iser-target: Change the recv buffers posting logic

iser target batches post recv operations to avoid
the overhead of acquiring the recv queue lock and
posting a HW doorbell for each command.

We change it to be per command in order to support
zcopy immediate data for IOs that fits in the 8K
transfer boundary (in the next patch).

(Fix minor patch fuzz due to ib_mr removal - nab)
Signed-off-by: Jenny Derzhavetz <jennyf@mellanox.com>
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/infiniband/ulp/isert/ib_isert.c

@@ -238,8 +238,6 @@ isert_alloc_rx_descriptors(struct isert_conn *isert_conn)
 		rx_sg->lkey = device->pd->local_dma_lkey;
 	}
 
-	isert_conn->rx_desc_head = 0;
-
 	return 0;
 
 dma_map_fail:
@@ -1002,22 +1000,19 @@ isert_cma_handler(struct rdma_cm_id *cma_id, struct rdma_cm_event *event)
 }
 
 static int
-isert_post_recv(struct isert_conn *isert_conn, u32 count)
+isert_post_recvm(struct isert_conn *isert_conn, u32 count)
 {
 	struct ib_recv_wr *rx_wr, *rx_wr_failed;
 	int i, ret;
-	unsigned int rx_head = isert_conn->rx_desc_head;
 	struct iser_rx_desc *rx_desc;
 
 	for (rx_wr = isert_conn->rx_wr, i = 0; i < count; i++, rx_wr++) {
-		rx_desc		= &isert_conn->rx_descs[rx_head];
+		rx_desc = &isert_conn->rx_descs[i];
 		rx_wr->wr_id = (uintptr_t)rx_desc;
 		rx_wr->sg_list = &rx_desc->rx_sg;
 		rx_wr->num_sge = 1;
 		rx_wr->next = rx_wr + 1;
-		rx_head = (rx_head + 1) & (ISERT_QP_MAX_RECV_DTOS - 1);
 	}
-
 	rx_wr--;
 	rx_wr->next = NULL; /* mark end of work requests list */
 
@@ -1027,10 +1022,29 @@ isert_post_recv(struct isert_conn *isert_conn, u32 count)
 	if (ret) {
 		isert_err("ib_post_recv() failed with ret: %d\n", ret);
 		isert_conn->post_recv_buf_count -= count;
-	} else {
-		isert_dbg("Posted %d RX buffers\n", count);
-		isert_conn->rx_desc_head = rx_head;
 	}
+
+	return ret;
+}
+
+static int
+isert_post_recv(struct isert_conn *isert_conn, struct iser_rx_desc *rx_desc)
+{
+	struct ib_recv_wr *rx_wr_failed, rx_wr;
+	int ret;
+
+	rx_wr.wr_id = (uintptr_t)rx_desc;
+	rx_wr.sg_list = &rx_desc->rx_sg;
+	rx_wr.num_sge = 1;
+	rx_wr.next = NULL;
+
+	isert_conn->post_recv_buf_count++;
+	ret = ib_post_recv(isert_conn->qp, &rx_wr, &rx_wr_failed);
+	if (ret) {
+		isert_err("ib_post_recv() failed with ret: %d\n", ret);
+		isert_conn->post_recv_buf_count--;
+	}
+
 	return ret;
 }
 
@@ -1201,7 +1215,8 @@ isert_put_login_tx(struct iscsi_conn *conn, struct iscsi_login *login,
 			if (ret)
 				return ret;
 
-			ret = isert_post_recv(isert_conn, ISERT_MIN_POSTED_RX);
+			ret = isert_post_recvm(isert_conn,
+					       ISERT_QP_MAX_RECV_DTOS);
 			if (ret)
 				return ret;
 
@@ -1274,7 +1289,7 @@ isert_rx_login_req(struct isert_conn *isert_conn)
 }
 
 static struct iscsi_cmd
-*isert_allocate_cmd(struct iscsi_conn *conn)
+*isert_allocate_cmd(struct iscsi_conn *conn, struct iser_rx_desc *rx_desc)
 {
 	struct isert_conn *isert_conn = conn->context;
 	struct isert_cmd *isert_cmd;
@@ -1288,6 +1303,7 @@ static struct iscsi_cmd
 	isert_cmd = iscsit_priv_cmd(cmd);
 	isert_cmd->conn = isert_conn;
 	isert_cmd->iscsi_cmd = cmd;
+	isert_cmd->rx_desc = rx_desc;
 
 	return cmd;
 }
@@ -1403,6 +1419,15 @@ isert_handle_iscsi_dataout(struct isert_conn *isert_conn,
 	if (rc < 0)
 		return rc;
 
+	/*
+	 * multiple data-outs on the same command can arrive -
+	 * so post the buffer before hand
+	 */
+	rc = isert_post_recv(isert_conn, rx_desc);
+	if (rc) {
+		isert_err("ib_post_recv failed with %d\n", rc);
+		return rc;
+	}
 	return 0;
 }
 
@@ -1475,7 +1500,7 @@ isert_rx_opcode(struct isert_conn *isert_conn, struct iser_rx_desc *rx_desc,
 
 	switch (opcode) {
 	case ISCSI_OP_SCSI_CMD:
-		cmd = isert_allocate_cmd(conn);
+		cmd = isert_allocate_cmd(conn, rx_desc);
 		if (!cmd)
 			break;
 
@@ -1489,7 +1514,7 @@ isert_rx_opcode(struct isert_conn *isert_conn, struct iser_rx_desc *rx_desc,
 					rx_desc, (unsigned char *)hdr);
 		break;
 	case ISCSI_OP_NOOP_OUT:
-		cmd = isert_allocate_cmd(conn);
+		cmd = isert_allocate_cmd(conn, rx_desc);
 		if (!cmd)
 			break;
 
@@ -1502,7 +1527,7 @@ isert_rx_opcode(struct isert_conn *isert_conn, struct iser_rx_desc *rx_desc,
 						(unsigned char *)hdr);
 		break;
 	case ISCSI_OP_SCSI_TMFUNC:
-		cmd = isert_allocate_cmd(conn);
+		cmd = isert_allocate_cmd(conn, rx_desc);
 		if (!cmd)
 			break;
 
@@ -1510,22 +1535,20 @@ isert_rx_opcode(struct isert_conn *isert_conn, struct iser_rx_desc *rx_desc,
 						(unsigned char *)hdr);
 		break;
 	case ISCSI_OP_LOGOUT:
-		cmd = isert_allocate_cmd(conn);
+		cmd = isert_allocate_cmd(conn, rx_desc);
 		if (!cmd)
 			break;
 
 		ret = iscsit_handle_logout_cmd(conn, cmd, (unsigned char *)hdr);
 		break;
 	case ISCSI_OP_TEXT:
-		if (be32_to_cpu(hdr->ttt) != 0xFFFFFFFF) {
+		if (be32_to_cpu(hdr->ttt) != 0xFFFFFFFF)
 			cmd = iscsit_find_cmd_from_itt(conn, hdr->itt);
+		else
+			cmd = isert_allocate_cmd(conn, rx_desc);
+
 		if (!cmd)
 			break;
-		} else {
-			cmd = isert_allocate_cmd(conn);
-			if (!cmd)
-				break;
-		}
 
 		isert_cmd = iscsit_priv_cmd(cmd);
 		ret = isert_handle_text_cmd(isert_conn, isert_cmd, cmd,
@@ -1585,7 +1608,7 @@ isert_rcv_completion(struct iser_rx_desc *desc,
 	struct ib_device *ib_dev = isert_conn->cm_id->device;
 	struct iscsi_hdr *hdr;
 	u64 rx_dma;
-	int rx_buflen, outstanding;
+	int rx_buflen;
 
 	if ((char *)desc == isert_conn->login_req_buf) {
 		rx_dma = isert_conn->login_req_dma;
@@ -1625,22 +1648,6 @@ isert_rcv_completion(struct iser_rx_desc *desc,
 				      DMA_FROM_DEVICE);
 
 	isert_conn->post_recv_buf_count--;
-	isert_dbg("Decremented post_recv_buf_count: %d\n",
-		  isert_conn->post_recv_buf_count);
-
-	if ((char *)desc == isert_conn->login_req_buf)
-		return;
-
-	outstanding = isert_conn->post_recv_buf_count;
-	if (outstanding + ISERT_MIN_POSTED_RX <= ISERT_QP_MAX_RECV_DTOS) {
-		int err, count = min(ISERT_QP_MAX_RECV_DTOS - outstanding,
-				ISERT_MIN_POSTED_RX);
-		err = isert_post_recv(isert_conn, count);
-		if (err) {
-			isert_err("isert_post_recv() count: %d failed, %d\n",
-			       count, err);
-		}
-	}
 }
 
 static int
@@ -2152,6 +2159,12 @@ isert_post_response(struct isert_conn *isert_conn, struct isert_cmd *isert_cmd)
 	struct ib_send_wr *wr_failed;
 	int ret;
 
+	ret = isert_post_recv(isert_conn, isert_cmd->rx_desc);
+	if (ret) {
+		isert_err("ib_post_recv failed with %d\n", ret);
+		return ret;
+	}
+
 	ret = ib_post_send(isert_conn->qp, &isert_cmd->tx_desc.send_wr,
 			   &wr_failed);
 	if (ret) {
@@ -2946,6 +2959,12 @@ isert_put_datain(struct iscsi_conn *conn, struct iscsi_cmd *cmd)
 				   &isert_cmd->tx_desc.send_wr);
 		isert_cmd->rdma_wr.s_send_wr.next = &isert_cmd->tx_desc.send_wr;
 		wr->send_wr_num += 1;
+
+		rc = isert_post_recv(isert_conn, isert_cmd->rx_desc);
+		if (rc) {
+			isert_err("ib_post_recv failed with %d\n", rc);
+			return rc;
+		}
 	}
 
 	rc = ib_post_send(isert_conn->qp, wr->send_wr, &wr_failed);

drivers/infiniband/ulp/isert/ib_isert.h

@@ -136,6 +136,7 @@ struct isert_cmd {
 	struct isert_conn	*conn;
 	struct iscsi_cmd	*iscsi_cmd;
 	struct iser_tx_desc	tx_desc;
+	struct iser_rx_desc	*rx_desc;
 	struct isert_rdma_wr	rdma_wr;
 	struct work_struct	comp_work;
 };
@@ -155,9 +156,8 @@ struct isert_conn {
 	u64			login_req_dma;
 	int			login_req_len;
 	u64			login_rsp_dma;
-	unsigned int		rx_desc_head;
 	struct iser_rx_desc	*rx_descs;
-	struct ib_recv_wr	rx_wr[ISERT_MIN_POSTED_RX];
+	struct ib_recv_wr	rx_wr[ISERT_QP_MAX_RECV_DTOS];
 	struct iscsi_conn	*conn;
 	struct list_head	node;
 	struct completion	login_comp;