iser-target: generalize rdma memory registration and cleanup

Current driver uses global dma key to register the memory pointed
by sg list provided by the target core.

This is the preparation step for adding more methods like fast
path memory registration, make the reg/unreg calls be function
pointers.
Signed-off-by: Vu Pham <vu@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/infiniband/ulp/isert/ib_isert.c

@@ -40,6 +40,12 @@ static LIST_HEAD(device_list);
 static struct workqueue_struct *isert_rx_wq;
 static struct workqueue_struct *isert_comp_wq;
 
+static void
+isert_unmap_cmd(struct isert_cmd *isert_cmd, struct isert_conn *isert_conn);
+static int
+isert_map_rdma(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
+	       struct isert_rdma_wr *wr);
+
 static void
 isert_qp_event_callback(struct ib_event *e, void *context)
 {
@@ -211,6 +217,10 @@ isert_create_device_ib_res(struct isert_device *device)
 	struct isert_cq_desc *cq_desc;
 	int ret = 0, i, j;
 
+	/* asign function handlers */
+	device->reg_rdma_mem = isert_map_rdma;
+	device->unreg_rdma_mem = isert_unmap_cmd;
+
 	device->cqs_used = min_t(int, num_online_cpus(),
 				 device->ib_device->num_comp_vectors);
 	device->cqs_used = min(ISERT_MAX_CQ, device->cqs_used);
@@ -1261,6 +1271,7 @@ isert_put_cmd(struct isert_cmd *isert_cmd)
 	struct iscsi_cmd *cmd = isert_cmd->iscsi_cmd;
 	struct isert_conn *isert_conn = isert_cmd->conn;
 	struct iscsi_conn *conn = isert_conn->conn;
+	struct isert_device *device = isert_conn->conn_device;
 
 	pr_debug("Entering isert_put_cmd: %p\n", isert_cmd);
 
@@ -1274,7 +1285,7 @@ isert_put_cmd(struct isert_cmd *isert_cmd)
 		if (cmd->data_direction == DMA_TO_DEVICE)
 			iscsit_stop_dataout_timer(cmd);
 
-		isert_unmap_cmd(isert_cmd, isert_conn);
+		device->unreg_rdma_mem(isert_cmd, isert_conn);
 		transport_generic_free_cmd(&cmd->se_cmd, 0);
 		break;
 	case ISCSI_OP_SCSI_TMFUNC:
@@ -1348,9 +1359,10 @@ isert_completion_rdma_read(struct iser_tx_desc *tx_desc,
 	struct iscsi_cmd *cmd = isert_cmd->iscsi_cmd;
 	struct se_cmd *se_cmd = &cmd->se_cmd;
 	struct isert_conn *isert_conn = isert_cmd->conn;
+	struct isert_device *device = isert_conn->conn_device;
 
 	iscsit_stop_dataout_timer(cmd);
-	isert_unmap_cmd(isert_cmd, isert_conn);
+	device->unreg_rdma_mem(isert_cmd, isert_conn);
 	cmd->write_data_done = wr->cur_rdma_length;
 
 	pr_debug("Cmd: %p RDMA_READ comp calling execute_cmd\n", isert_cmd);
@@ -1936,13 +1948,14 @@ isert_put_datain(struct iscsi_conn *conn, struct iscsi_cmd *cmd)
 					struct isert_cmd, iscsi_cmd);
 	struct isert_rdma_wr *wr = &isert_cmd->rdma_wr;
 	struct isert_conn *isert_conn = (struct isert_conn *)conn->context;
+	struct isert_device *device = isert_conn->conn_device;
 	struct ib_send_wr *wr_failed;
 	int rc;
 
 	pr_debug("Cmd: %p RDMA_WRITE data_length: %u\n",
 		 isert_cmd, se_cmd->data_length);
 	wr->iser_ib_op = ISER_IB_RDMA_WRITE;
-	rc = isert_map_rdma(conn, cmd, wr);
+	rc = device->reg_rdma_mem(conn, cmd, wr);
 	if (rc) {
 		pr_err("Cmd: %p failed to prepare RDMA res\n", isert_cmd);
 		return rc;
@@ -1977,13 +1990,14 @@ isert_get_dataout(struct iscsi_conn *conn, struct iscsi_cmd *cmd, bool recovery)
 	struct isert_cmd *isert_cmd = iscsit_priv_cmd(cmd);
 	struct isert_rdma_wr *wr = &isert_cmd->rdma_wr;
 	struct isert_conn *isert_conn = (struct isert_conn *)conn->context;
+	struct isert_device *device = isert_conn->conn_device;
 	struct ib_send_wr *wr_failed;
 	int rc;
 
 	pr_debug("Cmd: %p RDMA_READ data_length: %u write_data_done: %u\n",
 		 isert_cmd, se_cmd->data_length, cmd->write_data_done);
 	wr->iser_ib_op = ISER_IB_RDMA_READ;
-	rc = isert_map_rdma(conn, cmd, wr);
+	rc = device->reg_rdma_mem(conn, cmd, wr);
 	if (rc) {
 		pr_err("Cmd: %p failed to prepare RDMA res\n", isert_cmd);
 		return rc;

drivers/infiniband/ulp/isert/ib_isert.h

@@ -128,6 +128,11 @@ struct isert_device {
 	struct ib_cq		*dev_tx_cq[ISERT_MAX_CQ];
 	struct isert_cq_desc	*cq_desc;
 	struct list_head	dev_node;
+	int			(*reg_rdma_mem)(struct iscsi_conn *conn,
+						    struct iscsi_cmd *cmd,
+						    struct isert_rdma_wr *wr);
+	void			(*unreg_rdma_mem)(struct isert_cmd *isert_cmd,
+						  struct isert_conn *isert_conn);
 };
 
 struct isert_np {