @@ static blk_status_t nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
 	struct nvme_dev *dev = nvmeq->dev;
 	struct request *req = bd->rq;
 	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
-	struct nvme_command cmnd;
+	struct nvme_command *cmnd = &iod->cmd;
 	blk_status_t ret;
 
 	iod->aborted = 0;
@@ -931,24 +932,24 @@ static blk_status_t nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
 	if (unlikely(!test_bit(NVMEQ_ENABLED, &nvmeq->flags)))
 		return BLK_STS_IOERR;
 
-	ret = nvme_setup_cmd(ns, req, &cmnd);
+	ret = nvme_setup_cmd(ns, req, cmnd);
 	if (ret)
 		return ret;
 
 	if (blk_rq_nr_phys_segments(req)) {
-		ret = nvme_map_data(dev, req, &cmnd);
+		ret = nvme_map_data(dev, req, cmnd);
 		if (ret)
 			goto out_free_cmd;
 	}
 
 	if (blk_integrity_rq(req)) {
-		ret = nvme_map_metadata(dev, req, &cmnd);
+		ret = nvme_map_metadata(dev, req, cmnd);
 		if (ret)
 			goto out_unmap_data;
 	}
 
 	blk_mq_start_request(req);
-	nvme_submit_cmd(nvmeq, &cmnd, bd->last);
+	nvme_submit_cmd(nvmeq, cmnd, bd->last);
 	return BLK_STS_OK;
 out_unmap_data:
 	nvme_unmap_data(dev, req);