IB/iser: iSER RDMA CM (CMA) and IB verbs interaction

This file contains the low level interaction with the RDMA CM
and the IB verbs, where iSER is consumer of both.

Signed-off-by: Or Gerlitz <ogerlitz@voltaire.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 827 insertions, 0 deletions

diff --git a/drivers/infiniband/ulp/iser/iser_verbs.c b/drivers/infiniband/ulp/iser/iser_verbs.c
new file mode 100644
index 0000000..ff117bb
--- /dev/null
+++ b/drivers/infiniband/ulp/iser/iser_verbs.c
@@ -0,0 +1,827 @@
+/*
+ * Copyright (c) 2004, 2005, 2006 Voltaire, Inc. All rights reserved.
+ * Copyright (c) 2005, 2006 Cisco Systems.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *	- Redistributions of source code must retain the above
+ *	  copyright notice, this list of conditions and the following
+ *	  disclaimer.
+ *
+ *	- Redistributions in binary form must reproduce the above
+ *	  copyright notice, this list of conditions and the following
+ *	  disclaimer in the documentation and/or other materials
+ *	  provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * $Id: iser_verbs.c 7051 2006-05-10 12:29:11Z ogerlitz $
+ */
+#include <asm/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/smp_lock.h>
+#include <linux/delay.h>
+#include <linux/version.h>
+
+#include "iscsi_iser.h"
+
+#define ISCSI_ISER_MAX_CONN	8
+#define ISER_MAX_CQ_LEN		((ISER_QP_MAX_RECV_DTOS + \
+				ISER_QP_MAX_REQ_DTOS) *   \
+				 ISCSI_ISER_MAX_CONN)
+
+static void iser_cq_tasklet_fn(unsigned long data);
+static void iser_cq_callback(struct ib_cq *cq, void *cq_context);
+static void iser_comp_error_worker(void *data);
+
+static void iser_cq_event_callback(struct ib_event *cause, void *context)
+{
+	iser_err("got cq event %d \n", cause->event);
+}
+
+static void iser_qp_event_callback(struct ib_event *cause, void *context)
+{
+	iser_err("got qp event %d\n",cause->event);
+}
+
+/**
+ * iser_create_device_ib_res - creates Protection Domain (PD), Completion
+ * Queue (CQ), DMA Memory Region (DMA MR) with the device associated with
+ * the adapator.
+ *
+ * returns 0 on success, -1 on failure
+ */
+static int iser_create_device_ib_res(struct iser_device *device)
+{
+	device->pd = ib_alloc_pd(device->ib_device);
+	if (IS_ERR(device->pd))
+		goto pd_err;
+
+	device->cq = ib_create_cq(device->ib_device,
+				  iser_cq_callback,
+				  iser_cq_event_callback,
+				  (void *)device,
+				  ISER_MAX_CQ_LEN);
+	if (IS_ERR(device->cq))
+		goto cq_err;
+
+	if (ib_req_notify_cq(device->cq, IB_CQ_NEXT_COMP))
+		goto cq_arm_err;
+
+	tasklet_init(&device->cq_tasklet,
+		     iser_cq_tasklet_fn,
+		     (unsigned long)device);
+
+	device->mr = ib_get_dma_mr(device->pd,
+				   IB_ACCESS_LOCAL_WRITE);
+	if (IS_ERR(device->mr))
+		goto dma_mr_err;
+
+	return 0;
+
+dma_mr_err:
+	tasklet_kill(&device->cq_tasklet);
+cq_arm_err:
+	ib_destroy_cq(device->cq);
+cq_err:
+	ib_dealloc_pd(device->pd);
+pd_err:
+	iser_err("failed to allocate an IB resource\n");
+	return -1;
+}
+
+/**
+ * iser_free_device_ib_res - destory/dealloc/dereg the DMA MR,
+ * CQ and PD created with the device associated with the adapator.
+ */
+static void iser_free_device_ib_res(struct iser_device *device)
+{
+	BUG_ON(device->mr == NULL);
+
+	tasklet_kill(&device->cq_tasklet);
+
+	(void)ib_dereg_mr(device->mr);
+	(void)ib_destroy_cq(device->cq);
+	(void)ib_dealloc_pd(device->pd);
+
+	device->mr = NULL;
+	device->cq = NULL;
+	device->pd = NULL;
+}
+
+/**
+ * iser_create_ib_conn_res - Creates FMR pool and Queue-Pair (QP)
+ *
+ * returns 0 on success, -1 on failure
+ */
+static int iser_create_ib_conn_res(struct iser_conn *ib_conn)
+{
+	struct iser_device	*device;
+	struct ib_qp_init_attr	init_attr;
+	int			ret;
+	struct ib_fmr_pool_param params;
+
+	BUG_ON(ib_conn->device == NULL);
+
+	device = ib_conn->device;
+
+	ib_conn->page_vec = kmalloc(sizeof(struct iser_page_vec) +
+				    (sizeof(u64) * (ISCSI_ISER_SG_TABLESIZE +1)),
+				    GFP_KERNEL);
+	if (!ib_conn->page_vec) {
+		ret = -ENOMEM;
+		goto alloc_err;
+	}
+	ib_conn->page_vec->pages = (u64 *) (ib_conn->page_vec + 1);
+
+	params.page_shift        = PAGE_SHIFT;
+	/* when the first/last SG element are not start/end *
+	 * page aligned, the map whould be of N+1 pages     */
+	params.max_pages_per_fmr = ISCSI_ISER_SG_TABLESIZE + 1;
+	/* make the pool size twice the max number of SCSI commands *
+	 * the ML is expected to queue, watermark for unmap at 50%  */
+	params.pool_size	 = ISCSI_XMIT_CMDS_MAX * 2;
+	params.dirty_watermark	 = ISCSI_XMIT_CMDS_MAX;
+	params.cache		 = 0;
+	params.flush_function	 = NULL;
+	params.access		 = (IB_ACCESS_LOCAL_WRITE  |
+				    IB_ACCESS_REMOTE_WRITE |
+				    IB_ACCESS_REMOTE_READ);
+
+	ib_conn->fmr_pool = ib_create_fmr_pool(device->pd, &params);
+	if (IS_ERR(ib_conn->fmr_pool)) {
+		ret = PTR_ERR(ib_conn->fmr_pool);
+		goto fmr_pool_err;
+	}
+
+	memset(&init_attr, 0, sizeof init_attr);
+
+	init_attr.event_handler = iser_qp_event_callback;
+	init_attr.qp_context	= (void *)ib_conn;
+	init_attr.send_cq	= device->cq;
+	init_attr.recv_cq	= device->cq;
+	init_attr.cap.max_send_wr  = ISER_QP_MAX_REQ_DTOS;
+	init_attr.cap.max_recv_wr  = ISER_QP_MAX_RECV_DTOS;
+	init_attr.cap.max_send_sge = MAX_REGD_BUF_VECTOR_LEN;
+	init_attr.cap.max_recv_sge = 2;
+	init_attr.sq_sig_type	= IB_SIGNAL_REQ_WR;
+	init_attr.qp_type	= IB_QPT_RC;
+
+	ret = rdma_create_qp(ib_conn->cma_id, device->pd, &init_attr);
+	if (ret)
+		goto qp_err;
+
+	ib_conn->qp = ib_conn->cma_id->qp;
+	iser_err("setting conn %p cma_id %p: fmr_pool %p qp %p\n",
+		 ib_conn, ib_conn->cma_id,
+		 ib_conn->fmr_pool, ib_conn->cma_id->qp);
+	return ret;
+
+qp_err:
+	(void)ib_destroy_fmr_pool(ib_conn->fmr_pool);
+fmr_pool_err:
+	kfree(ib_conn->page_vec);
+alloc_err:
+	iser_err("unable to alloc mem or create resource, err %d\n", ret);
+	return ret;
+}
+
+/**
+ * releases the FMR pool, QP and CMA ID objects, returns 0 on success,
+ * -1 on failure
+ */
+static int iser_free_ib_conn_res(struct iser_conn *ib_conn)
+{
+	BUG_ON(ib_conn == NULL);
+
+	iser_err("freeing conn %p cma_id %p fmr pool %p qp %p\n",
+		 ib_conn, ib_conn->cma_id,
+		 ib_conn->fmr_pool, ib_conn->qp);
+
+	/* qp is created only once both addr & route are resolved */
+	if (ib_conn->fmr_pool != NULL)
+		ib_destroy_fmr_pool(ib_conn->fmr_pool);
+
+	if (ib_conn->qp != NULL)
+		rdma_destroy_qp(ib_conn->cma_id);
+
+	if (ib_conn->cma_id != NULL)
+		rdma_destroy_id(ib_conn->cma_id);
+
+	ib_conn->fmr_pool = NULL;
+	ib_conn->qp	  = NULL;
+	ib_conn->cma_id   = NULL;
+	kfree(ib_conn->page_vec);
+
+	return 0;
+}
+
+/**
+ * based on the resolved device node GUID see if there already allocated
+ * device for this device. If there's no such, create one.
+ */
+static
+struct iser_device *iser_device_find_by_ib_device(struct rdma_cm_id *cma_id)
+{
+	struct list_head    *p_list;
+	struct iser_device  *device = NULL;
+
+	mutex_lock(&ig.device_list_mutex);
+
+	p_list = ig.device_list.next;
+	while (p_list != &ig.device_list) {
+		device = list_entry(p_list, struct iser_device, ig_list);
+		/* find if there's a match using the node GUID */
+		if (device->ib_device->node_guid == cma_id->device->node_guid)
+			break;
+	}
+
+	if (device == NULL) {
+		device = kzalloc(sizeof *device, GFP_KERNEL);
+		if (device == NULL)
+			goto out;
+		/* assign this device to the device */
+		device->ib_device = cma_id->device;
+		/* init the device and link it into ig device list */
+		if (iser_create_device_ib_res(device)) {
+			kfree(device);
+			device = NULL;
+			goto out;
+		}
+		list_add(&device->ig_list, &ig.device_list);
+	}
+out:
+	BUG_ON(device == NULL);
+	device->refcount++;
+	mutex_unlock(&ig.device_list_mutex);
+	return device;
+}
+
+/* if there's no demand for this device, release it */
+static void iser_device_try_release(struct iser_device *device)
+{
+	mutex_lock(&ig.device_list_mutex);
+	device->refcount--;
+	iser_err("device %p refcount %d\n",device,device->refcount);
+	if (!device->refcount) {
+		iser_free_device_ib_res(device);
+		list_del(&device->ig_list);
+		kfree(device);
+	}
+	mutex_unlock(&ig.device_list_mutex);
+}
+
+int iser_conn_state_comp(struct iser_conn *ib_conn,
+			enum iser_ib_conn_state comp)
+{
+	int ret;
+
+	spin_lock_bh(&ib_conn->lock);
+	ret = (ib_conn->state == comp);
+	spin_unlock_bh(&ib_conn->lock);
+	return ret;
+}
+
+static int iser_conn_state_comp_exch(struct iser_conn *ib_conn,
+				     enum iser_ib_conn_state comp,
+				     enum iser_ib_conn_state exch)
+{
+	int ret;
+
+	spin_lock_bh(&ib_conn->lock);
+	if ((ret = (ib_conn->state == comp)))
+		ib_conn->state = exch;
+	spin_unlock_bh(&ib_conn->lock);
+	return ret;
+}
+
+/**
+ * triggers start of the disconnect procedures and wait for them to be done
+ */
+void iser_conn_terminate(struct iser_conn *ib_conn)
+{
+	int err = 0;
+
+	/* change the ib conn state only if the conn is UP, however always call
+	 * rdma_disconnect since this is the only way to cause the CMA to change
+	 * the QP state to ERROR
+	 */
+
+	iser_conn_state_comp_exch(ib_conn, ISER_CONN_UP, ISER_CONN_TERMINATING);
+	err = rdma_disconnect(ib_conn->cma_id);
+	if (err)
+		iser_err("Failed to disconnect, conn: 0x%p err %d\n",
+			 ib_conn,err);
+
+	wait_event_interruptible(ib_conn->wait,
+				 ib_conn->state == ISER_CONN_DOWN);
+
+	iser_conn_release(ib_conn);
+}
+
+static void iser_connect_error(struct rdma_cm_id *cma_id)
+{
+	struct iser_conn *ib_conn;
+	ib_conn = (struct iser_conn *)cma_id->context;
+
+	ib_conn->state = ISER_CONN_DOWN;
+	wake_up_interruptible(&ib_conn->wait);
+}
+
+static void iser_addr_handler(struct rdma_cm_id *cma_id)
+{
+	struct iser_device *device;
+	struct iser_conn   *ib_conn;
+	int    ret;
+
+	device = iser_device_find_by_ib_device(cma_id);
+	ib_conn = (struct iser_conn *)cma_id->context;
+	ib_conn->device = device;
+
+	ret = rdma_resolve_route(cma_id, 1000);
+	if (ret) {
+		iser_err("resolve route failed: %d\n", ret);
+		iser_connect_error(cma_id);
+	}
+	return;
+}
+
+static void iser_route_handler(struct rdma_cm_id *cma_id)
+{
+	struct rdma_conn_param conn_param;
+	int    ret;
+
+	ret = iser_create_ib_conn_res((struct iser_conn *)cma_id->context);
+	if (ret)
+		goto failure;
+
+	iser_dbg("path.mtu is %d setting it to %d\n",
+		 cma_id->route.path_rec->mtu, IB_MTU_1024);
+
+	/* we must set the MTU to 1024 as this is what the target is assuming */
+	if (cma_id->route.path_rec->mtu > IB_MTU_1024)
+		cma_id->route.path_rec->mtu = IB_MTU_1024;
+
+	memset(&conn_param, 0, sizeof conn_param);
+	conn_param.responder_resources = 4;
+	conn_param.initiator_depth     = 1;
+	conn_param.retry_count	       = 7;
+	conn_param.rnr_retry_count     = 6;
+
+	ret = rdma_connect(cma_id, &conn_param);
+	if (ret) {
+		iser_err("failure connecting: %d\n", ret);
+		goto failure;
+	}
+
+	return;
+failure:
+	iser_connect_error(cma_id);
+}
+
+static void iser_connected_handler(struct rdma_cm_id *cma_id)
+{
+	struct iser_conn *ib_conn;
+
+	ib_conn = (struct iser_conn *)cma_id->context;
+	ib_conn->state = ISER_CONN_UP;
+	wake_up_interruptible(&ib_conn->wait);
+}
+
+static void iser_disconnected_handler(struct rdma_cm_id *cma_id)
+{
+	struct iser_conn *ib_conn;
+
+	ib_conn = (struct iser_conn *)cma_id->context;
+	ib_conn->disc_evt_flag = 1;
+
+	/* getting here when the state is UP means that the conn is being *
+	 * terminated asynchronously from the iSCSI layer's perspective.  */
+	if (iser_conn_state_comp_exch(ib_conn, ISER_CONN_UP,
+				      ISER_CONN_TERMINATING))
+		iscsi_conn_failure(ib_conn->iser_conn->iscsi_conn,
+				   ISCSI_ERR_CONN_FAILED);
+
+	/* Complete the termination process if no posts are pending */
+	if ((atomic_read(&ib_conn->post_recv_buf_count) == 0) &&
+	    (atomic_read(&ib_conn->post_send_buf_count) == 0)) {
+		ib_conn->state = ISER_CONN_DOWN;
+		wake_up_interruptible(&ib_conn->wait);
+	}
+}
+
+static int iser_cma_handler(struct rdma_cm_id *cma_id, struct rdma_cm_event *event)
+{
+	int ret = 0;
+
+	iser_err("event %d conn %p id %p\n",event->event,cma_id->context,cma_id);
+
+	switch (event->event) {
+	case RDMA_CM_EVENT_ADDR_RESOLVED:
+		iser_addr_handler(cma_id);
+		break;
+	case RDMA_CM_EVENT_ROUTE_RESOLVED:
+		iser_route_handler(cma_id);
+		break;
+	case RDMA_CM_EVENT_ESTABLISHED:
+		iser_connected_handler(cma_id);
+		break;
+	case RDMA_CM_EVENT_ADDR_ERROR:
+	case RDMA_CM_EVENT_ROUTE_ERROR:
+	case RDMA_CM_EVENT_CONNECT_ERROR:
+	case RDMA_CM_EVENT_UNREACHABLE:
+	case RDMA_CM_EVENT_REJECTED:
+		iser_err("event: %d, error: %d\n", event->event, event->status);
+		iser_connect_error(cma_id);
+		break;
+	case RDMA_CM_EVENT_DISCONNECTED:
+		iser_disconnected_handler(cma_id);
+		break;
+	case RDMA_CM_EVENT_DEVICE_REMOVAL:
+		BUG();
+		break;
+	case RDMA_CM_EVENT_CONNECT_RESPONSE:
+		BUG();
+		break;
+	case RDMA_CM_EVENT_CONNECT_REQUEST:
+	default:
+		break;
+	}
+	return ret;
+}
+
+int iser_conn_init(struct iser_conn **ibconn)
+{
+	struct iser_conn *ib_conn;
+
+	ib_conn = kzalloc(sizeof *ib_conn, GFP_KERNEL);
+	if (!ib_conn) {
+		iser_err("can't alloc memory for struct iser_conn\n");
+		return -ENOMEM;
+	}
+	ib_conn->state = ISER_CONN_INIT;
+	init_waitqueue_head(&ib_conn->wait);
+	atomic_set(&ib_conn->post_recv_buf_count, 0);
+	atomic_set(&ib_conn->post_send_buf_count, 0);
+	INIT_WORK(&ib_conn->comperror_work, iser_comp_error_worker,
+		  ib_conn);
+	INIT_LIST_HEAD(&ib_conn->conn_list);
+	spin_lock_init(&ib_conn->lock);
+
+	*ibconn = ib_conn;
+	return 0;
+}
+
+ /**
+ * starts the process of connecting to the target
+ * sleeps untill the connection is established or rejected
+ */
+int iser_connect(struct iser_conn   *ib_conn,
+		 struct sockaddr_in *src_addr,
+		 struct sockaddr_in *dst_addr,
+		 int                 non_blocking)
+{
+	struct sockaddr *src, *dst;
+	int err = 0;
+
+	sprintf(ib_conn->name,"%d.%d.%d.%d:%d",
+		NIPQUAD(dst_addr->sin_addr.s_addr), dst_addr->sin_port);
+
+	/* the device is known only --after-- address resolution */
+	ib_conn->device = NULL;
+
+	iser_err("connecting to: %d.%d.%d.%d, port 0x%x\n",
+		 NIPQUAD(dst_addr->sin_addr), dst_addr->sin_port);
+
+	ib_conn->state = ISER_CONN_PENDING;
+
+	ib_conn->cma_id = rdma_create_id(iser_cma_handler,
+					     (void *)ib_conn,
+					     RDMA_PS_TCP);
+	if (IS_ERR(ib_conn->cma_id)) {
+		err = PTR_ERR(ib_conn->cma_id);
+		iser_err("rdma_create_id failed: %d\n", err);
+		goto id_failure;
+	}
+
+	src = (struct sockaddr *)src_addr;
+	dst = (struct sockaddr *)dst_addr;
+	err = rdma_resolve_addr(ib_conn->cma_id, src, dst, 1000);
+	if (err) {
+		iser_err("rdma_resolve_addr failed: %d\n", err);
+		goto addr_failure;
+	}
+
+	if (!non_blocking) {
+		wait_event_interruptible(ib_conn->wait,
+					 (ib_conn->state != ISER_CONN_PENDING));
+
+		if (ib_conn->state != ISER_CONN_UP) {
+			err =  -EIO;
+			goto connect_failure;
+		}
+	}
+
+	mutex_lock(&ig.connlist_mutex);
+	list_add(&ib_conn->conn_list, &ig.connlist);
+	mutex_unlock(&ig.connlist_mutex);
+	return 0;
+
+id_failure:
+	ib_conn->cma_id = NULL;
+addr_failure:
+	ib_conn->state = ISER_CONN_DOWN;
+connect_failure:
+	iser_conn_release(ib_conn);
+	return err;
+}
+
+/**
+ * Frees all conn objects and deallocs conn descriptor
+ */
+void iser_conn_release(struct iser_conn *ib_conn)
+{
+	struct iser_device  *device = ib_conn->device;
+
+	BUG_ON(ib_conn->state != ISER_CONN_DOWN);
+
+	mutex_lock(&ig.connlist_mutex);
+	list_del(&ib_conn->conn_list);
+	mutex_unlock(&ig.connlist_mutex);
+
+	iser_free_ib_conn_res(ib_conn);
+	ib_conn->device = NULL;
+	/* on EVENT_ADDR_ERROR there's no device yet for this conn */
+	if (device != NULL)
+		iser_device_try_release(device);
+	kfree(ib_conn);
+}
+
+
+/**
+ * iser_reg_page_vec - Register physical memory
+ *
+ * returns: 0 on success, errno code on failure
+ */
+int iser_reg_page_vec(struct iser_conn     *ib_conn,
+		      struct iser_page_vec *page_vec,
+		      struct iser_mem_reg  *mem_reg)
+{
+	struct ib_pool_fmr *mem;
+	u64		   io_addr;
+	u64		   *page_list;
+	int		   status;
+
+	page_list = page_vec->pages;
+	io_addr	  = page_list[0];
+
+	mem  = ib_fmr_pool_map_phys(ib_conn->fmr_pool,
+				    page_list,
+				    page_vec->length,
+				    &io_addr);
+
+	if (IS_ERR(mem)) {
+		status = (int)PTR_ERR(mem);
+		iser_err("ib_fmr_pool_map_phys failed: %d\n", status);
+		return status;
+	}
+
+	mem_reg->lkey  = mem->fmr->lkey;
+	mem_reg->rkey  = mem->fmr->rkey;
+	mem_reg->len   = page_vec->length * PAGE_SIZE;
+	mem_reg->va    = io_addr;
+	mem_reg->mem_h = (void *)mem;
+
+	mem_reg->va   += page_vec->offset;
+	mem_reg->len   = page_vec->data_size;
+
+	iser_dbg("PHYSICAL Mem.register, [PHYS p_array: 0x%p, sz: %d, "
+		 "entry[0]: (0x%08lx,%ld)] -> "
+		 "[lkey: 0x%08X mem_h: 0x%p va: 0x%08lX sz: %ld]\n",
+		 page_vec, page_vec->length,
+		 (unsigned long)page_vec->pages[0],
+		 (unsigned long)page_vec->data_size,
+		 (unsigned int)mem_reg->lkey, mem_reg->mem_h,
+		 (unsigned long)mem_reg->va, (unsigned long)mem_reg->len);
+	return 0;
+}
+
+/**
+ * Unregister (previosuly registered) memory.
+ */
+void iser_unreg_mem(struct iser_mem_reg *reg)
+{
+	int ret;
+
+	iser_dbg("PHYSICAL Mem.Unregister mem_h %p\n",reg->mem_h);
+
+	ret = ib_fmr_pool_unmap((struct ib_pool_fmr *)reg->mem_h);
+	if (ret)
+		iser_err("ib_fmr_pool_unmap failed %d\n", ret);
+
+	reg->mem_h = NULL;
+}
+
+/**
+ * iser_dto_to_iov - builds IOV from a dto descriptor
+ */
+static void iser_dto_to_iov(struct iser_dto *dto, struct ib_sge *iov, int iov_len)
+{
+	int		     i;
+	struct ib_sge	     *sge;
+	struct iser_regd_buf *regd_buf;
+
+	if (dto->regd_vector_len > iov_len) {
+		iser_err("iov size %d too small for posting dto of len %d\n",
+			 iov_len, dto->regd_vector_len);
+		BUG();
+	}
+
+	for (i = 0; i < dto->regd_vector_len; i++) {
+		sge	    = &iov[i];
+		regd_buf  = dto->regd[i];
+
+		sge->addr   = regd_buf->reg.va;
+		sge->length = regd_buf->reg.len;
+		sge->lkey   = regd_buf->reg.lkey;
+
+		if (dto->used_sz[i] > 0)  /* Adjust size */
+			sge->length = dto->used_sz[i];
+
+		/* offset and length should not exceed the regd buf length */
+		if (sge->length + dto->offset[i] > regd_buf->reg.len) {
+			iser_err("Used len:%ld + offset:%d, exceed reg.buf.len:"
+				 "%ld in dto:0x%p [%d], va:0x%08lX\n",
+				 (unsigned long)sge->length, dto->offset[i],
+				 (unsigned long)regd_buf->reg.len, dto, i,
+				 (unsigned long)sge->addr);
+			BUG();
+		}
+
+		sge->addr += dto->offset[i]; /* Adjust offset */
+	}
+}
+
+/**
+ * iser_post_recv - Posts a receive buffer.
+ *
+ * returns 0 on success, -1 on failure
+ */
+int iser_post_recv(struct iser_desc *rx_desc)
+{
+	int		  ib_ret, ret_val = 0;
+	struct ib_recv_wr recv_wr, *recv_wr_failed;
+	struct ib_sge	  iov[2];
+	struct iser_conn  *ib_conn;
+	struct iser_dto   *recv_dto = &rx_desc->dto;
+
+	/* Retrieve conn */
+	ib_conn = recv_dto->conn->ib_conn;
+
+	iser_dto_to_iov(recv_dto, iov, 2);
+
+	recv_wr.next	= NULL;
+	recv_wr.sg_list = iov;
+	recv_wr.num_sge = recv_dto->regd_vector_len;
+	recv_wr.wr_id	= (unsigned long)rx_desc;
+
+	atomic_inc(&ib_conn->post_recv_buf_count);
+	ib_ret	= ib_post_recv(ib_conn->qp, &recv_wr, &recv_wr_failed);
+	if (ib_ret) {
+		iser_err("ib_post_recv failed ret=%d\n", ib_ret);
+		atomic_dec(&ib_conn->post_recv_buf_count);
+		ret_val = -1;
+	}
+
+	return ret_val;
+}
+
+/**
+ * iser_start_send - Initiate a Send DTO operation
+ *
+ * returns 0 on success, -1 on failure
+ */
+int iser_post_send(struct iser_desc *tx_desc)
+{
+	int		  ib_ret, ret_val = 0;
+	struct ib_send_wr send_wr, *send_wr_failed;
+	struct ib_sge	  iov[MAX_REGD_BUF_VECTOR_LEN];
+	struct iser_conn  *ib_conn;
+	struct iser_dto   *dto = &tx_desc->dto;
+
+	ib_conn = dto->conn->ib_conn;
+
+	iser_dto_to_iov(dto, iov, MAX_REGD_BUF_VECTOR_LEN);
+
+	send_wr.next	   = NULL;
+	send_wr.wr_id	   = (unsigned long)tx_desc;
+	send_wr.sg_list	   = iov;
+	send_wr.num_sge	   = dto->regd_vector_len;
+	send_wr.opcode	   = IB_WR_SEND;
+	send_wr.send_flags = dto->notify_enable ? IB_SEND_SIGNALED : 0;
+
+	atomic_inc(&ib_conn->post_send_buf_count);
+
+	ib_ret = ib_post_send(ib_conn->qp, &send_wr, &send_wr_failed);
+	if (ib_ret) {
+		iser_err("Failed to start SEND DTO, dto: 0x%p, IOV len: %d\n",
+			 dto, dto->regd_vector_len);
+		iser_err("ib_post_send failed, ret:%d\n", ib_ret);
+		atomic_dec(&ib_conn->post_send_buf_count);
+		ret_val = -1;
+	}
+
+	return ret_val;
+}
+
+static void iser_comp_error_worker(void *data)
+{
+	struct iser_conn *ib_conn = data;
+
+	/* getting here when the state is UP means that the conn is being *
+	 * terminated asynchronously from the iSCSI layer's perspective.  */
+	if (iser_conn_state_comp_exch(ib_conn, ISER_CONN_UP,
+				      ISER_CONN_TERMINATING))
+		iscsi_conn_failure(ib_conn->iser_conn->iscsi_conn,
+					ISCSI_ERR_CONN_FAILED);
+
+	/* complete the termination process if disconnect event was delivered *
+	 * note there are no more non completed posts to the QP               */
+	if (ib_conn->disc_evt_flag) {
+		ib_conn->state = ISER_CONN_DOWN;
+		wake_up_interruptible(&ib_conn->wait);
+	}
+}
+
+static void iser_handle_comp_error(struct iser_desc *desc)
+{
+	struct iser_dto  *dto     = &desc->dto;
+	struct iser_conn *ib_conn = dto->conn->ib_conn;
+
+	iser_dto_buffs_release(dto);
+
+	if (desc->type == ISCSI_RX) {
+		kfree(desc->data);
+		kmem_cache_free(ig.desc_cache, desc);
+		atomic_dec(&ib_conn->post_recv_buf_count);
+	} else { /* type is TX control/command/dataout */
+		if (desc->type == ISCSI_TX_DATAOUT)
+			kmem_cache_free(ig.desc_cache, desc);
+		atomic_dec(&ib_conn->post_send_buf_count);
+	}
+
+	if (atomic_read(&ib_conn->post_recv_buf_count) == 0 &&
+	    atomic_read(&ib_conn->post_send_buf_count) == 0)
+		schedule_work(&ib_conn->comperror_work);
+}
+
+static void iser_cq_tasklet_fn(unsigned long data)
+{
+	 struct iser_device  *device = (struct iser_device *)data;
+	 struct ib_cq	     *cq = device->cq;
+	 struct ib_wc	     wc;
+	 struct iser_desc    *desc;
+	 unsigned long	     xfer_len;
+
+	while (ib_poll_cq(cq, 1, &wc) == 1) {
+		desc	 = (struct iser_desc *) (unsigned long) wc.wr_id;
+		BUG_ON(desc == NULL);
+
+		if (wc.status == IB_WC_SUCCESS) {
+			if (desc->type == ISCSI_RX) {
+				xfer_len = (unsigned long)wc.byte_len;
+				iser_rcv_completion(desc, xfer_len);
+			} else /* type == ISCSI_TX_CONTROL/SCSI_CMD/DOUT */
+				iser_snd_completion(desc);
+		} else {
+			iser_err("comp w. error op %d status %d\n",desc->type,wc.status);
+			iser_handle_comp_error(desc);
+		}
+	}
+	/* #warning "it is assumed here that arming CQ only once its empty" *
+	 * " would not cause interrupts to be missed"                       */
+	ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
+}
+
+static void iser_cq_callback(struct ib_cq *cq, void *cq_context)
+{
+	struct iser_device  *device = (struct iser_device *)cq_context;
+
+	tasklet_schedule(&device->cq_tasklet);
+}