nvme-fc: introduce struct nvme_fcp_op_w_sgl

This patch does not change any functionality but makes the intent of the
code more clear.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/fc.c

@@ -20,6 +20,7 @@
 #include <uapi/scsi/fc/fc_fs.h>
 #include <uapi/scsi/fc/fc_els.h>
 #include <linux/delay.h>
+#include <linux/overflow.h>
 
 #include "nvme.h"
 #include "fabrics.h"
@@ -104,6 +105,12 @@ struct nvme_fc_fcp_op {
 	struct nvme_fc_ersp_iu	rsp_iu;
 };
 
+struct nvme_fcp_op_w_sgl {
+	struct nvme_fc_fcp_op	op;
+	struct scatterlist	sgl[SG_CHUNK_SIZE];
+	uint8_t			priv[0];
+};
+
 struct nvme_fc_lport {
 	struct nvme_fc_local_port	localport;
 
@@ -1686,6 +1693,8 @@ __nvme_fc_init_request(struct nvme_fc_ctrl *ctrl,
 		struct nvme_fc_queue *queue, struct nvme_fc_fcp_op *op,
 		struct request *rq, u32 rqno)
 {
+	struct nvme_fcp_op_w_sgl *op_w_sgl =
+		container_of(op, typeof(*op_w_sgl), op);
 	struct nvme_fc_cmd_iu *cmdiu = &op->cmd_iu;
 	int ret = 0;
 
@@ -1695,7 +1704,7 @@ __nvme_fc_init_request(struct nvme_fc_ctrl *ctrl,
 	op->fcp_req.rspaddr = &op->rsp_iu;
 	op->fcp_req.rsplen = sizeof(op->rsp_iu);
 	op->fcp_req.done = nvme_fc_fcpio_done;
-	op->fcp_req.first_sgl = (struct scatterlist *)&op[1];
+	op->fcp_req.first_sgl = &op_w_sgl->sgl[0];
 	op->fcp_req.private = &op->fcp_req.first_sgl[SG_CHUNK_SIZE];
 	op->ctrl = ctrl;
 	op->queue = queue;
@@ -1734,12 +1743,12 @@ nvme_fc_init_request(struct blk_mq_tag_set *set, struct request *rq,
 		unsigned int hctx_idx, unsigned int numa_node)
 {
 	struct nvme_fc_ctrl *ctrl = set->driver_data;
-	struct nvme_fc_fcp_op *op = blk_mq_rq_to_pdu(rq);
+	struct nvme_fcp_op_w_sgl *op = blk_mq_rq_to_pdu(rq);
 	int queue_idx = (set == &ctrl->tag_set) ? hctx_idx + 1 : 0;
 	struct nvme_fc_queue *queue = &ctrl->queues[queue_idx];
 
 	nvme_req(rq)->ctrl = &ctrl->ctrl;
-	return __nvme_fc_init_request(ctrl, queue, op, rq, queue->rqcnt++);
+	return __nvme_fc_init_request(ctrl, queue, &op->op, rq, queue->rqcnt++);
 }
 
 static int
@@ -2423,10 +2432,9 @@ nvme_fc_create_io_queues(struct nvme_fc_ctrl *ctrl)
 	ctrl->tag_set.reserved_tags = 1; /* fabric connect */
 	ctrl->tag_set.numa_node = NUMA_NO_NODE;
 	ctrl->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
-	ctrl->tag_set.cmd_size = sizeof(struct nvme_fc_fcp_op) +
-					(SG_CHUNK_SIZE *
-						sizeof(struct scatterlist)) +
-					ctrl->lport->ops->fcprqst_priv_sz;
+	ctrl->tag_set.cmd_size =
+		struct_size((struct nvme_fcp_op_w_sgl *)NULL, priv,
+			    ctrl->lport->ops->fcprqst_priv_sz);
 	ctrl->tag_set.driver_data = ctrl;
 	ctrl->tag_set.nr_hw_queues = ctrl->ctrl.queue_count - 1;
 	ctrl->tag_set.timeout = NVME_IO_TIMEOUT;
@@ -3028,10 +3036,9 @@ nvme_fc_init_ctrl(struct device *dev, struct nvmf_ctrl_options *opts,
 	ctrl->admin_tag_set.queue_depth = NVME_AQ_MQ_TAG_DEPTH;
 	ctrl->admin_tag_set.reserved_tags = 2; /* fabric connect + Keep-Alive */
 	ctrl->admin_tag_set.numa_node = NUMA_NO_NODE;
-	ctrl->admin_tag_set.cmd_size = sizeof(struct nvme_fc_fcp_op) +
-					(SG_CHUNK_SIZE *
-						sizeof(struct scatterlist)) +
-					ctrl->lport->ops->fcprqst_priv_sz;
+	ctrl->admin_tag_set.cmd_size =
+		struct_size((struct nvme_fcp_op_w_sgl *)NULL, priv,
+			    ctrl->lport->ops->fcprqst_priv_sz);
 	ctrl->admin_tag_set.driver_data = ctrl;
 	ctrl->admin_tag_set.nr_hw_queues = 1;
 	ctrl->admin_tag_set.timeout = ADMIN_TIMEOUT;