/*
 * Copyright (c) 2006 - 2009 Mellanox Technology Inc.  All rights reserved.
 * Copyright (C) 2008 - 2011 Bart Van Assche <bvanassche@acm.org>.
 *
 * 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 <linux/atomic.h>
#include <scsi/scsi_tcq.h>
#include <target/configfs_macros.h>
#include <target/target_core_base.h>
#include <target/target_core_fabric_configfs.h>
#include <target/target_core_fabric.h>
#include <target/target_core_configfs.h>
#include "ib_srpt.h"

/* Name of this kernel module. */
#define DRV_NAME                "ib_srpt"
#define DRV_VERSION             "2.0.0"
#define DRV_RELDATE             "2011-02-14"

#define SRPT_ID_STRING  "Linux SRP target"

#undef pr_fmt
#define pr_fmt(fmt) DRV_NAME " " fmt

MODULE_AUTHOR("Vu Pham and Bart Van Assche");
MODULE_DESCRIPTION("InfiniBand SCSI RDMA Protocol target "
                   "v" DRV_VERSION " (" DRV_RELDATE ")");
MODULE_LICENSE("Dual BSD/GPL");

/*
 * Global Variables
 */

static u64 srpt_service_guid;
static DEFINE_SPINLOCK(srpt_dev_lock);  /* Protects srpt_dev_list. */
static LIST_HEAD(srpt_dev_list);        /* List of srpt_device structures. */

static unsigned srp_max_req_size = DEFAULT_MAX_REQ_SIZE;
module_param(srp_max_req_size, int, 0444);
MODULE_PARM_DESC(srp_max_req_size,
                 "Maximum size of SRP request 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_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 struct ib_client srpt_client;
static struct target_fabric_configfs *srpt_target;
static void srpt_release_channel(struct srpt_rdma_ch *ch);
static int srpt_queue_status(struct se_cmd *cmd);

/**
 * opposite_dma_dir() - Swap DMA_TO_DEVICE and DMA_FROM_DEVICE.
 */
static inline
enum dma_data_direction opposite_dma_dir(enum dma_data_direction dir)
{
        switch (dir) {
        case DMA_TO_DEVICE:     return DMA_FROM_DEVICE;
        case DMA_FROM_DEVICE:   return DMA_TO_DEVICE;
        default:                return dir;
        }
}

/**
 * srpt_sdev_name() - Return the name associated with the HCA.
 *
 * Examples are ib0, ib1, ...
 */
static inline const char *srpt_sdev_name(struct srpt_device *sdev)
{
        return sdev->device->name;
}

static enum rdma_ch_state srpt_get_ch_state(struct srpt_rdma_ch *ch)
{
        unsigned long flags;
        enum rdma_ch_state state;

        spin_lock_irqsave(&ch->spinlock, flags);
        state = ch->state;
        spin_unlock_irqrestore(&ch->spinlock, flags);
        return state;
}

static enum rdma_ch_state
srpt_set_ch_state(struct srpt_rdma_ch *ch, enum rdma_ch_state new_state)
{
        unsigned long flags;
        enum rdma_ch_state prev;

        spin_lock_irqsave(&ch->spinlock, flags);
        prev = ch->state;
        ch->state = new_state;
        spin_unlock_irqrestore(&ch->spinlock, flags);
        return prev;
}

/**
 * srpt_test_and_set_ch_state() - Test and set the channel state.
 *
 * Returns true if and only if the channel state has been set to the new state.
 */
static bool
srpt_test_and_set_ch_state(struct srpt_rdma_ch *ch, enum rdma_ch_state old,
                           enum rdma_ch_state new)
{
        unsigned long flags;
        enum rdma_ch_state prev;

        spin_lock_irqsave(&ch->spinlock, flags);
        prev = ch->state;
        if (prev == old)
                ch->state = new;
        spin_unlock_irqrestore(&ch->spinlock, flags);
        return prev == old;
}

/**
 * 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;

        pr_debug("ASYNC event= %d on device= %s\n", event->event,
                 srpt_sdev_name(sdev));

        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. */
                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:
                printk(KERN_ERR "received unrecognized IB event %d\n",
                       event->event);
                break;
        }
}

/**
 * srpt_srq_event() - SRQ event callback function.
 */
static void srpt_srq_event(struct ib_event *event, void *ctx)
{
        printk(KERN_INFO "SRQ event %d\n", event->event);
}

/**
 * srpt_qp_event() - QP event callback function.
 */
static void srpt_qp_event(struct ib_event *event, struct srpt_rdma_ch *ch)
{
        pr_debug("QP event %d on cm_id=%p sess_name=%s state=%d\n",
                 event->event, ch->cm_id, ch->sess_name, srpt_get_ch_state(ch));

        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_ch_state(ch, CH_DRAINING,
                                               CH_RELEASING))
                        srpt_release_channel(ch);
                else
                        pr_debug("%s: state %d - ignored LAST_WQE.\n",
                                 ch->sess_name, srpt_get_ch_state(ch));
                break;
        default:
                printk(KERN_ERR "received unrecognized IB QP event %d\n",
                       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 = __constant_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_port *sport, u32 slot,
                         struct ib_dm_mad *mad)
{
        struct srpt_device *sdev = sport->sdev;
        struct ib_dm_ioc_profile *iocp;

        iocp = (struct ib_dm_ioc_profile *)mad->data;

        if (!slot || slot > 16) {
                mad->mad_hdr.status
                        = __constant_cpu_to_be16(DM_MAD_STATUS_INVALID_FIELD);
                return;
        }

        if (slot > 2) {
                mad->mad_hdr.status
                        = __constant_cpu_to_be16(DM_MAD_STATUS_NO_IOC);
                return;
        }

        memset(iocp, 0, sizeof *iocp);
        strcpy(iocp->id_string, 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 = __constant_cpu_to_be16(SRP_REV16A_IB_IO_CLASS);
        iocp->io_subclass = __constant_cpu_to_be16(SRP_IO_SUBCLASS);
        iocp->protocol = __constant_cpu_to_be16(SRP_PROTOCOL);
        iocp->protocol_version = __constant_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_req_size);
        iocp->rdma_size = cpu_to_be32(min(sport->port_attrib.srp_max_rdma_size,
                                          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
                        = __constant_cpu_to_be16(DM_MAD_STATUS_INVALID_FIELD);
                return;
        }

        if (slot > 2 || lo > hi || hi > 1) {
                mad->mad_hdr.status
                        = __constant_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, 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 =
                    __constant_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 =
                    __constant_cpu_to_be16(DM_MAD_STATUS_UNSUP_METHOD_ATTR);
                break;
        default:
                dm_mad->mad_hdr.status =
                    __constant_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)
                        printk(KERN_ERR "disabling MAD processing failed.\n");
                if (sport->mad_agent) {
                        ib_unregister_mad_agent(sport->mad_agent);
                        sport->mad_agent = NULL;
                }
        }
}

/**
 * srpt_alloc_ioctx() - Allocate an SRPT I/O context structure.
 */
static struct srpt_ioctx *srpt_alloc_ioctx(struct srpt_device *sdev,
                                           int ioctx_size, int dma_size,
                                           enum dma_data_direction dir)
{
        struct srpt_ioctx *ioctx;

        ioctx = kmalloc(ioctx_size, GFP_KERNEL);
        if (!ioctx)
                goto err;

        ioctx->buf = kmalloc(dma_size, GFP_KERNEL);
        if (!ioctx->buf)
                goto err_free_ioctx;

        ioctx->dma = ib_dma_map_single(sdev->device, ioctx->buf, dma_size, dir);
        if (ib_dma_mapping_error(sdev->device, ioctx->dma))
                goto err_free_buf;

        return ioctx;

err_free_buf:
        kfree(ioctx->buf);
err_free_ioctx:
        kfree(ioctx);
err:
        return NULL;
}

/**
 * srpt_free_ioctx() - Free an SRPT I/O context structure.
 */
static void srpt_free_ioctx(struct srpt_device *sdev, struct srpt_ioctx *ioctx,
                            int dma_size, enum dma_data_direction dir)
{
        if (!ioctx)
                return;

        ib_dma_unmap_single(sdev->device, ioctx->dma, dma_size, dir);
        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.
 * @ring_size:  Number of elements in the I/O context ring.
 * @ioctx_size: I/O context size.
 * @dma_size:   DMA buffer size.
 * @dir:        DMA data direction.
 */
static struct srpt_ioctx **srpt_alloc_ioctx_ring(struct srpt_device *sdev,
                                int ring_size, int ioctx_size,
                                int dma_size, enum dma_data_direction dir)
{
        struct srpt_ioctx **ring;
        int i;

        WARN_ON(ioctx_size != sizeof(struct srpt_recv_ioctx)
                && ioctx_size != sizeof(struct srpt_send_ioctx));

        ring = kmalloc(ring_size * sizeof(ring[0]), GFP_KERNEL);
        if (!ring)
                goto out;
        for (i = 0; i < ring_size; ++i) {
                ring[i] = srpt_alloc_ioctx(sdev, ioctx_size, dma_size, dir);
                if (!ring[i])
                        goto err;
                ring[i]->index = i;
        }
        goto out;

err:
        while (--i >= 0)
                srpt_free_ioctx(sdev, ring[i], dma_size, dir);
        kfree(ring);
        ring = NULL;
out:
        return ring;
}

/**
 * srpt_free_ioctx_ring() - Free the ring of SRPT I/O context structures.
 */
static void srpt_free_ioctx_ring(struct srpt_ioctx **ioctx_ring,
                                 struct srpt_device *sdev, int ring_size,
                                 int dma_size, enum dma_data_direction dir)
{
        int i;

        for (i = 0; i < ring_size; ++i)
                srpt_free_ioctx(sdev, ioctx_ring[i], dma_size, dir);
        kfree(ioctx_ring);
}

/**
 * srpt_get_cmd_state() - Get the state of a SCSI command.
 */
static enum srpt_command_state srpt_get_cmd_state(struct srpt_send_ioctx *ioctx)
{
        enum srpt_command_state state;
        unsigned long flags;

        BUG_ON(!ioctx);

        spin_lock_irqsave(&ioctx->spinlock, flags);
        state = ioctx->state;
        spin_unlock_irqrestore(&ioctx->spinlock, flags);
        return state;
}

/**
 * srpt_set_cmd_state() - Set the state of a SCSI command.
 *
 * Does not modify the state of aborted commands. Returns the previous command
 * state.
 */
static enum srpt_command_state srpt_set_cmd_state(struct srpt_send_ioctx *ioctx,
                                                  enum srpt_command_state new)
{
        enum srpt_command_state previous;
        unsigned long flags;

        BUG_ON(!ioctx);

        spin_lock_irqsave(&ioctx->spinlock, flags);
        previous = ioctx->state;
        if (previous != SRPT_STATE_DONE)
                ioctx->state = new;
        spin_unlock_irqrestore(&ioctx->spinlock, flags);

        return previous;
}

/**
 * srpt_test_and_set_cmd_state() - Test and set the state of a command.
 *
 * Returns true if and only if the previous command state was equal to 'old'.
 */
static bool srpt_test_and_set_cmd_state(struct srpt_send_ioctx *ioctx,
                                        enum srpt_command_state old,
                                        enum srpt_command_state new)
{
        enum srpt_command_state previous;
        unsigned long flags;

        WARN_ON(!ioctx);
        WARN_ON(old == SRPT_STATE_DONE);
        WARN_ON(new == SRPT_STATE_NEW);

        spin_lock_irqsave(&ioctx->spinlock, flags);
        previous = ioctx->state;
        if (previous == old)
                ioctx->state = new;
        spin_unlock_irqrestore(&ioctx->spinlock, flags);
        return previous == old;
}

/**
 * srpt_post_recv() - Post an IB receive request.
 */
static int srpt_post_recv(struct srpt_device *sdev,
                          struct srpt_recv_ioctx *ioctx)
{
        struct ib_sge list;
        struct ib_recv_wr wr, *bad_wr;

        BUG_ON(!sdev);
        wr.wr_id = encode_wr_id(SRPT_RECV, ioctx->ioctx.index);

        list.addr = ioctx->ioctx.dma;
        list.length = srp_max_req_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.
 *
 * Returns zero upon success and a non-zero value upon failure.
 */
static int srpt_post_send(struct srpt_rdma_ch *ch,
                          struct srpt_send_ioctx *ioctx, int len)
{
        struct ib_sge list;
        struct ib_send_wr wr, *bad_wr;
        struct srpt_device *sdev = ch->sport->sdev;
        int ret;

        atomic_inc(&ch->req_lim);

        ret = -ENOMEM;
        if (unlikely(atomic_dec_return(&ch->sq_wr_avail) < 0)) {
                printk(KERN_WARNING "IB send queue full (needed 1)\n");
                goto out;
        }

        ib_dma_sync_single_for_device(sdev->device, ioctx->ioctx.dma, len,
                                      DMA_TO_DEVICE);

        list.addr = ioctx->ioctx.dma;
        list.length = len;
        list.lkey = sdev->mr->lkey;

        wr.next = NULL;
        wr.wr_id = encode_wr_id(SRPT_SEND, ioctx->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);
                atomic_dec(&ch->req_lim);
        }
        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_send_ioctx *ioctx,
                             struct srp_cmd *srp_cmd,
                             enum dma_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 = DMA_NONE;
        if (srp_cmd->buf_fmt & 0xf)
                /* DATA-IN: transfer data from target to initiator (read). */
                *dir = DMA_FROM_DEVICE;
        else if (srp_cmd->buf_fmt >> 4)
                /* DATA-OUT: transfer data from initiator to target (write). */
                *dir = DMA_TO_DEVICE;

        /*
         * 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)) {
                        printk(KERN_ERR "received unsupported SRP_CMD request"
                               " type (%u out + %u in != %u / %zu)\n",
                               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_ch_qp_err() - Set the channel queue pair state to 'error'.
 */
static int srpt_ch_qp_err(struct srpt_rdma_ch *ch)
{
        struct ib_qp_attr qp_attr;

        qp_attr.qp_state = IB_QPS_ERR;
        return ib_modify_qp(ch->qp, &qp_attr, IB_QP_STATE);
}

/**
 * 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_send_ioctx *ioctx)
{
        struct scatterlist *sg;
        enum dma_data_direction dir;

        BUG_ON(!ch);
        BUG_ON(!ioctx);
        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) {
                sg = ioctx->sg;
                WARN_ON(!sg);
                dir = ioctx->cmd.data_direction;
                BUG_ON(dir == DMA_NONE);
                ib_dma_unmap_sg(ch->sport->sdev->device, sg, ioctx->sg_cnt,
                                opposite_dma_dir(dir));
                ioctx->mapped_sg_count = 0;
        }
}

/**
 * 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_send_ioctx *ioctx)
{
        struct se_cmd *cmd;
        struct scatterlist *sg, *sg_orig;
        int sg_cnt;
        enum dma_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);
        cmd = &ioctx->cmd;
        dir = cmd->data_direction;
        BUG_ON(dir == DMA_NONE);

        ioctx->sg = sg = sg_orig = cmd->t_data_sg;
        ioctx->sg_cnt = sg_cnt = cmd->t_data_nents;

        count = ib_dma_map_sg(ch->sport->sdev->device, sg, sg_cnt,
                              opposite_dma_dir(dir));
        if (unlikely(!count))
                return -EAGAIN;

        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 - 1) / SRPT_DEF_SG_PER_WQE
                        + ioctx->n_rbuf;

                ioctx->rdma_ius = kzalloc(nrdma * sizeof *riu, GFP_KERNEL);
                if (!ioctx->rdma_ius)
                        goto free_mem;

                ioctx->n_rdma_ius = nrdma;
        }

        db = ioctx->rbufs;
        tsize = cmd->data_length;
        dma_len = sg_dma_len(&sg[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) {
                                                sg = sg_next(sg);
                                                dma_len = sg_dma_len(sg);
                                        }
                                }
                        } 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,
                                            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,
                                   GFP_KERNEL);
                if (!riu->sge)
                        goto free_mem;
        }

        db = ioctx->rbufs;
        tsize = cmd->data_length;
        riu = ioctx->rdma_ius;
        sg = sg_orig;
        dma_len = sg_dma_len(&sg[0]);
        dma_addr = sg_dma_address(&sg[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) {
                                                sg = sg_next(sg);
                                                dma_len = sg_dma_len(sg);
                                                dma_addr = sg_dma_address(sg);
                                        }
                                }
                        } 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 && tsize > 0) {
                                ++riu;
                                sge = riu->sge;
                                k = 0;
                        } else if (rsize > 0 && tsize > 0)
                                ++sge;
                }
        }

        return 0;

free_mem:
        srpt_unmap_sg_to_ib_sge(ch, ioctx);

        return -ENOMEM;
}

/**
 * srpt_get_send_ioctx() - Obtain an I/O context for sending to the initiator.
 */
static struct srpt_send_ioctx *srpt_get_send_ioctx(struct srpt_rdma_ch *ch)
{
        struct srpt_send_ioctx *ioctx;
        unsigned long flags;

        BUG_ON(!ch);

        ioctx = NULL;
        spin_lock_irqsave(&ch->spinlock, flags);
        if (!list_empty(&ch->free_list)) {
                ioctx = list_first_entry(&ch->free_list,
                                         struct srpt_send_ioctx, free_list);
                list_del(&ioctx->free_list);
        }
        spin_unlock_irqrestore(&ch->spinlock, flags);

        if (!ioctx)
                return ioctx;

        BUG_ON(ioctx->ch != ch);
        kref_init(&ioctx->kref);
        spin_lock_init(&ioctx->spinlock);
        ioctx->state = SRPT_STATE_NEW;
        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;
        init_completion(&ioctx->tx_done);
        ioctx->queue_status_only = false;
        /*
         * transport_init_se_cmd() does not initialize all fields, so do it
         * here.
         */
        memset(&ioctx->cmd, 0, sizeof(ioctx->cmd));
        memset(&ioctx->sense_data, 0, sizeof(ioctx->sense_data));

        return ioctx;
}

/**
 * srpt_put_send_ioctx() - Free up resources.
 */
static void srpt_put_send_ioctx(struct srpt_send_ioctx *ioctx)
{
        struct srpt_rdma_ch *ch;
        unsigned long flags;

        BUG_ON(!ioctx);
        ch = ioctx->ch;
        BUG_ON(!ch);

        WARN_ON(srpt_get_cmd_state(ioctx) != SRPT_STATE_DONE);

        srpt_unmap_sg_to_ib_sge(ioctx->ch, ioctx);
        transport_generic_free_cmd(&ioctx->cmd, 0);

        if (ioctx->n_rbuf > 1) {
                kfree(ioctx->rbufs);
                ioctx->rbufs = NULL;
                ioctx->n_rbuf = 0;
        }

        spin_lock_irqsave(&ch->spinlock, flags);
        list_add(&ioctx->free_list, &ch->free_list);
        spin_unlock_irqrestore(&ch->spinlock, flags);
}

static void srpt_put_send_ioctx_kref(struct kref *kref)
{
        srpt_put_send_ioctx(container_of(kref, struct srpt_send_ioctx, kref));
}

/**
 * srpt_abort_cmd() - Abort a SCSI command.
 * @ioctx:   I/O context associated with the SCSI command.
 * @context: Preferred execution context.
 */
static int srpt_abort_cmd(struct srpt_send_ioctx *ioctx)
{
        enum srpt_command_state state;
        unsigned long flags;

        BUG_ON(!ioctx);

        /*
         * If the command is in a state where the target core is waiting for
         * the ib_srpt driver, change the state to the next state. Changing
         * the state of the command from SRPT_STATE_NEED_DATA to
         * SRPT_STATE_DATA_IN ensures that srpt_xmit_response() will call this
         * function a second time.
         */

        spin_lock_irqsave(&ioctx->spinlock, flags);
        state = ioctx->state;
        switch (state) {
        case SRPT_STATE_NEED_DATA:
                ioctx->state = SRPT_STATE_DATA_IN;
                break;
        case SRPT_STATE_DATA_IN:
        case SRPT_STATE_CMD_RSP_SENT:
        case SRPT_STATE_MGMT_RSP_SENT:
                ioctx->state = SRPT_STATE_DONE;
                break;
        default:
                break;
        }
        spin_unlock_irqrestore(&ioctx->spinlock, flags);

        if (state == SRPT_STATE_DONE)
                goto out;

        pr_debug("Aborting cmd with state %d and tag %lld\n", state,
                 ioctx->tag);

        switch (state) {
        case SRPT_STATE_NEW:
        case SRPT_STATE_DATA_IN:
        case SRPT_STATE_MGMT:
                /*
                 * Do nothing - defer abort processing until
                 * srpt_queue_response() is invoked.
                 */
                WARN_ON(!transport_check_aborted_status(&ioctx->cmd, false));
                break;
        case SRPT_STATE_NEED_DATA:
                /* DMA_TO_DEVICE (write) - RDMA read error. */

                /* XXX(hch): this is a horrible layering violation.. */
                spin_lock_irqsave(&ioctx->cmd.t_state_lock, flags);
                ioctx->cmd.transport_state |= CMD_T_LUN_STOP;
                ioctx->cmd.transport_state &= ~CMD_T_ACTIVE;
                spin_unlock_irqrestore(&ioctx->cmd.t_state_lock, flags);

                complete(&ioctx->cmd.transport_lun_stop_comp);
                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);
                spin_lock_irqsave(&ioctx->cmd.t_state_lock, flags);
                ioctx->cmd.transport_state |= CMD_T_LUN_STOP;
                spin_unlock_irqrestore(&ioctx->cmd.t_state_lock, flags);
                kref_put(&ioctx->kref, srpt_put_send_ioctx_kref);
                break;
        case SRPT_STATE_MGMT_RSP_SENT:
                srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);
                kref_put(&ioctx->kref, srpt_put_send_ioctx_kref);
                break;
        default:
                WARN_ON("ERROR: unexpected command state");
                break;
        }

out:
        return state;
}

/**
 * srpt_handle_send_err_comp() - Process an IB_WC_SEND error completion.
 */
static void srpt_handle_send_err_comp(struct srpt_rdma_ch *ch, u64 wr_id)
{
        struct srpt_send_ioctx *ioctx;
        enum srpt_command_state state;
        struct se_cmd *cmd;
        u32 index;

        atomic_inc(&ch->sq_wr_avail);

        index = idx_from_wr_id(wr_id);
        ioctx = ch->ioctx_ring[index];
        state = srpt_get_cmd_state(ioctx);
        cmd = &ioctx->cmd;

        WARN_ON(state != SRPT_STATE_CMD_RSP_SENT
                && state != SRPT_STATE_MGMT_RSP_SENT
                && state != SRPT_STATE_NEED_DATA
                && state != SRPT_STATE_DONE);

        /* If SRP_RSP sending failed, undo the ch->req_lim change. */
        if (state == SRPT_STATE_CMD_RSP_SENT
            || state == SRPT_STATE_MGMT_RSP_SENT)
                atomic_dec(&ch->req_lim);

        srpt_abort_cmd(ioctx);
}

/**
 * srpt_handle_send_comp() - Process an IB send completion notification.
 */
static void srpt_handle_send_comp(struct srpt_rdma_ch *ch,
                                  struct srpt_send_ioctx *ioctx)
{
        enum srpt_command_state state;

        atomic_inc(&ch->sq_wr_avail);

        state = srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);

        if (WARN_ON(state != SRPT_STATE_CMD_RSP_SENT
                    && state != SRPT_STATE_MGMT_RSP_SENT
                    && state != SRPT_STATE_DONE))
                pr_debug("state = %d\n", state);

        if (state != SRPT_STATE_DONE)
                kref_put(&ioctx->kref, srpt_put_send_ioctx_kref);
        else
                printk(KERN_ERR "IB completion has been received too late for"
                       " wr_id = %u.\n", ioctx->ioctx.index);
}

/**
 * srpt_handle_rdma_comp() - Process an IB RDMA completion notification.
 *
 * XXX: what is now target_execute_cmd used to be asynchronous, and unmapping
 * the data that has been transferred via IB RDMA had to be postponed until the
 * check_stop_free() callback.  None of this is necessary anymore and needs to
 * be cleaned up.
 */
static void srpt_handle_rdma_comp(struct srpt_rdma_ch *ch,
                                  struct srpt_send_ioctx *ioctx,
                                  enum srpt_opcode opcode)
{
        WARN_ON(ioctx->n_rdma <= 0);
        atomic_add(ioctx->n_rdma, &ch->sq_wr_avail);

        if (opcode == SRPT_RDMA_READ_LAST) {
                if (srpt_test_and_set_cmd_state(ioctx, SRPT_STATE_NEED_DATA,
                                                SRPT_STATE_DATA_IN))
                        target_execute_cmd(&ioctx->cmd);
                else
                        printk(KERN_ERR "%s[%d]: wrong state = %d\n", __func__,
                               __LINE__, srpt_get_cmd_state(ioctx));
        } else if (opcode == SRPT_RDMA_ABORT) {
                ioctx->rdma_aborted = true;
        } else {
                WARN(true, "unexpected opcode %d\n", opcode);
        }
}

/**
 * srpt_handle_rdma_err_comp() - Process an IB RDMA error completion.
 */
static void srpt_handle_rdma_err_comp(struct srpt_rdma_ch *ch,
                                      struct srpt_send_ioctx *ioctx,
                                      enum srpt_opcode opcode)
{
        struct se_cmd *cmd;
        enum srpt_command_state state;
        unsigned long flags;

        cmd = &ioctx->cmd;
        state = srpt_get_cmd_state(ioctx);
        switch (opcode) {
        case SRPT_RDMA_READ_LAST:
                if (ioctx->n_rdma <= 0) {
                        printk(KERN_ERR "Received invalid RDMA read"
                               " error completion with idx %d\n",
                               ioctx->ioctx.index);
                        break;
                }
                atomic_add(ioctx->n_rdma, &ch->sq_wr_avail);
                if (state == SRPT_STATE_NEED_DATA)
                        srpt_abort_cmd(ioctx);
                else
                        printk(KERN_ERR "%s[%d]: wrong state = %d\n",
                               __func__, __LINE__, state);
                break;
        case SRPT_RDMA_WRITE_LAST:
                spin_lock_irqsave(&ioctx->cmd.t_state_lock, flags);
                ioctx->cmd.transport_state |= CMD_T_LUN_STOP;
                spin_unlock_irqrestore(&ioctx->cmd.t_state_lock, flags);
                break;
        default:
                printk(KERN_ERR "%s[%d]: opcode = %u\n", __func__,
                       __LINE__, opcode);
                break;
        }
}

/**
 * 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.
 *
 * 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_send_ioctx *ioctx, u64 tag,
                              int status)
{
        struct srp_rsp *srp_rsp;
        const u8 *sense_data;
        int sense_data_len, max_sense_len;

        /*
         * The lowest bit of all SAM-3 status codes is zero (see also
         * paragraph 5.3 in SAM-3).
         */
        WARN_ON(status & 1);

        srp_rsp = ioctx->ioctx.buf;
        BUG_ON(!srp_rsp);

        sense_data = ioctx->sense_data;
        sense_data_len = ioctx->cmd.scsi_sense_length;
        WARN_ON(sense_data_len > sizeof(ioctx->sense_data));

        memset(srp_rsp, 0, sizeof *srp_rsp);
        srp_rsp->opcode = SRP_RSP;
        srp_rsp->req_lim_delta =
                __constant_cpu_to_be32(1 + atomic_xchg(&ch->req_lim_delta, 0));
        srp_rsp->tag = tag;
        srp_rsp->status = status;

        if (sense_data_len) {
                BUILD_BUG_ON(MIN_MAX_RSP_SIZE <= sizeof(*srp_rsp));
                max_sense_len = ch->max_ti_iu_len - sizeof(*srp_rsp);
                if (sense_data_len > max_sense_len) {
                        printk(KERN_WARNING "truncated sense data from %d to %d"
                               " bytes\n", 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_send_ioctx *ioctx,
                                  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->ioctx.buf;
        BUG_ON(!srp_rsp);
        memset(srp_rsp, 0, sizeof *srp_rsp);

        srp_rsp->opcode = SRP_RSP;
        srp_rsp->req_lim_delta = __constant_cpu_to_be32(1
                                    + atomic_xchg(&ch->req_lim_delta, 0));
        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;
}

#define NO_SUCH_LUN ((uint64_t)-1LL)

/*
 * SCSI LUN addressing method. See also SAM-2 and the section about
 * eight byte LUNs.
 */
enum scsi_lun_addr_method {
        SCSI_LUN_ADDR_METHOD_PERIPHERAL   = 0,
        SCSI_LUN_ADDR_METHOD_FLAT         = 1,
        SCSI_LUN_ADDR_METHOD_LUN          = 2,
        SCSI_LUN_ADDR_METHOD_EXTENDED_LUN = 3,
};

/*
 * srpt_unpack_lun() - Convert from network LUN to linear LUN.
 *
 * Convert an 2-byte, 4-byte, 6-byte or 8-byte LUN structure in network byte
 * order (big endian) to a linear LUN. Supports three LUN addressing methods:
 * peripheral, flat and logical unit. See also SAM-2, section 4.9.4 (page 40).
 */
static uint64_t srpt_unpack_lun(const uint8_t *lun, int len)
{
        uint64_t res = NO_SUCH_LUN;
        int addressing_method;

        if (unlikely(len < 2)) {
                printk(KERN_ERR "Illegal LUN length %d, expected 2 bytes or "
                       "more", len);
                goto out;
        }

        switch (len) {
        case 8:
                if ((*((__be64 *)lun) &
                     __constant_cpu_to_be64(0x0000FFFFFFFFFFFFLL)) != 0)
                        goto out_err;
                break;
        case 4:
                if (*((__be16 *)&lun[2]) != 0)
                        goto out_err;
                break;
        case 6:
                if (*((__be32 *)&lun[2]) != 0)
                        goto out_err;
                break;
        case 2:
                break;
        default:
                goto out_err;
        }

        addressing_method = (*lun) >> 6; /* highest two bits of byte 0 */
        switch (addressing_method) {
        case SCSI_LUN_ADDR_METHOD_PERIPHERAL:
        case SCSI_LUN_ADDR_METHOD_FLAT:
        case SCSI_LUN_ADDR_METHOD_LUN:
                res = *(lun + 1) | (((*lun) & 0x3f) << 8);
                break;

        case SCSI_LUN_ADDR_METHOD_EXTENDED_LUN:
        default:
                printk(KERN_ERR "Unimplemented LUN addressing method %u",
                       addressing_method);
                break;
        }

out:
        return res;

out_err:
        printk(KERN_ERR "Support for multi-level LUNs has not yet been"
               " implemented");
        goto out;
}

static int srpt_check_stop_free(struct se_cmd *cmd)
{
        struct srpt_send_ioctx *ioctx;

        ioctx = container_of(cmd, struct srpt_send_ioctx, cmd);
        return kref_put(&ioctx->kref, srpt_put_send_ioctx_kref);
}

/**
 * srpt_handle_cmd() - Process SRP_CMD.
 */
static int srpt_handle_cmd(struct srpt_rdma_ch *ch,
                           struct srpt_recv_ioctx *recv_ioctx,
                           struct srpt_send_ioctx *send_ioctx)
{
        struct se_cmd *cmd;
        struct srp_cmd *srp_cmd;
        uint64_t unpacked_lun;
        u64 data_len;
        enum dma_data_direction dir;
        int ret;

        BUG_ON(!send_ioctx);

        srp_cmd = recv_ioctx->ioctx.buf;
        kref_get(&send_ioctx->kref);
        cmd = &send_ioctx->cmd;
        send_ioctx->tag = srp_cmd->tag;

        switch (srp_cmd->task_attr) {
        case SRP_CMD_SIMPLE_Q:
                cmd->sam_task_attr = MSG_SIMPLE_TAG;
                break;
        case SRP_CMD_ORDERED_Q:
        default:
                cmd->sam_task_attr = MSG_ORDERED_TAG;
                break;
        case SRP_CMD_HEAD_OF_Q:
                cmd->sam_task_attr = MSG_HEAD_TAG;
                break;
        case SRP_CMD_ACA:
                cmd->sam_task_attr = MSG_ACA_TAG;
                break;
        }

        ret = srpt_get_desc_tbl(send_ioctx, srp_cmd, &dir, &data_len);
        if (ret) {
                printk(KERN_ERR "0x%llx: parsing SRP descriptor table failed.\n",
                       srp_cmd->tag);
                cmd->se_cmd_flags |= SCF_SCSI_CDB_EXCEPTION;
                cmd->scsi_sense_reason = TCM_INVALID_CDB_FIELD;
                kref_put(&send_ioctx->kref, srpt_put_send_ioctx_kref);
                goto send_sense;
        }

        cmd->data_length = data_len;
        cmd->data_direction = dir;
        unpacked_lun = srpt_unpack_lun((uint8_t *)&srp_cmd->lun,
                                       sizeof(srp_cmd->lun));
        if (transport_lookup_cmd_lun(cmd, unpacked_lun) < 0) {
                kref_put(&send_ioctx->kref, srpt_put_send_ioctx_kref);
                goto send_sense;
        }
        ret = target_setup_cmd_from_cdb(cmd, srp_cmd->cdb);
        if (ret < 0) {
                kref_put(&send_ioctx->kref, srpt_put_send_ioctx_kref);
                if (cmd->se_cmd_flags & SCF_SCSI_RESERVATION_CONFLICT) {
                        srpt_queue_status(cmd);
                        return 0;
                } else
                        goto send_sense;
        }

        transport_handle_cdb_direct(cmd);
        return 0;

send_sense:
        transport_send_check_condition_and_sense(cmd, cmd->scsi_sense_reason,
                                                 0);
        return -1;
}

/**
 * srpt_rx_mgmt_fn_tag() - Process a task management function by tag.
 * @ch: RDMA channel of the task management request.
 * @fn: Task management function to perform.
 * @req_tag: Tag of the SRP task management request.
 * @mgmt_ioctx: I/O context of the task management request.
 *
 * Returns zero if the target core will process the task management
 * request asynchronously.
 *
 * Note: It is assumed that the initiator serializes tag-based task management
 * requests.
 */
static int srpt_rx_mgmt_fn_tag(struct srpt_send_ioctx *ioctx, u64 tag)
{
        struct srpt_device *sdev;
        struct srpt_rdma_ch *ch;
        struct srpt_send_ioctx *target;
        int ret, i;

        ret = -EINVAL;
        ch = ioctx->ch;
        BUG_ON(!ch);
        BUG_ON(!ch->sport);
        sdev = ch->sport->sdev;
        BUG_ON(!sdev);
        spin_lock_irq(&sdev->spinlock);
        for (i = 0; i < ch->rq_size; ++i) {
                target = ch->ioctx_ring[i];
                if (target->cmd.se_lun == ioctx->cmd.se_lun &&
                    target->tag == tag &&
                    srpt_get_cmd_state(target) != SRPT_STATE_DONE) {
                        ret = 0;
                        /* now let the target core abort &target->cmd; */
                        break;
                }
        }
        spin_unlock_irq(&sdev->spinlock);
        return ret;
}

static int srp_tmr_to_tcm(int fn)
{
        switch (fn) {
        case SRP_TSK_ABORT_TASK:
                return TMR_ABORT_TASK;
        case SRP_TSK_ABORT_TASK_SET:
                return TMR_ABORT_TASK_SET;
        case SRP_TSK_CLEAR_TASK_SET:
                return TMR_CLEAR_TASK_SET;
        case SRP_TSK_LUN_RESET:
                return TMR_LUN_RESET;
        case SRP_TSK_CLEAR_ACA:
                return TMR_CLEAR_ACA;
        default:
                return -1;
        }
}

/**
 * srpt_handle_tsk_mgmt() - Process an SRP_TSK_MGMT information unit.
 *
 * Returns 0 if and only if the request will be processed by the target core.
 *
 * For more information about SRP_TSK_MGMT information units, see also section
 * 6.7 in the SRP r16a document.
 */
static void srpt_handle_tsk_mgmt(struct srpt_rdma_ch *ch,
                                 struct srpt_recv_ioctx *recv_ioctx,
                                 struct srpt_send_ioctx *send_ioctx)
{
        struct srp_tsk_mgmt *srp_tsk;
        struct se_cmd *cmd;
        uint64_t unpacked_lun;
        int tcm_tmr;
        int res;

        BUG_ON(!send_ioctx);

        srp_tsk = recv_ioctx->ioctx.buf;
        cmd = &send_ioctx->cmd;

        pr_debug("recv tsk_mgmt fn %d for task_tag %lld and cmd tag %lld"
                 " cm_id %p sess %p\n", srp_tsk->tsk_mgmt_func,
                 srp_tsk->task_tag, srp_tsk->tag, ch->cm_id, ch->sess);

        srpt_set_cmd_state(send_ioctx, SRPT_STATE_MGMT);
        send_ioctx->tag = srp_tsk->tag;
        tcm_tmr = srp_tmr_to_tcm(srp_tsk->tsk_mgmt_func);
        if (tcm_tmr < 0) {
                send_ioctx->cmd.se_cmd_flags |= SCF_SCSI_CDB_EXCEPTION;
                send_ioctx->cmd.se_tmr_req->response =
                        TMR_TASK_MGMT_FUNCTION_NOT_SUPPORTED;
                goto process_tmr;
        }
        res = core_tmr_alloc_req(cmd, NULL, tcm_tmr, GFP_KERNEL);
        if (res < 0) {
                send_ioctx->cmd.se_cmd_flags |= SCF_SCSI_CDB_EXCEPTION;
                send_ioctx->cmd.se_tmr_req->response = TMR_FUNCTION_REJECTED;
                goto process_tmr;
        }

        unpacked_lun = srpt_unpack_lun((uint8_t *)&srp_tsk->lun,
                                       sizeof(srp_tsk->lun));
        res = transport_lookup_tmr_lun(&send_ioctx->cmd, unpacked_lun);
        if (res) {
                pr_debug("rejecting TMR for LUN %lld\n", unpacked_lun);
                send_ioctx->cmd.se_cmd_flags |= SCF_SCSI_CDB_EXCEPTION;
                send_ioctx->cmd.se_tmr_req->response = TMR_LUN_DOES_NOT_EXIST;
                goto process_tmr;
        }

        if (srp_tsk->tsk_mgmt_func == SRP_TSK_ABORT_TASK)
                srpt_rx_mgmt_fn_tag(send_ioctx, srp_tsk->task_tag);

process_tmr:
        kref_get(&send_ioctx->kref);
        if (!(send_ioctx->cmd.se_cmd_flags & SCF_SCSI_CDB_EXCEPTION))
                transport_generic_handle_tmr(&send_ioctx->cmd);
        else
                transport_send_check_condition_and_sense(cmd,
                                                cmd->scsi_sense_reason, 0);

}

/**
 * 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_recv_ioctx *recv_ioctx,
                               struct srpt_send_ioctx *send_ioctx)
{
        struct srp_cmd *srp_cmd;
        enum rdma_ch_state ch_state;

        BUG_ON(!ch);
        BUG_ON(!recv_ioctx);

        ib_dma_sync_single_for_cpu(ch->sport->sdev->device,
                                   recv_ioctx->ioctx.dma, srp_max_req_size,
                                   DMA_FROM_DEVICE);

        ch_state = srpt_get_ch_state(ch);
        if (unlikely(ch_state == CH_CONNECTING)) {
                list_add_tail(&recv_ioctx->wait_list, &ch->cmd_wait_list);
                goto out;
        }

        if (unlikely(ch_state != CH_LIVE))
                goto out;

        srp_cmd = recv_ioctx->ioctx.buf;
        if (srp_cmd->opcode == SRP_CMD || srp_cmd->opcode == SRP_TSK_MGMT) {
                if (!send_ioctx)
                        send_ioctx = srpt_get_send_ioctx(ch);
                if (unlikely(!send_ioctx)) {
                        list_add_tail(&recv_ioctx->wait_list,
                                      &ch->cmd_wait_list);
                        goto out;
                }
        }

        transport_init_se_cmd(&send_ioctx->cmd, &srpt_target->tf_ops, ch->sess,
                              0, DMA_NONE, MSG_SIMPLE_TAG,
                              send_ioctx->sense_data);

        switch (srp_cmd->opcode) {
        case SRP_CMD:
                srpt_handle_cmd(ch, recv_ioctx, send_ioctx);
                break;
        case SRP_TSK_MGMT:
                srpt_handle_tsk_mgmt(ch, recv_ioctx, send_ioctx);
                break;
        case SRP_I_LOGOUT:
                printk(KERN_ERR "Not yet implemented: SRP_I_LOGOUT\n");
                break;
        case SRP_CRED_RSP:
                pr_debug("received SRP_CRED_RSP\n");
                break;
        case SRP_AER_RSP:
                pr_debug("received SRP_AER_RSP\n");
                break;
        case SRP_RSP:
                printk(KERN_ERR "Received SRP_RSP\n");
                break;
        default:
                printk(KERN_ERR "received IU with unknown opcode 0x%x\n",
                       srp_cmd->opcode);
                break;
        }

        srpt_post_recv(ch->sport->sdev, recv_ioctx);
out:
        return;
}

static void srpt_process_rcv_completion(struct ib_cq *cq,
                                        struct srpt_rdma_ch *ch,
                                        struct ib_wc *wc)
{
        struct srpt_device *sdev = ch->sport->sdev;
        struct srpt_recv_ioctx *ioctx;
        u32 index;

        index = idx_from_wr_id(wc->wr_id);
        if (wc->status == IB_WC_SUCCESS) {
                int req_lim;

                req_lim = atomic_dec_return(&ch->req_lim);
                if (unlikely(req_lim < 0))
                        printk(KERN_ERR "req_lim = %d < 0\n", req_lim);
                ioctx = sdev->ioctx_ring[index];
                srpt_handle_new_iu(ch, ioctx, NULL);
        } else {
                printk(KERN_INFO "receiving failed for idx %u with status %d\n",
                       index, wc->status);
        }
}

/**
 * srpt_process_send_completion() - Process an IB send completion.
 *
 * Note: Although this has not yet been observed during tests, at least in
 * theory it is possible that the srpt_get_send_ioctx() call invoked by
 * srpt_handle_new_iu() fails. This is possible because the req_lim_delta
 * value in each response is set to one, and it is possible that this response
 * makes the initiator send a new request before the send completion for that
 * response has been processed. This could e.g. happen if the call to
 * srpt_put_send_iotcx() is delayed because of a higher priority interrupt or
 * if IB retransmission causes generation of the send completion to be
 * delayed. Incoming information units for which srpt_get_send_ioctx() fails
 * are queued on cmd_wait_list. The code below processes these delayed
 * requests one at a time.
 */
static void srpt_process_send_completion(struct ib_cq *cq,
                                         struct srpt_rdma_ch *ch,
                                         struct ib_wc *wc)
{
        struct srpt_send_ioctx *send_ioctx;
        uint32_t index;
        enum srpt_opcode opcode;

        index = idx_from_wr_id(wc->wr_id);
        opcode = opcode_from_wr_id(wc->wr_id);
        send_ioctx = ch->ioctx_ring[index];
        if (wc->status == IB_WC_SUCCESS) {
                if (opcode == SRPT_SEND)
                        srpt_handle_send_comp(ch, send_ioctx);
                else {
                        WARN_ON(opcode != SRPT_RDMA_ABORT &&
                                wc->opcode != IB_WC_RDMA_READ);
                        srpt_handle_rdma_comp(ch, send_ioctx, opcode);
                }
        } else {
                if (opcode == SRPT_SEND) {
                        printk(KERN_INFO "sending response for idx %u failed"
                               " with status %d\n", index, wc->status);
                        srpt_handle_send_err_comp(ch, wc->wr_id);
                } else if (opcode != SRPT_RDMA_MID) {
                        printk(KERN_INFO "RDMA t %d for idx %u failed with"
                                " status %d", opcode, index, wc->status);
                        srpt_handle_rdma_err_comp(ch, send_ioctx, opcode);
                }
        }

        while (unlikely(opcode == SRPT_SEND
                        && !list_empty(&ch->cmd_wait_list)
                        && srpt_get_ch_state(ch) == CH_LIVE
                        && (send_ioctx = srpt_get_send_ioctx(ch)) != NULL)) {
                struct srpt_recv_ioctx *recv_ioctx;

                recv_ioctx = list_first_entry(&ch->cmd_wait_list,
                                              struct srpt_recv_ioctx,
                                              wait_list);
                list_del(&recv_ioctx->wait_list);
                srpt_handle_new_iu(ch, recv_ioctx, send_ioctx);
        }
}

static void srpt_process_completion(struct ib_cq *cq, struct srpt_rdma_ch *ch)
{
        struct ib_wc *const wc = ch->wc;
        int i, n;

        WARN_ON(cq != ch->cq);

        ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
        while ((n = ib_poll_cq(cq, ARRAY_SIZE(ch->wc), wc)) > 0) {
                for (i = 0; i < n; i++) {
                        if (opcode_from_wr_id(wc[i].wr_id) == SRPT_RECV)
                                srpt_process_rcv_completion(cq, ch, &wc[i]);
                        else
                                srpt_process_send_completion(cq, ch, &wc[i]);
                }
        }
}

/**
 * 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;

        wake_up_interruptible(&ch->wait_queue);
}

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);
        printk(KERN_INFO "Session %s: kernel thread %s (PID %d) started\n",
               ch->sess_name, ch->thread->comm, current->pid);
        while (!kthread_should_stop()) {
                wait_event_interruptible(ch->wait_queue,
                        (srpt_process_completion(ch->cq, ch),
                         kthread_should_stop()));
        }
        printk(KERN_INFO "Session %s: kernel thread %s (PID %d) stopped\n",
               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_port *sport = ch->sport;
        struct srpt_device *sdev = sport->sdev;
        u32 srp_sq_size = sport->port_attrib.srp_sq_size;
        int ret;

        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 + srp_sq_size, 0);
        if (IS_ERR(ch->cq)) {
                ret = PTR_ERR(ch->cq);
                printk(KERN_ERR "failed to create CQ cqe= %d ret= %d\n",
                       ch->rq_size + srp_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 = srp_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);
                printk(KERN_ERR "failed to create_qp ret= %d\n", ret);
                goto err_destroy_cq;
        }

        atomic_set(&ch->sq_wr_avail, qp_init->cap.max_send_wr);

        pr_debug("%s: max_cqe= %d max_sge= %d sq_size = %d cm_id= %p\n",
                 __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;

        init_waitqueue_head(&ch->wait_queue);

        pr_debug("creating thread for session %s\n", ch->sess_name);

        ch->thread = kthread_run(srpt_compl_thread, ch, "ib_srpt_compl");
        if (IS_ERR(ch->thread)) {
                printk(KERN_ERR "failed to create kernel thread %ld\n",
                       PTR_ERR(ch->thread));
                ch->thread = NULL;
                goto err_destroy_qp;
        }

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)
{
        if (ch->thread)
                kthread_stop(ch->thread);

        ib_destroy_qp(ch->qp);
        ib_destroy_cq(ch->cq);
}

/**
 * __srpt_close_ch() - Close an RDMA channel by setting the QP error state.
 *
 * Reset the QP and make sure all resources associated with the channel will
 * be deallocated at an appropriate time.
 *
 * Note: The caller must hold ch->sport->sdev->spinlock.
 */
static void __srpt_close_ch(struct srpt_rdma_ch *ch)
{
        struct srpt_device *sdev;
        enum rdma_ch_state prev_state;
        unsigned long flags;

        sdev = ch->sport->sdev;

        spin_lock_irqsave(&ch->spinlock, flags);
        prev_state = ch->state;
        switch (prev_state) {
        case CH_CONNECTING:
        case CH_LIVE:
                ch->state = CH_DISCONNECTING;
                break;
        default:
                break;
        }
        spin_unlock_irqrestore(&ch->spinlock, flags);

        switch (prev_state) {
        case CH_CONNECTING:
                ib_send_cm_rej(ch->cm_id, IB_CM_REJ_NO_RESOURCES, NULL, 0,
                               NULL, 0);
                /* fall through */
        case CH_LIVE:
                if (ib_send_cm_dreq(ch->cm_id, NULL, 0) < 0)
                        printk(KERN_ERR "sending CM DREQ failed.\n");
                break;
        case CH_DISCONNECTING:
                break;
        case CH_DRAINING:
        case CH_RELEASING:
                break;
        }
}

/**
 * srpt_close_ch() - Close an RDMA channel.
 */
static void srpt_close_ch(struct srpt_rdma_ch *ch)
{
        struct srpt_device *sdev;

        sdev = ch->sport->sdev;
        spin_lock_irq(&sdev->spinlock);
        __srpt_close_ch(ch);
        spin_unlock_irq(&sdev->spinlock);
}

/**
 * srpt_drain_channel() - Drain a channel by resetting the IB queue pair.
 * @cm_id: Pointer to the CM ID of the channel to be drained.
 *
 * 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 target sessions for the associated IB device have been
 * unregistered and target 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_drain_channel(struct ib_cm_id *cm_id)
{
        struct srpt_device *sdev;
        struct srpt_rdma_ch *ch;
        int ret;
        bool do_reset = false;

        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) {
                        do_reset = srpt_test_and_set_ch_state(ch,
                                        CH_CONNECTING, CH_DRAINING) ||
                                   srpt_test_and_set_ch_state(ch,
                                        CH_LIVE, CH_DRAINING) ||
                                   srpt_test_and_set_ch_state(ch,
                                        CH_DISCONNECTING, CH_DRAINING);
                        break;
                }
        }
        spin_unlock_irq(&sdev->spinlock);

        if (do_reset) {
                ret = srpt_ch_qp_err(ch);
                if (ret < 0)
                        printk(KERN_ERR "Setting queue pair in error state"
                               " failed: %d\n", ret);
        }
}

/**
 * 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;

        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 channel resources.
 *
 * Schedules the actual release because:
 * - Calling the ib_destroy_cm_id() call from inside an IB CM callback would
 *   trigger a deadlock.
 * - It is not safe to call TCM transport_* functions from interrupt context.
 */
static void srpt_release_channel(struct srpt_rdma_ch *ch)
{
        schedule_work(&ch->release_work);
}

static void srpt_release_channel_work(struct work_struct *w)
{
        struct srpt_rdma_ch *ch;
        struct srpt_device *sdev;

        ch = container_of(w, struct srpt_rdma_ch, release_work);
        pr_debug("ch = %p; ch->sess = %p; release_done = %p\n", ch, ch->sess,
                 ch->release_done);

        sdev = ch->sport->sdev;
        BUG_ON(!sdev);

        transport_deregister_session_configfs(ch->sess);
        transport_deregister_session(ch->sess);
        ch->sess = NULL;

        srpt_destroy_ch_ib(ch);

        srpt_free_ioctx_ring((struct srpt_ioctx **)ch->ioctx_ring,
                             ch->sport->sdev, ch->rq_size,
                             ch->rsp_size, DMA_TO_DEVICE);

        spin_lock_irq(&sdev->spinlock);
        list_del(&ch->list);
        spin_unlock_irq(&sdev->spinlock);

        ib_destroy_cm_id(ch->cm_id);

        if (ch->release_done)
                complete(ch->release_done);

        wake_up(&sdev->ch_releaseQ);

        kfree(ch);
}

static struct srpt_node_acl *__srpt_lookup_acl(struct srpt_port *sport,
                                               u8 i_port_id[16])
{
        struct srpt_node_acl *nacl;

        list_for_each_entry(nacl, &sport->port_acl_list, list)
                if (memcmp(nacl->i_port_id, i_port_id,
                           sizeof(nacl->i_port_id)) == 0)
                        return nacl;

        return NULL;
}

static struct srpt_node_acl *srpt_lookup_acl(struct srpt_port *sport,
                                             u8 i_port_id[16])
{
        struct srpt_node_acl *nacl;

        spin_lock_irq(&sport->port_acl_lock);
        nacl = __srpt_lookup_acl(sport, i_port_id);
        spin_unlock_irq(&sport->port_acl_lock);

        return nacl;
}

/**
 * srpt_cm_req_recv() - Process the event IB_CM_REQ_RECEIVED.
 *
 * Ownership of the cm_id is transferred to the target 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 srpt_port *sport = &sdev->port[param->port - 1];
        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;
        struct srpt_node_acl *nacl;
        u32 it_iu_len;
        int i;
        int ret = 0;

        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);

        printk(KERN_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)\n",
               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_req_size || it_iu_len < 64) {
                rej->reason = __constant_cpu_to_be32(
                                SRP_LOGIN_REJ_REQ_IT_IU_LENGTH_TOO_LARGE);
                ret = -EINVAL;
                printk(KERN_ERR "rejected SRP_LOGIN_REQ because its"
                       " length (%d bytes) is out of range (%d .. %d)\n",
                       it_iu_len, 64, srp_max_req_size);
                goto reject;
        }

        if (!sport->enabled) {
                rej->reason = __constant_cpu_to_be32(
                             SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                ret = -EINVAL;
                printk(KERN_ERR "rejected SRP_LOGIN_REQ because the target port"
                       " has not yet been enabled\n");
                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 ch_state;

                                ch_state = srpt_get_ch_state(ch);
                                if (ch_state != CH_CONNECTING
                                    && ch_state != CH_LIVE)
                                        continue;

                                /* found an existing channel */
                                pr_debug("Found existing channel %s"
                                         " cm_id= %p state= %d\n",
                                         ch->sess_name, ch->cm_id, ch_state);

                                __srpt_close_ch(ch);

                                rsp->rsp_flags =
                                        SRP_LOGIN_RSP_MULTICHAN_TERMINATED;
                        }
                }

                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 = __constant_cpu_to_be32(
                                SRP_LOGIN_REJ_UNABLE_ASSOCIATE_CHANNEL);
                ret = -ENOMEM;
                printk(KERN_ERR "rejected SRP_LOGIN_REQ because it"
                       " has an invalid target port identifier.\n");
                goto reject;
        }

        ch = kzalloc(sizeof *ch, GFP_KERNEL);
        if (!ch) {
                rej->reason = __constant_cpu_to_be32(
                                        SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                printk(KERN_ERR "rejected SRP_LOGIN_REQ because no memory.\n");
                ret = -ENOMEM;
                goto reject;
        }

        INIT_WORK(&ch->release_work, srpt_release_channel_work);
        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;
        /*
         * Avoid QUEUE_FULL conditions by limiting the number of buffers used
         * for the SRP protocol to the command queue size.
         */
        ch->rq_size = SRPT_RQ_SIZE;
        spin_lock_init(&ch->spinlock);
        ch->state = CH_CONNECTING;
        INIT_LIST_HEAD(&ch->cmd_wait_list);
        ch->rsp_size = ch->sport->port_attrib.srp_max_rsp_size;

        ch->ioctx_ring = (struct srpt_send_ioctx **)
                srpt_alloc_ioctx_ring(ch->sport->sdev, ch->rq_size,
                                      sizeof(*ch->ioctx_ring[0]),
                                      ch->rsp_size, DMA_TO_DEVICE);
        if (!ch->ioctx_ring)
                goto free_ch;

        INIT_LIST_HEAD(&ch->free_list);
        for (i = 0; i < ch->rq_size; i++) {
                ch->ioctx_ring[i]->ch = ch;
                list_add_tail(&ch->ioctx_ring[i]->free_list, &ch->free_list);
        }

        ret = srpt_create_ch_ib(ch);
        if (ret) {
                rej->reason = __constant_cpu_to_be32(
                                SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                printk(KERN_ERR "rejected SRP_LOGIN_REQ because creating"
                       " a new RDMA channel failed.\n");
                goto free_ring;
        }

        ret = srpt_ch_qp_rtr(ch, ch->qp);
        if (ret) {
                rej->reason = __constant_cpu_to_be32(
                                SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                printk(KERN_ERR "rejected SRP_LOGIN_REQ because enabling"
                       " RTR failed (error code = %d)\n", ret);
                goto destroy_ib;
        }
        /*
         * 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)));

        pr_debug("registering session %s\n", ch->sess_name);

        nacl = srpt_lookup_acl(sport, ch->i_port_id);
        if (!nacl) {
                printk(KERN_INFO "Rejected login because no ACL has been"
                       " configured yet for initiator %s.\n", ch->sess_name);
                rej->reason = __constant_cpu_to_be32(
                                SRP_LOGIN_REJ_CHANNEL_LIMIT_REACHED);
                goto destroy_ib;
        }

        ch->sess = transport_init_session();
        if (IS_ERR(ch->sess)) {
                rej->reason = __constant_cpu_to_be32(
                                SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                pr_debug("Failed to create session\n");
                goto deregister_session;
        }
        ch->sess->se_node_acl = &nacl->nacl;
        transport_register_session(&sport->port_tpg_1, &nacl->nacl, ch->sess, ch);

        pr_debug("Establish connection sess=%p name=%s cm_id=%p\n", ch->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;
        rsp->buf_fmt = __constant_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);

        /* 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) {
                printk(KERN_ERR "sending SRP_LOGIN_REQ response failed"
                       " (error code = %d)\n", 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:
        srpt_set_ch_state(ch, CH_RELEASING);
        transport_deregister_session_configfs(ch->sess);

deregister_session:
        transport_deregister_session(ch->sess);
        ch->sess = NULL;

destroy_ib:
        srpt_destroy_ch_ib(ch);

free_ring:
        srpt_free_ioctx_ring((struct srpt_ioctx **)ch->ioctx_ring,
                             ch->sport->sdev, ch->rq_size,
                             ch->rsp_size, DMA_TO_DEVICE);
free_ch:
        kfree(ch);

reject:
        rej->opcode = SRP_LOGIN_REJ;
        rej->tag = req->tag;
        rej->buf_fmt = __constant_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)
{
        printk(KERN_INFO "Received IB REJ for cm_id %p.\n", cm_id);
        srpt_drain_channel(cm_id);
}

/**
 * srpt_cm_rtu_recv() - Process an IB_CM_RTU_RECEIVED or 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);
        BUG_ON(!ch);

        if (srpt_test_and_set_ch_state(ch, CH_CONNECTING, CH_LIVE)) {
                struct srpt_recv_ioctx *ioctx, *ioctx_tmp;

                ret = srpt_ch_qp_rts(ch, ch->qp);

                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, NULL);
                }
                if (ret)
                        srpt_close_ch(ch);
        }
}

static void srpt_cm_timewait_exit(struct ib_cm_id *cm_id)
{
        printk(KERN_INFO "Received IB TimeWait exit for cm_id %p.\n", cm_id);
        srpt_drain_channel(cm_id);
}

static void srpt_cm_rep_error(struct ib_cm_id *cm_id)
{
        printk(KERN_INFO "Received IB REP error for cm_id %p.\n", cm_id);
        srpt_drain_channel(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;
        unsigned long flags;
        bool send_drep = false;

        ch = srpt_find_channel(cm_id->context, cm_id);
        BUG_ON(!ch);

        pr_debug("cm_id= %p ch->state= %d\n", cm_id, srpt_get_ch_state(ch));

        spin_lock_irqsave(&ch->spinlock, flags);
        switch (ch->state) {
        case CH_CONNECTING:
        case CH_LIVE:
                send_drep = true;
                ch->state = CH_DISCONNECTING;
                break;
        case CH_DISCONNECTING:
        case CH_DRAINING:
        case CH_RELEASING:
                WARN(true, "unexpected channel state %d\n", ch->state);
                break;
        }
        spin_unlock_irqrestore(&ch->spinlock, flags);

        if (send_drep) {
                if (ib_send_cm_drep(ch->cm_id, NULL, 0) < 0)
                        printk(KERN_ERR "Sending IB DREP failed.\n");
                printk(KERN_INFO "Received DREQ and sent DREP for session %s.\n",
                       ch->sess_name);
        }
}

/**
 * srpt_cm_drep_recv() - Process reception of a DREP message.
 */
static void srpt_cm_drep_recv(struct ib_cm_id *cm_id)
{
        printk(KERN_INFO "Received InfiniBand DREP message for cm_id %p.\n",
               cm_id);
        srpt_drain_channel(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:
                printk(KERN_INFO "Received IB DREQ ERROR event.\n");
                break;
        case IB_CM_MRA_RECEIVED:
                printk(KERN_INFO "Received IB MRA event\n");
                break;
        default:
                printk(KERN_ERR "received unrecognized IB CM event %d\n",
                       event->event);
                break;
        }

        return ret;
}

/**
 * srpt_perform_rdmas() - Perform IB RDMA.
 *
 * Returns zero upon success or a negative number upon failure.
 */
static int srpt_perform_rdmas(struct srpt_rdma_ch *ch,
                              struct srpt_send_ioctx *ioctx)
{
        struct ib_send_wr wr;
        struct ib_send_wr *bad_wr;
        struct rdma_iu *riu;
        int i;
        int ret;
        int sq_wr_avail;
        enum dma_data_direction dir;
        const int n_rdma = ioctx->n_rdma;

        dir = ioctx->cmd.data_direction;
        if (dir == DMA_TO_DEVICE) {
                /* write */
                ret = -ENOMEM;
                sq_wr_avail = atomic_sub_return(n_rdma, &ch->sq_wr_avail);
                if (sq_wr_avail < 0) {
                        printk(KERN_WARNING "IB send queue full (needed %d)\n",
                               n_rdma);
                        goto out;
                }
        }

        ioctx->rdma_aborted = false;
        ret = 0;
        riu = ioctx->rdma_ius;
        memset(&wr, 0, sizeof wr);

        for (i = 0; i < n_rdma; ++i, ++riu) {
                if (dir == DMA_FROM_DEVICE) {
                        wr.opcode = IB_WR_RDMA_WRITE;
                        wr.wr_id = encode_wr_id(i == n_rdma - 1 ?
                                                SRPT_RDMA_WRITE_LAST :
                                                SRPT_RDMA_MID,
                                                ioctx->ioctx.index);
                } else {
                        wr.opcode = IB_WR_RDMA_READ;
                        wr.wr_id = encode_wr_id(i == n_rdma - 1 ?
                                                SRPT_RDMA_READ_LAST :
                                                SRPT_RDMA_MID,
                                                ioctx->ioctx.index);
                }
                wr.next = NULL;
                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 write */
                if (i == (n_rdma - 1) && dir == DMA_TO_DEVICE)
                        wr.send_flags = IB_SEND_SIGNALED;

                ret = ib_post_send(ch->qp, &wr, &bad_wr);
                if (ret)
                        break;
        }

        if (ret)
                printk(KERN_ERR "%s[%d]: ib_post_send() returned %d for %d/%d",
                                 __func__, __LINE__, ret, i, n_rdma);
        if (ret && i > 0) {
                wr.num_sge = 0;
                wr.wr_id = encode_wr_id(SRPT_RDMA_ABORT, ioctx->ioctx.index);
                wr.send_flags = IB_SEND_SIGNALED;
                while (ch->state == CH_LIVE &&
                        ib_post_send(ch->qp, &wr, &bad_wr) != 0) {
                        printk(KERN_INFO "Trying to abort failed RDMA transfer [%d]",
                                ioctx->ioctx.index);
                        msleep(1000);
                }
                while (ch->state != CH_RELEASING && !ioctx->rdma_aborted) {
                        printk(KERN_INFO "Waiting until RDMA abort finished [%d]",
                                ioctx->ioctx.index);
                        msleep(1000);
                }
        }
out:
        if (unlikely(dir == DMA_TO_DEVICE && ret < 0))
                atomic_add(n_rdma, &ch->sq_wr_avail);
        return ret;
}

/**
 * srpt_xfer_data() - Start data transfer from initiator to target.
 */
static int srpt_xfer_data(struct srpt_rdma_ch *ch,
                          struct srpt_send_ioctx *ioctx)
{
        int ret;

        ret = srpt_map_sg_to_ib_sge(ch, ioctx);
        if (ret) {
                printk(KERN_ERR "%s[%d] ret=%d\n", __func__, __LINE__, ret);
                goto out;
        }

        ret = srpt_perform_rdmas(ch, ioctx);
        if (ret) {
                if (ret == -EAGAIN || ret == -ENOMEM)
                        printk(KERN_INFO "%s[%d] queue full -- ret=%d\n",
                                   __func__, __LINE__, ret);
                else
                        printk(KERN_ERR "%s[%d] fatal error -- ret=%d\n",
                               __func__, __LINE__, ret);
                goto out_unmap;
        }

out:
        return ret;
out_unmap:
        srpt_unmap_sg_to_ib_sge(ch, ioctx);
        goto out;
}

static int srpt_write_pending_status(struct se_cmd *se_cmd)
{
        struct srpt_send_ioctx *ioctx;

        ioctx = container_of(se_cmd, struct srpt_send_ioctx, cmd);
        return srpt_get_cmd_state(ioctx) == SRPT_STATE_NEED_DATA;
}

/*
 * srpt_write_pending() - Start data transfer from initiator to target (write).
 */
static int srpt_write_pending(struct se_cmd *se_cmd)
{
        struct srpt_rdma_ch *ch;
        struct srpt_send_ioctx *ioctx;
        enum srpt_command_state new_state;
        enum rdma_ch_state ch_state;
        int ret;

        ioctx = container_of(se_cmd, struct srpt_send_ioctx, cmd);

        new_state = srpt_set_cmd_state(ioctx, SRPT_STATE_NEED_DATA);
        WARN_ON(new_state == SRPT_STATE_DONE);

        ch = ioctx->ch;
        BUG_ON(!ch);

        ch_state = srpt_get_ch_state(ch);
        switch (ch_state) {
        case CH_CONNECTING:
                WARN(true, "unexpected channel state %d\n", ch_state);
                ret = -EINVAL;
                goto out;
        case CH_LIVE:
                break;