iser-target: Use single CQ for TX and RX

Using TX and RX CQs attached to the same vector might
create a throttling effect coming from the serial processing
of a work-queue. Use one CQ instead, it will do better in interrupt
processing and it provides a simpler code. Also, We get rid of
redundant isert_rx_wq.

Next we can remove the atomic post_send_buf_count from the IO path.
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/infiniband/ulp/isert/ib_isert.c

@@ -35,10 +35,10 @@
 #define	ISERT_MAX_CONN		8
 #define ISER_MAX_RX_CQ_LEN	(ISERT_QP_MAX_RECV_DTOS * ISERT_MAX_CONN)
 #define ISER_MAX_TX_CQ_LEN	(ISERT_QP_MAX_REQ_DTOS  * ISERT_MAX_CONN)
+#define ISER_MAX_CQ_LEN		(ISER_MAX_RX_CQ_LEN + ISER_MAX_TX_CQ_LEN)
 
 static DEFINE_MUTEX(device_list_mutex);
 static LIST_HEAD(device_list);
-static struct workqueue_struct *isert_rx_wq;
 static struct workqueue_struct *isert_comp_wq;
 static struct workqueue_struct *isert_release_wq;
 
@@ -124,8 +124,8 @@ isert_conn_setup_qp(struct isert_conn *isert_conn, struct rdma_cm_id *cma_id)
 	memset(&attr, 0, sizeof(struct ib_qp_init_attr));
 	attr.event_handler = isert_qp_event_callback;
 	attr.qp_context = isert_conn;
-	attr.send_cq = comp->tx_cq;
-	attr.recv_cq = comp->rx_cq;
+	attr.send_cq = comp->cq;
+	attr.recv_cq = comp->cq;
 	attr.cap.max_send_wr = ISERT_QP_MAX_REQ_DTOS;
 	attr.cap.max_recv_wr = ISERT_QP_MAX_RECV_DTOS;
 	/*
@@ -237,10 +237,8 @@ isert_free_rx_descriptors(struct isert_conn *isert_conn)
 	isert_conn->conn_rx_descs = NULL;
 }
 
-static void isert_cq_tx_work(struct work_struct *);
-static void isert_cq_tx_callback(struct ib_cq *, void *);
-static void isert_cq_rx_work(struct work_struct *);
-static void isert_cq_rx_callback(struct ib_cq *, void *);
+static void isert_cq_work(struct work_struct *);
+static void isert_cq_callback(struct ib_cq *, void *);
 
 static int
 isert_create_device_ib_res(struct isert_device *device)
@@ -248,15 +246,14 @@ isert_create_device_ib_res(struct isert_device *device)
 	struct ib_device *ib_dev = device->ib_device;
 	struct ib_device_attr *dev_attr;
 	int ret = 0, i;
-	int max_rx_cqe, max_tx_cqe;
+	int max_cqe;
 
 	dev_attr = &device->dev_attr;
 	ret = isert_query_device(ib_dev, dev_attr);
 	if (ret)
 		return ret;
 
-	max_rx_cqe = min(ISER_MAX_RX_CQ_LEN, dev_attr->max_cqe);
-	max_tx_cqe = min(ISER_MAX_TX_CQ_LEN, dev_attr->max_cqe);
+	max_cqe = min(ISER_MAX_CQ_LEN, dev_attr->max_cqe);
 
 	/* asign function handlers */
 	if (dev_attr->device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS &&
@@ -293,35 +290,19 @@ isert_create_device_ib_res(struct isert_device *device)
 		struct isert_comp *comp = &device->comps[i];
 
 		comp->device = device;
-		INIT_WORK(&comp->rx_work, isert_cq_rx_work);
-		comp->rx_cq = ib_create_cq(device->ib_device,
-					   isert_cq_rx_callback,
-					   isert_cq_event_callback,
-					   (void *)comp,
-					   max_rx_cqe, i);
-		if (IS_ERR(comp->rx_cq)) {
-			ret = PTR_ERR(comp->rx_cq);
-			comp->rx_cq = NULL;
+		INIT_WORK(&comp->work, isert_cq_work);
+		comp->cq = ib_create_cq(device->ib_device,
+					isert_cq_callback,
+					isert_cq_event_callback,
+					(void *)comp,
+					max_cqe, i);
+		if (IS_ERR(comp->cq)) {
+			ret = PTR_ERR(comp->cq);
+			comp->cq = NULL;
 			goto out_cq;
 		}
 
-		INIT_WORK(&comp->tx_work, isert_cq_tx_work);
-		comp->tx_cq = ib_create_cq(device->ib_device,
-					   isert_cq_tx_callback,
-					   isert_cq_event_callback,
-					   (void *)comp,
-					   max_tx_cqe, i);
-		if (IS_ERR(comp->tx_cq)) {
-			ret = PTR_ERR(comp->tx_cq);
-			comp->tx_cq = NULL;
-			goto out_cq;
-		}
-
-		ret = ib_req_notify_cq(comp->rx_cq, IB_CQ_NEXT_COMP);
-		if (ret)
-			goto out_cq;
-
-		ret = ib_req_notify_cq(comp->tx_cq, IB_CQ_NEXT_COMP);
+		ret = ib_req_notify_cq(comp->cq, IB_CQ_NEXT_COMP);
 		if (ret)
 			goto out_cq;
 	}
@@ -332,13 +313,9 @@ isert_create_device_ib_res(struct isert_device *device)
 	for (i = 0; i < device->comps_used; i++) {
 		struct isert_comp *comp = &device->comps[i];
 
-		if (comp->rx_cq) {
-			cancel_work_sync(&comp->rx_work);
-			ib_destroy_cq(comp->rx_cq);
-		}
-		if (comp->tx_cq) {
-			cancel_work_sync(&comp->tx_work);
-			ib_destroy_cq(comp->tx_cq);
+		if (comp->cq) {
+			cancel_work_sync(&comp->work);
+			ib_destroy_cq(comp->cq);
 		}
 	}
 	kfree(device->comps);
@@ -356,12 +333,9 @@ isert_free_device_ib_res(struct isert_device *device)
 	for (i = 0; i < device->comps_used; i++) {
 		struct isert_comp *comp = &device->comps[i];
 
-		cancel_work_sync(&comp->rx_work);
-		cancel_work_sync(&comp->tx_work);
-		ib_destroy_cq(comp->rx_cq);
-		ib_destroy_cq(comp->tx_cq);
-		comp->rx_cq = NULL;
-		comp->tx_cq = NULL;
+		cancel_work_sync(&comp->work);
+		ib_destroy_cq(comp->cq);
+		comp->cq = NULL;
 	}
 	kfree(device->comps);
 }
@@ -2013,14 +1987,39 @@ isert_send_completion(struct iser_tx_desc *tx_desc,
 	}
 }
 
+/**
+ * is_isert_tx_desc() - Indicate if the completion wr_id
+ *     is a TX descriptor or not.
+ * @isert_conn: iser connection
+ * @wr_id: completion WR identifier
+ *
+ * Since we cannot rely on wc opcode in FLUSH errors
+ * we must work around it by checking if the wr_id address
+ * falls in the iser connection rx_descs buffer. If so
+ * it is an RX descriptor, otherwize it is a TX.
+ */
+static inline bool
+is_isert_tx_desc(struct isert_conn *isert_conn, void *wr_id)
+{
+	void *start = isert_conn->conn_rx_descs;
+	int len = ISERT_QP_MAX_RECV_DTOS * sizeof(*isert_conn->conn_rx_descs);
+
+	if (wr_id >= start && wr_id < start + len)
+		return false;
+
+	return true;
+}
+
 static void
-isert_cq_comp_err(void *desc, struct isert_conn *isert_conn, bool tx)
+isert_cq_comp_err(struct isert_conn *isert_conn, struct ib_wc *wc)
 {
-	if (tx) {
+	if (is_isert_tx_desc(isert_conn, (void *)wc->wr_id)) {
 		struct ib_device *ib_dev = isert_conn->conn_cm_id->device;
 		struct isert_cmd *isert_cmd;
+		struct iser_tx_desc *desc;
 
-		isert_cmd = ((struct iser_tx_desc *)desc)->isert_cmd;
+		desc = (struct iser_tx_desc *)(uintptr_t)wc->wr_id;
+		isert_cmd = desc->isert_cmd;
 		if (!isert_cmd)
 			isert_unmap_tx_desc(desc, ib_dev);
 		else
@@ -2049,80 +2048,52 @@ isert_cq_comp_err(void *desc, struct isert_conn *isert_conn, bool tx)
 }
 
 static void
-isert_cq_tx_work(struct work_struct *work)
+isert_handle_wc(struct ib_wc *wc)
 {
-	struct isert_comp *comp = container_of(work, struct isert_comp,
-					       tx_work);
-	struct ib_cq *cq = comp->tx_cq;
 	struct isert_conn *isert_conn;
 	struct iser_tx_desc *tx_desc;
-	struct ib_wc wc;
-
-	while (ib_poll_cq(cq, 1, &wc) == 1) {
-		isert_conn = wc.qp->qp_context;
-		tx_desc = (struct iser_tx_desc *)(uintptr_t)wc.wr_id;
+	struct iser_rx_desc *rx_desc;
 
-		if (wc.status == IB_WC_SUCCESS) {
-			isert_send_completion(tx_desc, isert_conn);
+	isert_conn = wc->qp->qp_context;
+	if (likely(wc->status == IB_WC_SUCCESS)) {
+		if (wc->opcode == IB_WC_RECV) {
+			rx_desc = (struct iser_rx_desc *)(uintptr_t)wc->wr_id;
+			isert_rx_completion(rx_desc, isert_conn, wc->byte_len);
 		} else {
-			pr_debug("TX wc.status != IB_WC_SUCCESS >>>>>>>>>>>>>>\n");
-			pr_debug("TX wc.status: 0x%08x\n", wc.status);
-			pr_debug("TX wc.vendor_err: 0x%08x\n", wc.vendor_err);
-
-			if (wc.wr_id != ISER_FASTREG_LI_WRID)
-				isert_cq_comp_err(tx_desc, isert_conn, true);
+			tx_desc = (struct iser_tx_desc *)(uintptr_t)wc->wr_id;
+			isert_send_completion(tx_desc, isert_conn);
 		}
-	}
-
-	ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
-}
-
-static void
-isert_cq_tx_callback(struct ib_cq *cq, void *context)
-{
-	struct isert_comp *comp = context;
+	} else {
+		if (wc->status != IB_WC_WR_FLUSH_ERR)
+			pr_err("wr id %llx status %d vend_err %x\n",
+				  wc->wr_id, wc->status, wc->vendor_err);
+		else
+			pr_debug("flush error: wr id %llx\n", wc->wr_id);
 
-	queue_work(isert_comp_wq, &comp->tx_work);
+		if (wc->wr_id != ISER_FASTREG_LI_WRID)
+			isert_cq_comp_err(isert_conn, wc);
+	}
 }
 
 static void
-isert_cq_rx_work(struct work_struct *work)
+isert_cq_work(struct work_struct *work)
 {
 	struct isert_comp *comp = container_of(work, struct isert_comp,
-					       rx_work);
-	struct ib_cq *cq = comp->rx_cq;
-	struct isert_conn *isert_conn;
-	struct iser_rx_desc *rx_desc;
+					       work);
 	struct ib_wc wc;
-	u32 xfer_len;
-
-	while (ib_poll_cq(cq, 1, &wc) == 1) {
-		isert_conn = wc.qp->qp_context;
-		rx_desc = (struct iser_rx_desc *)(uintptr_t)wc.wr_id;
 
-		if (wc.status == IB_WC_SUCCESS) {
-			xfer_len = wc.byte_len;
-			isert_rx_completion(rx_desc, isert_conn, xfer_len);
-		} else {
-			pr_debug("RX wc.status != IB_WC_SUCCESS >>>>>>>>>>>>>>\n");
-			if (wc.status != IB_WC_WR_FLUSH_ERR) {
-				pr_debug("RX wc.status: 0x%08x\n", wc.status);
-				pr_debug("RX wc.vendor_err: 0x%08x\n",
-					 wc.vendor_err);
-			}
-			isert_cq_comp_err(rx_desc, isert_conn, false);
-		}
-	}
+	while (ib_poll_cq(comp->cq, 1, &wc) == 1)
+		isert_handle_wc(&wc);
 
-	ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
+	ib_req_notify_cq(comp->cq, IB_CQ_NEXT_COMP);
 }
 
 static void
-isert_cq_rx_callback(struct ib_cq *cq, void *context)
+isert_cq_callback(struct ib_cq *cq, void *context)
 {
 	struct isert_comp *comp = context;
 
-	queue_work(isert_rx_wq, &comp->rx_work);
+	queue_work(isert_comp_wq, &comp->work);
 }
 
 static int
@@ -3363,17 +3334,11 @@ static int __init isert_init(void)
 {
 	int ret;
 
-	isert_rx_wq = alloc_workqueue("isert_rx_wq", 0, 0);
-	if (!isert_rx_wq) {
-		pr_err("Unable to allocate isert_rx_wq\n");
-		return -ENOMEM;
-	}
-
 	isert_comp_wq = alloc_workqueue("isert_comp_wq", 0, 0);
 	if (!isert_comp_wq) {
 		pr_err("Unable to allocate isert_comp_wq\n");
 		ret = -ENOMEM;
-		goto destroy_rx_wq;
+		return -ENOMEM;
 	}
 
 	isert_release_wq = alloc_workqueue("isert_release_wq", WQ_UNBOUND,
@@ -3391,8 +3356,7 @@ static int __init isert_init(void)
 
 destroy_comp_wq:
 	destroy_workqueue(isert_comp_wq);
-destroy_rx_wq:
-	destroy_workqueue(isert_rx_wq);
+
 	return ret;
 }
 
@@ -3401,7 +3365,6 @@ static void __exit isert_exit(void)
 	flush_scheduled_work();
 	destroy_workqueue(isert_release_wq);
 	destroy_workqueue(isert_comp_wq);
-	destroy_workqueue(isert_rx_wq);
 	iscsit_unregister_transport(&iser_target_transport);
 	pr_debug("iSER_TARGET[0] - Released iser_target_transport\n");
 }

drivers/infiniband/ulp/isert/ib_isert.h

@@ -163,20 +163,16 @@ struct isert_conn {
  * struct isert_comp - iSER completion context
  *
  * @device:     pointer to device handle
- * @rx_cq:      RX completion queue
- * @tx_cq:      TX completion queue
+ * @cq:         completion queue
  * @active_qps: Number of active QPs attached
  *              to completion context
- * @rx_work:    RX work handle
- * @tx_work:    TX work handle
+ * @work:       completion work handle
  */
 struct isert_comp {
-	struct isert_device      *device;
-	struct ib_cq		*rx_cq;
-	struct ib_cq		*tx_cq;
+	struct isert_device     *device;
+	struct ib_cq		*cq;
 	int                      active_qps;
-	struct work_struct	 rx_work;
-	struct work_struct	 tx_work;
+	struct work_struct	 work;
 };
 
 struct isert_device {