[PATCH 09/20] iser-target: Parallelize CM connection establishment

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There is no point in accepting a new CM request only
when we are completely done with the last iscsi login.
Instead we accept immediately, this will also cause the
CM connection to reach connected state and the initiator
is allowed to send the first login. We mark that we got
the initial login and let iscsi layer pick it up when it
gets there.

This reduces the parallel login sequence by a factor of
more then 4 (and more for multi-login) and also prevents
the initiator (who does all logins in parallel) from
giving up on login timeout expiration.

Signed-off-by: Sagi Grimberg <sagig@xxxxxxxxxxxx>
---
 drivers/infiniband/ulp/isert/ib_isert.c |   50 +++++++++++++++++++++---------
 drivers/infiniband/ulp/isert/ib_isert.h |    2 +
 2 files changed, 37 insertions(+), 15 deletions(-)

diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
index 239f58d..4beeb90 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/drivers/infiniband/ulp/isert/ib_isert.c
@@ -59,6 +59,10 @@ isert_reg_rdma(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 	       struct isert_rdma_wr *wr);
 static int
 isert_put_response(struct iscsi_conn *conn, struct iscsi_cmd *cmd);
+static int
+isert_rdma_post_recvl(struct isert_conn *isert_conn);
+static int
+isert_rdma_accept(struct isert_conn *isert_conn);
 
 static void
 isert_qp_event_callback(struct ib_event *e, void *context)
@@ -604,6 +608,7 @@ isert_connect_request(struct rdma_cm_id *cma_id, struct rdma_cm_event *event)
 	isert_conn->state = ISER_CONN_INIT;
 	INIT_LIST_HEAD(&isert_conn->conn_accept_node);
 	init_completion(&isert_conn->conn_login_comp);
+	init_completion(&isert_conn->login_req_comp);
 	init_completion(&isert_conn->conn_wait);
 	init_completion(&isert_conn->conn_wait_comp_err);
 	kref_init(&isert_conn->conn_kref);
@@ -695,6 +700,14 @@ isert_connect_request(struct rdma_cm_id *cma_id, struct rdma_cm_event *event)
 	if (ret)
 		goto out_conn_dev;
 
+	ret = isert_rdma_post_recvl(isert_conn);
+	if (ret)
+		goto out_conn_dev;
+
+	ret = isert_rdma_accept(isert_conn);
+	if (ret)
+		goto out_conn_dev;
+
 	mutex_lock(&isert_np->np_accept_mutex);
 	list_add_tail(&isert_conn->conn_accept_node, &isert_np->np_accept_list);
 	mutex_unlock(&isert_np->np_accept_mutex);
@@ -1149,9 +1162,10 @@ post_send:
 }
 
 static void
-isert_rx_login_req(struct iser_rx_desc *rx_desc, int rx_buflen,
-		   struct isert_conn *isert_conn)
+isert_rx_login_req(struct isert_conn *isert_conn)
 {
+	struct iser_rx_desc *rx_desc = (void *)isert_conn->login_req_buf;
+	int rx_buflen = isert_conn->login_req_len;
 	struct iscsi_conn *conn = isert_conn->conn;
 	struct iscsi_login *login = conn->conn_login;
 	int size;
@@ -1530,11 +1544,14 @@ isert_rx_completion(struct iser_rx_desc *desc, struct isert_conn *isert_conn,
 		 hdr->opcode, hdr->itt, hdr->flags,
 		 (int)(xfer_len - ISER_HEADERS_LEN));
 
-	if ((char *)desc == isert_conn->login_req_buf)
-		isert_rx_login_req(desc, xfer_len - ISER_HEADERS_LEN,
-				   isert_conn);
-	else
+	if ((char *)desc == isert_conn->login_req_buf) {
+		mutex_lock(&isert_conn->conn_mutex);
+		isert_conn->login_req_len = xfer_len - ISER_HEADERS_LEN;
+		complete(&isert_conn->login_req_comp);
+		mutex_unlock(&isert_conn->conn_mutex);
+	} else {
 		isert_rx_do_work(desc, isert_conn);
+	}
 
 	ib_dma_sync_single_for_device(ib_dev, rx_dma, rx_buflen,
 				      DMA_FROM_DEVICE);
@@ -3142,7 +3159,15 @@ isert_get_login_rx(struct iscsi_conn *conn, struct iscsi_login *login)
 	struct isert_conn *isert_conn = (struct isert_conn *)conn->context;
 	int ret;
 
-	isert_dbg("before conn_login_comp conn: %p\n", conn);
+	isert_info("before login_req comp conn: %p\n", conn);
+	ret = wait_for_completion_interruptible(&isert_conn->login_req_comp);
+	if (ret) {
+		isert_err("isert_conn %p interrupted before got login req\n",
+			  isert_conn);
+		return ret;
+	}
+	isert_rx_login_req(isert_conn);
+
 	/*
 	 * For login requests after the first PDU, isert_rx_login_req() will
 	 * kick schedule_delayed_work(&conn->login_work) as the packet is
@@ -3152,11 +3177,13 @@ isert_get_login_rx(struct iscsi_conn *conn, struct iscsi_login *login)
 	if (!login->first_request)
 		return 0;
 
+	isert_info("before conn_login_comp conn: %p\n", conn);
 	ret = wait_for_completion_interruptible(&isert_conn->conn_login_comp);
 	if (ret)
 		return ret;
 
 	isert_dbg("processing login->req: %p\n", login->req);
+
 	return 0;
 }
 
@@ -3234,17 +3261,10 @@ accept_wait:
 	isert_conn->conn = conn;
 	max_accept = 0;
 
-	ret = isert_rdma_post_recvl(isert_conn);
-	if (ret)
-		return ret;
-
-	ret = isert_rdma_accept(isert_conn);
-	if (ret)
-		return ret;
-
 	isert_set_conn_info(np, conn, isert_conn);
 
 	isert_dbg("Processing isert_conn: %p\n", isert_conn);
+
 	return 0;
 }
 
diff --git a/drivers/infiniband/ulp/isert/ib_isert.h b/drivers/infiniband/ulp/isert/ib_isert.h
index 9a88a3b..0f7d343 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.h
+++ b/drivers/infiniband/ulp/isert/ib_isert.h
@@ -153,6 +153,7 @@ struct isert_conn {
 	char			*login_req_buf;
 	char			*login_rsp_buf;
 	u64			login_req_dma;
+	int			login_req_len;
 	u64			login_rsp_dma;
 	unsigned int		conn_rx_desc_head;
 	struct iser_rx_desc	*conn_rx_descs;
@@ -160,6 +161,7 @@ struct isert_conn {
 	struct iscsi_conn	*conn;
 	struct list_head	conn_accept_node;
 	struct completion	conn_login_comp;
+	struct completion	login_req_comp;
 	struct iser_tx_desc	conn_login_tx_desc;
 	struct rdma_cm_id	*conn_cm_id;
 	struct ib_pd		*conn_pd;
-- 
1.7.1

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