[PATCH 17/17]: SCST InfiniBand SRP target driver

[Vladislav Bolkhovitin]

This patch contains SCST InfiniBand SRP target driver.

This driver works directly on top of InfiniBand stack and SCST.

It was originally developed by Vu Pham/Mellanox, currently
Bart Van Assche is maintaining and improving it.

Signed-off-by: Vu Pham <vu@xxxxxxxxxxxx>
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxx>
Signed-off-by: Vladislav Bolkhovitin <vst@xxxxxxxx>
---
 Documentation/scst/README.srpt |  109 +
 drivers/scst/srpt/Kconfig      |   12 
 drivers/scst/srpt/Makefile     |    1 
 drivers/scst/srpt/ib_dm_mad.h  |  139 +
 drivers/scst/srpt/ib_srpt.c    | 3800 +++++++++++++++++++++++++++++++++++++++++
 drivers/scst/srpt/ib_srpt.h    |  368 +++
 6 files changed, 4429 insertions(+)

diff -uprN orig/linux-2.6.35/drivers/scst/srpt/Kconfig linux-2.6.35/drivers/scst/srpt/Kconfig
--- orig/linux-2.6.35/drivers/scst/srpt/Kconfig
+++ linux-2.6.35/drivers/scst/srpt/Kconfig
@@ -0,0 +1,12 @@
+config SCST_SRPT
+	tristate "InfiniBand SCSI RDMA Protocol target support"
+	depends on INFINIBAND && SCST
+	---help---
+
+	  Support for the SCSI RDMA Protocol (SRP) Target driver. The
+	  SRP protocol is a protocol that allows an initiator to access
+	  a block storage device on another host (target) over a network
+	  that supports the RDMA protocol. Currently the RDMA protocol is
+	  supported by InfiniBand and by iWarp network hardware. More
+	  information about the SRP protocol can be found on the website
+	  of the INCITS T10 technical committee (http://www.t10.org/).
diff -uprN orig/linux-2.6.35/drivers/scst/srpt/Makefile linux-2.6.35/drivers/scst/srpt/Makefile
--- orig/linux-2.6.35/drivers/scst/srpt/Makefile
+++ linux-2.6.35/drivers/scst/srpt/Makefile
@@ -0,0 +1,1 @@
+obj-$(CONFIG_SCST_SRPT)			+= ib_srpt.o
diff -uprN orig/linux-2.6.35/drivers/scst/srpt/ib_dm_mad.h linux-2.6.35/drivers/scst/srpt/ib_dm_mad.h
--- orig/linux-2.6.35/drivers/scst/srpt/ib_dm_mad.h
+++ linux-2.6.35/drivers/scst/srpt/ib_dm_mad.h
@@ -0,0 +1,139 @@
+/*
+ * Copyright (c) 2006 - 2009 Mellanox Technology Inc.  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.
+ *
+ */
+
+#ifndef IB_DM_MAD_H
+#define IB_DM_MAD_H
+
+#include <linux/types.h>
+
+#include <rdma/ib_mad.h>
+
+enum {
+	/*
+	 * See also section 13.4.7 Status Field, table 115 MAD Common Status
+	 * Field Bit Values and also section 16.3.1.1 Status Field in the
+	 * InfiniBand Architecture Specification.
+	 */
+	DM_MAD_STATUS_UNSUP_METHOD = 0x0008,
+	DM_MAD_STATUS_UNSUP_METHOD_ATTR = 0x000c,
+	DM_MAD_STATUS_INVALID_FIELD = 0x001c,
+	DM_MAD_STATUS_NO_IOC = 0x0100,
+
+	/*
+	 * See also the Device Management chapter, section 16.3.3 Attributes,
+	 * table 279 Device Management Attributes in the InfiniBand
+	 * Architecture Specification.
+	 */
+	DM_ATTR_CLASS_PORT_INFO = 0x01,
+	DM_ATTR_IOU_INFO = 0x10,
+	DM_ATTR_IOC_PROFILE = 0x11,
+	DM_ATTR_SVC_ENTRIES = 0x12
+};
+
+struct ib_dm_hdr {
+	u8 reserved[28];
+};
+
+/*
+ * Structure of management datagram sent by the SRP target implementation.
+ * Contains a management datagram header, reliable multi-packet transaction
+ * protocol (RMPP) header and ib_dm_hdr. Notes:
+ * - The SRP target implementation does not use RMPP or ib_dm_hdr when sending
+ *   management datagrams.
+ * - The header size must be exactly 64 bytes (IB_MGMT_DEVICE_HDR), since this
+ *   is the header size that is passed to ib_create_send_mad() in ib_srpt.c.
+ * - The maximum supported size for a management datagram when not using RMPP
+ *   is 256 bytes -- 64 bytes header and 192 (IB_MGMT_DEVICE_DATA) bytes data.
+ */
+struct ib_dm_mad {
+	struct ib_mad_hdr mad_hdr;
+	struct ib_rmpp_hdr rmpp_hdr;
+	struct ib_dm_hdr dm_hdr;
+	u8 data[IB_MGMT_DEVICE_DATA];
+};
+
+/*
+ * IOUnitInfo as defined in section 16.3.3.3 IOUnitInfo of the InfiniBand
+ * Architecture Specification.
+ */
+struct ib_dm_iou_info {
+	__be16 change_id;
+	u8 max_controllers;
+	u8 op_rom;
+	u8 controller_list[128];
+};
+
+/*
+ * IOControllerprofile as defined in section 16.3.3.4 IOControllerProfile of
+ * the InfiniBand Architecture Specification.
+ */
+struct ib_dm_ioc_profile {
+	__be64 guid;
+	__be32 vendor_id;
+	__be32 device_id;
+	__be16 device_version;
+	__be16 reserved1;
+	__be32 subsys_vendor_id;
+	__be32 subsys_device_id;
+	__be16 io_class;
+	__be16 io_subclass;
+	__be16 protocol;
+	__be16 protocol_version;
+	__be16 service_conn;
+	__be16 initiators_supported;
+	__be16 send_queue_depth;
+	u8 reserved2;
+	u8 rdma_read_depth;
+	__be32 send_size;
+	__be32 rdma_size;
+	u8 op_cap_mask;
+	u8 svc_cap_mask;
+	u8 num_svc_entries;
+	u8 reserved3[9];
+	u8 id_string[64];
+};
+
+struct ib_dm_svc_entry {
+	u8 name[40];
+	__be64 id;
+};
+
+/*
+ * See also section 16.3.3.5 ServiceEntries in the InfiniBand Architecture
+ * Specification. See also section B.7, table B.8 in the T10 SRP r16a document.
+ */
+struct ib_dm_svc_entries {
+	struct ib_dm_svc_entry service_entries[4];
+};
+
+#endif
diff -uprN orig/linux-2.6.35/drivers/scst/srpt/ib_srpt.c linux-2.6.35/drivers/scst/srpt/ib_srpt.c
--- orig/linux-2.6.35/drivers/scst/srpt/ib_srpt.c
+++ linux-2.6.35/drivers/scst/srpt/ib_srpt.c
@@ -0,0 +1,3800 @@
+/*
+ * Copyright (c) 2006 - 2009 Mellanox Technology Inc.  All rights reserved.
+ * Copyright (C) 2008 Vladislav Bolkhovitin <vst@xxxxxxxx>
+ * Copyright (C) 2008 - 2010 Bart Van Assche <bart.vanassche@xxxxxxxxx>
+ *
+ * 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.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/ctype.h>
+#include <linux/kthread.h>
+#include <linux/string.h>
+#include <linux/delay.h>
+#include <asm/atomic.h>
+#include "ib_srpt.h"
+#define LOG_PREFIX "ib_srpt" /* Prefix for SCST tracing macros. */
+#include <scst/scst_debug.h>
+
+/* Name of this kernel module. */
+#define DRV_NAME		"ib_srpt"
+#define DRV_VERSION		"1.0.1"
+#define DRV_RELDATE		"July 10, 2008"
+#if defined(CONFIG_SCST_DEBUG) || defined(CONFIG_SCST_TRACING)
+/* Flags to be used in SCST debug tracing statements. */
+#define DEFAULT_SRPT_TRACE_FLAGS (TRACE_OUT_OF_MEM | TRACE_MINOR \
+				  | TRACE_MGMT | TRACE_SPECIAL)
+/* Name of the entry that will be created under /proc/scsi_tgt/ib_srpt. */
+#define SRPT_PROC_TRACE_LEVEL_NAME	"trace_level"
+#endif
+
+#define MELLANOX_SRPT_ID_STRING	"SCST SRP target"
+
+MODULE_AUTHOR("Vu Pham");
+MODULE_DESCRIPTION("InfiniBand SCSI RDMA Protocol target "
+		   "v" DRV_VERSION " (" DRV_RELDATE ")");
+MODULE_LICENSE("Dual BSD/GPL");
+
+/*
+ * Local data types.
+ */
+
+enum threading_mode {
+	MODE_ALL_IN_SIRQ             = 0,
+	MODE_IB_COMPLETION_IN_THREAD = 1,
+	MODE_IB_COMPLETION_IN_SIRQ   = 2,
+};
+
+/*
+ * Global Variables
+ */
+
+static u64 srpt_service_guid;
+/* List of srpt_device structures. */
+static atomic_t srpt_device_count;
+#if defined(CONFIG_SCST_DEBUG) || defined(CONFIG_SCST_TRACING)
+static unsigned long trace_flag = DEFAULT_SRPT_TRACE_FLAGS;
+module_param(trace_flag, long, 0644);
+MODULE_PARM_DESC(trace_flag, "SCST trace flags.");
+#endif
+#if defined(CONFIG_SCST_DEBUG)
+static unsigned long processing_delay_in_us;
+module_param(processing_delay_in_us, long, 0744);
+MODULE_PARM_DESC(processing_delay_in_us,
+		 "SRP_CMD processing delay in microseconds. Useful for"
+		 " testing the initiator lockup avoidance algorithm.");
+#endif
+
+static int thread = 1;
+module_param(thread, int, 0444);
+MODULE_PARM_DESC(thread,
+		 "IB completion and SCSI command processing context. Defaults"
+		 " to one, i.e. process IB completions and SCSI commands in"
+		 " kernel thread context. 0 means soft IRQ whenever possible"
+		 " and 2 means process IB completions in soft IRQ context and"
+		 " SCSI commands in kernel thread context.");
+
+static unsigned srp_max_rdma_size = DEFAULT_MAX_RDMA_SIZE;
+module_param(srp_max_rdma_size, int, 0744);
+MODULE_PARM_DESC(srp_max_rdma_size,
+		 "Maximum size of SRP RDMA transfers for new connections.");
+
+static unsigned srp_max_message_size = DEFAULT_MAX_MESSAGE_SIZE;
+module_param(srp_max_message_size, int, 0444);
+MODULE_PARM_DESC(srp_max_message_size,
+		 "Maximum size of SRP control messages in bytes.");
+
+static int srpt_srq_size = DEFAULT_SRPT_SRQ_SIZE;
+module_param(srpt_srq_size, int, 0444);
+MODULE_PARM_DESC(srpt_srq_size,
+		 "Shared receive queue (SRQ) size.");
+
+static int srpt_sq_size = DEF_SRPT_SQ_SIZE;
+module_param(srpt_sq_size, int, 0444);
+MODULE_PARM_DESC(srpt_sq_size,
+		 "Per-channel send queue (SQ) size.");
+
+static bool srpt_autodetect_cred_req;
+module_param(srpt_autodetect_cred_req, bool, 0444);
+MODULE_PARM_DESC(srpt_autodetect_cred_req,
+		 "Whether or not to autodetect whether the initiator supports"
+		 " SRP_CRED_REQ.");
+
+static bool use_port_guid_in_session_name;
+module_param(use_port_guid_in_session_name, bool, 0444);
+MODULE_PARM_DESC(use_port_guid_in_session_name,
+		 "Use target port ID in the SCST session name such that"
+		 " redundant paths between multiport systems can be masked.");
+
+static int srpt_get_u64_x(char *buffer, struct kernel_param *kp)
+{
+	return sprintf(buffer, "0x%016llx", *(u64 *)kp->arg);
+}
+module_param_call(srpt_service_guid, NULL, srpt_get_u64_x, &srpt_service_guid,
+		  0444);
+MODULE_PARM_DESC(srpt_service_guid,
+		 "Using this value for ioc_guid, id_ext, and cm_listen_id"
+		 " instead of using the node_guid of the first HCA.");
+
+static void srpt_add_one(struct ib_device *device);
+static void srpt_remove_one(struct ib_device *device);
+static void srpt_unregister_mad_agent(struct srpt_device *sdev);
+static void srpt_unmap_sg_to_ib_sge(struct srpt_rdma_ch *ch,
+				    struct srpt_ioctx *ioctx);
+static void srpt_release_channel(struct scst_session *scst_sess);
+
+static struct ib_client srpt_client = {
+	.name = DRV_NAME,
+	.add = srpt_add_one,
+	.remove = srpt_remove_one
+};
+
+/**
+ * srpt_test_and_set_channel_state() - Test and set the channel state.
+ *
+ * @ch: RDMA channel.
+ * @old: channel state to compare with.
+ * @new: state to change the channel state to if the current state matches the
+ *       argument 'old'.
+ *
+ * Returns the previous channel state.
+ */
+static enum rdma_ch_state
+srpt_test_and_set_channel_state(struct srpt_rdma_ch *ch,
+				enum rdma_ch_state old,
+				enum rdma_ch_state new)
+{
+	return atomic_cmpxchg(&ch->state, old, new);
+}
+
+/**
+ * srpt_event_handler() - Asynchronous IB event callback function.
+ *
+ * Callback function called by the InfiniBand core when an asynchronous IB
+ * event occurs. This callback may occur in interrupt context. See also
+ * section 11.5.2, Set Asynchronous Event Handler in the InfiniBand
+ * Architecture Specification.
+ */
+static void srpt_event_handler(struct ib_event_handler *handler,
+			       struct ib_event *event)
+{
+	struct srpt_device *sdev;
+	struct srpt_port *sport;
+
+	sdev = ib_get_client_data(event->device, &srpt_client);
+	if (!sdev || sdev->device != event->device)
+		return;
+
+	TRACE_DBG("ASYNC event= %d on device= %s",
+		  event->event, sdev->device->name);
+
+	switch (event->event) {
+	case IB_EVENT_PORT_ERR:
+		if (event->element.port_num <= sdev->device->phys_port_cnt) {
+			sport = &sdev->port[event->element.port_num - 1];
+			sport->lid = 0;
+			sport->sm_lid = 0;
+		}
+		break;
+	case IB_EVENT_PORT_ACTIVE:
+	case IB_EVENT_LID_CHANGE:
+	case IB_EVENT_PKEY_CHANGE:
+	case IB_EVENT_SM_CHANGE:
+	case IB_EVENT_CLIENT_REREGISTER:
+		/*
+		 * Refresh port data asynchronously. Note: it is safe to call
+		 * schedule_work() even if &sport->work is already on the
+		 * global workqueue because schedule_work() tests for the
+		 * work_pending() condition before adding &sport->work to the
+		 * global work queue.
+		 */
+		if (event->element.port_num <= sdev->device->phys_port_cnt) {
+			sport = &sdev->port[event->element.port_num - 1];
+			if (!sport->lid && !sport->sm_lid)
+				schedule_work(&sport->work);
+		}
+		break;
+	default:
+		PRINT_ERROR("received unrecognized IB event %d", event->event);
+		break;
+	}
+}
+
+/**
+ * srpt_srq_event() - SRQ event callback function.
+ */
+static void srpt_srq_event(struct ib_event *event, void *ctx)
+{
+	PRINT_INFO("SRQ event %d", event->event);
+}
+
+/**
+ * srpt_qp_event() - QP event callback function.
+ */
+static void srpt_qp_event(struct ib_event *event, struct srpt_rdma_ch *ch)
+{
+	TRACE_DBG("QP event %d on cm_id=%p sess_name=%s state=%d",
+		  event->event, ch->cm_id, ch->sess_name,
+		  atomic_read(&ch->state));
+
+	switch (event->event) {
+	case IB_EVENT_COMM_EST:
+		ib_cm_notify(ch->cm_id, event->event);
+		break;
+	case IB_EVENT_QP_LAST_WQE_REACHED:
+		if (srpt_test_and_set_channel_state(ch, RDMA_CHANNEL_LIVE,
+			RDMA_CHANNEL_DISCONNECTING) == RDMA_CHANNEL_LIVE) {
+			PRINT_INFO("disconnected session %s.", ch->sess_name);
+			ib_send_cm_dreq(ch->cm_id, NULL, 0);
+		}
+		break;
+	default:
+		PRINT_ERROR("received unrecognized IB QP event %d",
+			    event->event);
+		break;
+	}
+}
+
+/**
+ * srpt_set_ioc() - Helper function for initializing an IOUnitInfo structure.
+ *
+ * @slot: one-based slot number.
+ * @value: four-bit value.
+ *
+ * Copies the lowest four bits of value in element slot of the array of four
+ * bit elements called c_list (controller list). The index slot is one-based.
+ */
+static void srpt_set_ioc(u8 *c_list, u32 slot, u8 value)
+{
+	u16 id;
+	u8 tmp;
+
+	id = (slot - 1) / 2;
+	if (slot & 0x1) {
+		tmp = c_list[id] & 0xf;
+		c_list[id] = (value << 4) | tmp;
+	} else {
+		tmp = c_list[id] & 0xf0;
+		c_list[id] = (value & 0xf) | tmp;
+	}
+}
+
+/**
+ * srpt_get_class_port_info() - Copy ClassPortInfo to a management datagram.
+ *
+ * See also section 16.3.3.1 ClassPortInfo in the InfiniBand Architecture
+ * Specification.
+ */
+static void srpt_get_class_port_info(struct ib_dm_mad *mad)
+{
+	struct ib_class_port_info *cif;
+
+	cif = (struct ib_class_port_info *)mad->data;
+	memset(cif, 0, sizeof *cif);
+	cif->base_version = 1;
+	cif->class_version = 1;
+	cif->resp_time_value = 20;
+
+	mad->mad_hdr.status = 0;
+}
+
+/**
+ * srpt_get_iou() - Write IOUnitInfo to a management datagram.
+ *
+ * See also section 16.3.3.3 IOUnitInfo in the InfiniBand Architecture
+ * Specification. See also section B.7, table B.6 in the SRP r16a document.
+ */
+static void srpt_get_iou(struct ib_dm_mad *mad)
+{
+	struct ib_dm_iou_info *ioui;
+	u8 slot;
+	int i;
+
+	ioui = (struct ib_dm_iou_info *)mad->data;
+	ioui->change_id = cpu_to_be16(1);
+	ioui->max_controllers = 16;
+
+	/* set present for slot 1 and empty for the rest */
+	srpt_set_ioc(ioui->controller_list, 1, 1);
+	for (i = 1, slot = 2; i < 16; i++, slot++)
+		srpt_set_ioc(ioui->controller_list, slot, 0);
+
+	mad->mad_hdr.status = 0;
+}
+
+/**
+ * srpt_get_ioc() - Write IOControllerprofile to a management datagram.
+ *
+ * See also section 16.3.3.4 IOControllerProfile in the InfiniBand
+ * Architecture Specification. See also section B.7, table B.7 in the SRP
+ * r16a document.
+ */
+static void srpt_get_ioc(struct srpt_device *sdev, u32 slot,
+			 struct ib_dm_mad *mad)
+{
+	struct ib_dm_ioc_profile *iocp;
+
+	iocp = (struct ib_dm_ioc_profile *)mad->data;
+
+	if (!slot || slot > 16) {
+		mad->mad_hdr.status = cpu_to_be16(DM_MAD_STATUS_INVALID_FIELD);
+		return;
+	}
+
+	if (slot > 2) {
+		mad->mad_hdr.status = cpu_to_be16(DM_MAD_STATUS_NO_IOC);
+		return;
+	}
+
+	memset(iocp, 0, sizeof *iocp);
+	strcpy(iocp->id_string, MELLANOX_SRPT_ID_STRING);
+	iocp->guid = cpu_to_be64(srpt_service_guid);
+	iocp->vendor_id = cpu_to_be32(sdev->dev_attr.vendor_id);
+	iocp->device_id = cpu_to_be32(sdev->dev_attr.vendor_part_id);
+	iocp->device_version = cpu_to_be16(sdev->dev_attr.hw_ver);
+	iocp->subsys_vendor_id = cpu_to_be32(sdev->dev_attr.vendor_id);
+	iocp->subsys_device_id = 0x0;
+	iocp->io_class = cpu_to_be16(SRP_REV16A_IB_IO_CLASS);
+	iocp->io_subclass = cpu_to_be16(SRP_IO_SUBCLASS);
+	iocp->protocol = cpu_to_be16(SRP_PROTOCOL);
+	iocp->protocol_version = cpu_to_be16(SRP_PROTOCOL_VERSION);
+	iocp->send_queue_depth = cpu_to_be16(sdev->srq_size);
+	iocp->rdma_read_depth = 4;
+	iocp->send_size = cpu_to_be32(srp_max_message_size);
+	iocp->rdma_size = cpu_to_be32(min(max(srp_max_rdma_size, 256U),
+					  1U << 24));
+	iocp->num_svc_entries = 1;
+	iocp->op_cap_mask = SRP_SEND_TO_IOC | SRP_SEND_FROM_IOC |
+		SRP_RDMA_READ_FROM_IOC | SRP_RDMA_WRITE_FROM_IOC;
+
+	mad->mad_hdr.status = 0;
+}
+
+/**
+ * srpt_get_svc_entries() - Write ServiceEntries to a management datagram.
+ *
+ * See also section 16.3.3.5 ServiceEntries in the InfiniBand Architecture
+ * Specification. See also section B.7, table B.8 in the SRP r16a document.
+ */
+static void srpt_get_svc_entries(u64 ioc_guid,
+				 u16 slot, u8 hi, u8 lo, struct ib_dm_mad *mad)
+{
+	struct ib_dm_svc_entries *svc_entries;
+
+	WARN_ON(!ioc_guid);
+
+	if (!slot || slot > 16) {
+		mad->mad_hdr.status = cpu_to_be16(DM_MAD_STATUS_INVALID_FIELD);
+		return;
+	}
+
+	if (slot > 2 || lo > hi || hi > 1) {
+		mad->mad_hdr.status = cpu_to_be16(DM_MAD_STATUS_NO_IOC);
+		return;
+	}
+
+	svc_entries = (struct ib_dm_svc_entries *)mad->data;
+	memset(svc_entries, 0, sizeof *svc_entries);
+	svc_entries->service_entries[0].id = cpu_to_be64(ioc_guid);
+	snprintf(svc_entries->service_entries[0].name,
+		 sizeof(svc_entries->service_entries[0].name),
+		 "%s%016llx",
+		 SRP_SERVICE_NAME_PREFIX,
+		 ioc_guid);
+
+	mad->mad_hdr.status = 0;
+}
+
+/**
+ * srpt_mgmt_method_get() - Process a received management datagram.
+ * @sp:      source port through which the MAD has been received.
+ * @rq_mad:  received MAD.
+ * @rsp_mad: response MAD.
+ */
+static void srpt_mgmt_method_get(struct srpt_port *sp, struct ib_mad *rq_mad,
+				 struct ib_dm_mad *rsp_mad)
+{
+	u16 attr_id;
+	u32 slot;
+	u8 hi, lo;
+
+	attr_id = be16_to_cpu(rq_mad->mad_hdr.attr_id);
+	switch (attr_id) {
+	case DM_ATTR_CLASS_PORT_INFO:
+		srpt_get_class_port_info(rsp_mad);
+		break;
+	case DM_ATTR_IOU_INFO:
+		srpt_get_iou(rsp_mad);
+		break;
+	case DM_ATTR_IOC_PROFILE:
+		slot = be32_to_cpu(rq_mad->mad_hdr.attr_mod);
+		srpt_get_ioc(sp->sdev, slot, rsp_mad);
+		break;
+	case DM_ATTR_SVC_ENTRIES:
+		slot = be32_to_cpu(rq_mad->mad_hdr.attr_mod);
+		hi = (u8) ((slot >> 8) & 0xff);
+		lo = (u8) (slot & 0xff);
+		slot = (u16) ((slot >> 16) & 0xffff);
+		srpt_get_svc_entries(srpt_service_guid,
+				     slot, hi, lo, rsp_mad);
+		break;
+	default:
+		rsp_mad->mad_hdr.status =
+		    cpu_to_be16(DM_MAD_STATUS_UNSUP_METHOD_ATTR);
+		break;
+	}
+}
+
+/**
+ * srpt_mad_send_handler() - Post MAD-send callback function.
+ */
+static void srpt_mad_send_handler(struct ib_mad_agent *mad_agent,
+				  struct ib_mad_send_wc *mad_wc)
+{
+	ib_destroy_ah(mad_wc->send_buf->ah);
+	ib_free_send_mad(mad_wc->send_buf);
+}
+
+/**
+ * srpt_mad_recv_handler() - MAD reception callback function.
+ */
+static void srpt_mad_recv_handler(struct ib_mad_agent *mad_agent,
+				  struct ib_mad_recv_wc *mad_wc)
+{
+	struct srpt_port *sport = (struct srpt_port *)mad_agent->context;
+	struct ib_ah *ah;
+	struct ib_mad_send_buf *rsp;
+	struct ib_dm_mad *dm_mad;
+
+	if (!mad_wc || !mad_wc->recv_buf.mad)
+		return;
+
+	ah = ib_create_ah_from_wc(mad_agent->qp->pd, mad_wc->wc,
+				  mad_wc->recv_buf.grh, mad_agent->port_num);
+	if (IS_ERR(ah))
+		goto err;
+
+	BUILD_BUG_ON(offsetof(struct ib_dm_mad, data) != IB_MGMT_DEVICE_HDR);
+
+	rsp = ib_create_send_mad(mad_agent, mad_wc->wc->src_qp,
+				 mad_wc->wc->pkey_index, 0,
+				 IB_MGMT_DEVICE_HDR, IB_MGMT_DEVICE_DATA,
+				 GFP_KERNEL);
+	if (IS_ERR(rsp))
+		goto err_rsp;
+
+	rsp->ah = ah;
+
+	dm_mad = rsp->mad;
+	memcpy(dm_mad, mad_wc->recv_buf.mad, sizeof *dm_mad);
+	dm_mad->mad_hdr.method = IB_MGMT_METHOD_GET_RESP;
+	dm_mad->mad_hdr.status = 0;
+
+	switch (mad_wc->recv_buf.mad->mad_hdr.method) {
+	case IB_MGMT_METHOD_GET:
+		srpt_mgmt_method_get(sport, mad_wc->recv_buf.mad, dm_mad);
+		break;
+	case IB_MGMT_METHOD_SET:
+		dm_mad->mad_hdr.status =
+		    cpu_to_be16(DM_MAD_STATUS_UNSUP_METHOD_ATTR);
+		break;
+	default:
+		dm_mad->mad_hdr.status =
+		    cpu_to_be16(DM_MAD_STATUS_UNSUP_METHOD);
+		break;
+	}
+
+	if (!ib_post_send_mad(rsp, NULL)) {
+		ib_free_recv_mad(mad_wc);
+		/* will destroy_ah & free_send_mad in send completion */
+		return;
+	}
+
+	ib_free_send_mad(rsp);
+
+err_rsp:
+	ib_destroy_ah(ah);
+err:
+	ib_free_recv_mad(mad_wc);
+}
+
+/**
+ * srpt_refresh_port() - Configure a HCA port.
+ *
+ * Enable InfiniBand management datagram processing, update the cached sm_lid,
+ * lid and gid values, and register a callback function for processing MADs
+ * on the specified port.
+ *
+ * Note: It is safe to call this function more than once for the same port.
+ */
+static int srpt_refresh_port(struct srpt_port *sport)
+{
+	struct ib_mad_reg_req reg_req;
+	struct ib_port_modify port_modify;
+	struct ib_port_attr port_attr;
+	int ret;
+
+	memset(&port_modify, 0, sizeof port_modify);
+	port_modify.set_port_cap_mask = IB_PORT_DEVICE_MGMT_SUP;
+	port_modify.clr_port_cap_mask = 0;
+
+	ret = ib_modify_port(sport->sdev->device, sport->port, 0, &port_modify);
+	if (ret)
+		goto err_mod_port;
+
+	ret = ib_query_port(sport->sdev->device, sport->port, &port_attr);
+	if (ret)
+		goto err_query_port;
+
+	sport->sm_lid = port_attr.sm_lid;
+	sport->lid = port_attr.lid;
+
+	ret = ib_query_gid(sport->sdev->device, sport->port, 0, &sport->gid);
+	if (ret)
+		goto err_query_port;
+
+	if (!sport->mad_agent) {
+		memset(&reg_req, 0, sizeof reg_req);
+		reg_req.mgmt_class = IB_MGMT_CLASS_DEVICE_MGMT;
+		reg_req.mgmt_class_version = IB_MGMT_BASE_VERSION;
+		set_bit(IB_MGMT_METHOD_GET, reg_req.method_mask);
+		set_bit(IB_MGMT_METHOD_SET, reg_req.method_mask);
+
+		sport->mad_agent = ib_register_mad_agent(sport->sdev->device,
+							 sport->port,
+							 IB_QPT_GSI,
+							 &reg_req, 0,
+							 srpt_mad_send_handler,
+							 srpt_mad_recv_handler,
+							 sport);
+		if (IS_ERR(sport->mad_agent)) {
+			ret = PTR_ERR(sport->mad_agent);
+			sport->mad_agent = NULL;
+			goto err_query_port;
+		}
+	}
+
+	return 0;
+
+err_query_port:
+
+	port_modify.set_port_cap_mask = 0;
+	port_modify.clr_port_cap_mask = IB_PORT_DEVICE_MGMT_SUP;
+	ib_modify_port(sport->sdev->device, sport->port, 0, &port_modify);
+
+err_mod_port:
+
+	return ret;
+}
+
+/**
+ * srpt_unregister_mad_agent() - Unregister MAD callback functions.
+ *
+ * Note: It is safe to call this function more than once for the same device.
+ */
+static void srpt_unregister_mad_agent(struct srpt_device *sdev)
+{
+	struct ib_port_modify port_modify = {
+		.clr_port_cap_mask = IB_PORT_DEVICE_MGMT_SUP,
+	};
+	struct srpt_port *sport;
+	int i;
+
+	for (i = 1; i <= sdev->device->phys_port_cnt; i++) {
+		sport = &sdev->port[i - 1];
+		WARN_ON(sport->port != i);
+		if (ib_modify_port(sdev->device, i, 0, &port_modify) < 0)
+			PRINT_ERROR("%s", "disabling MAD processing failed.");
+		if (sport->mad_agent) {
+			ib_unregister_mad_agent(sport->mad_agent);
+			sport->mad_agent = NULL;
+		}
+	}
+}
+
+/**
+ * srpt_alloc_ioctx() - Allocate and initialize an SRPT I/O context structure.
+ */
+static struct srpt_ioctx *srpt_alloc_ioctx(struct srpt_device *sdev)
+{
+	struct srpt_ioctx *ioctx;
+
+	ioctx = kmalloc(sizeof *ioctx, GFP_KERNEL);
+	if (!ioctx)
+		goto out;
+
+	ioctx->buf = kzalloc(srp_max_message_size, GFP_KERNEL);
+	if (!ioctx->buf)
+		goto out_free_ioctx;
+
+	ioctx->dma = ib_dma_map_single(sdev->device, ioctx->buf,
+				       srp_max_message_size, DMA_BIDIRECTIONAL);
+	if (ib_dma_mapping_error(sdev->device, ioctx->dma))
+		goto out_free_buf;
+
+	return ioctx;
+
+out_free_buf:
+	kfree(ioctx->buf);
+out_free_ioctx:
+	kfree(ioctx);
+out:
+	return NULL;
+}
+
+/**
+ * srpt_free_ioctx() - Deallocate an SRPT I/O context structure.
+ */
+static void srpt_free_ioctx(struct srpt_device *sdev, struct srpt_ioctx *ioctx)
+{
+	if (!ioctx)
+		return;
+
+	ib_dma_unmap_single(sdev->device, ioctx->dma,
+			    srp_max_message_size, DMA_BIDIRECTIONAL);
+	kfree(ioctx->buf);
+	kfree(ioctx);
+}
+
+/**
+ * srpt_alloc_ioctx_ring() - Allocate a ring of SRPT I/O context structures.
+ * @sdev:       Device to allocate the I/O context ring for.
+ * @ioctx_ring: Pointer to an array of I/O contexts.
+ * @ring_size:  Number of elements in the I/O context ring.
+ * @flags:      Flags to be set in the ring index.
+ */
+static int srpt_alloc_ioctx_ring(struct srpt_device *sdev,
+				 struct srpt_ioctx **ioctx_ring,
+				 int ring_size,
+				 int flags)
+{
+	int res;
+	int i;
+
+	res = -ENOMEM;
+	for (i = 0; i < ring_size; ++i) {
+		ioctx_ring[i] = srpt_alloc_ioctx(sdev);
+
+		if (!ioctx_ring[i])
+			goto err;
+
+		EXTRACHECKS_WARN_ON(i & flags);
+		ioctx_ring[i]->index = i | flags;
+	}
+	res = 0;
+	goto out;
+
+err:
+	while (--i >= 0) {
+		srpt_free_ioctx(sdev, ioctx_ring[i]);
+		ioctx_ring[i] = NULL;
+	}
+out:
+	return res;
+}
+
+/**
+ * srpt_free_ioctx_ring() - Free the ring of SRPT I/O context structures.
+ */
+static void srpt_free_ioctx_ring(struct srpt_device *sdev,
+				 struct srpt_ioctx **ioctx_ring,
+				 int ring_size)
+{
+	int i;
+
+	for (i = 0; i < ring_size; ++i) {
+		srpt_free_ioctx(sdev, ioctx_ring[i]);
+		ioctx_ring[i] = NULL;
+	}
+}
+
+/**
+ * srpt_alloc_tti_ring() - Allocate target-to-initiator I/O contexts.
+ */
+static int srpt_alloc_tti_ioctx(struct srpt_rdma_ch *ch)
+{
+	return srpt_alloc_ioctx_ring(ch->sport->sdev, ch->tti_ioctx,
+				     ARRAY_SIZE(ch->tti_ioctx),
+				     SRPT_OP_TTI);
+}
+
+/**
+ * srpt_free_tti_ring() - Free target-to-initiator I/O contexts.
+ */
+static void srpt_free_tti_ioctx(struct srpt_rdma_ch *ch)
+{
+	srpt_free_ioctx_ring(ch->sport->sdev, ch->tti_ioctx,
+			     ARRAY_SIZE(ch->tti_ioctx));
+}
+
+/**
+ * srpt_get_tti_ioctx() - Get a target-to-initiator I/O context.
+ */
+static struct srpt_ioctx *srpt_get_tti_ioctx(struct srpt_rdma_ch *ch)
+{
+	struct srpt_ioctx *ioctx;
+	struct srpt_device *sdev;
+	unsigned long flags;
+
+	sdev = ch->sport->sdev;
+	spin_lock_irqsave(&sdev->spinlock, flags);
+	EXTRACHECKS_WARN_ON(ch->tti_head - ch->tti_tail < 0);
+	if (ch->tti_head - ch->tti_tail < TTI_IOCTX_COUNT)
+		ioctx = ch->tti_ioctx[ch->tti_head++ & TTI_IOCTX_MASK];
+	else
+		ioctx = NULL;
+	spin_unlock_irqrestore(&sdev->spinlock, flags);
+	return ioctx;
+}
+
+/**
+ * srpt_put_tti_ioctx() - Put back a target-to-initiator I/O context.
+ */
+static void srpt_put_tti_ioctx(struct srpt_rdma_ch *ch)
+{
+	struct srpt_device *sdev;
+	unsigned long flags;
+
+	sdev = ch->sport->sdev;
+	spin_lock_irqsave(&sdev->spinlock, flags);
+	EXTRACHECKS_WARN_ON(ch->tti_head - ch->tti_tail < 0);
+	ch->tti_tail++;
+	EXTRACHECKS_WARN_ON(ch->tti_head - ch->tti_tail < 0);
+	spin_unlock_irqrestore(&sdev->spinlock, flags);
+}
+
+/**
+ * srpt_get_cmd_state() - Get the state of a SCSI command.
+ */
+static enum srpt_command_state srpt_get_cmd_state(struct srpt_ioctx *ioctx)
+{
+	BUG_ON(!ioctx);
+
+	return atomic_read(&ioctx->state);
+}
+
+/**
+ * srpt_set_cmd_state() - Set the state of a SCSI command.
+ * @new: New state to be set.
+ *
+ * Does not modify the state of aborted commands. Returns the previous command
+ * state.
+ */
+static enum srpt_command_state srpt_set_cmd_state(struct srpt_ioctx *ioctx,
+						  enum srpt_command_state new)
+{
+	enum srpt_command_state previous;
+
+	BUG_ON(!ioctx);
+
+	do {
+		previous = atomic_read(&ioctx->state);
+	} while (previous != SRPT_STATE_DONE
+	       && atomic_cmpxchg(&ioctx->state, previous, new) != previous);
+
+	return previous;
+}
+
+/**
+ * srpt_test_and_set_cmd_state() - Test and set the state of a command.
+ * @old: State to compare against.
+ * @new: New state to be set if the current state matches 'old'.
+ *
+ * Returns the previous command state.
+ */
+static enum srpt_command_state
+srpt_test_and_set_cmd_state(struct srpt_ioctx *ioctx,
+			    enum srpt_command_state old,
+			    enum srpt_command_state new)
+{
+	WARN_ON(!ioctx);
+	WARN_ON(old == SRPT_STATE_DONE);
+	WARN_ON(new == SRPT_STATE_NEW);
+
+	return atomic_cmpxchg(&ioctx->state, old, new);
+}
+
+/**
+ * srpt_post_recv() - Post an IB receive request.
+ */
+static int srpt_post_recv(struct srpt_device *sdev, struct srpt_ioctx *ioctx)
+{
+	struct ib_sge list;
+	struct ib_recv_wr wr, *bad_wr;
+
+	wr.wr_id = ioctx->index | SRPT_OP_RECV;
+
+	list.addr = ioctx->dma;
+	list.length = srp_max_message_size;
+	list.lkey = sdev->mr->lkey;
+
+	wr.next = NULL;
+	wr.sg_list = &list;
+	wr.num_sge = 1;
+
+	return ib_post_srq_recv(sdev->srq, &wr, &bad_wr);
+}
+
+/**
+ * srpt_post_send() - Post an IB send request.
+ * @ch: RDMA channel to post the send request on.
+ * @ioctx: I/O context of the send request.
+ * @len: length of the request to be sent in bytes.
+ *
+ * Returns zero upon success and a non-zero value upon failure.
+ */
+static int srpt_post_send(struct srpt_rdma_ch *ch, struct srpt_ioctx *ioctx,
+			  int len)
+{
+	struct ib_sge list;
+	struct ib_send_wr wr, *bad_wr;
+	struct srpt_device *sdev = ch->sport->sdev;
+	int ret;
+
+	ret = -ENOMEM;
+	if (atomic_dec_return(&ch->sq_wr_avail) < 0) {
+		PRINT_ERROR("%s[%d]: send queue full", __func__, __LINE__);
+		goto out;
+	}
+
+	ib_dma_sync_single_for_device(sdev->device, ioctx->dma,
+				      len, DMA_TO_DEVICE);
+
+	list.addr = ioctx->dma;
+	list.length = len;
+	list.lkey = sdev->mr->lkey;
+
+	wr.next = NULL;
+	wr.wr_id = ioctx->index;
+	wr.sg_list = &list;
+	wr.num_sge = 1;
+	wr.opcode = IB_WR_SEND;
+	wr.send_flags = IB_SEND_SIGNALED;
+
+	ret = ib_post_send(ch->qp, &wr, &bad_wr);
+
+out:
+	if (ret < 0)
+		atomic_inc(&ch->sq_wr_avail);
+	return ret;
+}
+
+/**
+ * srpt_get_desc_tbl() - Parse the data descriptors of an SRP_CMD request.
+ * @ioctx: Pointer to the I/O context associated with the request.
+ * @srp_cmd: Pointer to the SRP_CMD request data.
+ * @dir: Pointer to the variable to which the transfer direction will be
+ *   written.
+ * @data_len: Pointer to the variable to which the total data length of all
+ *   descriptors in the SRP_CMD request will be written.
+ *
+ * This function initializes ioctx->nrbuf and ioctx->r_bufs.
+ *
+ * Returns -EINVAL when the SRP_CMD request contains inconsistent descriptors;
+ * -ENOMEM when memory allocation fails and zero upon success.
+ */
+static int srpt_get_desc_tbl(struct srpt_ioctx *ioctx, struct srp_cmd *srp_cmd,
+			     scst_data_direction *dir, u64 *data_len)
+{
+	struct srp_indirect_buf *idb;
+	struct srp_direct_buf *db;
+	unsigned add_cdb_offset;
+	int ret;
+
+	/*
+	 * The pointer computations below will only be compiled correctly
+	 * if srp_cmd::add_data is declared as s8*, u8*, s8[] or u8[], so check
+	 * whether srp_cmd::add_data has been declared as a byte pointer.
+	 */
+	BUILD_BUG_ON(!__same_type(srp_cmd->add_data[0], (s8)0)
+		     && !__same_type(srp_cmd->add_data[0], (u8)0));
+
+	BUG_ON(!dir);
+	BUG_ON(!data_len);
+
+	ret = 0;
+	*data_len = 0;
+
+	/*
+	 * The lower four bits of the buffer format field contain the DATA-IN
+	 * buffer descriptor format, and the highest four bits contain the
+	 * DATA-OUT buffer descriptor format.
+	 */
+	*dir = SCST_DATA_NONE;
+	if (srp_cmd->buf_fmt & 0xf)
+		/* DATA-IN: transfer data from target to initiator. */
+		*dir = SCST_DATA_READ;
+	else if (srp_cmd->buf_fmt >> 4)
+		/* DATA-OUT: transfer data from initiator to target. */
+		*dir = SCST_DATA_WRITE;
+
+	/*
+	 * According to the SRP spec, the lower two bits of the 'ADDITIONAL
+	 * CDB LENGTH' field are reserved and the size in bytes of this field
+	 * is four times the value specified in bits 3..7. Hence the "& ~3".
+	 */
+	add_cdb_offset = srp_cmd->add_cdb_len & ~3;
+	if (((srp_cmd->buf_fmt & 0xf) == SRP_DATA_DESC_DIRECT) ||
+	    ((srp_cmd->buf_fmt >> 4) == SRP_DATA_DESC_DIRECT)) {
+		ioctx->n_rbuf = 1;
+		ioctx->rbufs = &ioctx->single_rbuf;
+
+		db = (struct srp_direct_buf *)(srp_cmd->add_data
+					       + add_cdb_offset);
+		memcpy(ioctx->rbufs, db, sizeof *db);
+		*data_len = be32_to_cpu(db->len);
+	} else if (((srp_cmd->buf_fmt & 0xf) == SRP_DATA_DESC_INDIRECT) ||
+		   ((srp_cmd->buf_fmt >> 4) == SRP_DATA_DESC_INDIRECT)) {
+		idb = (struct srp_indirect_buf *)(srp_cmd->add_data
+						  + add_cdb_offset);
+
+		ioctx->n_rbuf = be32_to_cpu(idb->table_desc.len) / sizeof *db;
+
+		if (ioctx->n_rbuf >
+		    (srp_cmd->data_out_desc_cnt + srp_cmd->data_in_desc_cnt)) {
+			PRINT_ERROR("received unsupported SRP_CMD request type"
+				    " (%u out + %u in != %u / %zu)",
+				    srp_cmd->data_out_desc_cnt,
+				    srp_cmd->data_in_desc_cnt,
+				    be32_to_cpu(idb->table_desc.len),
+				    sizeof(*db));
+			ioctx->n_rbuf = 0;
+			ret = -EINVAL;
+			goto out;
+		}
+
+		if (ioctx->n_rbuf == 1)
+			ioctx->rbufs = &ioctx->single_rbuf;
+		else {
+			ioctx->rbufs =
+				kmalloc(ioctx->n_rbuf * sizeof *db, GFP_ATOMIC);
+			if (!ioctx->rbufs) {
+				ioctx->n_rbuf = 0;
+				ret = -ENOMEM;
+				goto out;
+			}
+		}
+
+		db = idb->desc_list;
+		memcpy(ioctx->rbufs, db, ioctx->n_rbuf * sizeof *db);
+		*data_len = be32_to_cpu(idb->len);
+	}
+out:
+	return ret;
+}
+
+/**
+ * srpt_init_ch_qp() - Initialize queue pair attributes.
+ *
+ * Initialized the attributes of queue pair 'qp' by allowing local write,
+ * remote read and remote write. Also transitions 'qp' to state IB_QPS_INIT.
+ */
+static int srpt_init_ch_qp(struct srpt_rdma_ch *ch, struct ib_qp *qp)
+{
+	struct ib_qp_attr *attr;
+	int ret;
+
+	attr = kzalloc(sizeof *attr, GFP_KERNEL);
+	if (!attr)
+		return -ENOMEM;
+
+	attr->qp_state = IB_QPS_INIT;
+	attr->qp_access_flags = IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_READ |
+	    IB_ACCESS_REMOTE_WRITE;
+	attr->port_num = ch->sport->port;
+	attr->pkey_index = 0;
+
+	ret = ib_modify_qp(qp, attr,
+			   IB_QP_STATE | IB_QP_ACCESS_FLAGS | IB_QP_PORT |
+			   IB_QP_PKEY_INDEX);
+
+	kfree(attr);
+	return ret;
+}
+
+/**
+ * srpt_ch_qp_rtr() - Change the state of a channel to 'ready to receive' (RTR).
+ * @ch: channel of the queue pair.
+ * @qp: queue pair to change the state of.
+ *
+ * Returns zero upon success and a negative value upon failure.
+ *
+ * Note: currently a struct ib_qp_attr takes 136 bytes on a 64-bit system.
+ * If this structure ever becomes larger, it might be necessary to allocate
+ * it dynamically instead of on the stack.
+ */
+static int srpt_ch_qp_rtr(struct srpt_rdma_ch *ch, struct ib_qp *qp)
+{
+	struct ib_qp_attr qp_attr;
+	int attr_mask;
+	int ret;
+
+	qp_attr.qp_state = IB_QPS_RTR;
+	ret = ib_cm_init_qp_attr(ch->cm_id, &qp_attr, &attr_mask);
+	if (ret)
+		goto out;
+
+	qp_attr.max_dest_rd_atomic = 4;
+
+	ret = ib_modify_qp(qp, &qp_attr, attr_mask);
+
+out:
+	return ret;
+}
+
+/**
+ * srpt_ch_qp_rts() - Change the state of a channel to 'ready to send' (RTS).
+ * @ch: channel of the queue pair.
+ * @qp: queue pair to change the state of.
+ *
+ * Returns zero upon success and a negative value upon failure.
+ *
+ * Note: currently a struct ib_qp_attr takes 136 bytes on a 64-bit system.
+ * If this structure ever becomes larger, it might be necessary to allocate
+ * it dynamically instead of on the stack.
+ */
+static int srpt_ch_qp_rts(struct srpt_rdma_ch *ch, struct ib_qp *qp)
+{
+	struct ib_qp_attr qp_attr;
+	int attr_mask;
+	int ret;
+
+	qp_attr.qp_state = IB_QPS_RTS;
+	ret = ib_cm_init_qp_attr(ch->cm_id, &qp_attr, &attr_mask);
+	if (ret)
+		goto out;
+
+	qp_attr.max_rd_atomic = 4;
+
+	ret = ib_modify_qp(qp, &qp_attr, attr_mask);
+
+out:
+	return ret;
+}
+
+/**
+ * srpt_req_lim_delta() - Compute req_lim delta.
+ *
+ * Compute by how much req_lim changed since the last time this function has
+ * been called. This value is necessary for filling in the REQUEST LIMIT DELTA
+ * field of an SRP_RSP response.
+ *
+ * Side Effect:
+ * Resets ch->req_lim_delta.
+ *
+ * Note:
+ * The caller must either pass the returned value to the initiator in the
+ * REQUEST LIMIT DELTA field of an SRP information unit or pass the returned
+ * value to srpt_undo_req_lim_delta(). Any other approach will result in an
+ * SRP protocol violation.
+ */
+static int srpt_req_lim_delta(struct srpt_rdma_ch *ch)
+{
+	return atomic_xchg(&ch->req_lim_delta, 0);
+}
+
+/**
+ * srpt_undo_req_lim_delta() - Undo the side effect of srpt_req_lim_delta().
+ * @ch: Channel pointer.
+ * @delta: return value of srpt_req_lim_delta().
+ */
+static void srpt_undo_req_lim_delta(struct srpt_rdma_ch *ch, int delta)
+{
+	atomic_add(delta, &ch->req_lim_delta);
+}
+
+/**
+ * srpt_send_cred_req() - Send an SRP_CRED_REQ IU to the initiator.
+ *
+ * The previous value of ch->req_lim_delta is restored if sending fails
+ * synchronously or asynchronously.
+ */
+static void srpt_send_cred_req(struct srpt_rdma_ch *ch, s32 req_lim_delta)
+{
+	struct srpt_ioctx *ioctx;
+	struct srp_cred_req *srp_cred_req;
+	int res;
+
+	ioctx = srpt_get_tti_ioctx(ch);
+	if (!ioctx) {
+		PRINT_ERROR("%s",
+		    "Sending SRP_CRED_REQ failed -- no I/O context"
+		    " available ! This will sooner or later result"
+		    " in an initiator lockup.");
+		goto err;
+	}
+
+	BUG_ON(!ch);
+	srp_cred_req = ioctx->buf;
+	BUG_ON(!srp_cred_req);
+	memset(srp_cred_req, 0, sizeof(*srp_cred_req));
+	srp_cred_req->opcode = SRP_CRED_REQ;
+	srp_cred_req->req_lim_delta = cpu_to_be32(req_lim_delta);
+	srp_cred_req->tag = cpu_to_be64(0);
+	res = srpt_post_send(ch, ioctx, sizeof(*srp_cred_req));
+	if (res) {
+		PRINT_ERROR("sending SRP_CRED_REQ failed (res = %d)", res);
+		goto err_put;
+	}
+
+	TRACE_DBG("Sent SRP_CRED_REQ with req_lim_delta = %d and tag %lld",
+		  req_lim_delta, 0ULL);
+
+	goto out;
+
+err_put:
+	srpt_put_tti_ioctx(ch);
+err:
+	srpt_undo_req_lim_delta(ch, req_lim_delta);
+out:
+	return;
+}
+
+/**
+ * srpt_reset_ioctx() - Free up resources and post again for receiving.
+ *
+ * Note: Do NOT modify *ioctx after this function has finished. Otherwise a
+ * race condition will be triggered between srpt_rcv_completion() and the
+ * caller of this function on *ioctx.
+ */
+static void srpt_reset_ioctx(struct srpt_rdma_ch *ch, struct srpt_ioctx *ioctx,
+			     bool inc_req_lim)
+{
+	BUG_ON(!ch);
+	BUG_ON(!ioctx);
+
+	WARN_ON(srpt_get_cmd_state(ioctx) != SRPT_STATE_DONE);
+
+	ioctx->scmnd = NULL;
+	ioctx->ch = NULL;
+
+	/*
+	 * If the WARN_ON() below gets triggered this means that
+	 * srpt_unmap_sg_to_ib_sge() has not been called before
+	 * scst_tgt_cmd_done().
+	 */
+	WARN_ON(ioctx->mapped_sg_count);
+
+	if (ioctx->n_rbuf > 1) {
+		kfree(ioctx->rbufs);
+		ioctx->rbufs = NULL;
+		ioctx->n_rbuf = 0;
+	}
+
+	if (srpt_post_recv(ch->sport->sdev, ioctx))
+		PRINT_ERROR("%s", "SRQ post_recv failed - this is serious.");
+	else if (inc_req_lim) {
+		int req_lim;
+
+		atomic_inc(&ch->req_lim_delta);
+		req_lim = atomic_inc_return(&ch->req_lim);
+		if (req_lim < 0 || req_lim > ch->rq_size)
+			PRINT_ERROR("req_lim = %d out of range %d .. %d",
+				    req_lim, 0, ch->rq_size);
+		if (atomic_read(&ch->supports_cred_req)) {
+			if (req_lim == ch->rq_size / 2
+			    && atomic_read(&ch->req_lim_delta) > ch->rq_size/4)
+				srpt_send_cred_req(ch, srpt_req_lim_delta(ch));
+		} else {
+			if (atomic_add_unless(&ch->req_lim_waiter_count, -1, 0))
+				complete(&ch->req_lim_compl);
+		}
+	}
+}
+
+/**
+ * srpt_abort_scst_cmd() - Abort a SCSI command.
+ * @ioctx:   I/O context associated with the SCSI command.
+ * @context: Preferred execution context.
+ */
+static void srpt_abort_scst_cmd(struct srpt_ioctx *ioctx,
+				enum scst_exec_context context)
+{
+	struct scst_cmd *scmnd;
+	enum srpt_command_state state;
+
+	BUG_ON(!ioctx);
+
+	/*
+	 * If the command is in a state where the SCST core is waiting for the
+	 * ib_srpt driver, change the state to the next state. Changing the
+	 * state of the command from SRPT_NEED_DATA to SRPT_STATE_DATA_IN
+	 * ensures that srpt_xmit_response() will call this function a second
+	 * time.
+	 */
+	state = srpt_test_and_set_cmd_state(ioctx, SRPT_STATE_NEED_DATA,
+					    SRPT_STATE_DATA_IN);
+	if (state != SRPT_STATE_NEED_DATA) {
+		state = srpt_test_and_set_cmd_state(ioctx, SRPT_STATE_DATA_IN,
+						    SRPT_STATE_DONE);
+		if (state != SRPT_STATE_DATA_IN) {
+			state = srpt_test_and_set_cmd_state(ioctx,
+				    SRPT_STATE_CMD_RSP_SENT, SRPT_STATE_DONE);
+			if (state != SRPT_STATE_CMD_RSP_SENT)
+				state = srpt_test_and_set_cmd_state(ioctx,
+					    SRPT_STATE_MGMT_RSP_SENT,
+					    SRPT_STATE_DONE);
+		}
+	}
+	if (state == SRPT_STATE_DONE)
+		goto out;
+
+	scmnd = ioctx->scmnd;
+	WARN_ON(!scmnd);
+	if (!scmnd)
+		goto out;
+
+	WARN_ON(ioctx != scst_cmd_get_tgt_priv(scmnd));
+
+	TRACE_DBG("Aborting cmd with state %d and tag %lld",
+		  state, scst_cmd_get_tag(scmnd));
+
+	switch (state) {
+	case SRPT_STATE_NEW:
+		/*
+		 * Do nothing - defer abort processing until
+		 * srpt_xmit_response() is invoked.
+		 */
+		WARN_ON(!scst_cmd_aborted(scmnd));
+		break;
+	case SRPT_STATE_DATA_IN:
+		/*
+		 * Invocation of srpt_pending_cmd_timeout() after
+		 * srpt_handle_rdma_comp() set the state to SRPT_STATE_DATA_IN
+		 * and before srpt_xmit_response() set the state to
+		 * SRPT_STATE_CMD_RSP_SENT. Ignore the timeout and let
+		 * srpt_handle_xmit_response() proceed.
+		 */
+		break;
+	case SRPT_STATE_NEED_DATA:
+		/* SCST_DATA_WRITE - RDMA read error or RDMA read timeout. */
+		scst_rx_data(ioctx->scmnd, SCST_RX_STATUS_ERROR, context);
+		break;
+	case SRPT_STATE_CMD_RSP_SENT:
+		/*
+		 * SRP_RSP sending failed or the SRP_RSP send completion has
+		 * not been received in time.
+		 */
+		srpt_unmap_sg_to_ib_sge(ioctx->ch, ioctx);
+		scst_set_delivery_status(scmnd, SCST_CMD_DELIVERY_ABORTED);
+		scst_tgt_cmd_done(scmnd, context);
+		break;
+	case SRPT_STATE_MGMT_RSP_SENT:
+		/*
+		 * Management command response sending failed. This state is
+		 * never reached since there is no scmnd associated with
+		 * management commands. Note: the SCST core frees these
+		 * commands immediately after srpt_tsk_mgmt_done() returned.
+		 */
+		WARN_ON("ERROR: unexpected command state");
+		break;
+	default:
+		WARN_ON("ERROR: unexpected command state");
+		break;
+	}
+
+out:
+	;
+}
+
+/**
+ * srpt_handle_send_err_comp() - Process an IB_WC_SEND or RDMA error completion.
+ */
+static void srpt_handle_send_err_comp(struct srpt_rdma_ch *ch, u64 wr_id,
+				      enum scst_exec_context context)
+{
+	struct srpt_ioctx *ioctx;
+	struct srpt_device *sdev = ch->sport->sdev;
+	enum srpt_command_state state;
+	struct scst_cmd *scmnd;
+
+	EXTRACHECKS_WARN_ON(wr_id & SRPT_OP_RECV);
+
+	ioctx = sdev->ioctx_ring[wr_id & ~SRPT_OP_TTI];
+
+	if ((wr_id & SRPT_OP_TTI) == 0) {
+		state = srpt_get_cmd_state(ioctx);
+		scmnd = ioctx->scmnd;
+
+		EXTRACHECKS_WARN_ON(state != SRPT_STATE_CMD_RSP_SENT
+				    && state != SRPT_STATE_MGMT_RSP_SENT
+				    && state != SRPT_STATE_NEED_DATA
+				    && state != SRPT_STATE_DONE);
+
+		if (state != SRPT_STATE_DONE) {
+			if (scmnd)
+				srpt_abort_scst_cmd(ioctx, context);
+			else {
+				srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);
+				srpt_reset_ioctx(ch, ioctx, 1);
+			}
+		} else
+			PRINT_ERROR("Received more than one IB error completion"
+				    " for wr_id = %u.", (unsigned)wr_id);
+	} else {
+		struct srp_cred_req *srp_cred_req;
+		s32 req_lim_delta;
+
+		srp_cred_req = ioctx->buf;
+		req_lim_delta = be32_to_cpu(srp_cred_req->req_lim_delta);
+		srpt_undo_req_lim_delta(ch, req_lim_delta);
+		srpt_put_tti_ioctx(ch);
+		PRINT_ERROR("Sending SRP_CRED_REQ with delta = %d failed.",
+			    req_lim_delta);
+	}
+}
+
+/**
+ * srpt_handle_send_comp() - Process an IB send completion notification.
+ */
+static void srpt_handle_send_comp(struct srpt_rdma_ch *ch,
+				  struct srpt_ioctx *ioctx,
+				  enum scst_exec_context context)
+{
+	enum srpt_command_state state;
+
+	atomic_inc(&ch->sq_wr_avail);
+
+	state = srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);
+
+	EXTRACHECKS_WARN_ON(state != SRPT_STATE_CMD_RSP_SENT
+			    && state != SRPT_STATE_MGMT_RSP_SENT
+			    && state != SRPT_STATE_DONE);
+
+	if (state != SRPT_STATE_DONE) {
+		struct scst_cmd *scmnd;
+
+		scmnd = ioctx->scmnd;
+		EXTRACHECKS_WARN_ON((state == SRPT_STATE_MGMT_RSP_SENT)
+				    != (scmnd == NULL));
+		if (scmnd) {
+			srpt_unmap_sg_to_ib_sge(ch, ioctx);
+			scst_tgt_cmd_done(scmnd, context);
+		} else
+			srpt_reset_ioctx(ch, ioctx, 1);
+	} else {
+		PRINT_ERROR("IB completion has been received too late for"
+			    " wr_id = %u.", ioctx->index);
+	}
+}
+
+/**
+ * srpt_handle_rdma_comp() - Process an IB RDMA completion notification.
+ */
+static void srpt_handle_rdma_comp(struct srpt_rdma_ch *ch,
+				  struct srpt_ioctx *ioctx,
+				  enum scst_exec_context context)
+{
+	enum srpt_command_state state;
+	struct scst_cmd *scmnd;
+
+	EXTRACHECKS_WARN_ON(ioctx->n_rdma <= 0);
+	atomic_add(ioctx->n_rdma, &ch->sq_wr_avail);
+
+	scmnd = ioctx->scmnd;
+	if (scmnd) {
+		state = srpt_test_and_set_cmd_state(ioctx, SRPT_STATE_NEED_DATA,
+						    SRPT_STATE_DATA_IN);
+
+		EXTRACHECKS_WARN_ON(state != SRPT_STATE_NEED_DATA);
+
+		scst_rx_data(ioctx->scmnd, SCST_RX_STATUS_SUCCESS, context);
+	} else
+		PRINT_ERROR("%s[%d]: scmnd == NULL", __func__, __LINE__);
+}
+
+/**
+ * srpt_build_cmd_rsp() - Build an SRP_RSP response.
+ * @ch: RDMA channel through which the request has been received.
+ * @ioctx: I/O context associated with the SRP_CMD request. The response will
+ *   be built in the buffer ioctx->buf points at and hence this function will
+ *   overwrite the request data.
+ * @tag: tag of the request for which this response is being generated.
+ * @status: value for the STATUS field of the SRP_RSP information unit.
+ * @sense_data: pointer to sense data to be included in the response.
+ * @sense_data_len: length in bytes of the sense data.
+ *
+ * Returns the size in bytes of the SRP_RSP response.
+ *
+ * An SRP_RSP response contains a SCSI status or service response. See also
+ * section 6.9 in the SRP r16a document for the format of an SRP_RSP
+ * response. See also SPC-2 for more information about sense data.
+ */
+static int srpt_build_cmd_rsp(struct srpt_rdma_ch *ch,
+			      struct srpt_ioctx *ioctx, s32 req_lim_delta,
+			      u64 tag, int status,
+			      const u8 *sense_data, int sense_data_len)
+{
+	struct srp_rsp *srp_rsp;
+	int max_sense_len;
+
+	/*
+	 * The lowest bit of all SAM-3 status codes is zero (see also
+	 * paragraph 5.3 in SAM-3).
+	 */
+	EXTRACHECKS_WARN_ON(status & 1);
+
+	srp_rsp = ioctx->buf;
+	BUG_ON(!srp_rsp);
+	memset(srp_rsp, 0, sizeof *srp_rsp);
+
+	srp_rsp->opcode = SRP_RSP;
+	srp_rsp->req_lim_delta = cpu_to_be32(req_lim_delta);
+	srp_rsp->tag = tag;
+	srp_rsp->status = status;
+
+	if (!SCST_SENSE_VALID(sense_data))
+		sense_data_len = 0;
+	else {
+		BUILD_BUG_ON(MIN_MAX_MESSAGE_SIZE <= sizeof(*srp_rsp));
+		max_sense_len = ch->max_ti_iu_len - sizeof(*srp_rsp);
+		if (sense_data_len > max_sense_len) {
+			PRINT_WARNING("truncated sense data from %d to %d"
+				" bytes", sense_data_len,
+				max_sense_len);
+			sense_data_len = max_sense_len;
+		}
+
+		srp_rsp->flags |= SRP_RSP_FLAG_SNSVALID;
+		srp_rsp->sense_data_len = cpu_to_be32(sense_data_len);
+		memcpy(srp_rsp + 1, sense_data, sense_data_len);
+	}
+
+	return sizeof(*srp_rsp) + sense_data_len;
+}
+
+/**
+ * srpt_build_tskmgmt_rsp() - Build a task management response.
+ * @ch:       RDMA channel through which the request has been received.
+ * @ioctx:    I/O context in which the SRP_RSP response will be built.
+ * @rsp_code: RSP_CODE that will be stored in the response.
+ * @tag:      Tag of the request for which this response is being generated.
+ *
+ * Returns the size in bytes of the SRP_RSP response.
+ *
+ * An SRP_RSP response contains a SCSI status or service response. See also
+ * section 6.9 in the SRP r16a document for the format of an SRP_RSP
+ * response.
+ */
+static int srpt_build_tskmgmt_rsp(struct srpt_rdma_ch *ch,
+				  struct srpt_ioctx *ioctx, s32 req_lim_delta,
+				  u8 rsp_code, u64 tag)
+{
+	struct srp_rsp *srp_rsp;
+	int resp_data_len;
+	int resp_len;
+
+	resp_data_len = (rsp_code == SRP_TSK_MGMT_SUCCESS) ? 0 : 4;
+	resp_len = sizeof(*srp_rsp) + resp_data_len;
+
+	srp_rsp = ioctx->buf;
+	memset(srp_rsp, 0, sizeof *srp_rsp);
+
+	srp_rsp->opcode = SRP_RSP;
+	srp_rsp->req_lim_delta = cpu_to_be32(req_lim_delta);
+	srp_rsp->tag = tag;
+
+	if (rsp_code != SRP_TSK_MGMT_SUCCESS) {
+		srp_rsp->flags |= SRP_RSP_FLAG_RSPVALID;
+		srp_rsp->resp_data_len = cpu_to_be32(resp_data_len);
+		srp_rsp->data[3] = rsp_code;
+	}
+
+	return resp_len;
+}
+
+/**
+ * srpt_handle_cmd() - Process SRP_CMD.
+ */
+static int srpt_handle_cmd(struct srpt_rdma_ch *ch, struct srpt_ioctx *ioctx,
+			   enum scst_exec_context context)
+{
+	struct scst_cmd *scmnd;
+	struct srp_cmd *srp_cmd;
+	scst_data_direction dir;
+	u64 data_len;
+	int ret;
+
+	srp_cmd = ioctx->buf;
+
+	scmnd = scst_rx_cmd(ch->scst_sess, (u8 *) &srp_cmd->lun,
+			    sizeof srp_cmd->lun, srp_cmd->cdb,
+			    sizeof srp_cmd->cdb, context);
+	if (!scmnd)
+		goto err;
+
+	ioctx->scmnd = scmnd;
+
+	ret = srpt_get_desc_tbl(ioctx, srp_cmd, &dir, &data_len);
+	if (ret) {
+		scst_set_cmd_error(scmnd,
+			SCST_LOAD_SENSE(scst_sense_invalid_field_in_cdb));
+		goto err;
+	}
+
+	switch (srp_cmd->task_attr) {
+	case SRP_CMD_HEAD_OF_Q:
+		scst_cmd_set_queue_type(scmnd, SCST_CMD_QUEUE_HEAD_OF_QUEUE);
+		break;
+	case SRP_CMD_ORDERED_Q:
+		scst_cmd_set_queue_type(scmnd, SCST_CMD_QUEUE_ORDERED);
+		break;
+	case SRP_CMD_SIMPLE_Q:
+		scst_cmd_set_queue_type(scmnd, SCST_CMD_QUEUE_SIMPLE);
+		break;
+	case SRP_CMD_ACA:
+		scst_cmd_set_queue_type(scmnd, SCST_CMD_QUEUE_ACA);
+		break;
+	default:
+		scst_cmd_set_queue_type(scmnd, SCST_CMD_QUEUE_ORDERED);
+		break;
+	}
+
+	scst_cmd_set_tag(scmnd, srp_cmd->tag);
+	scst_cmd_set_tgt_priv(scmnd, ioctx);
+	scst_cmd_set_expected(scmnd, dir, data_len);
+	scst_cmd_init_done(scmnd, context);
+
+	return 0;
+
+err:
+	return -1;
+}
+
+/**
+ * srpt_handle_tsk_mgmt() - Process an SRP_TSK_MGMT information unit.
+ *
+ * Returns SCST_MGMT_STATUS_SUCCESS upon success.
+ *
+ * Each task management function is performed by calling one of the
+ * scst_rx_mgmt_fn*() functions. These functions will either report failure
+ * or process the task management function asynchronously. The function
+ * srpt_tsk_mgmt_done() will be called by the SCST core upon completion of the
+ * task management function. When srpt_handle_tsk_mgmt() reports failure
+ * (i.e. returns -1) a response will have been built in ioctx->buf. This
+ * information unit has to be sent back by the caller.
+ *
+ * For more information about SRP_TSK_MGMT information units, see also section
+ * 6.7 in the SRP r16a document.
+ */
+static u8 srpt_handle_tsk_mgmt(struct srpt_rdma_ch *ch,
+			       struct srpt_ioctx *ioctx)
+{
+	struct srp_tsk_mgmt *srp_tsk;
+	struct srpt_mgmt_ioctx *mgmt_ioctx;
+	int ret;
+
+	srp_tsk = ioctx->buf;
+
+	TRACE_DBG("recv_tsk_mgmt= %d for task_tag= %lld"
+		  " using tag= %lld cm_id= %p sess= %p",
+		  srp_tsk->tsk_mgmt_func, srp_tsk->task_tag, srp_tsk->tag,
+		  ch->cm_id, ch->scst_sess);
+
+	ret = SCST_MGMT_STATUS_FAILED;
+	mgmt_ioctx = kmalloc(sizeof *mgmt_ioctx, GFP_ATOMIC);
+	if (!mgmt_ioctx)
+		goto err;
+
+	mgmt_ioctx->ioctx = ioctx;
+	mgmt_ioctx->ch = ch;
+	mgmt_ioctx->tag = srp_tsk->tag;
+
+	switch (srp_tsk->tsk_mgmt_func) {
+	case SRP_TSK_ABORT_TASK:
+		TRACE_DBG("%s", "Processing SRP_TSK_ABORT_TASK");
+		ret = scst_rx_mgmt_fn_tag(ch->scst_sess,
+					  SCST_ABORT_TASK,
+					  srp_tsk->task_tag,
+					  SCST_ATOMIC, mgmt_ioctx);
+		break;
+	case SRP_TSK_ABORT_TASK_SET:
+		TRACE_DBG("%s", "Processing SRP_TSK_ABORT_TASK_SET");
+		ret = scst_rx_mgmt_fn_lun(ch->scst_sess,
+					  SCST_ABORT_TASK_SET,
+					  (u8 *) &srp_tsk->lun,
+					  sizeof srp_tsk->lun,
+					  SCST_ATOMIC, mgmt_ioctx);
+		break;
+	case SRP_TSK_CLEAR_TASK_SET:
+		TRACE_DBG("%s", "Processing SRP_TSK_CLEAR_TASK_SET");
+		ret = scst_rx_mgmt_fn_lun(ch->scst_sess,
+					  SCST_CLEAR_TASK_SET,
+					  (u8 *) &srp_tsk->lun,
+					  sizeof srp_tsk->lun,
+					  SCST_ATOMIC, mgmt_ioctx);
+		break;
+	case SRP_TSK_LUN_RESET:
+		TRACE_DBG("%s", "Processing SRP_TSK_LUN_RESET");
+		ret = scst_rx_mgmt_fn_lun(ch->scst_sess,
+					  SCST_LUN_RESET,
+					  (u8 *) &srp_tsk->lun,
+					  sizeof srp_tsk->lun,
+					  SCST_ATOMIC, mgmt_ioctx);
+		break;
+	case SRP_TSK_CLEAR_ACA:
+		TRACE_DBG("%s", "Processing SRP_TSK_CLEAR_ACA");
+		ret = scst_rx_mgmt_fn_lun(ch->scst_sess,
+					  SCST_CLEAR_ACA,
+					  (u8 *) &srp_tsk->lun,
+					  sizeof srp_tsk->lun,
+					  SCST_ATOMIC, mgmt_ioctx);
+		break;
+	default:
+		TRACE_DBG("%s", "Unsupported task management function.");
+		ret = SCST_MGMT_STATUS_FN_NOT_SUPPORTED;
+	}
+
+	if (ret != SCST_MGMT_STATUS_SUCCESS)
+		goto err;
+	return ret;
+
+err:
+	kfree(mgmt_ioctx);
+	return ret;
+}
+
+static void srpt_handle_cred_rsp(struct srpt_rdma_ch *ch,
+				 struct srpt_ioctx *ioctx)
+{
+	int max_lun_commands;
+	int req_lim_delta;
+
+	if (!atomic_read(&ch->supports_cred_req)) {
+		atomic_set(&ch->supports_cred_req, true);
+		PRINT_INFO("Enabled SRP_CRED_REQ support for session %s",
+			   ch->sess_name);
+
+		max_lun_commands = scst_get_max_lun_commands(NULL, 0);
+		if (4 <= max_lun_commands && max_lun_commands < ch->rq_size) {
+			req_lim_delta = ch->rq_size - max_lun_commands;
+			PRINT_INFO("Decreasing initiator request limit from %d"
+				   " to %d", ch->rq_size, max_lun_commands);
+			/*
+			 * Note: at least in theory this may make the req_lim
+			 * variable managed by the initiator temporarily
+			 * negative.
+			 */
+			ch->rq_size -= req_lim_delta;
+			atomic_sub(req_lim_delta, &ch->req_lim);
+			atomic_sub(req_lim_delta, &ch->req_lim_delta);
+		}
+	}
+}
+
+static u8 scst_to_srp_tsk_mgmt_status(const int scst_mgmt_status)
+{
+	switch (scst_mgmt_status) {
+	case SCST_MGMT_STATUS_SUCCESS:
+		return SRP_TSK_MGMT_SUCCESS;
+	case SCST_MGMT_STATUS_FN_NOT_SUPPORTED:
+		return SRP_TSK_MGMT_FUNC_NOT_SUPP;
+	case SCST_MGMT_STATUS_TASK_NOT_EXIST:
+	case SCST_MGMT_STATUS_LUN_NOT_EXIST:
+	case SCST_MGMT_STATUS_REJECTED:
+	case SCST_MGMT_STATUS_FAILED:
+	default:
+		break;
+	}
+	return SRP_TSK_MGMT_FAILED;
+}
+
+/**
+ * srpt_handle_new_iu() - Process a newly received information unit.
+ * @ch:    RDMA channel through which the information unit has been received.
+ * @ioctx: SRPT I/O context associated with the information unit.
+ */
+static void srpt_handle_new_iu(struct srpt_rdma_ch *ch,
+			       struct srpt_ioctx *ioctx,
+			       enum scst_exec_context context)
+{
+	struct srp_cmd *srp_cmd;
+	struct scst_cmd *scmnd;
+	enum rdma_ch_state ch_state;
+	u8 srp_response_status;
+	int tsk_mgmt_status;
+	int len;
+	int send_rsp_res;
+
+	ch_state = atomic_read(&ch->state);
+	if (ch_state == RDMA_CHANNEL_CONNECTING) {
+		list_add_tail(&ioctx->wait_list, &ch->cmd_wait_list);
+		return;
+	}
+
+	ioctx->n_rbuf = 0;
+	ioctx->rbufs = NULL;
+	ioctx->n_rdma = 0;
+	ioctx->n_rdma_ius = 0;
+	ioctx->rdma_ius = NULL;
+	ioctx->mapped_sg_count = 0;
+	ioctx->scmnd = NULL;
+	ioctx->ch = ch;
+	atomic_set(&ioctx->state, SRPT_STATE_NEW);
+
+	if (unlikely(ch_state == RDMA_CHANNEL_DISCONNECTING)) {
+		srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);
+		srpt_reset_ioctx(ch, ioctx, 0);
+		return;
+	}
+
+	WARN_ON(ch_state != RDMA_CHANNEL_LIVE);
+
+	scmnd = NULL;
+
+	srp_response_status = SAM_STAT_BUSY;
+	/* To keep the compiler happy. */
+	tsk_mgmt_status = SCST_MGMT_STATUS_FAILED;
+
+	ib_dma_sync_single_for_cpu(ch->sport->sdev->device,
+				   ioctx->dma, srp_max_message_size,
+				   DMA_FROM_DEVICE);
+
+	srp_cmd = ioctx->buf;
+
+	if (srp_cmd->opcode == SRP_CMD || srp_cmd->opcode == SRP_TSK_MGMT
+	    || srp_cmd->opcode == SRP_I_LOGOUT) {
+		int req_lim;
+
+		req_lim = atomic_dec_return(&ch->req_lim);
+		if (unlikely(req_lim < 0))
+			PRINT_ERROR("req_lim = %d < 0", req_lim);
+	}
+
+	switch (srp_cmd->opcode) {
+	case SRP_CMD:
+		if (srpt_handle_cmd(ch, ioctx, context) < 0) {
+			scmnd = ioctx->scmnd;
+			if (scmnd)
+				srp_response_status =
+					scst_cmd_get_status(scmnd);
+			goto err;
+		}
+		break;
+
+	case SRP_TSK_MGMT:
+		tsk_mgmt_status = srpt_handle_tsk_mgmt(ch, ioctx);
+		if (tsk_mgmt_status != SCST_MGMT_STATUS_SUCCESS)
+			goto err;
+		break;
+
+	case SRP_I_LOGOUT:
+		goto err;
+
+	case SRP_CRED_RSP:
+		TRACE_DBG("%s", "received SRP_CRED_RSP");
+		srpt_handle_cred_rsp(ch, ioctx);
+		srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);
+		srpt_reset_ioctx(ch, ioctx, 0);
+		break;
+
+	case SRP_AER_RSP:
+		TRACE_DBG("%s", "received SRP_AER_RSP");
+		srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);
+		srpt_reset_ioctx(ch, ioctx, 0);
+		break;
+
+	case SRP_RSP:
+	default:
+		PRINT_ERROR("received IU with unknown opcode 0x%x",
+			    srp_cmd->opcode);
+		srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);
+		srpt_reset_ioctx(ch, ioctx, 0);
+		break;
+	}
+
+	return;
+
+err:
+	send_rsp_res = -ENOTCONN;
+
+	if (atomic_read(&ch->state) != RDMA_CHANNEL_LIVE) {
+		/* Give up if another thread modified the channel state. */
+		PRINT_ERROR("%s", "channel is no longer in connected state.");
+	} else {
+		s32 req_lim_delta;
+
+		req_lim_delta = srpt_req_lim_delta(ch);
+		if (srp_cmd->opcode == SRP_TSK_MGMT)
+			len = srpt_build_tskmgmt_rsp(ch, ioctx, req_lim_delta,
+				scst_to_srp_tsk_mgmt_status(tsk_mgmt_status),
+				((struct srp_tsk_mgmt *)srp_cmd)->tag);
+		else if (scmnd)
+			len = srpt_build_cmd_rsp(ch, ioctx, req_lim_delta,
+				srp_cmd->tag, srp_response_status,
+				scst_cmd_get_sense_buffer(scmnd),
+				scst_cmd_get_sense_buffer_len(scmnd));
+		else
+			len = srpt_build_cmd_rsp(ch, ioctx, srp_cmd->tag,
+						 req_lim_delta,
+						 srp_response_status,
+						 NULL, 0);
+		srpt_set_cmd_state(ioctx,
+				   srp_cmd->opcode == SRP_TSK_MGMT
+				   ? SRPT_STATE_MGMT_RSP_SENT
+				   : SRPT_STATE_CMD_RSP_SENT);
+		send_rsp_res = srpt_post_send(ch, ioctx, len);
+		if (send_rsp_res) {
+			PRINT_ERROR("%s", "Sending SRP_RSP response failed.");
+			srpt_undo_req_lim_delta(ch, req_lim_delta - 1);
+		}
+	}
+	if (send_rsp_res) {
+		if (scmnd)
+			srpt_abort_scst_cmd(ioctx, context);
+		else {
+			srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);
+			srpt_reset_ioctx(ch, ioctx, 1);
+		}
+	}
+}
+
+static void srpt_process_rcv_completion(struct ib_cq *cq,
+					struct srpt_rdma_ch *ch,
+					enum scst_exec_context context,
+					struct ib_wc *wc)
+{
+	struct srpt_device *sdev = ch->sport->sdev;
+	struct srpt_ioctx *ioctx;
+
+	EXTRACHECKS_WARN_ON((wc->wr_id & SRPT_OP_RECV) == 0);
+	EXTRACHECKS_WARN_ON((wc->wr_id & SRPT_OP_TTI) != 0);
+
+	if (wc->status == IB_WC_SUCCESS) {
+		ioctx = sdev->ioctx_ring[wc->wr_id & ~SRPT_OP_RECV];
+		srpt_handle_new_iu(ch, ioctx, context);
+	} else {
+		PRINT_INFO("receiving wr_id %u failed with status %d",
+			   (unsigned)(wc->wr_id & ~SRPT_OP_RECV), wc->status);
+	}
+}
+
+static void srpt_process_send_completion(struct ib_cq *cq,
+					 struct srpt_rdma_ch *ch,
+					 enum scst_exec_context context,
+					 struct ib_wc *wc)
+{
+	struct srpt_device *sdev = ch->sport->sdev;
+	struct srpt_ioctx *ioctx;
+
+	EXTRACHECKS_WARN_ON((wc->wr_id & SRPT_OP_RECV) != 0);
+
+	if (wc->status == IB_WC_SUCCESS) {
+		if ((wc->wr_id & SRPT_OP_TTI) == 0) {
+			ioctx = sdev->ioctx_ring[wc->wr_id];
+			if (wc->opcode == IB_WC_SEND)
+				srpt_handle_send_comp(ch, ioctx, context);
+			else {
+				EXTRACHECKS_WARN_ON(wc->opcode
+						    != IB_WC_RDMA_READ);
+				srpt_handle_rdma_comp(ch, ioctx, context);
+			}
+		} else
+			srpt_put_tti_ioctx(ch);
+	} else {
+		PRINT_INFO("sending %s for wr_id %u failed with status %d",
+			   wc->wr_id & SRPT_OP_TTI ? "request" : "response",
+			   (unsigned)(wc->wr_id & ~SRPT_OP_FLAGS), wc->status);
+		srpt_handle_send_err_comp(ch, wc->wr_id, context);
+	}
+}
+
+static void srpt_process_completion(struct ib_cq *cq,
+				    struct srpt_rdma_ch *ch,
+				    enum scst_exec_context context)
+{
+	struct ib_wc wc[16];
+	int i, n;
+
+	EXTRACHECKS_WARN_ON(cq != ch->cq);
+
+	do {
+		while ((n = ib_poll_cq(cq, ARRAY_SIZE(wc), wc)) > 0) {
+			for (i = 0; i < n; i++) {
+				if (wc[i].wr_id & SRPT_OP_RECV)
+					srpt_process_rcv_completion(cq, ch,
+								    context,
+								    &wc[i]);
+				else
+					srpt_process_send_completion(cq, ch,
+								     context,
+								     &wc[i]);
+			}
+		}
+	} while (ib_req_notify_cq(cq, IB_CQ_NEXT_COMP
+				  | IB_CQ_REPORT_MISSED_EVENTS) > 0);
+}
+
+/**
+ * srpt_completion() - IB completion queue callback function.
+ *
+ * Notes:
+ * - It is guaranteed that a completion handler will never be invoked
+ *   concurrently on two different CPUs for the same completion queue. See also
+ *   Documentation/infiniband/core_locking.txt and the implementation of
+ *   handle_edge_irq() in kernel/irq/chip.c.
+ * - When threaded IRQs are enabled, completion handlers are invoked in thread
+ *   context instead of interrupt context.
+ */
+static void srpt_completion(struct ib_cq *cq, void *ctx)
+{
+	struct srpt_rdma_ch *ch = ctx;
+
+	atomic_inc(&ch->processing_compl);
+	switch (thread) {
+	case MODE_IB_COMPLETION_IN_THREAD:
+		wake_up_interruptible(&ch->wait_queue);
+		break;
+	case MODE_IB_COMPLETION_IN_SIRQ:
+		srpt_process_completion(cq, ch, SCST_CONTEXT_THREAD);
+		break;
+	case MODE_ALL_IN_SIRQ:
+		srpt_process_completion(cq, ch, SCST_CONTEXT_TASKLET);
+		break;
+	}
+	atomic_dec(&ch->processing_compl);
+}
+
+static int srpt_compl_thread(void *arg)
+{
+	struct srpt_rdma_ch *ch;
+
+	/* Hibernation / freezing of the SRPT kernel thread is not supported. */
+	current->flags |= PF_NOFREEZE;
+
+	ch = arg;
+	BUG_ON(!ch);
+	PRINT_INFO("Session %s: kernel thread %s (PID %d) started",
+		   ch->sess_name, ch->thread->comm, current->pid);
+	while (!kthread_should_stop()) {
+		wait_event_interruptible(ch->wait_queue,
+			(srpt_process_completion(ch->cq, ch,
+						 SCST_CONTEXT_THREAD),
+			 kthread_should_stop()));
+	}
+	PRINT_INFO("Session %s: kernel thread %s (PID %d) stopped",
+		   ch->sess_name, ch->thread->comm, current->pid);
+	return 0;
+}
+
+/**
+ * srpt_create_ch_ib() - Create receive and send completion queues.
+ */
+static int srpt_create_ch_ib(struct srpt_rdma_ch *ch)
+{
+	struct ib_qp_init_attr *qp_init;
+	struct srpt_device *sdev = ch->sport->sdev;
+	int ret;
+
+	EXTRACHECKS_WARN_ON(ch->rq_size < 1);
+
+	ret = -ENOMEM;
+	qp_init = kzalloc(sizeof *qp_init, GFP_KERNEL);
+	if (!qp_init)
+		goto out;
+
+	ch->cq = ib_create_cq(sdev->device, srpt_completion, NULL, ch,
+			      ch->rq_size + srpt_sq_size, 0);
+	if (IS_ERR(ch->cq)) {
+		ret = PTR_ERR(ch->cq);
+		PRINT_ERROR("failed to create CQ cqe= %d ret= %d",
+			    ch->rq_size + srpt_sq_size, ret);
+		goto out;
+	}
+
+	qp_init->qp_context = (void *)ch;
+	qp_init->event_handler
+		= (void(*)(struct ib_event *, void*))srpt_qp_event;
+	qp_init->send_cq = ch->cq;
+	qp_init->recv_cq = ch->cq;
+	qp_init->srq = sdev->srq;
+	qp_init->sq_sig_type = IB_SIGNAL_REQ_WR;
+	qp_init->qp_type = IB_QPT_RC;
+	qp_init->cap.max_send_wr = srpt_sq_size;
+	qp_init->cap.max_send_sge = SRPT_DEF_SG_PER_WQE;
+
+	ch->qp = ib_create_qp(sdev->pd, qp_init);
+	if (IS_ERR(ch->qp)) {
+		ret = PTR_ERR(ch->qp);
+		PRINT_ERROR("failed to create_qp ret= %d", ret);
+		goto err_destroy_cq;
+	}
+
+	atomic_set(&ch->sq_wr_avail, qp_init->cap.max_send_wr);
+
+	TRACE_DBG("%s: max_cqe= %d max_sge= %d sq_size = %d"
+		  " cm_id= %p", __func__, ch->cq->cqe,
+		  qp_init->cap.max_send_sge, qp_init->cap.max_send_wr,
+		  ch->cm_id);
+
+	ret = srpt_init_ch_qp(ch, ch->qp);
+	if (ret)
+		goto err_destroy_qp;
+
+	if (thread == MODE_IB_COMPLETION_IN_THREAD) {
+		init_waitqueue_head(&ch->wait_queue);
+
+		TRACE_DBG("creating IB completion thread for session %s",
+			  ch->sess_name);
+
+		ch->thread = kthread_run(srpt_compl_thread, ch,
+					 "ib_srpt_compl");
+		if (IS_ERR(ch->thread)) {
+			PRINT_ERROR("failed to create kernel thread %ld",
+				    PTR_ERR(ch->thread));
+			ch->thread = NULL;
+			goto err_destroy_qp;
+		}
+	} else
+		ib_req_notify_cq(ch->cq, IB_CQ_NEXT_COMP);
+
+out:
+	kfree(qp_init);
+	return ret;
+
+err_destroy_qp:
+	ib_destroy_qp(ch->qp);
+err_destroy_cq:
+	ib_destroy_cq(ch->cq);
+	goto out;
+}
+
+static void srpt_destroy_ch_ib(struct srpt_rdma_ch *ch)
+{
+	struct ib_qp_attr qp_attr;
+	int ret;
+
+	if (ch->thread)
+		kthread_stop(ch->thread);
+
+	qp_attr.qp_state = IB_QPS_RESET;
+	ret = ib_modify_qp(ch->qp, &qp_attr, IB_QP_STATE);
+	if (ret < 0)
+		PRINT_ERROR("Resetting queue pair state failed: %d", ret);
+
+	while (atomic_read(&ch->processing_compl))
+		;
+
+	ib_destroy_qp(ch->qp);
+	ib_destroy_cq(ch->cq);
+}
+
+/**
+ * srpt_unregister_channel() - Start RDMA channel disconnection.
+ *
+ * Note: The caller must hold ch->sdev->spinlock.
+ */
+static void srpt_unregister_channel(struct srpt_rdma_ch *ch)
+	__acquires(&ch->sport->sdev->spinlock)
+	__releases(&ch->sport->sdev->spinlock)
+{
+	struct srpt_device *sdev;
+
+	sdev = ch->sport->sdev;
+	list_del(&ch->list);
+	atomic_set(&ch->state, RDMA_CHANNEL_DISCONNECTING);
+	spin_unlock_irq(&sdev->spinlock);
+
+	/*
+	 * At this point it is guaranteed that no new commands will be sent to
+	 * the SCST core for channel ch, which is a requirement for
+	 * scst_unregister_session().
+	 */
+
+	TRACE_DBG("unregistering session %p", ch->scst_sess);
+	scst_unregister_session(ch->scst_sess, 0, srpt_release_channel);
+	spin_lock_irq(&sdev->spinlock);
+}
+
+/**
+ * srpt_release_channel_by_cmid() - Release a channel.
+ * @cm_id: Pointer to the CM ID of the channel to be released.
+ *
+ * Note: Must be called from inside srpt_cm_handler to avoid a race between
+ * accessing sdev->spinlock and the call to kfree(sdev) in srpt_remove_one()
+ * (the caller of srpt_cm_handler holds the cm_id spinlock; srpt_remove_one()
+ * waits until all SCST sessions for the associated IB device have been
+ * unregistered and SCST session registration involves a call to
+ * ib_destroy_cm_id(), which locks the cm_id spinlock and hence waits until
+ * this function has finished).
+ */
+static void srpt_release_channel_by_cmid(struct ib_cm_id *cm_id)
+{
+	struct srpt_device *sdev;
+	struct srpt_rdma_ch *ch;
+
+	EXTRACHECKS_WARN_ON_ONCE(irqs_disabled());
+
+	sdev = cm_id->context;
+	BUG_ON(!sdev);
+	spin_lock_irq(&sdev->spinlock);
+	list_for_each_entry(ch, &sdev->rch_list, list) {
+		if (ch->cm_id == cm_id) {
+			srpt_unregister_channel(ch);
+			break;
+		}
+	}
+	spin_unlock_irq(&sdev->spinlock);
+}
+
+/**
+ * srpt_find_channel() - Look up an RDMA channel.
+ * @cm_id: Pointer to the CM ID of the channel to be looked up.
+ *
+ * Return NULL if no matching RDMA channel has been found.
+ */
+static struct srpt_rdma_ch *srpt_find_channel(struct srpt_device *sdev,
+					      struct ib_cm_id *cm_id)
+{
+	struct srpt_rdma_ch *ch;
+	bool found;
+
+	EXTRACHECKS_WARN_ON_ONCE(irqs_disabled());
+	BUG_ON(!sdev);
+
+	found = false;
+	spin_lock_irq(&sdev->spinlock);
+	list_for_each_entry(ch, &sdev->rch_list, list) {
+		if (ch->cm_id == cm_id) {
+			found = true;
+			break;
+		}
+	}
+	spin_unlock_irq(&sdev->spinlock);
+
+	return found ? ch : NULL;
+}
+
+/**
+ * srpt_release_channel() - Release all resources associated with an RDMA channel.
+ *
+ * Notes:
+ * - The caller must have removed the channel from the channel list before
+ *   calling this function.
+ * - Must be called as a callback function via scst_unregister_session(). Never
+ *   call this function directly because doing so would trigger several race
+ *   conditions.
+ * - Do not access ch->sport or ch->sport->sdev in this function because the
+ *   memory that was allocated for the sport and/or sdev data structures may
+ *   already have been freed at the time this function is called.
+ */
+static void srpt_release_channel(struct scst_session *scst_sess)
+{
+	struct srpt_rdma_ch *ch;
+
+	ch = scst_sess_get_tgt_priv(scst_sess);
+	BUG_ON(!ch);
+	WARN_ON(atomic_read(&ch->state) != RDMA_CHANNEL_DISCONNECTING);
+
+	TRACE_DBG("destroying cm_id %p", ch->cm_id);
+	BUG_ON(!ch->cm_id);
+	ib_destroy_cm_id(ch->cm_id);
+
+	srpt_destroy_ch_ib(ch);
+	srpt_free_tti_ioctx(ch);
+
+	kfree(ch);
+}
+
+/**
+ * srpt_enable_target() - Allows to enable a target via sysfs.
+ */
+static int srpt_enable_target(struct scst_tgt *scst_tgt, bool enable)
+{
+	struct srpt_device *sdev = scst_tgt_get_tgt_priv(scst_tgt);
+
+	EXTRACHECKS_WARN_ON_ONCE(irqs_disabled());
+
+	TRACE_DBG("%s target %s", enable ? "Enabling" : "Disabling",
+		  sdev->device->name);
+
+	spin_lock_irq(&sdev->spinlock);
+	sdev->enabled = enable;
+	spin_unlock_irq(&sdev->spinlock);
+
+	return 0;
+}
+
+/**
+ * srpt_is_target_enabled() - Allows to query a targets status via sysfs.
+ */
+static bool srpt_is_target_enabled(struct scst_tgt *scst_tgt)
+{
+	struct srpt_device *sdev = scst_tgt_get_tgt_priv(scst_tgt);
+	bool res;
+
+	EXTRACHECKS_WARN_ON_ONCE(irqs_disabled());
+
+	spin_lock_irq(&sdev->spinlock);
+	res = sdev->enabled;
+	spin_unlock_irq(&sdev->spinlock);
+	return res;
+}
+
+/**
+ * srpt_cm_req_recv() - Process the event IB_CM_REQ_RECEIVED.
+ *
+ * Ownership of the cm_id is transferred to the SCST session if this functions
+ * returns zero. Otherwise the caller remains the owner of cm_id.
+ */
+static int srpt_cm_req_recv(struct ib_cm_id *cm_id,
+			    struct ib_cm_req_event_param *param,
+			    void *private_data)
+{
+	struct srpt_device *sdev = cm_id->context;
+	struct srp_login_req *req;
+	struct srp_login_rsp *rsp;
+	struct srp_login_rej *rej;
+	struct ib_cm_rep_param *rep_param;
+	struct srpt_rdma_ch *ch, *tmp_ch;
+	u32 it_iu_len;
+	int ret = 0;
+
+	EXTRACHECKS_WARN_ON_ONCE(irqs_disabled());
+
+	if (WARN_ON(!sdev || !private_data))
+		return -EINVAL;
+
+	req = (struct srp_login_req *)private_data;
+
+	it_iu_len = be32_to_cpu(req->req_it_iu_len);
+
+	PRINT_INFO("Received SRP_LOGIN_REQ with"
+	    " i_port_id 0x%llx:0x%llx, t_port_id 0x%llx:0x%llx and it_iu_len %d"
+	    " on port %d (guid=0x%llx:0x%llx)",
+	    be64_to_cpu(*(__be64 *)&req->initiator_port_id[0]),
+	    be64_to_cpu(*(__be64 *)&req->initiator_port_id[8]),
+	    be64_to_cpu(*(__be64 *)&req->target_port_id[0]),
+	    be64_to_cpu(*(__be64 *)&req->target_port_id[8]),
+	    it_iu_len,
+	    param->port,
+	    be64_to_cpu(*(__be64 *)&sdev->port[param->port - 1].gid.raw[0]),
+	    be64_to_cpu(*(__be64 *)&sdev->port[param->port - 1].gid.raw[8]));
+
+	rsp = kzalloc(sizeof *rsp, GFP_KERNEL);
+	rej = kzalloc(sizeof *rej, GFP_KERNEL);
+	rep_param = kzalloc(sizeof *rep_param, GFP_KERNEL);
+
+	if (!rsp || !rej || !rep_param) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	if (it_iu_len > srp_max_message_size || it_iu_len < 64) {
+		rej->reason =
+		    cpu_to_be32(SRP_LOGIN_REJ_REQ_IT_IU_LENGTH_TOO_LARGE);
+		ret = -EINVAL;
+		PRINT_ERROR("rejected SRP_LOGIN_REQ because its"
+			    " length (%d bytes) is out of range (%d .. %d)",
+			    it_iu_len, 64, srp_max_message_size);
+		goto reject;
+	}
+
+	if (!srpt_is_target_enabled(sdev->scst_tgt)) {
+		rej->reason =
+		    cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
+		ret = -EINVAL;
+		PRINT_ERROR("rejected SRP_LOGIN_REQ because the target %s"
+			    " has not yet been enabled", sdev->device->name);
+		goto reject;
+	}
+
+	if ((req->req_flags & SRP_MTCH_ACTION) == SRP_MULTICHAN_SINGLE) {
+		rsp->rsp_flags = SRP_LOGIN_RSP_MULTICHAN_NO_CHAN;
+
+		spin_lock_irq(&sdev->spinlock);
+
+		list_for_each_entry_safe(ch, tmp_ch, &sdev->rch_list, list) {
+			if (!memcmp(ch->i_port_id, req->initiator_port_id, 16)
+			    && !memcmp(ch->t_port_id, req->target_port_id, 16)
+			    && param->port == ch->sport->port
+			    && param->listen_id == ch->sport->sdev->cm_id
+			    && ch->cm_id) {
+				enum rdma_ch_state prev_state;
+
+				/* found an existing channel */
+				TRACE_DBG("Found existing channel name= %s"
+					  " cm_id= %p state= %d",
+					  ch->sess_name, ch->cm_id,
+					  atomic_read(&ch->state));
+
+				prev_state = atomic_xchg(&ch->state,
+						RDMA_CHANNEL_DISCONNECTING);
+				if (prev_state == RDMA_CHANNEL_CONNECTING)
+					srpt_unregister_channel(ch);
+
+				spin_unlock_irq(&sdev->spinlock);
+
+				rsp->rsp_flags =
+					SRP_LOGIN_RSP_MULTICHAN_TERMINATED;
+
+				if (prev_state == RDMA_CHANNEL_LIVE) {
+					ib_send_cm_dreq(ch->cm_id, NULL, 0);
+					PRINT_INFO("disconnected"
+					  " session %s because a new"
+					  " SRP_LOGIN_REQ has been received.",
+					  ch->sess_name);
+				} else if (prev_state ==
+					 RDMA_CHANNEL_CONNECTING) {
+					PRINT_ERROR("%s", "rejected"
+					  " SRP_LOGIN_REQ because another login"
+					  " request is being processed.");
+					ib_send_cm_rej(ch->cm_id,
+						       IB_CM_REJ_NO_RESOURCES,
+						       NULL, 0, NULL, 0);
+				}
+
+				spin_lock_irq(&sdev->spinlock);
+			}
+		}
+
+		spin_unlock_irq(&sdev->spinlock);
+
+	} else
+		rsp->rsp_flags = SRP_LOGIN_RSP_MULTICHAN_MAINTAINED;
+
+	if (*(__be64 *)req->target_port_id != cpu_to_be64(srpt_service_guid)
+	    || *(__be64 *)(req->target_port_id + 8) !=
+	    cpu_to_be64(srpt_service_guid)) {
+		rej->reason =
+		    cpu_to_be32(SRP_LOGIN_REJ_UNABLE_ASSOCIATE_CHANNEL);
+		ret = -ENOMEM;
+		PRINT_ERROR("%s", "rejected SRP_LOGIN_REQ because it"
+		       " has an invalid target port identifier.");
+		goto reject;
+	}
+
+	ch = kzalloc(sizeof *ch, GFP_KERNEL);
+	if (!ch) {
+		rej->reason = cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
+		PRINT_ERROR("%s",
+			    "rejected SRP_LOGIN_REQ because out of memory.");
+		ret = -ENOMEM;
+		goto reject;
+	}
+
+	memcpy(ch->i_port_id, req->initiator_port_id, 16);
+	memcpy(ch->t_port_id, req->target_port_id, 16);
+	ch->sport = &sdev->port[param->port - 1];
+	ch->cm_id = cm_id;
+	ch->rq_size = max(SRPT_RQ_SIZE, scst_get_max_lun_commands(NULL, 0));
+	atomic_set(&ch->processing_compl, 0);
+	atomic_set(&ch->state, RDMA_CHANNEL_CONNECTING);
+	INIT_LIST_HEAD(&ch->cmd_wait_list);
+
+	ch->tti_head = 0;
+	ch->tti_tail = 0;
+	ret = srpt_alloc_tti_ioctx(ch);
+	if (ret) {
+		PRINT_ERROR("%s", "send ring allocation failed");
+		goto free_ch;
+	}
+
+	ret = srpt_create_ch_ib(ch);
+	if (ret) {
+		rej->reason = cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
+		PRINT_ERROR("%s", "rejected SRP_LOGIN_REQ because creating"
+			    " a new RDMA channel failed.");
+		goto free_req_ring;
+	}
+
+	ret = srpt_ch_qp_rtr(ch, ch->qp);
+	if (ret) {
+		rej->reason = cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
+		PRINT_ERROR("rejected SRP_LOGIN_REQ because enabling"
+		       " RTR failed (error code = %d)", ret);
+		goto destroy_ib;
+	}
+
+	if (use_port_guid_in_session_name) {
+		/*
+		 * If the kernel module parameter use_port_guid_in_session_name
+		 * has been specified, use a combination of the target port
+		 * GUID and the initiator port ID as the session name. This
+		 * was the original behavior of the SRP target implementation
+		 * (i.e. before the SRPT was included in OFED 1.3).
+		 */
+		snprintf(ch->sess_name, sizeof(ch->sess_name),
+			 "0x%016llx%016llx",
+			 be64_to_cpu(*(__be64 *)
+				&sdev->port[param->port - 1].gid.raw[8]),
+			 be64_to_cpu(*(__be64 *)(ch->i_port_id + 8)));
+	} else {
+		/*
+		 * Default behavior: use the initator port identifier as the
+		 * session name.
+		 */
+		snprintf(ch->sess_name, sizeof(ch->sess_name),
+			 "0x%016llx%016llx",
+			 be64_to_cpu(*(__be64 *)ch->i_port_id),
+			 be64_to_cpu(*(__be64 *)(ch->i_port_id + 8)));
+	}
+
+	TRACE_DBG("registering session %s", ch->sess_name);
+
+	BUG_ON(!sdev->scst_tgt);
+	ch->scst_sess = scst_register_session(sdev->scst_tgt, 0, ch->sess_name,
+					      ch, NULL, NULL);
+	if (!ch->scst_sess) {
+		rej->reason = cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
+		TRACE_DBG("%s", "Failed to create SCST session");
+		goto release_channel;
+	}
+
+	TRACE_DBG("Establish connection sess=%p name=%s cm_id=%p",
+		  ch->scst_sess, ch->sess_name, ch->cm_id);
+
+	/* create srp_login_response */
+	rsp->opcode = SRP_LOGIN_RSP;
+	rsp->tag = req->tag;
+	rsp->max_it_iu_len = req->req_it_iu_len;
+	rsp->max_ti_iu_len = req->req_it_iu_len;
+	ch->max_ti_iu_len = it_iu_len;
+	atomic_set(&ch->supports_cred_req, false);
+	rsp->buf_fmt =
+	    cpu_to_be16(SRP_BUF_FORMAT_DIRECT | SRP_BUF_FORMAT_INDIRECT);
+	rsp->req_lim_delta = cpu_to_be32(ch->rq_size);
+	atomic_set(&ch->req_lim, ch->rq_size);
+	atomic_set(&ch->req_lim_delta, 0);
+	atomic_set(&ch->req_lim_waiter_count, 0);
+	init_completion(&ch->req_lim_compl);
+
+	/* create cm reply */
+	rep_param->qp_num = ch->qp->qp_num;
+	rep_param->private_data = (void *)rsp;
+	rep_param->private_data_len = sizeof *rsp;
+	rep_param->rnr_retry_count = 7;
+	rep_param->flow_control = 1;
+	rep_param->failover_accepted = 0;
+	rep_param->srq = 1;
+	rep_param->responder_resources = 4;
+	rep_param->initiator_depth = 4;
+
+	ret = ib_send_cm_rep(cm_id, rep_param);
+	if (ret) {
+		PRINT_ERROR("sending SRP_LOGIN_REQ response failed"
+			    " (error code = %d)", ret);
+		goto release_channel;
+	}
+
+	spin_lock_irq(&sdev->spinlock);
+	list_add_tail(&ch->list, &sdev->rch_list);
+	spin_unlock_irq(&sdev->spinlock);
+
+	goto out;
+
+release_channel:
+	atomic_set(&ch->state, RDMA_CHANNEL_DISCONNECTING);
+	scst_unregister_session(ch->scst_sess, 0, NULL);
+	ch->scst_sess = NULL;
+
+destroy_ib:
+	srpt_destroy_ch_ib(ch);
+
+free_req_ring:
+	srpt_free_tti_ioctx(ch);
+
+free_ch:
+	kfree(ch);
+
+reject:
+	rej->opcode = SRP_LOGIN_REJ;
+	rej->tag = req->tag;
+	rej->buf_fmt =
+	    cpu_to_be16(SRP_BUF_FORMAT_DIRECT | SRP_BUF_FORMAT_INDIRECT);
+
+	ib_send_cm_rej(cm_id, IB_CM_REJ_CONSUMER_DEFINED, NULL, 0,
+			     (void *)rej, sizeof *rej);
+
+out:
+	kfree(rep_param);
+	kfree(rsp);
+	kfree(rej);
+
+	return ret;
+}
+
+static void srpt_cm_rej_recv(struct ib_cm_id *cm_id)
+{
+	PRINT_INFO("Received InfiniBand REJ packet for cm_id %p.", cm_id);
+	srpt_release_channel_by_cmid(cm_id);
+}
+
+/**
+ * srpt_cm_rtu_recv() - Process an IB_CM_RTU_RECEIVED or IB_CM_USER_ESTABLISHED event.
+ *
+ * An IB_CM_RTU_RECEIVED message indicates that the connection is established
+ * and that the recipient may begin transmitting (RTU = ready to use).
+ */
+static void srpt_cm_rtu_recv(struct ib_cm_id *cm_id)
+{
+	struct srpt_rdma_ch *ch;
+	int ret;
+
+	ch = srpt_find_channel(cm_id->context, cm_id);
+	WARN_ON(!ch);
+	if (!ch)
+		goto out;
+
+	if (srpt_test_and_set_channel_state(ch, RDMA_CHANNEL_CONNECTING,
+			RDMA_CHANNEL_LIVE) == RDMA_CHANNEL_CONNECTING) {
+		struct srpt_ioctx *ioctx, *ioctx_tmp;
+
+		ret = srpt_ch_qp_rts(ch, ch->qp);
+
+		if (srpt_autodetect_cred_req)
+			srpt_send_cred_req(ch, 0);
+
+		list_for_each_entry_safe(ioctx, ioctx_tmp, &ch->cmd_wait_list,
+					 wait_list) {
+			list_del(&ioctx->wait_list);
+			srpt_handle_new_iu(ch, ioctx, SCST_CONTEXT_THREAD);
+		}
+		if (ret && srpt_test_and_set_channel_state(ch,
+			RDMA_CHANNEL_LIVE,
+			RDMA_CHANNEL_DISCONNECTING) == RDMA_CHANNEL_LIVE) {
+			TRACE_DBG("cm_id=%p sess_name=%s state=%d",
+				  cm_id, ch->sess_name,
+				  atomic_read(&ch->state));
+			ib_send_cm_dreq(ch->cm_id, NULL, 0);
+		}
+	}
+
+out:
+	;
+}
+
+static void srpt_cm_timewait_exit(struct ib_cm_id *cm_id)
+{
+	PRINT_INFO("Received InfiniBand TimeWait exit for cm_id %p.", cm_id);
+	srpt_release_channel_by_cmid(cm_id);
+}
+
+static void srpt_cm_rep_error(struct ib_cm_id *cm_id)
+{
+	PRINT_INFO("Received InfiniBand REP error for cm_id %p.", cm_id);
+	srpt_release_channel_by_cmid(cm_id);
+}
+
+/**
+ * srpt_cm_dreq_recv() - Process reception of a DREQ message.
+ */
+static void srpt_cm_dreq_recv(struct ib_cm_id *cm_id)
+{
+	struct srpt_rdma_ch *ch;
+
+	ch = srpt_find_channel(cm_id->context, cm_id);
+	if (!ch) {
+		TRACE_DBG("Received DREQ for channel %p which is already"
+			  " being unregistered.", cm_id);
+		goto out;
+	}
+
+	TRACE_DBG("cm_id= %p ch->state= %d", cm_id, atomic_read(&ch->state));
+
+	switch (atomic_read(&ch->state)) {
+	case RDMA_CHANNEL_LIVE:
+	case RDMA_CHANNEL_CONNECTING:
+		ib_send_cm_drep(ch->cm_id, NULL, 0);
+		PRINT_INFO("Received DREQ and sent DREP for session %s.",
+			   ch->sess_name);
+		break;
+	case RDMA_CHANNEL_DISCONNECTING:
+	default:
+		break;
+	}
+
+out:
+	;
+}
+
+/**
+ * srpt_cm_drep_recv() - Process reception of a DREP message.
+ */
+static void srpt_cm_drep_recv(struct ib_cm_id *cm_id)
+{
+	PRINT_INFO("Received InfiniBand DREP message for cm_id %p.", cm_id);
+	srpt_release_channel_by_cmid(cm_id);
+}
+
+/**
+ * srpt_cm_handler() - IB connection manager callback function.
+ *
+ * A non-zero return value will cause the caller destroy the CM ID.
+ *
+ * Note: srpt_cm_handler() must only return a non-zero value when transferring
+ * ownership of the cm_id to a channel by srpt_cm_req_recv() failed. Returning
+ * a non-zero value in any other case will trigger a race with the
+ * ib_destroy_cm_id() call in srpt_release_channel().
+ */
+static int srpt_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
+{
+	int ret;
+
+	ret = 0;
+	switch (event->event) {
+	case IB_CM_REQ_RECEIVED:
+		ret = srpt_cm_req_recv(cm_id, &event->param.req_rcvd,
+				       event->private_data);
+		break;
+	case IB_CM_REJ_RECEIVED:
+		srpt_cm_rej_recv(cm_id);
+		break;
+	case IB_CM_RTU_RECEIVED:
+	case IB_CM_USER_ESTABLISHED:
+		srpt_cm_rtu_recv(cm_id);
+		break;
+	case IB_CM_DREQ_RECEIVED:
+		srpt_cm_dreq_recv(cm_id);
+		break;
+	case IB_CM_DREP_RECEIVED:
+		srpt_cm_drep_recv(cm_id);
+		break;
+	case IB_CM_TIMEWAIT_EXIT:
+		srpt_cm_timewait_exit(cm_id);
+		break;
+	case IB_CM_REP_ERROR:
+		srpt_cm_rep_error(cm_id);
+		break;
+	case IB_CM_DREQ_ERROR:
+		PRINT_INFO("%s", "Received IB DREQ ERROR event.");
+		break;
+	case IB_CM_MRA_RECEIVED:
+		PRINT_INFO("%s", "Received IB MRA event");
+		break;
+	default:
+		PRINT_ERROR("received unrecognized IB CM event %d",
+			    event->event);
+		break;
+	}
+
+	return ret;
+}
+
+/**
+ * srpt_map_sg_to_ib_sge() - Map an SG list to an IB SGE list.
+ */
+static int srpt_map_sg_to_ib_sge(struct srpt_rdma_ch *ch,
+				 struct srpt_ioctx *ioctx,
+				 struct scst_cmd *scmnd)
+{
+	struct scatterlist *scat;
+	scst_data_direction dir;
+	struct rdma_iu *riu;
+	struct srp_direct_buf *db;
+	dma_addr_t dma_addr;
+	struct ib_sge *sge;
+	u64 raddr;
+	u32 rsize;
+	u32 tsize;
+	u32 dma_len;
+	int count, nrdma;
+	int i, j, k;
+
+	BUG_ON(!ch);
+	BUG_ON(!ioctx);
+	BUG_ON(!scmnd);
+	scat = scst_cmd_get_sg(scmnd);
+	WARN_ON(!scat);
+	dir = scst_cmd_get_data_direction(scmnd);
+	BUG_ON(dir == SCST_DATA_NONE);
+	/*
+	 * Cache 'dir' because it is needed in srpt_unmap_sg_to_ib_sge()
+	 * and because scst_set_cmd_error_status() resets scmnd->data_direction.
+	 */
+	ioctx->dir = dir;
+	count = ib_dma_map_sg(ch->sport->sdev->device, scat,
+			      scst_cmd_get_sg_cnt(scmnd),
+			      scst_to_tgt_dma_dir(dir));
+	if (unlikely(!count))
+		return -EBUSY;
+
+	ioctx->mapped_sg_count = count;
+
+	if (ioctx->rdma_ius && ioctx->n_rdma_ius)
+		nrdma = ioctx->n_rdma_ius;
+	else {
+		nrdma = count / SRPT_DEF_SG_PER_WQE + ioctx->n_rbuf;
+
+		ioctx->rdma_ius = kzalloc(nrdma * sizeof *riu,
+					  scst_cmd_atomic(scmnd)
+					  ? GFP_ATOMIC : GFP_KERNEL);
+		if (!ioctx->rdma_ius)
+			goto free_mem;
+
+		ioctx->n_rdma_ius = nrdma;
+	}
+
+	db = ioctx->rbufs;
+	tsize = (dir == SCST_DATA_READ) ?
+		scst_cmd_get_resp_data_len(scmnd) : scst_cmd_get_bufflen(scmnd);
+	dma_len = sg_dma_len(&scat[0]);
+	riu = ioctx->rdma_ius;
+
+	/*
+	 * For each remote desc - calculate the #ib_sge.
+	 * If #ib_sge < SRPT_DEF_SG_PER_WQE per rdma operation then
+	 *      each remote desc rdma_iu is required a rdma wr;
+	 * else
+	 *      we need to allocate extra rdma_iu to carry extra #ib_sge in
+	 *      another rdma wr
+	 */
+	for (i = 0, j = 0;
+	     j < count && i < ioctx->n_rbuf && tsize > 0; ++i, ++riu, ++db) {
+		rsize = be32_to_cpu(db->len);
+		raddr = be64_to_cpu(db->va);
+		riu->raddr = raddr;
+		riu->rkey = be32_to_cpu(db->key);
+		riu->sge_cnt = 0;
+
+		/* calculate how many sge required for this remote_buf */
+		while (rsize > 0 && tsize > 0) {
+
+			if (rsize >= dma_len) {
+				tsize -= dma_len;
+				rsize -= dma_len;
+				raddr += dma_len;
+
+				if (tsize > 0) {
+					++j;
+					if (j < count)
+						dma_len = sg_dma_len(&scat[j]);
+				}
+			} else {
+				tsize -= rsize;
+				dma_len -= rsize;
+				rsize = 0;
+			}
+
+			++riu->sge_cnt;
+
+			if (rsize > 0 && riu->sge_cnt == SRPT_DEF_SG_PER_WQE) {
+				++ioctx->n_rdma;
+				riu->sge =
+				    kmalloc(riu->sge_cnt * sizeof *riu->sge,
+					    scst_cmd_atomic(scmnd)
+					    ? GFP_ATOMIC : GFP_KERNEL);
+				if (!riu->sge)
+					goto free_mem;
+
+				++riu;
+				riu->sge_cnt = 0;
+				riu->raddr = raddr;
+				riu->rkey = be32_to_cpu(db->key);
+			}
+		}
+
+		++ioctx->n_rdma;
+		riu->sge = kmalloc(riu->sge_cnt * sizeof *riu->sge,
+				   scst_cmd_atomic(scmnd)
+				   ? GFP_ATOMIC : GFP_KERNEL);
+		if (!riu->sge)
+			goto free_mem;
+	}
+
+	db = ioctx->rbufs;
+	scat = scst_cmd_get_sg(scmnd);
+	tsize = (dir == SCST_DATA_READ) ?
+		scst_cmd_get_resp_data_len(scmnd) : scst_cmd_get_bufflen(scmnd);
+	riu = ioctx->rdma_ius;
+	dma_len = sg_dma_len(&scat[0]);
+	dma_addr = sg_dma_address(&scat[0]);
+
+	/* this second loop is really mapped sg_addres to rdma_iu->ib_sge */
+	for (i = 0, j = 0;
+	     j < count && i < ioctx->n_rbuf && tsize > 0; ++i, ++riu, ++db) {
+		rsize = be32_to_cpu(db->len);
+		sge = riu->sge;
+		k = 0;
+
+		while (rsize > 0 && tsize > 0) {
+			sge->addr = dma_addr;
+			sge->lkey = ch->sport->sdev->mr->lkey;
+
+			if (rsize >= dma_len) {
+				sge->length =
+					(tsize < dma_len) ? tsize : dma_len;
+				tsize -= dma_len;
+				rsize -= dma_len;
+
+				if (tsize > 0) {
+					++j;
+					if (j < count) {
+						dma_len = sg_dma_len(&scat[j]);
+						dma_addr =
+						    sg_dma_address(&scat[j]);
+					}
+				}
+			} else {
+				sge->length = (tsize < rsize) ? tsize : rsize;
+				tsize -= rsize;
+				dma_len -= rsize;
+				dma_addr += rsize;
+				rsize = 0;
+			}
+
+			++k;
+			if (k == riu->sge_cnt && rsize > 0) {
+				++riu;
+				sge = riu->sge;
+				k = 0;
+			} else if (rsize > 0)
+				++sge;
+		}
+	}
+
+	return 0;
+
+free_mem:
+	srpt_unmap_sg_to_ib_sge(ch, ioctx);
+
+	return -ENOMEM;
+}
+
+/**
+ * srpt_unmap_sg_to_ib_sge() - Unmap an IB SGE list.
+ */
+static void srpt_unmap_sg_to_ib_sge(struct srpt_rdma_ch *ch,
+				    struct srpt_ioctx *ioctx)
+{
+	struct scst_cmd *scmnd;
+	struct scatterlist *scat;
+	scst_data_direction dir;
+
+	EXTRACHECKS_BUG_ON(!ch);
+	EXTRACHECKS_BUG_ON(!ioctx);
+	EXTRACHECKS_BUG_ON(ioctx->n_rdma && !ioctx->rdma_ius);
+
+	while (ioctx->n_rdma)
+		kfree(ioctx->rdma_ius[--ioctx->n_rdma].sge);
+
+	kfree(ioctx->rdma_ius);
+	ioctx->rdma_ius = NULL;
+
+	if (ioctx->mapped_sg_count) {
+		scmnd = ioctx->scmnd;
+		EXTRACHECKS_BUG_ON(!scmnd);
+		EXTRACHECKS_WARN_ON(ioctx->scmnd != scmnd);
+		EXTRACHECKS_WARN_ON(ioctx != scst_cmd_get_tgt_priv(scmnd));
+		scat = scst_cmd_get_sg(scmnd);
+		EXTRACHECKS_WARN_ON(!scat);
+		dir = ioctx->dir;
+		EXTRACHECKS_BUG_ON(dir == SCST_DATA_NONE);
+		ib_dma_unmap_sg(ch->sport->sdev->device, scat,
+				scst_cmd_get_sg_cnt(scmnd),
+				scst_to_tgt_dma_dir(dir));
+		ioctx->mapped_sg_count = 0;
+	}
+}
+
+/**
+ * srpt_perform_rdmas() - Perform IB RDMA.
+ */
+static int srpt_perform_rdmas(struct srpt_rdma_ch *ch, struct srpt_ioctx *ioctx,
+			      scst_data_direction dir)
+{
+	struct ib_send_wr wr;
+	struct ib_send_wr *bad_wr;
+	struct rdma_iu *riu;
+	int i;
+	int ret;
+	int sq_wr_avail;
+
+	if (dir == SCST_DATA_WRITE) {
+		ret = -ENOMEM;
+		sq_wr_avail = atomic_sub_return(ioctx->n_rdma,
+						 &ch->sq_wr_avail);
+		if (sq_wr_avail < 0) {
+			atomic_add(ioctx->n_rdma, &ch->sq_wr_avail);
+			PRINT_ERROR("%s[%d]: send queue full",
+				    __func__, __LINE__);
+			goto out;
+		}
+	}
+
+	ret = 0;
+	riu = ioctx->rdma_ius;
+	memset(&wr, 0, sizeof wr);
+
+	for (i = 0; i < ioctx->n_rdma; ++i, ++riu) {
+		wr.opcode = (dir == SCST_DATA_READ) ?
+		    IB_WR_RDMA_WRITE : IB_WR_RDMA_READ;
+		wr.next = NULL;
+		wr.wr_id = ioctx->index;
+		wr.wr.rdma.remote_addr = riu->raddr;
+		wr.wr.rdma.rkey = riu->rkey;
+		wr.num_sge = riu->sge_cnt;
+		wr.sg_list = riu->sge;
+
+		/* only get completion event for the last rdma wr */
+		if (i == (ioctx->n_rdma - 1) && dir == SCST_DATA_WRITE)
+			wr.send_flags = IB_SEND_SIGNALED;
+
+		ret = ib_post_send(ch->qp, &wr, &bad_wr);
+		if (ret)
+			goto out;
+	}
+
+out:
+	return ret;
+}
+
+/**
+ * srpt_xfer_data() - Start data transfer from initiator to target.
+ *
+ * Note: Must not block.
+ */
+static int srpt_xfer_data(struct srpt_rdma_ch *ch, struct srpt_ioctx *ioctx,
+			  struct scst_cmd *scmnd)
+{
+	int ret;
+
+	ret = srpt_map_sg_to_ib_sge(ch, ioctx, scmnd);
+	if (ret) {
+		PRINT_ERROR("%s[%d] ret=%d", __func__, __LINE__, ret);
+		ret = SCST_TGT_RES_QUEUE_FULL;
+		goto out;
+	}
+
+	ret = srpt_perform_rdmas(ch, ioctx, scst_cmd_get_data_direction(scmnd));
+	if (ret) {
+		if (ret == -EAGAIN || ret == -ENOMEM) {
+			PRINT_INFO("%s[%d] queue full -- ret=%d",
+				   __func__, __LINE__, ret);
+			ret = SCST_TGT_RES_QUEUE_FULL;
+		} else {
+			PRINT_ERROR("%s[%d] fatal error -- ret=%d",
+				    __func__, __LINE__, ret);
+			ret = SCST_TGT_RES_FATAL_ERROR;
+		}
+		goto out_unmap;
+	}
+
+	ret = SCST_TGT_RES_SUCCESS;
+
+out:
+	return ret;
+out_unmap:
+	srpt_unmap_sg_to_ib_sge(ch, ioctx);
+	goto out;
+}
+
+/**
+ * srpt_pending_cmd_timeout() - SCST command hw processing timeout callback.
+ *
+ * Called by the SCST core if no IB completion notification has been received
+ * within max_hw_pending_time seconds.
+ */
+static void srpt_pending_cmd_timeout(struct scst_cmd *scmnd)
+{
+	struct srpt_ioctx *ioctx;
+	enum srpt_command_state state;
+
+	ioctx = scst_cmd_get_tgt_priv(scmnd);
+	BUG_ON(!ioctx);
+
+	state = srpt_get_cmd_state(ioctx);
+	switch (state) {
+	case SRPT_STATE_NEW:
+	case SRPT_STATE_DATA_IN:
+	case SRPT_STATE_DONE:
+		/*
+		 * srpt_pending_cmd_timeout() should never be invoked for
+		 * commands in this state.
+		 */
+		PRINT_ERROR("Processing SCST command %p (SRPT state %d) took"
+			    " too long -- aborting", scmnd, state);
+		break;
+	case SRPT_STATE_NEED_DATA:
+	case SRPT_STATE_CMD_RSP_SENT:
+	case SRPT_STATE_MGMT_RSP_SENT:
+	default:
+		PRINT_ERROR("Command %p: IB completion for wr_id %u has not"
+			    " been received in time (SRPT command state %d)",
+			    scmnd, ioctx->index, state);
+		break;
+	}
+
+	srpt_abort_scst_cmd(ioctx, SCST_CONTEXT_SAME);
+}
+
+/**
+ * srpt_rdy_to_xfer() - Transfers data from initiator to target.
+ *
+ * Called by the SCST core to transfer data from the initiator to the target
+ * (SCST_DATA_WRITE). Must not block.
+ */
+static int srpt_rdy_to_xfer(struct scst_cmd *scmnd)
+{
+	struct srpt_rdma_ch *ch;
+	struct srpt_ioctx *ioctx;
+	enum srpt_command_state new_state;
+	enum rdma_ch_state ch_state;
+	int ret;
+
+	ioctx = scst_cmd_get_tgt_priv(scmnd);
+	BUG_ON(!ioctx);
+
+	new_state = srpt_set_cmd_state(ioctx, SRPT_STATE_NEED_DATA);
+	WARN_ON(new_state == SRPT_STATE_DONE);
+
+	ch = ioctx->ch;
+	WARN_ON(ch != scst_sess_get_tgt_priv(scst_cmd_get_session(scmnd)));
+	BUG_ON(!ch);
+
+	ch_state = atomic_read(&ch->state);
+	if (ch_state == RDMA_CHANNEL_DISCONNECTING) {
+		TRACE_DBG("cmd with tag %lld: channel disconnecting",
+			  scst_cmd_get_tag(scmnd));
+		ret = SCST_TGT_RES_FATAL_ERROR;
+		goto out;
+	} else if (ch_state == RDMA_CHANNEL_CONNECTING) {
+		ret = SCST_TGT_RES_QUEUE_FULL;
+		goto out;
+	}
+	ret = srpt_xfer_data(ch, ioctx, scmnd);
+
+out:
+	return ret;
+}
+
+/**
+ * srpt_must_wait_for_cred() - Whether or not the target must wait with
+ * sending a response towards the initiator in order to avoid that the
+ * initiator locks up. The Linux SRP initiator locks up when
+ * initiator.req_lim <= req_lim_min (req_lim_min equals 1 for SRP_CMD and
+ * equals 0 for SRP_TSK_MGMT) and either no new SRP_RSP will be received by the
+ * initiator or none of the received SRP_RSP responses increases
+ * initiator.req_lim.  One possible strategy to avoid an initiator lockup is
+ * that the target does not send an SRP_RSP that makes initiator.req_lim <=
+ * req_lim_min. While the target does not know the value of initiator.req_lim,
+ * one can deduce from the credit mechanism specified in the SRP standard that
+ * when target.req_lim == req_lim_min, initiator.req_lim must also equal
+ * req_lim_min. Hence wait with sending a response when target.req_lim <=
+ * req_lim_min if that response would not increase initiator.req_lim. The last
+ * condition is equivalent to srpt_req_lim_delta(ch) <= 0.
+ *
+ * If this function returns false, the caller must either send a response to
+ * the initiator with the REQUEST LIMIT DELTA field set to delta or call
+ * srpt_undo_req_lim_delta(ch, delta); where delta is the value written to
+ * the address that is the third argument of this function.
+ *
+ * Note: The constant 'compensation' compensates for the fact that multiple
+ * threads are processing SRP commands simultaneously.
+ *
+ * See also: For more information about how to reproduce the initiator lockup,
+ * see also http://bugzilla.kernel.org/show_bug.cgi?id=14235.
+ */
+static bool srpt_must_wait_for_cred(struct srpt_rdma_ch *ch, int req_lim_min,
+				    int *req_lim_delta)
+{
+	int delta;
+	bool res;
+	int compensation;
+	enum { default_vdisk_threads = 8 };
+
+	EXTRACHECKS_BUG_ON(!req_lim_delta);
+
+	compensation = min_t(int, default_vdisk_threads, num_online_cpus()) + 1;
+	res = true;
+	if (atomic_read(&ch->supports_cred_req)
+	    || atomic_read(&ch->req_lim) > req_lim_min + compensation) {
+		res = false;
+		*req_lim_delta = srpt_req_lim_delta(ch);
+	} else {
+		bool again;
+		do {
+			again = false;
+			delta = atomic_read(&ch->req_lim_delta);
+			if (delta > 0) {
+				if (atomic_cmpxchg(&ch->req_lim_delta, delta, 0)
+				    == delta) {
+					res = false;
+					*req_lim_delta = delta;
+				} else
+					again = true;
+			}
+		} while (again);
+	}
+	return res;
+}
+
+/**
+ * srpt_wait_for_cred() - Wait until sending a response won't lock up the
+ * initiator.
+ *
+ * The caller must either send a response to the initiator with the REQUEST
+ * LIMIT DELTA field set to delta + 1 or call srpt_undo_req_lim_delta(ch,
+ * delta); where delta is the return value of this function.
+ */
+static int srpt_wait_for_cred(struct srpt_rdma_ch *ch, int req_lim_min)
+{
+	int delta;
+
+#if 0
+	bool debug_print = atomic_read(&ch->req_lim) <= req_lim_min + 1;
+	if (debug_print)
+		PRINT_INFO("srpt_wait_for_cred(): min %d, req_lim %d,"
+			   " req_lim_delta %d", req_lim_min,
+			   atomic_read(&ch->req_lim),
+			   atomic_read(&ch->req_lim_delta));
+#endif
+#if defined(CONFIG_SCST_DEBUG)
+	if (processing_delay_in_us <= MAX_UDELAY_MS * 1000)
+		udelay(processing_delay_in_us);
+#endif
+	delta = 0; /* superfluous -- to keep sparse happy */
+	while (unlikely(srpt_must_wait_for_cred(ch, req_lim_min, &delta))) {
+		atomic_inc(&ch->req_lim_waiter_count);
+		wait_for_completion(&ch->req_lim_compl);
+	}
+#if 0
+	if (debug_print)
+		PRINT_INFO("srpt_wait_for_cred() returns %d", delta);
+#endif
+	return delta;
+}
+
+/**
+ * srpt_xmit_response() - Transmits the response to a SCSI command.
+ *
+ * Callback function called by the SCST core. Must not block. Must ensure that
+ * scst_tgt_cmd_done() will get invoked when returning SCST_TGT_RES_SUCCESS.
+ */
+static int srpt_xmit_response(struct scst_cmd *scmnd)
+{
+	struct srpt_rdma_ch *ch;
+	struct srpt_ioctx *ioctx;
+	enum srpt_command_state state;
+	s32 req_lim_delta;
+	int ret;
+	scst_data_direction dir;
+	int resp_len;
+
+	ret = SCST_TGT_RES_SUCCESS;
+
+	ioctx = scst_cmd_get_tgt_priv(scmnd);
+	BUG_ON(!ioctx);
+
+	ch = scst_sess_get_tgt_priv(scst_cmd_get_session(scmnd));
+	BUG_ON(!ch);
+
+	state = srpt_test_and_set_cmd_state(ioctx, SRPT_STATE_NEW,
+					    SRPT_STATE_CMD_RSP_SENT);
+	if (state != SRPT_STATE_NEW) {
+		state = srpt_test_and_set_cmd_state(ioctx, SRPT_STATE_DATA_IN,
+						    SRPT_STATE_CMD_RSP_SENT);
+		if (state != SRPT_STATE_DATA_IN)
+			PRINT_ERROR("Unexpected command state %d",
+				    srpt_get_cmd_state(ioctx));
+	}
+
+	if (unlikely(scst_cmd_aborted(scmnd))) {
+		srpt_abort_scst_cmd(ioctx, SCST_CONTEXT_SAME);
+		goto out;
+	}
+
+	EXTRACHECKS_BUG_ON(scst_cmd_atomic(scmnd));
+
+	dir = scst_cmd_get_data_direction(scmnd);
+
+	/* For read commands, transfer the data to the initiator. */
+	if (dir == SCST_DATA_READ && scst_cmd_get_resp_data_len(scmnd)) {
+		ret = srpt_xfer_data(ch, ioctx, scmnd);
+		if (ret != SCST_TGT_RES_SUCCESS) {
+			PRINT_ERROR("%s: tag= %llu xfer_data failed",
+				    __func__, scst_cmd_get_tag(scmnd));
+			goto out;
+		}
+	}
+
+	req_lim_delta = srpt_wait_for_cred(ch, 1);
+
+	resp_len = srpt_build_cmd_rsp(ch, ioctx, req_lim_delta,
+				      scst_cmd_get_tag(scmnd),
+				      scst_cmd_get_status(scmnd),
+				      scst_cmd_get_sense_buffer(scmnd),
+				      scst_cmd_get_sense_buffer_len(scmnd));
+
+	if (srpt_post_send(ch, ioctx, resp_len)) {
+		srpt_unmap_sg_to_ib_sge(ch, ioctx);
+		srpt_set_cmd_state(ioctx, state);
+		scst_set_delivery_status(scmnd, SCST_CMD_DELIVERY_FAILED);
+		PRINT_ERROR("%s[%d]: ch->state %d cmd state %d tag %llu",
+			    __func__, __LINE__, atomic_read(&ch->state),
+			    state, scst_cmd_get_tag(scmnd));
+		srpt_undo_req_lim_delta(ch, req_lim_delta - 1);
+		ret = SCST_TGT_RES_QUEUE_FULL;
+	}
+
+out:
+	return ret;
+}
+
+/**
+ * srpt_tsk_mgmt_done() - SCST callback function that sends back the response
+ * for a task management request.
+ *
+ * Must not block.
+ */
+static void srpt_tsk_mgmt_done(struct scst_mgmt_cmd *mcmnd)
+{
+	struct srpt_rdma_ch *ch;
+	struct srpt_mgmt_ioctx *mgmt_ioctx;
+	struct srpt_ioctx *ioctx;
+	enum srpt_command_state new_state;
+	s32 req_lim_delta;
+	int rsp_len;
+
+	mgmt_ioctx = scst_mgmt_cmd_get_tgt_priv(mcmnd);
+	BUG_ON(!mgmt_ioctx);
+
+	ch = mgmt_ioctx->ch;
+	BUG_ON(!ch);
+
+	ioctx = mgmt_ioctx->ioctx;
+	BUG_ON(!ioctx);
+
+	TRACE_DBG("%s: tsk_mgmt_done for tag= %lld status=%d",
+		  __func__, mgmt_ioctx->tag, scst_mgmt_cmd_get_status(mcmnd));
+
+	WARN_ON(in_irq());
+
+	new_state = srpt_set_cmd_state(ioctx, SRPT_STATE_MGMT_RSP_SENT);
+	WARN_ON(new_state == SRPT_STATE_DONE);
+
+	req_lim_delta = srpt_wait_for_cred(ch, 0);
+
+	rsp_len = srpt_build_tskmgmt_rsp(ch, ioctx, req_lim_delta,
+					 scst_to_srp_tsk_mgmt_status(
+					 scst_mgmt_cmd_get_status(mcmnd)),
+					 mgmt_ioctx->tag);
+	/*
+	 * Note: the srpt_post_send() call below sends the task management
+	 * response asynchronously. It is possible that the SCST core has
+	 * already freed the struct scst_mgmt_cmd structure before the
+	 * response is sent. This is fine.
+	 */
+	if (srpt_post_send(ch, ioctx, rsp_len)) {
+		PRINT_ERROR("%s", "Sending SRP_RSP response failed.");
+		srpt_undo_req_lim_delta(ch, req_lim_delta - 1);
+	}
+
+	scst_mgmt_cmd_set_tgt_priv(mcmnd, NULL);
+
+	kfree(mgmt_ioctx);
+}
+
+/**
+ * srpt_get_initiator_port_transport_id() - SCST TransportID callback function.
+ *
+ * See also SPC-3, section 7.5.4.5, TransportID for initiator ports using SRP.
+ */
+static int srpt_get_initiator_port_transport_id(struct scst_session *scst_sess,
+						uint8_t **transport_id)
+{
+	struct srpt_rdma_ch *ch;
+	struct spc_rdma_transport_id {
+		uint8_t protocol_identifier;
+		uint8_t reserved[7];
+		uint8_t i_port_id[16];
+	};
+	struct spc_rdma_transport_id *tr_id;
+	int res;
+
+	if (!scst_sess) {
+		res = SCSI_TRANSPORTID_PROTOCOLID_SRP;
+		goto out;
+	}
+
+	ch = scst_sess_get_tgt_priv(scst_sess);
+	BUG_ON(!ch);
+
+	BUILD_BUG_ON(sizeof(*tr_id) != 24);
+
+	tr_id = kzalloc(sizeof(struct spc_rdma_transport_id), GFP_KERNEL);
+	if (!tr_id) {
+		PRINT_ERROR("%s", "Allocation of TransportID failed");
+		res = -ENOMEM;
+		goto out;
+	}
+
+	res = 0;
+	tr_id->protocol_identifier = SCSI_TRANSPORTID_PROTOCOLID_SRP;
+	memcpy(tr_id->i_port_id, ch->i_port_id, sizeof(ch->i_port_id));
+
+	*transport_id = (uint8_t *)tr_id;
+
+out:
+	return res;
+}
+
+/**
+ * srpt_on_free_cmd() - Free command-private data.
+ *
+ * Called by the SCST core. May be called in IRQ context.
+ */
+static void srpt_on_free_cmd(struct scst_cmd *scmnd)
+{
+	struct srpt_rdma_ch *ch;
+	struct srpt_ioctx *ioctx;
+
+	ioctx = scst_cmd_get_tgt_priv(scmnd);
+	BUG_ON(!ioctx);
+
+	WARN_ON(srpt_get_cmd_state(ioctx) != SRPT_STATE_DONE);
+
+	ch = ioctx->ch;
+	BUG_ON(!ch);
+
+	srpt_reset_ioctx(ch, ioctx, 1);
+}
+
+static void srpt_refresh_port_work(struct work_struct *work)
+{
+	struct srpt_port *sport = container_of(work, struct srpt_port, work);
+
+	srpt_refresh_port(sport);
+}
+
+/**
+ * srpt_detect() - Returns the number of target adapters.
+ *
+ * Callback function called by the SCST core.
+ */
+static int srpt_detect(struct scst_tgt_template *tp)
+{
+	int device_count;
+
+	device_count = atomic_read(&srpt_device_count);
+
+	return device_count;
+}
+
+/**
+ * srpt_release() - Free the resources associated with an SCST target.
+ *
+ * Callback function called by the SCST core from scst_unregister_target().
+ */
+static int srpt_release(struct scst_tgt *scst_tgt)
+{
+	struct srpt_device *sdev = scst_tgt_get_tgt_priv(scst_tgt);
+	struct srpt_rdma_ch *ch;
+
+	EXTRACHECKS_WARN_ON_ONCE(irqs_disabled());
+
+	BUG_ON(!scst_tgt);
+	if (WARN_ON(!sdev))
+		return -ENODEV;
+
+	spin_lock_irq(&sdev->spinlock);
+	while (!list_empty(&sdev->rch_list)) {
+		ch = list_first_entry(&sdev->rch_list, typeof(*ch), list);
+		srpt_unregister_channel(ch);
+	}
+	spin_unlock_irq(&sdev->spinlock);
+
+	scst_tgt_set_tgt_priv(scst_tgt, NULL);
+
+	return 0;
+}
+
+/**
+ * srpt_get_scsi_transport_version() - Returns the SCSI transport version.
+ * This function is called from scst_pres.c, the code that implements
+ * persistent reservation support.
+ */
+static uint16_t srpt_get_scsi_transport_version(struct scst_tgt *scst_tgt)
+{
+	return 0x0940; /* SRP */
+}
+
+/* SCST target template for the SRP target implementation. */
+static struct scst_tgt_template srpt_template = {
+	.name				 = DRV_NAME,
+	.sg_tablesize			 = SRPT_DEF_SG_TABLESIZE,
+	.max_hw_pending_time		 = 60/*seconds*/,
+	.enable_target			 = srpt_enable_target,
+	.is_target_enabled		 = srpt_is_target_enabled,
+#if defined(CONFIG_SCST_DEBUG) || defined(CONFIG_SCST_TRACING)
+	.default_trace_flags		 = DEFAULT_SRPT_TRACE_FLAGS,
+	.trace_flags			 = &trace_flag,
+#endif
+	.detect				 = srpt_detect,
+	.release			 = srpt_release,
+	.xmit_response			 = srpt_xmit_response,
+	.rdy_to_xfer			 = srpt_rdy_to_xfer,
+	.on_hw_pending_cmd_timeout	 = srpt_pending_cmd_timeout,
+	.on_free_cmd			 = srpt_on_free_cmd,
+	.task_mgmt_fn_done		 = srpt_tsk_mgmt_done,
+	.get_initiator_port_transport_id = srpt_get_initiator_port_transport_id,
+	.get_scsi_transport_version	 = srpt_get_scsi_transport_version,
+};
+
+/**
+ * srpt_dev_release() - Device release callback function.
+ *
+ * The callback function srpt_dev_release() is called whenever a
+ * device is removed from the /sys/class/infiniband_srpt device class.
+ * Although this function has been left empty, a release function has been
+ * defined such that upon module removal no complaint is logged about a
+ * missing release function.
+ */
+static void srpt_dev_release(struct device *dev)
+{
+}
+
+static ssize_t show_login_info(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct srpt_device *sdev =
+		container_of(dev, struct srpt_device, dev);
+	struct srpt_port *sport;
+	int i;
+	int len = 0;
+
+	for (i = 0; i < sdev->device->phys_port_cnt; i++) {
+		sport = &sdev->port[i];
+
+		len += sprintf(buf + len,
+			       "tid_ext=%016llx,ioc_guid=%016llx,pkey=ffff,"
+			       "dgid=%04x%04x%04x%04x%04x%04x%04x%04x,"
+			       "service_id=%016llx\n",
+			       srpt_service_guid,
+			       srpt_service_guid,
+			       be16_to_cpu(((__be16 *) sport->gid.raw)[0]),
+			       be16_to_cpu(((__be16 *) sport->gid.raw)[1]),
+			       be16_to_cpu(((__be16 *) sport->gid.raw)[2]),
+			       be16_to_cpu(((__be16 *) sport->gid.raw)[3]),
+			       be16_to_cpu(((__be16 *) sport->gid.raw)[4]),
+			       be16_to_cpu(((__be16 *) sport->gid.raw)[5]),
+			       be16_to_cpu(((__be16 *) sport->gid.raw)[6]),
+			       be16_to_cpu(((__be16 *) sport->gid.raw)[7]),
+			       srpt_service_guid);
+	}
+
+	return len;
+}
+
+static struct class_attribute srpt_class_attrs[] = {
+	__ATTR_NULL,
+};
+
+static struct device_attribute srpt_dev_attrs[] = {
+	__ATTR(login_info, S_IRUGO, show_login_info, NULL),
+	__ATTR_NULL,
+};
+
+static struct class srpt_class = {
+	.name        = "infiniband_srpt",
+	.dev_release = srpt_dev_release,
+	.class_attrs = srpt_class_attrs,
+	.dev_attrs   = srpt_dev_attrs,
+};
+
+/**
+ * srpt_add_one() - Infiniband device addition callback function.
+ */
+static void srpt_add_one(struct ib_device *device)
+{
+	struct srpt_device *sdev;
+	struct srpt_port *sport;
+	struct ib_srq_init_attr srq_attr;
+	int i;
+
+	TRACE_DBG("device = %p, device->dma_ops = %p", device, device->dma_ops);
+
+	sdev = kzalloc(sizeof *sdev, GFP_KERNEL);
+	if (!sdev)
+		return;
+
+	sdev->scst_tgt = scst_register_target(&srpt_template, NULL);
+	if (!sdev->scst_tgt) {
+		PRINT_ERROR("SCST registration failed for %s.",
+			    sdev->device->name);
+		goto free_dev;
+	}
+
+	scst_tgt_set_tgt_priv(sdev->scst_tgt, sdev);
+
+	sdev->device = device;
+
+	sdev->dev.class = &srpt_class;
+	sdev->dev.parent = device->dma_device;
+	dev_set_name(&sdev->dev, "srpt-%s", device->name);
+
+	if (device_register(&sdev->dev))
+		goto unregister_tgt;
+
+	if (ib_query_device(device, &sdev->dev_attr))
+		goto err_dev;
+
+	sdev->pd = ib_alloc_pd(device);
+	if (IS_ERR(sdev->pd))
+		goto err_dev;
+
+	sdev->mr = ib_get_dma_mr(sdev->pd, IB_ACCESS_LOCAL_WRITE);
+	if (IS_ERR(sdev->mr))
+		goto err_pd;
+
+	sdev->srq_size = min(srpt_srq_size, sdev->dev_attr.max_srq_wr);
+
+	srq_attr.event_handler = srpt_srq_event;
+	srq_attr.srq_context = (void *)sdev;
+	srq_attr.attr.max_wr = sdev->srq_size;
+	srq_attr.attr.max_sge = 1;
+	srq_attr.attr.srq_limit = 0;
+
+	sdev->srq = ib_create_srq(sdev->pd, &srq_attr);
+	if (IS_ERR(sdev->srq))
+		goto err_mr;
+
+	TRACE_DBG("%s: create SRQ #wr= %d max_allow=%d dev= %s",
+	      __func__, sdev->srq_size,
+	      sdev->dev_attr.max_srq_wr, device->name);
+
+	if (!srpt_service_guid)
+		srpt_service_guid = be64_to_cpu(device->node_guid);
+
+	sdev->cm_id = ib_create_cm_id(device, srpt_cm_handler, sdev);
+	if (IS_ERR(sdev->cm_id))
+		goto err_srq;
+
+	/* print out target login information */
+	TRACE_DBG("Target login info: id_ext=%016llx,"
+		  "ioc_guid=%016llx,pkey=ffff,service_id=%016llx",
+		  srpt_service_guid, srpt_service_guid, srpt_service_guid);
+
+	/*
+	 * We do not have a consistent service_id (ie. also id_ext of target_id)
+	 * to identify this target. We currently use the guid of the first HCA
+	 * in the system as service_id; therefore, the target_id will change
+	 * if this HCA is gone bad and replaced by different HCA
+	 */
+	if (ib_cm_listen(sdev->cm_id, cpu_to_be64(srpt_service_guid), 0, NULL))
+		goto err_cm;
+
+	INIT_IB_EVENT_HANDLER(&sdev->event_handler, sdev->device,
+			      srpt_event_handler);
+	if (ib_register_event_handler(&sdev->event_handler))
+		goto err_cm;
+
+	sdev->ioctx_ring = kmalloc(sdev->srq_size * sizeof sdev->ioctx_ring[0],
+				   GFP_KERNEL);
+	if (!sdev->ioctx_ring)
+		goto err_event;
+
+	if (srpt_alloc_ioctx_ring(sdev, sdev->ioctx_ring, sdev->srq_size, 0))
+		goto err_alloc_ring;
+
+	INIT_LIST_HEAD(&sdev->rch_list);
+	spin_lock_init(&sdev->spinlock);
+
+	for (i = 0; i < sdev->srq_size; ++i)
+		srpt_post_recv(sdev, sdev->ioctx_ring[i]);
+
+	ib_set_client_data(device, &srpt_client, sdev);
+
+	WARN_ON(sdev->device->phys_port_cnt
+		> sizeof(sdev->port)/sizeof(sdev->port[0]));
+
+	for (i = 1; i <= sdev->device->phys_port_cnt; i++) {
+		sport = &sdev->port[i - 1];
+		sport->sdev = sdev;
+		sport->port = i;
+		INIT_WORK(&sport->work, srpt_refresh_port_work);
+		if (srpt_refresh_port(sport)) {
+			PRINT_ERROR("MAD registration failed for %s-%d.",
+				    sdev->device->name, i);
+			goto err_ring;
+		}
+	}
+
+	atomic_inc(&srpt_device_count);
+
+	return;
+
+err_ring:
+	ib_set_client_data(device, &srpt_client, NULL);
+	srpt_free_ioctx_ring(sdev, sdev->ioctx_ring, sdev->srq_size);
+err_alloc_ring:
+	kfree(sdev->ioctx_ring);
+err_event:
+	ib_unregister_event_handler(&sdev->event_handler);
+err_cm:
+	ib_destroy_cm_id(sdev->cm_id);
+err_srq:
+	ib_destroy_srq(sdev->srq);
+err_mr:
+	ib_dereg_mr(sdev->mr);
+err_pd:
+	ib_dealloc_pd(sdev->pd);
+err_dev:
+	device_unregister(&sdev->dev);
+unregister_tgt:
+	scst_unregister_target(sdev->scst_tgt);
+free_dev:
+	kfree(sdev);
+}
+
+/**
+ * srpt_remove_one() - InfiniBand device removal callback function.
+ */
+static void srpt_remove_one(struct ib_device *device)
+{
+	int i;
+	struct srpt_device *sdev;
+
+	sdev = ib_get_client_data(device, &srpt_client);
+	if (WARN_ON(!sdev))
+		return;
+
+	srpt_unregister_mad_agent(sdev);
+
+	ib_unregister_event_handler(&sdev->event_handler);
+
+	/* Cancel any work queued by the just unregistered IB event handler. */
+	for (i = 0; i < sdev->device->phys_port_cnt; i++)
+		cancel_work_sync(&sdev->port[i].work);
+
+	ib_destroy_cm_id(sdev->cm_id);
+	ib_destroy_srq(sdev->srq);
+	ib_dereg_mr(sdev->mr);
+	ib_dealloc_pd(sdev->pd);
+
+	device_unregister(&sdev->dev);
+
+	/*
+	 * Unregistering an SCST target must happen after destroying sdev->cm_id
+	 * such that no new SRP_LOGIN_REQ information units can arrive while
+	 * destroying the SCST target.
+	 */
+	scst_unregister_target(sdev->scst_tgt);
+	sdev->scst_tgt = NULL;
+
+	srpt_free_ioctx_ring(sdev, sdev->ioctx_ring, sdev->srq_size);
+	kfree(sdev->ioctx_ring);
+	sdev->ioctx_ring = NULL;
+	kfree(sdev);
+}
+
+/**
+ * srpt_init_module() - Kernel module initialization.
+ *
+ * Note: Since ib_register_client() registers callback functions, and since at
+ * least one of these callback functions (srpt_add_one()) calls SCST functions,
+ * the SCST target template must be registered before ib_register_client() is
+ * called.
+ */
+static int __init srpt_init_module(void)
+{
+	int ret;
+
+	ret = -EINVAL;
+	if (srp_max_message_size < MIN_MAX_MESSAGE_SIZE) {
+		PRINT_ERROR("invalid value %d for kernel module parameter"
+			    " srp_max_message_size -- must be at least %d.",
+			    srp_max_message_size,
+			    MIN_MAX_MESSAGE_SIZE);
+		goto out;
+	}
+
+	if (srpt_srq_size < MIN_SRPT_SRQ_SIZE
+	    || srpt_srq_size > MAX_SRPT_SRQ_SIZE) {
+		PRINT_ERROR("invalid value %d for kernel module parameter"
+			    " srpt_srq_size -- must be in the range [%d..%d].",
+			    srpt_srq_size, MIN_SRPT_SRQ_SIZE,
+			    MAX_SRPT_SRQ_SIZE);
+		goto out;
+	}
+
+	if (srpt_sq_size < MIN_SRPT_SQ_SIZE) {
+		PRINT_ERROR("invalid value %d for kernel module parameter"
+			    " srpt_sq_size -- must be at least %d.",
+			    srpt_srq_size, MIN_SRPT_SQ_SIZE);
+		goto out;
+	}
+
+	ret = class_register(&srpt_class);
+	if (ret) {
+		PRINT_ERROR("%s", "couldn't register class ib_srpt");
+		goto out;
+	}
+
+	switch (thread) {
+	case MODE_ALL_IN_SIRQ:
+		/*
+		 * Process both IB completions and SCST commands in SIRQ
+		 * context. May lead to soft lockups and other scary behavior
+		 * under sufficient load.
+		 */
+		srpt_template.rdy_to_xfer_atomic = true;
+		break;
+	case MODE_IB_COMPLETION_IN_THREAD:
+		/*
+		 * Process IB completions in the kernel thread associated with
+		 * the RDMA channel, and process SCST commands in the kernel
+		 * threads created by the SCST core.
+		 */
+		srpt_template.rdy_to_xfer_atomic = false;
+		break;
+	case MODE_IB_COMPLETION_IN_SIRQ:
+	default:
+		/*
+		 * Process IB completions in SIRQ context and SCST commands in
+		 * the kernel threads created by the SCST core.
+		 */
+		srpt_template.rdy_to_xfer_atomic = false;
+		break;
+	}
+
+	ret = scst_register_target_template(&srpt_template);
+	if (ret < 0) {
+		PRINT_ERROR("%s", "couldn't register with scst");
+		ret = -ENODEV;
+		goto out_unregister_class;
+	}
+
+	ret = ib_register_client(&srpt_client);
+	if (ret) {
+		PRINT_ERROR("%s", "couldn't register IB client");
+		goto out_unregister_procfs;
+	}
+
+	return 0;
+
+out_unregister_procfs:
+	scst_unregister_target_template(&srpt_template);
+out_unregister_class:
+	class_unregister(&srpt_class);
+out:
+	return ret;
+}
+
+static void __exit srpt_cleanup_module(void)
+{
+
+	ib_unregister_client(&srpt_client);
+	scst_unregister_target_template(&srpt_template);
+	class_unregister(&srpt_class);
+}
+
+module_init(srpt_init_module);
+module_exit(srpt_cleanup_module);
+
+/*
+ * Local variables:
+ * c-basic-offset:   8
+ * indent-tabs-mode: t
+ * End:
+ */
diff -uprN orig/linux-2.6.35/drivers/scst/srpt/ib_srpt.h linux-2.6.35/drivers/scst/srpt/ib_srpt.h
--- orig/linux-2.6.35/drivers/scst/srpt/ib_srpt.h
+++ linux-2.6.35/drivers/scst/srpt/ib_srpt.h
@@ -0,0 +1,368 @@
+/*
+ * Copyright (c) 2006 - 2009 Mellanox Technology Inc.  All rights reserved.
+ * Copyright (C) 2009 - 2010 Bart Van Assche <bart.vanassche@xxxxxxxxx>
+ *
+ * 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.
+ *
+ */
+
+#ifndef IB_SRPT_H
+#define IB_SRPT_H
+
+#include <linux/version.h>
+#include <linux/types.h>
+#include <linux/list.h>
+
+#include <rdma/ib_verbs.h>
+#include <rdma/ib_sa.h>
+#include <rdma/ib_cm.h>
+
+#include <scsi/srp.h>
+
+#include <scst/scst.h>
+
+#include "ib_dm_mad.h"
+
+/*
+ * The prefix the ServiceName field must start with in the device management
+ * ServiceEntries attribute pair. See also the SRP r16a document.
+ */
+#define SRP_SERVICE_NAME_PREFIX		"SRP.T10:"
+
+enum {
+	/*
+	 * SRP IOControllerProfile attributes for SRP target ports that have
+	 * not been defined in <scsi/srp.h>. Source: section B.7, table B.7
+	 * in the SRP r16a document.
+	 */
+	SRP_PROTOCOL = 0x0108,
+	SRP_PROTOCOL_VERSION = 0x0001,
+	SRP_IO_SUBCLASS = 0x609e,
+	SRP_SEND_TO_IOC = 0x01,
+	SRP_SEND_FROM_IOC = 0x02,
+	SRP_RDMA_READ_FROM_IOC = 0x08,
+	SRP_RDMA_WRITE_FROM_IOC = 0x20,
+
+	/*
+	 * srp_login_cmd::req_flags bitmasks. See also table 9 in the SRP r16a
+	 * document.
+	 */
+	SRP_MTCH_ACTION = 0x03, /* MULTI-CHANNEL ACTION */
+	SRP_LOSOLNT = 0x10, /* logout solicited notification */
+	SRP_CRSOLNT = 0x20, /* credit request solicited notification */
+	SRP_AESOLNT = 0x40, /* asynchronous event solicited notification */
+
+	/*
+	 * srp_cmd::sol_nt / srp_tsk_mgmt::sol_not bitmasks. See also tables
+	 * 18 and 20 in the T10 r16a document.
+	 */
+	SRP_SCSOLNT = 0x02, /* SCSOLNT = successful solicited notification */
+	SRP_UCSOLNT = 0x04, /* UCSOLNT = unsuccessful solicited notification */
+
+	/*
+	 * srp_rsp::sol_not / srp_t_logout::sol_not bitmasks. See also tables
+	 * 16 and 22 in the T10 r16a document.
+	 */
+	SRP_SOLNT = 0x01, /* SOLNT = solicited notification */
+
+	/* See also table 24 in the T10 r16a document. */
+	SRP_TSK_MGMT_SUCCESS = 0x00,
+	SRP_TSK_MGMT_FUNC_NOT_SUPP = 0x04,
+	SRP_TSK_MGMT_FAILED = 0x05,
+
+	/* See also table 21 in the T10 r16a document. */
+	SRP_CMD_SIMPLE_Q = 0x0,
+	SRP_CMD_HEAD_OF_Q = 0x1,
+	SRP_CMD_ORDERED_Q = 0x2,
+	SRP_CMD_ACA = 0x4,
+
+	SRP_LOGIN_RSP_MULTICHAN_NO_CHAN = 0x0,
+	SRP_LOGIN_RSP_MULTICHAN_TERMINATED = 0x1,
+	SRP_LOGIN_RSP_MULTICHAN_MAINTAINED = 0x2,
+
+	SRPT_DEF_SG_TABLESIZE = 128,
+	SRPT_DEF_SG_PER_WQE = 16,
+
+	MIN_SRPT_SQ_SIZE = 16,
+	DEF_SRPT_SQ_SIZE = 4096,
+	SRPT_RQ_SIZE = 128,
+	MIN_SRPT_SRQ_SIZE = 4,
+	DEFAULT_SRPT_SRQ_SIZE = 4095,
+	MAX_SRPT_SRQ_SIZE = 65535,
+
+	MIN_MAX_MESSAGE_SIZE = 996,
+	DEFAULT_MAX_MESSAGE_SIZE
+		= sizeof(struct srp_cmd)/*48*/
+		+ sizeof(struct srp_indirect_buf)/*20*/
+		+ 128 * sizeof(struct srp_direct_buf)/*16*/,
+
+	DEFAULT_MAX_RDMA_SIZE = 65536,
+
+	/*
+	 * Number of I/O contexts to be allocated for sending back requests
+	 * from the target to the initiator. Must be a power of two.
+	 */
+	TTI_IOCTX_COUNT = 2,
+	TTI_IOCTX_MASK = TTI_IOCTX_COUNT - 1,
+};
+
+/**
+ * @SRPT_OP_TTI:  wr_id flag for marking requests sent by the target to the
+ *                initiator.
+ * @SRPT_OP_RECV: wr_id flag for marking receive operations.
+ */
+enum {
+	SRPT_OP_TTI	= (1 << 30),
+	SRPT_OP_RECV	= (1 << 31),
+
+	SRPT_OP_FLAGS = SRPT_OP_TTI | SRPT_OP_RECV,
+};
+
+/*
+ * SRP_CRED_REQ information unit, as defined in section 6.10 of the T10 SRP
+ * r16a document.
+ */
+struct srp_cred_req {
+	u8 opcode;
+	u8 sol_not;
+	u8 reserved[2];
+	__be32 req_lim_delta;
+	__be64 tag;
+};
+
+struct rdma_iu {
+	u64 raddr;
+	u32 rkey;
+	struct ib_sge *sge;
+	u32 sge_cnt;
+	int mem_id;
+};
+
+/**
+ * enum srpt_command_state - SCSI command states managed by SRPT.
+ * @SRPT_STATE_NEW:           New command arrived and is being processed.
+ * @SRPT_STATE_NEED_DATA:     Processing a write or bidir command and waiting
+ *                            for data arrival.
+ * @SRPT_STATE_DATA_IN:       Data for the write or bidir command arrived and is
+ *                            being processed.
+ * @SRPT_STATE_CMD_RSP_SENT:  SRP_RSP for SRP_CMD has been sent.
+ * @SRPT_STATE_MGMT_RSP_SENT: SRP_RSP for SRP_TSK_MGMT has been sent.
+ * @SRPT_STATE_DONE:          Command processing finished successfully, command
+ *                            processing has been aborted or command processing
+ *                            failed.
+ */
+enum srpt_command_state {
+	SRPT_STATE_NEW = 0,
+	SRPT_STATE_NEED_DATA = 1,
+	SRPT_STATE_DATA_IN = 2,
+	SRPT_STATE_CMD_RSP_SENT = 3,
+	SRPT_STATE_MGMT_RSP_SENT = 4,
+	SRPT_STATE_DONE = 5,
+};
+
+/**
+ * struct srpt_ioctx - SRPT-private data associated with a struct scst_cmd.
+ * @index:     Index of the I/O context in ioctx_ring.
+ * @buf:       Pointer to the message transferred via this I/O context.
+ * @dma:       DMA address of buf.
+ * @wait_list: Node for insertion in srpt_rdma_ch::cmd_wait_list.
+ * @state:     I/O context state. See also enum srpt_command_state.
+ */
+struct srpt_ioctx {
+	int index;
+	void *buf;
+	dma_addr_t dma;
+	struct rdma_iu *rdma_ius;
+	struct srp_direct_buf *rbufs;
+	struct srp_direct_buf single_rbuf;
+	struct list_head wait_list;
+	int mapped_sg_count;
+	u16 n_rdma_ius;
+	u8 n_rdma;
+	u8 n_rbuf;
+
+	u64 wr_id;
+	enum ib_wc_status status;
+	enum ib_wc_opcode opcode;
+	struct srpt_rdma_ch *ch;
+	struct scst_cmd *scmnd;
+	scst_data_direction dir;
+	atomic_t state;
+};
+
+/**
+ * struct srpt_mgmt_ioctx - SCST management command context information.
+ * @ioctx: SRPT I/O context associated with the management command.
+ * @ch:    RDMA channel over which the management command has been received.
+ * @tag:   SCSI tag of the management command.
+ */
+struct srpt_mgmt_ioctx {
+	struct srpt_ioctx *ioctx;
+	struct srpt_rdma_ch *ch;
+	u64 tag;
+};
+
+/**
+ * enum rdma_ch_state - SRP channel state.
+ */
+enum rdma_ch_state {
+	RDMA_CHANNEL_CONNECTING,
+	RDMA_CHANNEL_LIVE,
+	RDMA_CHANNEL_DISCONNECTING
+};
+
+/**
+ * struct srpt_rdma_ch - RDMA channel.
+ * @wait_queue:    Allows the kernel thread to wait for more work.
+ * @thread:        Kernel thread that processes the IB queues associated with
+ *                 the channel.
+ * @cm_id:         IB CM ID associated with the channel.
+ * @rq_size:       IB receive queue size.
+ * @processing_compl: whether or not an IB completion is being processed.
+ * @qp:            IB queue pair used for communicating over this channel.
+ * @sq_wr_avail:   number of work requests available in the send queue.
+ * @cq:            IB completion queue for this channel.
+ * @sport:         pointer to the information of the HCA port used by this
+ *                 channel.
+ * @i_port_id:     128-bit initiator port identifier copied from SRP_LOGIN_REQ.
+ * @t_port_id:     128-bit target port identifier copied from SRP_LOGIN_REQ.
+ * @max_ti_iu_len: maximum target-to-initiator information unit length.
+ * @supports_cred_req: whether or not the initiator supports SRP_CRED_REQ.
+ * @req_lim:       request limit: maximum number of requests that may be sent
+ *                 by the initiator without having received a response or
+ *                 SRP_CRED_REQ.
+ * @req_lim_delta: req_lim_delta to be sent in the next SRP_RSP.
+ * @req_lim_waiter_count: number of threads waiting on req_lim_wait.
+ * @req_lim_compl: completion variable that is signalled every time req_lim
+ *                 has been incremented.
+ * @state:         channel state. See also enum rdma_ch_state.
+ * @list:          node for insertion in the srpt_device::rch_list list.
+ * @cmd_wait_list: list of SCST commands that arrived before the RTU event. This
+ *                 list contains struct srpt_ioctx elements and is protected
+ *                 against concurrent modification by the cm_id spinlock.
+ * @tti_head:      Index of first element of tti_ioctx that is not in use.
+ * @tti_tail:      Index of first element of tti_ioctx that is in use.
+ * @tti_ioctx:     Circular buffer with I/O contexts for sending requests from
+ *                 target to initiator.
+ * @scst_sess:     SCST session information associated with this SRP channel.
+ * @sess_name:     SCST session name.
+ */
+struct srpt_rdma_ch {
+	wait_queue_head_t wait_queue;
+	struct task_struct *thread;
+	struct ib_cm_id *cm_id;
+	struct ib_qp *qp;
+	int rq_size;
+	atomic_t processing_compl;
+	struct ib_cq *cq;
+	atomic_t sq_wr_avail;
+	struct srpt_port *sport;
+	u8 i_port_id[16];
+	u8 t_port_id[16];
+	int max_ti_iu_len;
+	atomic_t supports_cred_req;
+	atomic_t req_lim;
+	atomic_t req_lim_delta;
+	atomic_t req_lim_waiter_count;
+	struct completion req_lim_compl;
+	atomic_t state;
+	struct list_head list;
+	struct list_head cmd_wait_list;
+	int tti_head;
+	int tti_tail;
+	struct srpt_ioctx *tti_ioctx[TTI_IOCTX_COUNT];
+
+	struct scst_session *scst_sess;
+	u8 sess_name[36];
+};
+
+/**
+ * struct srpt_port - Information associated by SRPT with a single IB port.
+ * @sdev:      backpointer to the HCA information.
+ * @mad_agent: per-port management datagram processing information.
+ * @port:      one-based port number.
+ * @sm_lid:    cached value of the port's sm_lid.
+ * @lid:       cached value of the port's lid.
+ * @gid:       cached value of the port's gid.
+ * @work:      work structure for refreshing the aforementioned cached values.
+ */
+struct srpt_port {
+	struct srpt_device *sdev;
+	struct ib_mad_agent *mad_agent;
+	u8 port;
+	u16 sm_lid;
+	u16 lid;
+	union ib_gid gid;
+	struct work_struct work;
+};
+
+/**
+ * struct srpt_device - Information associated by SRPT with a single HCA.
+ * @device:        backpointer to the struct ib_device managed by the IB core.
+ * @pd:            IB protection domain.
+ * @mr:            L_Key (local key) with write access to all local memory.
+ * @srq:           Per-HCA SRQ (shared receive queue).
+ * @cm_id:         connection identifier.
+ * @dev_attr:      attributes of the InfiniBand device as obtained during the
+ *                 ib_client::add() callback.
+ * @ioctx_ring:    Per-HCA I/O context ring.
+ * @rch_list:      per-device channel list -- see also srpt_rdma_ch::list.
+ * @spinlock:      protects rch_list.
+ * @srpt_port:     information about the ports owned by this HCA.
+ * @event_handler: per-HCA asynchronous IB event handler.
+ * @dev:           per-port srpt-<portname> device instance.
+ * @scst_tgt:      SCST target information associated with this HCA.
+ * @enabled:       Whether or not this SCST target is enabled.
+ */
+struct srpt_device {
+	struct ib_device *device;
+	struct ib_pd *pd;
+	struct ib_mr *mr;
+	struct ib_srq *srq;
+	struct ib_cm_id *cm_id;
+	struct ib_device_attr dev_attr;
+	int srq_size;
+	struct srpt_ioctx **ioctx_ring;
+	struct list_head rch_list;
+	spinlock_t spinlock;
+	struct srpt_port port[2];
+	struct ib_event_handler event_handler;
+	struct device dev;
+	struct scst_tgt *scst_tgt;
+	bool enabled;
+};
+
+#endif				/* IB_SRPT_H */
+
+/*
+ * Local variables:
+ * c-basic-offset:   8
+ * indent-tabs-mode: t
+ * End:
+ */
Signed-off-by: 

diff -uprN orig/linux-2.6.35/Documentation/scst/README.srpt linux-2.6.35/Documentation/scst/README.srpt
--- orig/linux-2.6.35/Documentation/scst/README.srpt
+++ linux-2.6.35/Documentation/scst/README.srpt
@@ -0,0 +1,109 @@
+SCSI RDMA Protocol (SRP) Target driver for Linux
+=================================================
+
+The SRP Target driver is designed to work directly on top of the
+OpenFabrics OFED-1.x software stack (http://www.openfabrics.org) or
+the Infiniband drivers in the Linux kernel tree
+(http://www.kernel.org). The SRP target driver also interfaces with
+the generic SCSI target mid-level driver called SCST
+(http://scst.sourceforge.net).
+
+How-to run
+-----------
+
+A. On srp target machine
+1. Please refer to SCST's README for loading scst driver and its
+dev_handlers drivers (scst_disk, scst_vdisk block or file IO mode, nullio, ...)
+
+Example 1: working with real back-end scsi disks
+a. modprobe scst
+b. modprobe scst_disk
+c. cat /proc/scsi_tgt/scsi_tgt
+
+ibstor00:~ # cat /proc/scsi_tgt/scsi_tgt
+Device (host:ch:id:lun or name)                             Device handler
+0:0:0:0                                                     dev_disk
+4:0:0:0                                                     dev_disk
+5:0:0:0                                                     dev_disk
+6:0:0:0                                                     dev_disk
+7:0:0:0                                                     dev_disk
+
+Now you want to exclude the first scsi disk and expose the last 4 scsi disks as
+IB/SRP luns for I/O
+echo "add 4:0:0:0 0" >/proc/scsi_tgt/groups/Default/devices
+echo "add 5:0:0:0 1" >/proc/scsi_tgt/groups/Default/devices
+echo "add 6:0:0:0 2" >/proc/scsi_tgt/groups/Default/devices
+echo "add 7:0:0:0 3" >/proc/scsi_tgt/groups/Default/devices
+
+Example 2: working with VDISK FILEIO mode (using md0 device and file 10G-file)
+a. modprobe scst
+b. modprobe scst_vdisk
+c. echo "open vdisk0 /dev/md0" > /proc/scsi_tgt/vdisk/vdisk
+d. echo "open vdisk1 /10G-file" > /proc/scsi_tgt/vdisk/vdisk
+e. echo "add vdisk0 0" >/proc/scsi_tgt/groups/Default/devices
+f. echo "add vdisk1 1" >/proc/scsi_tgt/groups/Default/devices
+
+Example 3: working with VDISK BLOCKIO mode (using md0 device, sda, and cciss/c1d0)
+a. modprobe scst
+b. modprobe scst_vdisk
+c. echo "open vdisk0 /dev/md0 BLOCKIO" > /proc/scsi_tgt/vdisk/vdisk
+d. echo "open vdisk1 /dev/sda BLOCKIO" > /proc/scsi_tgt/vdisk/vdisk
+e. echo "open vdisk2 /dev/cciss/c1d0 BLOCKIO" > /proc/scsi_tgt/vdisk/vdisk
+f. echo "add vdisk0 0" >/proc/scsi_tgt/groups/Default/devices
+g. echo "add vdisk1 1" >/proc/scsi_tgt/groups/Default/devices
+h. echo "add vdisk2 2" >/proc/scsi_tgt/groups/Default/devices
+
+2. modprobe ib_srpt
+
+B. On initiator machines you can manualy do the following steps:
+1. modprobe ib_srp
+2. ibsrpdm -c (to discover new SRP target)
+3. echo <new target info> > /sys/class/infiniband_srp/srp-mthca0-1/add_target
+4. fdisk -l (will show new discovered scsi disks)
+
+Example:
+Assume that you use port 1 of first HCA in the system ie. mthca0
+
+[root@lab104 ~]# ibsrpdm -c -d /dev/infiniband/umad0
+id_ext=0002c90200226cf4,ioc_guid=0002c90200226cf4,
+dgid=fe800000000000000002c90200226cf5,pkey=ffff,service_id=0002c90200226cf4
+[root@lab104 ~]# echo id_ext=0002c90200226cf4,ioc_guid=0002c90200226cf4,
+dgid=fe800000000000000002c90200226cf5,pkey=ffff,service_id=0002c90200226cf4 >
+/sys/class/infiniband_srp/srp-mthca0-1/add_target
+
+OR
+
++ You can edit /etc/infiniband/openib.conf to load srp driver and srp HA daemon
+automatically ie. set SRP_LOAD=yes, and SRPHA_ENABLE=yes
++ To set up and use high availability feature you need dm-multipath driver
+and multipath tool
++ Please refer to OFED-1.x SRP's user manual for more in-details instructions
+on how-to enable/use HA feature
+
+To minimize QUEUE_FULL conditions, you can apply scst_increase_max_tgt_cmds
+patch from SRPT package from http://sourceforge.net/project/showfiles.php?group_id=110471
+
+Performance notes
+-----------------
+
+In some cases, for instance working with SSD devices, which consume 100%
+of a single CPU load for data transfers in their internal threads, to
+maximize IOPS it can be needed to assign for those threads dedicated
+CPUs using Linux CPU affinity facilities. No IRQ processing should be
+done on those CPUs. Check that using /proc/interrupts. See taskset
+command and Documentation/IRQ-affinity.txt in your kernel's source tree
+for how to assign CPU affinity to tasks and IRQs.
+
+The reason for that is that processing of coming commands in SIRQ context
+can be done on the same CPUs as SSD devices' threads doing data
+transfers. As the result, those threads won't receive all the CPU power
+and perform worse.
+
+Alternatively to CPU affinity assignment, you can try to enable SRP
+target's internal thread. It will allows Linux CPU scheduler to better
+distribute load among available CPUs. To enable SRP target driver's
+internal thread you should load ib_srpt module with parameter
+"thread=1".
+
+Send questions about this driver to scst-devel@xxxxxxxxxxxxxxxxxxxxx, CC:
+Vu Pham <vuhuong@xxxxxxxxxxxx> and Bart Van Assche <bart.vanassche@xxxxxxxxx>.

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