/*
 * 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 <linux/inet.h>
#include <rdma/ib_cache.h>
#include <scsi/scsi_proto.h>
#include <scsi/scsi_tcq.h>
#include <target/target_core_base.h>
#include <target/target_core_fabric.h>
#include "ib_srpt.h"

/* Name of this kernel module. */
#define DRV_NAME                "ib_srpt"

#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("SCSI RDMA Protocol target driver");
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, const 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;
/* Protects both rdma_cm_port and rdma_cm_id. */
static DEFINE_MUTEX(rdma_cm_mutex);
/* Port number RDMA/CM will bind to. */
static u16 rdma_cm_port;
static struct rdma_cm_id *rdma_cm_id;
static void srpt_release_cmd(struct se_cmd *se_cmd);
static void srpt_free_ch(struct kref *kref);
static int srpt_queue_status(struct se_cmd *cmd);
static void srpt_recv_done(struct ib_cq *cq, struct ib_wc *wc);
static void srpt_send_done(struct ib_cq *cq, struct ib_wc *wc);
static void srpt_process_wait_list(struct srpt_rdma_ch *ch);

/*
 * The only allowed channel state changes are those that change the channel
 * state into a state with a higher numerical value. Hence the new > prev test.
 */
static bool srpt_set_ch_state(struct srpt_rdma_ch *ch, enum rdma_ch_state new)
{
        unsigned long flags;
        enum rdma_ch_state prev;
        bool changed = false;

        spin_lock_irqsave(&ch->spinlock, flags);
        prev = ch->state;
        if (new > prev) {
                ch->state = new;
                changed = true;
        }
        spin_unlock_irqrestore(&ch->spinlock, flags);

        return changed;
}

/**
 * srpt_event_handler - asynchronous IB event callback function
 * @handler: IB event handler registered by ib_register_event_handler().
 * @event: Description of the event that occurred.
 *
 * 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;
        u8 port_num;

        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,
                 dev_name(&sdev->device->dev));

        switch (event->event) {
        case IB_EVENT_PORT_ERR:
                port_num = event->element.port_num - 1;
                if (port_num < sdev->device->phys_port_cnt) {
                        sport = &sdev->port[port_num];
                        sport->lid = 0;
                        sport->sm_lid = 0;
                } else {
                        WARN(true, "event %d: port_num %d out of range 1..%d\n",
                             event->event, port_num + 1,
                             sdev->device->phys_port_cnt);
                }
                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:
        case IB_EVENT_GID_CHANGE:
                /* Refresh port data asynchronously. */
                port_num = event->element.port_num - 1;
                if (port_num < sdev->device->phys_port_cnt) {
                        sport = &sdev->port[port_num];
                        if (!sport->lid && !sport->sm_lid)
                                schedule_work(&sport->work);
                } else {
                        WARN(true, "event %d: port_num %d out of range 1..%d\n",
                             event->event, port_num + 1,
                             sdev->device->phys_port_cnt);
                }
                break;
        default:
                pr_err("received unrecognized IB event %d\n", event->event);
                break;
        }
}

/**
 * srpt_srq_event - SRQ event callback function
 * @event: Description of the event that occurred.
 * @ctx: Context pointer specified at SRQ creation time.
 */
static void srpt_srq_event(struct ib_event *event, void *ctx)
{
        pr_debug("SRQ event %d\n", event->event);
}

static const char *get_ch_state_name(enum rdma_ch_state s)
{
        switch (s) {
        case CH_CONNECTING:
                return "connecting";
        case CH_LIVE:
                return "live";
        case CH_DISCONNECTING:
                return "disconnecting";
        case CH_DRAINING:
                return "draining";
        case CH_DISCONNECTED:
                return "disconnected";
        }
        return "???";
}

/**
 * srpt_qp_event - QP event callback function
 * @event: Description of the event that occurred.
 * @ch: SRPT RDMA channel.
 */
static void srpt_qp_event(struct ib_event *event, struct srpt_rdma_ch *ch)
{
        pr_debug("QP event %d on ch=%p sess_name=%s state=%d\n",
                 event->event, ch, ch->sess_name, ch->state);

        switch (event->event) {
        case IB_EVENT_COMM_EST:
                if (ch->using_rdma_cm)
                        rdma_notify(ch->rdma_cm.cm_id, event->event);
                else
                        ib_cm_notify(ch->ib_cm.cm_id, event->event);
                break;
        case IB_EVENT_QP_LAST_WQE_REACHED:
                pr_debug("%s-%d, state %s: received Last WQE event.\n",
                         ch->sess_name, ch->qp->qp_num,
                         get_ch_state_name(ch->state));
                break;
        default:
                pr_err("received unrecognized IB QP event %d\n", event->event);
                break;
        }
}

/**
 * srpt_set_ioc - initialize a IOUnitInfo structure
 * @c_list: controller list.
 * @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
 * @mad: Datagram that will be sent as response to DM_ATTR_CLASS_PORT_INFO.
 *
 * 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;

        ib_set_cpi_resp_time(cif, 20);
        mad->mad_hdr.status = 0;
}

/**
 * srpt_get_iou - write IOUnitInfo to a management datagram
 * @mad: Datagram that will be sent as response to DM_ATTR_IOU_INFO.
 *
 * See also section 16.3.3.3 IOUnitInfo in the InfiniBand Architecture
 * Specification. See also section B.7, table B.6 in the SRP r16a document.
 */
static void srpt_get_iou(struct ib_dm_mad *mad)
{
        struct ib_dm_iou_info *ioui;
        u8 slot;
        int i;

        ioui = (struct ib_dm_iou_info *)mad->data;
        ioui->change_id = cpu_to_be16(1);
        ioui->max_controllers = 16;

        /* set present for slot 1 and empty for the rest */
        srpt_set_ioc(ioui->controller_list, 1, 1);
        for (i = 1, slot = 2; i < 16; i++, slot++)
                srpt_set_ioc(ioui->controller_list, slot, 0);

        mad->mad_hdr.status = 0;
}

/**
 * srpt_get_ioc - write IOControllerprofile to a management datagram
 * @sport: HCA port through which the MAD has been received.
 * @slot: Slot number specified in DM_ATTR_IOC_PROFILE query.
 * @mad: Datagram that will be sent as response to DM_ATTR_IOC_PROFILE.
 *
 * 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;
        int send_queue_depth;

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

        if (!slot || slot > 16) {
                mad->mad_hdr.status
                        = cpu_to_be16(DM_MAD_STATUS_INVALID_FIELD);
                return;
        }

        if (slot > 2) {
                mad->mad_hdr.status
                        = cpu_to_be16(DM_MAD_STATUS_NO_IOC);
                return;
        }

        if (sdev->use_srq)
                send_queue_depth = sdev->srq_size;
        else
                send_queue_depth = min(MAX_SRPT_RQ_SIZE,
                                       sdev->device->attrs.max_qp_wr);

        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->device->attrs.vendor_id);
        iocp->device_id = cpu_to_be32(sdev->device->attrs.vendor_part_id);
        iocp->device_version = cpu_to_be16(sdev->device->attrs.hw_ver);
        iocp->subsys_vendor_id = cpu_to_be32(sdev->device->attrs.vendor_id);
        iocp->subsys_device_id = 0x0;
        iocp->io_class = cpu_to_be16(SRP_REV16A_IB_IO_CLASS);
        iocp->io_subclass = cpu_to_be16(SRP_IO_SUBCLASS);
        iocp->protocol = cpu_to_be16(SRP_PROTOCOL);
        iocp->protocol_version = cpu_to_be16(SRP_PROTOCOL_VERSION);
        iocp->send_queue_depth = cpu_to_be16(send_queue_depth);
        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
 * @ioc_guid: I/O controller GUID to use in reply.
 * @slot: I/O controller number.
 * @hi: End of the range of service entries to be specified in the reply.
 * @lo: Start of the range of service entries to be specified in the reply..
 * @mad: Datagram that will be sent as response to DM_ATTR_SVC_ENTRIES.
 *
 * See also section 16.3.3.5 ServiceEntries in the InfiniBand Architecture
 * Specification. See also section B.7, table B.8 in the SRP r16a document.
 */
static void srpt_get_svc_entries(u64 ioc_guid,
                                 u16 slot, u8 hi, u8 lo, struct ib_dm_mad *mad)
{
        struct ib_dm_svc_entries *svc_entries;

        WARN_ON(!ioc_guid);

        if (!slot || slot > 16) {
                mad->mad_hdr.status
                        = cpu_to_be16(DM_MAD_STATUS_INVALID_FIELD);
                return;
        }

        if (slot > 2 || lo > hi || hi > 1) {
                mad->mad_hdr.status
                        = cpu_to_be16(DM_MAD_STATUS_NO_IOC);
                return;
        }

        svc_entries = (struct ib_dm_svc_entries *)mad->data;
        memset(svc_entries, 0, sizeof(*svc_entries));
        svc_entries->service_entries[0].id = cpu_to_be64(ioc_guid);
        snprintf(svc_entries->service_entries[0].name,
                 sizeof(svc_entries->service_entries[0].name),
                 "%s%016llx",
                 SRP_SERVICE_NAME_PREFIX,
                 ioc_guid);

        mad->mad_hdr.status = 0;
}

/**
 * srpt_mgmt_method_get - process a received management datagram
 * @sp:      HCA 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 =
                    cpu_to_be16(DM_MAD_STATUS_UNSUP_METHOD_ATTR);
                break;
        }
}

/**
 * srpt_mad_send_handler - MAD send completion callback
 * @mad_agent: Return value of ib_register_mad_agent().
 * @mad_wc: Work completion reporting that the MAD has been sent.
 */
static void srpt_mad_send_handler(struct ib_mad_agent *mad_agent,
                                  struct ib_mad_send_wc *mad_wc)
{
        rdma_destroy_ah(mad_wc->send_buf->ah, RDMA_DESTROY_AH_SLEEPABLE);
        ib_free_send_mad(mad_wc->send_buf);
}

/**
 * srpt_mad_recv_handler - MAD reception callback function
 * @mad_agent: Return value of ib_register_mad_agent().
 * @send_buf: Not used.
 * @mad_wc: Work completion reporting that a MAD has been received.
 */
static void srpt_mad_recv_handler(struct ib_mad_agent *mad_agent,
                                  struct ib_mad_send_buf *send_buf,
                                  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,
                                 IB_MGMT_BASE_VERSION);
        if (IS_ERR(rsp))
                goto err_rsp;

        rsp->ah = ah;

        dm_mad = rsp->mad;
        memcpy(dm_mad, mad_wc->recv_buf.mad, sizeof(*dm_mad));
        dm_mad->mad_hdr.method = IB_MGMT_METHOD_GET_RESP;
        dm_mad->mad_hdr.status = 0;

        switch (mad_wc->recv_buf.mad->mad_hdr.method) {
        case IB_MGMT_METHOD_GET:
                srpt_mgmt_method_get(sport, mad_wc->recv_buf.mad, dm_mad);
                break;
        case IB_MGMT_METHOD_SET:
                dm_mad->mad_hdr.status =
                    cpu_to_be16(DM_MAD_STATUS_UNSUP_METHOD_ATTR);
                break;
        default:
                dm_mad->mad_hdr.status =
                    cpu_to_be16(DM_MAD_STATUS_UNSUP_METHOD);
                break;
        }

        if (!ib_post_send_mad(rsp, NULL)) {
                ib_free_recv_mad(mad_wc);
                /* will destroy_ah & free_send_mad in send completion */
                return;
        }

        ib_free_send_mad(rsp);

err_rsp:
        rdma_destroy_ah(ah, RDMA_DESTROY_AH_SLEEPABLE);
err:
        ib_free_recv_mad(mad_wc);
}

static int srpt_format_guid(char *buf, unsigned int size, const __be64 *guid)
{
        const __be16 *g = (const __be16 *)guid;

        return snprintf(buf, size, "%04x:%04x:%04x:%04x",
                        be16_to_cpu(g[0]), be16_to_cpu(g[1]),
                        be16_to_cpu(g[2]), be16_to_cpu(g[3]));
}

/**
 * srpt_refresh_port - configure a HCA port
 * @sport: SRPT 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;

        ret = ib_query_port(sport->sdev->device, sport->port, &port_attr);
        if (ret)
                return ret;

        sport->sm_lid = port_attr.sm_lid;
        sport->lid = port_attr.lid;

        ret = rdma_query_gid(sport->sdev->device, sport->port, 0, &sport->gid);
        if (ret)
                return ret;

        sport->port_guid_id.wwn.priv = sport;
        srpt_format_guid(sport->port_guid_id.name,
                         sizeof(sport->port_guid_id.name),
                         &sport->gid.global.interface_id);
        sport->port_gid_id.wwn.priv = sport;
        snprintf(sport->port_gid_id.name, sizeof(sport->port_gid_id.name),
                 "0x%016llx%016llx",
                 be64_to_cpu(sport->gid.global.subnet_prefix),
                 be64_to_cpu(sport->gid.global.interface_id));

        if (rdma_protocol_iwarp(sport->sdev->device, sport->port))
                return 0;

        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) {
                pr_warn("%s-%d: enabling device management failed (%d). Note: this is expected if SR-IOV is enabled.\n",
                        dev_name(&sport->sdev->device->dev), sport->port, ret);
                return 0;
        }

        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, 0);
                if (IS_ERR(sport->mad_agent)) {
                        pr_err("%s-%d: MAD agent registration failed (%ld). Note: this is expected if SR-IOV is enabled.\n",
                               dev_name(&sport->sdev->device->dev), sport->port,
                               PTR_ERR(sport->mad_agent));
                        sport->mad_agent = NULL;
                }
        }

        return 0;
}

/**
 * srpt_unregister_mad_agent - unregister MAD callback functions
 * @sdev: SRPT HCA pointer.
 *
 * 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)
                        pr_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 a SRPT I/O context structure
 * @sdev: SRPT HCA pointer.
 * @ioctx_size: I/O context size.
 * @buf_cache: I/O buffer cache.
 * @dir: DMA data direction.
 */
static struct srpt_ioctx *srpt_alloc_ioctx(struct srpt_device *sdev,
                                           int ioctx_size,
                                           struct kmem_cache *buf_cache,
                                           enum dma_data_direction dir)
{
        struct srpt_ioctx *ioctx;

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

        ioctx->buf = kmem_cache_alloc(buf_cache, GFP_KERNEL);
        if (!ioctx->buf)
                goto err_free_ioctx;

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

        return ioctx;

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

/**
 * srpt_free_ioctx - free a SRPT I/O context structure
 * @sdev: SRPT HCA pointer.
 * @ioctx: I/O context pointer.
 * @buf_cache: I/O buffer cache.
 * @dir: DMA data direction.
 */
static void srpt_free_ioctx(struct srpt_device *sdev, struct srpt_ioctx *ioctx,
                            struct kmem_cache *buf_cache,
                            enum dma_data_direction dir)
{
        if (!ioctx)
                return;

        ib_dma_unmap_single(sdev->device, ioctx->dma,
                            kmem_cache_size(buf_cache), dir);
        kmem_cache_free(buf_cache, 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.
 * @buf_cache:  I/O buffer cache.
 * @alignment_offset: Offset in each ring buffer at which the SRP information
 *              unit starts.
 * @dir:        DMA data direction.
 */
static struct srpt_ioctx **srpt_alloc_ioctx_ring(struct srpt_device *sdev,
                                int ring_size, int ioctx_size,
                                struct kmem_cache *buf_cache,
                                int alignment_offset,
                                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 = kvmalloc_array(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, buf_cache, dir);
                if (!ring[i])
                        goto err;
                ring[i]->index = i;
                ring[i]->offset = alignment_offset;
        }
        goto out;

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

/**
 * srpt_free_ioctx_ring - free the ring of SRPT I/O context structures
 * @ioctx_ring: I/O context ring to be freed.
 * @sdev: SRPT HCA pointer.
 * @ring_size: Number of ring elements.
 * @buf_cache: I/O buffer cache.
 * @dir: DMA data direction.
 */
static void srpt_free_ioctx_ring(struct srpt_ioctx **ioctx_ring,
                                 struct srpt_device *sdev, int ring_size,
                                 struct kmem_cache *buf_cache,
                                 enum dma_data_direction dir)
{
        int i;

        if (!ioctx_ring)
                return;

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

/**
 * srpt_set_cmd_state - set the state of a SCSI command
 * @ioctx: Send I/O context.
 * @new: New I/O context state.
 *
 * 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;

        previous = ioctx->state;
        if (previous != SRPT_STATE_DONE)
                ioctx->state = new;

        return previous;
}

/**
 * srpt_test_and_set_cmd_state - test and set the state of a command
 * @ioctx: Send I/O context.
 * @old: Current I/O context state.
 * @new: New I/O context state.
 *
 * 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;

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

        previous = ioctx->state;
        if (previous == old)
                ioctx->state = new;

        return previous == old;
}

/**
 * srpt_post_recv - post an IB receive request
 * @sdev: SRPT HCA pointer.
 * @ch: SRPT RDMA channel.
 * @ioctx: Receive I/O context pointer.
 */
static int srpt_post_recv(struct srpt_device *sdev, struct srpt_rdma_ch *ch,
                          struct srpt_recv_ioctx *ioctx)
{
        struct ib_sge list;
        struct ib_recv_wr wr;

        BUG_ON(!sdev);
        list.addr = ioctx->ioctx.dma + ioctx->ioctx.offset;
        list.length = srp_max_req_size;
        list.lkey = sdev->lkey;

        ioctx->ioctx.cqe.done = srpt_recv_done;
        wr.wr_cqe = &ioctx->ioctx.cqe;
        wr.next = NULL;
        wr.sg_list = &list;
        wr.num_sge = 1;

        if (sdev->use_srq)
                return ib_post_srq_recv(sdev->srq, &wr, NULL);
        else
                return ib_post_recv(ch->qp, &wr, NULL);
}

/**
 * srpt_zerolength_write - perform a zero-length RDMA write
 * @ch: SRPT RDMA channel.
 *
 * A quote from the InfiniBand specification: C9-88: For an HCA responder
 * using Reliable Connection service, for each zero-length RDMA READ or WRITE
 * request, the R_Key shall not be validated, even if the request includes
 * Immediate data.
 */
static int srpt_zerolength_write(struct srpt_rdma_ch *ch)
{
        struct ib_rdma_wr wr = {
                .wr = {
                        .next           = NULL,
                        { .wr_cqe       = &ch->zw_cqe, },
                        .opcode         = IB_WR_RDMA_WRITE,
                        .send_flags     = IB_SEND_SIGNALED,
                }
        };

        pr_debug("%s-%d: queued zerolength write\n", ch->sess_name,
                 ch->qp->qp_num);

        return ib_post_send(ch->qp, &wr.wr, NULL);
}

static void srpt_zerolength_write_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct srpt_rdma_ch *ch = cq->cq_context;

        pr_debug("%s-%d wc->status %d\n", ch->sess_name, ch->qp->qp_num,
                 wc->status);

        if (wc->status == IB_WC_SUCCESS) {
                srpt_process_wait_list(ch);
        } else {
                if (srpt_set_ch_state(ch, CH_DISCONNECTED))
                        schedule_work(&ch->release_work);
                else
                        pr_debug("%s-%d: already disconnected.\n",
                                 ch->sess_name, ch->qp->qp_num);
        }
}

static int srpt_alloc_rw_ctxs(struct srpt_send_ioctx *ioctx,
                struct srp_direct_buf *db, int nbufs, struct scatterlist **sg,
                unsigned *sg_cnt)
{
        enum dma_data_direction dir = target_reverse_dma_direction(&ioctx->cmd);
        struct srpt_rdma_ch *ch = ioctx->ch;
        struct scatterlist *prev = NULL;
        unsigned prev_nents;
        int ret, i;

        if (nbufs == 1) {
                ioctx->rw_ctxs = &ioctx->s_rw_ctx;
        } else {
                ioctx->rw_ctxs = kmalloc_array(nbufs, sizeof(*ioctx->rw_ctxs),
                        GFP_KERNEL);
                if (!ioctx->rw_ctxs)
                        return -ENOMEM;
        }

        for (i = ioctx->n_rw_ctx; i < nbufs; i++, db++) {
                struct srpt_rw_ctx *ctx = &ioctx->rw_ctxs[i];
                u64 remote_addr = be64_to_cpu(db->va);
                u32 size = be32_to_cpu(db->len);
                u32 rkey = be32_to_cpu(db->key);

                ret = target_alloc_sgl(&ctx->sg, &ctx->nents, size, false,
                                i < nbufs - 1);
                if (ret)
                        goto unwind;

                ret = rdma_rw_ctx_init(&ctx->rw, ch->qp, ch->sport->port,
                                ctx->sg, ctx->nents, 0, remote_addr, rkey, dir);
                if (ret < 0) {
                        target_free_sgl(ctx->sg, ctx->nents);
                        goto unwind;
                }

                ioctx->n_rdma += ret;
                ioctx->n_rw_ctx++;

                if (prev) {
                        sg_unmark_end(&prev[prev_nents - 1]);
                        sg_chain(prev, prev_nents + 1, ctx->sg);
                } else {
                        *sg = ctx->sg;
                }

                prev = ctx->sg;
                prev_nents = ctx->nents;

                *sg_cnt += ctx->nents;
        }

        return 0;

unwind:
        while (--i >= 0) {
                struct srpt_rw_ctx *ctx = &ioctx->rw_ctxs[i];

                rdma_rw_ctx_destroy(&ctx->rw, ch->qp, ch->sport->port,
                                ctx->sg, ctx->nents, dir);
                target_free_sgl(ctx->sg, ctx->nents);
        }
        if (ioctx->rw_ctxs != &ioctx->s_rw_ctx)
                kfree(ioctx->rw_ctxs);
        return ret;
}

static void srpt_free_rw_ctxs(struct srpt_rdma_ch *ch,
                                    struct srpt_send_ioctx *ioctx)
{
        enum dma_data_direction dir = target_reverse_dma_direction(&ioctx->cmd);
        int i;

        for (i = 0; i < ioctx->n_rw_ctx; i++) {
                struct srpt_rw_ctx *ctx = &ioctx->rw_ctxs[i];

                rdma_rw_ctx_destroy(&ctx->rw, ch->qp, ch->sport->port,
                                ctx->sg, ctx->nents, dir);
                target_free_sgl(ctx->sg, ctx->nents);
        }

        if (ioctx->rw_ctxs != &ioctx->s_rw_ctx)
                kfree(ioctx->rw_ctxs);
}

static inline void *srpt_get_desc_buf(struct srp_cmd *srp_cmd)
{
        /*
         * 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));

        /*
         * 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".
         */
        return srp_cmd->add_data + (srp_cmd->add_cdb_len & ~3);
}

/**
 * srpt_get_desc_tbl - parse the data descriptors of a SRP_CMD request
 * @recv_ioctx: I/O context associated with the received command @srp_cmd.
 * @ioctx: I/O context that will be used for responding to the initiator.
 * @srp_cmd: Pointer to the SRP_CMD request data.
 * @dir: Pointer to the variable to which the transfer direction will be
 *   written.
 * @sg: [out] scatterlist for the parsed SRP_CMD.
 * @sg_cnt: [out] length of @sg.
 * @data_len: Pointer to the variable to which the total data length of all
 *   descriptors in the SRP_CMD request will be written.

 * @imm_data_offset: [in] Offset in SRP_CMD requests at which immediate data
 *   starts.
 *
 * 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_recv_ioctx *recv_ioctx,
                struct srpt_send_ioctx *ioctx,
                struct srp_cmd *srp_cmd, enum dma_data_direction *dir,
                struct scatterlist **sg, unsigned int *sg_cnt, u64 *data_len,
                u16 imm_data_offset)
{
        BUG_ON(!dir);
        BUG_ON(!data_len);

        /*
         * 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.
         */
        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;
        else
                *dir = DMA_NONE;

        /* initialize data_direction early as srpt_alloc_rw_ctxs needs it */
        ioctx->cmd.data_direction = *dir;

        if (((srp_cmd->buf_fmt & 0xf) == SRP_DATA_DESC_DIRECT) ||
            ((srp_cmd->buf_fmt >> 4) == SRP_DATA_DESC_DIRECT)) {
                struct srp_direct_buf *db = srpt_get_desc_buf(srp_cmd);

                *data_len = be32_to_cpu(db->len);
                return srpt_alloc_rw_ctxs(ioctx, db, 1, sg, sg_cnt);
        } else if (((srp_cmd->buf_fmt & 0xf) == SRP_DATA_DESC_INDIRECT) ||
                   ((srp_cmd->buf_fmt >> 4) == SRP_DATA_DESC_INDIRECT)) {
                struct srp_indirect_buf *idb = srpt_get_desc_buf(srp_cmd);
                int nbufs = be32_to_cpu(idb->table_desc.len) /
                                sizeof(struct srp_direct_buf);

                if (nbufs >
                    (srp_cmd->data_out_desc_cnt + srp_cmd->data_in_desc_cnt)) {
                        pr_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(struct srp_direct_buf));
                        return -EINVAL;
                }

                *data_len = be32_to_cpu(idb->len);
                return srpt_alloc_rw_ctxs(ioctx, idb->desc_list, nbufs,
                                sg, sg_cnt);
        } else if ((srp_cmd->buf_fmt >> 4) == SRP_DATA_DESC_IMM) {
                struct srp_imm_buf *imm_buf = srpt_get_desc_buf(srp_cmd);
                void *data = (void *)srp_cmd + imm_data_offset;
                uint32_t len = be32_to_cpu(imm_buf->len);
                uint32_t req_size = imm_data_offset + len;

                if (req_size > srp_max_req_size) {
                        pr_err("Immediate data (length %d + %d) exceeds request size %d\n",
                               imm_data_offset, len, srp_max_req_size);
                        return -EINVAL;
                }
                if (recv_ioctx->byte_len < req_size) {
                        pr_err("Received too few data - %d < %d\n",
                               recv_ioctx->byte_len, req_size);
                        return -EIO;
                }
                /*
                 * The immediate data buffer descriptor must occur before the
                 * immediate data itself.
                 */
                if ((void *)(imm_buf + 1) > (void *)data) {
                        pr_err("Received invalid write request\n");
                        return -EINVAL;
                }
                *data_len = len;
                ioctx->recv_ioctx = recv_ioctx;
                if ((uintptr_t)data & 511) {
                        pr_warn_once("Internal error - the receive buffers are not aligned properly.\n");
                        return -EINVAL;
                }
                sg_init_one(&ioctx->imm_sg, data, len);
                *sg = &ioctx->imm_sg;
                *sg_cnt = 1;
                return 0;
        } else {
                *data_len = 0;
                return 0;
        }
}

/**
 * srpt_init_ch_qp - initialize queue pair attributes
 * @ch: SRPT RDMA channel.
 * @qp: Queue pair pointer.
 *
 * 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;

        WARN_ON_ONCE(ch->using_rdma_cm);

        attr = kzalloc(sizeof(*attr), GFP_KERNEL);
        if (!attr)
                return -ENOMEM;

        attr->qp_state = IB_QPS_INIT;
        attr->qp_access_flags = IB_ACCESS_LOCAL_WRITE;
        attr->port_num = ch->sport->port;

        ret = ib_find_cached_pkey(ch->sport->sdev->device, ch->sport->port,
                                  ch->pkey, &attr->pkey_index);
        if (ret < 0)
                pr_err("Translating pkey %#x failed (%d) - using index 0\n",
                       ch->pkey, ret);

        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;

        WARN_ON_ONCE(ch->using_rdma_cm);

        qp_attr.qp_state = IB_QPS_RTR;
        ret = ib_cm_init_qp_attr(ch->ib_cm.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->ib_cm.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'
 * @ch: SRPT RDMA channel.
 */
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_get_send_ioctx - obtain an I/O context for sending to the initiator
 * @ch: SRPT RDMA channel.
 */
static struct srpt_send_ioctx *srpt_get_send_ioctx(struct srpt_rdma_ch *ch)
{
        struct srpt_send_ioctx *ioctx;
        int tag, cpu;

        BUG_ON(!ch);

        tag = sbitmap_queue_get(&ch->sess->sess_tag_pool, &cpu);
        if (tag < 0)
                return NULL;

        ioctx = ch->ioctx_ring[tag];
        BUG_ON(ioctx->ch != ch);
        ioctx->state = SRPT_STATE_NEW;
        WARN_ON_ONCE(ioctx->recv_ioctx);
        ioctx->n_rdma = 0;
        ioctx->n_rw_ctx = 0;
        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));
        ioctx->cmd.map_tag = tag;
        ioctx->cmd.map_cpu = cpu;

        return ioctx;
}

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

        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.
         */

        state = ioctx->state;
        switch (state) {
        case SRPT_STATE_NEED_DATA:
                ioctx->state = SRPT_STATE_DATA_IN;
                break;
        case SRPT_STATE_CMD_RSP_SENT:
        case SRPT_STATE_MGMT_RSP_SENT:
                ioctx->state = SRPT_STATE_DONE;
                break;
        default:
                WARN_ONCE(true, "%s: unexpected I/O context state %d\n",
                          __func__, state);
                break;
        }

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

        switch (state) {
        case SRPT_STATE_NEW:
        case SRPT_STATE_DATA_IN:
        case SRPT_STATE_MGMT:
        case SRPT_STATE_DONE:
                /*
                 * Do nothing - defer abort processing until
                 * srpt_queue_response() is invoked.
                 */
                break;
        case SRPT_STATE_NEED_DATA:
                pr_debug("tag %#llx: RDMA read error\n", ioctx->cmd.tag);
                transport_generic_request_failure(&ioctx->cmd,
                                        TCM_CHECK_CONDITION_ABORT_CMD);
                break;
        case SRPT_STATE_CMD_RSP_SENT:
                /*
                 * SRP_RSP sending failed or the SRP_RSP send completion has
                 * not been received in time.
                 */
                transport_generic_free_cmd(&ioctx->cmd, 0);
                break;
        case SRPT_STATE_MGMT_RSP_SENT:
                transport_generic_free_cmd(&ioctx->cmd, 0);
                break;
        default:
                WARN(1, "Unexpected command state (%d)", state);
                break;
        }

        return state;
}

/**
 * srpt_rdma_read_done - RDMA read completion callback
 * @cq: Completion queue.
 * @wc: Work completion.
 *
 * 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_rdma_read_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct srpt_rdma_ch *ch = cq->cq_context;
        struct srpt_send_ioctx *ioctx =
                container_of(wc->wr_cqe, struct srpt_send_ioctx, rdma_cqe);

        WARN_ON(ioctx->n_rdma <= 0);
        atomic_add(ioctx->n_rdma, &ch->sq_wr_avail);
        ioctx->n_rdma = 0;

        if (unlikely(wc->status != IB_WC_SUCCESS)) {
                pr_info("RDMA_READ for ioctx 0x%p failed with status %d\n",
                        ioctx, wc->status);
                srpt_abort_cmd(ioctx);
                return;
        }

        if (srpt_test_and_set_cmd_state(ioctx, SRPT_STATE_NEED_DATA,
                                        SRPT_STATE_DATA_IN))
                target_execute_cmd(&ioctx->cmd);
        else
                pr_err("%s[%d]: wrong state = %d\n", __func__,
                       __LINE__, ioctx->state);
}

/**
 * srpt_build_cmd_rsp - build a 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 se_cmd *cmd = &ioctx->cmd;
        struct srp_rsp *srp_rsp;
        const u8 *sense_data;
        int sense_data_len, max_sense_len;
        u32 resid = cmd->residual_count;

        /*
         * 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 =
                cpu_to_be32(1 + atomic_xchg(&ch->req_lim_delta, 0));
        srp_rsp->tag = tag;
        srp_rsp->status = status;

        if (cmd->se_cmd_flags & SCF_UNDERFLOW_BIT) {
                if (cmd->data_direction == DMA_TO_DEVICE) {
                        /* residual data from an underflow write */
                        srp_rsp->flags = SRP_RSP_FLAG_DOUNDER;
                        srp_rsp->data_out_res_cnt = cpu_to_be32(resid);
                } else if (cmd->data_direction == DMA_FROM_DEVICE) {
                        /* residual data from an underflow read */
                        srp_rsp->flags = SRP_RSP_FLAG_DIUNDER;
                        srp_rsp->data_in_res_cnt = cpu_to_be32(resid);
                }
        } else if (cmd->se_cmd_flags & SCF_OVERFLOW_BIT) {
                if (cmd->data_direction == DMA_TO_DEVICE) {
                        /* residual data from an overflow write */
                        srp_rsp->flags = SRP_RSP_FLAG_DOOVER;
                        srp_rsp->data_out_res_cnt = cpu_to_be32(resid);
                } else if (cmd->data_direction == DMA_FROM_DEVICE) {
                        /* residual data from an overflow read */
                        srp_rsp->flags = SRP_RSP_FLAG_DIOVER;
                        srp_rsp->data_in_res_cnt = cpu_to_be32(resid);
                }
        }

        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) {
                        pr_warn("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 = 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 =
                cpu_to_be32(1 + atomic_xchg(&ch->req_lim_delta, 0));
        srp_rsp->tag = tag;

        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;
}

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

        return target_put_sess_cmd(&ioctx->cmd);
}

/**
 * srpt_handle_cmd - process a SRP_CMD information unit
 * @ch: SRPT RDMA channel.
 * @recv_ioctx: Receive I/O context.
 * @send_ioctx: Send I/O context.
 */
static void 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;
        struct scatterlist *sg = NULL;
        unsigned sg_cnt = 0;
        u64 data_len;
        enum dma_data_direction dir;
        int rc;

        BUG_ON(!send_ioctx);

        srp_cmd = recv_ioctx->ioctx.buf + recv_ioctx->ioctx.offset;
        cmd = &send_ioctx->cmd;
        cmd->tag = srp_cmd->tag;

        switch (srp_cmd->task_attr) {
        case SRP_CMD_SIMPLE_Q:
                cmd->sam_task_attr = TCM_SIMPLE_TAG;
                break;
        case SRP_CMD_ORDERED_Q:
        default:
                cmd->sam_task_attr = TCM_ORDERED_TAG;
                break;
        case SRP_CMD_HEAD_OF_Q:
                cmd->sam_task_attr = TCM_HEAD_TAG;
                break;
        case SRP_CMD_ACA:
                cmd->sam_task_attr = TCM_ACA_TAG;
                break;
        }

        rc = srpt_get_desc_tbl(recv_ioctx, send_ioctx, srp_cmd, &dir,
                               &sg, &sg_cnt, &data_len, ch->imm_data_offset);
        if (rc) {
                if (rc != -EAGAIN) {
                        pr_err("0x%llx: parsing SRP descriptor table failed.\n",
                               srp_cmd->tag);
                }
                goto busy;
        }

        rc = target_submit_cmd_map_sgls(cmd, ch->sess, srp_cmd->cdb,
                               &send_ioctx->sense_data[0],
                               scsilun_to_int(&srp_cmd->lun), data_len,
                               TCM_SIMPLE_TAG, dir, TARGET_SCF_ACK_KREF,
                               sg, sg_cnt, NULL, 0, NULL, 0);
        if (rc != 0) {
                pr_debug("target_submit_cmd() returned %d for tag %#llx\n", rc,
                         srp_cmd->tag);
                goto busy;
        }
        return;

busy:
        target_send_busy(cmd);
}

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 a SRP_TSK_MGMT information unit
 * @ch: SRPT RDMA channel.
 * @recv_ioctx: Receive I/O context.
 * @send_ioctx: Send I/O context.
 *
 * 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;
        struct se_session *sess = ch->sess;
        int tcm_tmr;
        int rc;

        BUG_ON(!send_ioctx);

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

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

        srpt_set_cmd_state(send_ioctx, SRPT_STATE_MGMT);
        send_ioctx->cmd.tag = srp_tsk->tag;
        tcm_tmr = srp_tmr_to_tcm(srp_tsk->tsk_mgmt_func);
        rc = target_submit_tmr(&send_ioctx->cmd, sess, NULL,
                               scsilun_to_int(&srp_tsk->lun), srp_tsk, tcm_tmr,
                               GFP_KERNEL, srp_tsk->task_tag,
                               TARGET_SCF_ACK_KREF);
        if (rc != 0) {
                send_ioctx->cmd.se_tmr_req->response = TMR_FUNCTION_REJECTED;
                cmd->se_tfo->queue_tm_rsp(cmd);
        }
        return;
}

/**
 * srpt_handle_new_iu - process a newly received information unit
 * @ch:    RDMA channel through which the information unit has been received.
 * @recv_ioctx: Receive I/O context associated with the information unit.
 */
static bool
srpt_handle_new_iu(struct srpt_rdma_ch *ch, struct srpt_recv_ioctx *recv_ioctx)
{
        struct srpt_send_ioctx *send_ioctx = NULL;
        struct srp_cmd *srp_cmd;
        bool res = false;
        u8 opcode;

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

        if (unlikely(ch->state == CH_CONNECTING))
                goto push;

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

        srp_cmd = recv_ioctx->ioctx.buf + recv_ioctx->ioctx.offset;
        opcode = srp_cmd->opcode;
        if (opcode == SRP_CMD || opcode == SRP_TSK_MGMT) {
                send_ioctx = srpt_get_send_ioctx(ch);
                if (unlikely(!send_ioctx))
                        goto push;
        }

        if (!list_empty(&recv_ioctx->wait_list)) {
                WARN_ON_ONCE(!ch->processing_wait_list);
                list_del_init(&recv_ioctx->wait_list);
        }

        switch (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:
                pr_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:
                pr_err("Received SRP_RSP\n");
                break;
        default:
                pr_err("received IU with unknown opcode 0x%x\n", opcode);
                break;
        }

        if (!send_ioctx || !send_ioctx->recv_ioctx)
                srpt_post_recv(ch->sport->sdev, ch, recv_ioctx);
        res = true;

out:
        return res;

push:
        if (list_empty(&recv_ioctx->wait_list)) {
                WARN_ON_ONCE(ch->processing_wait_list);
                list_add_tail(&recv_ioctx->wait_list, &ch->cmd_wait_list);
        }
        goto out;
}

static void srpt_recv_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct srpt_rdma_ch *ch = cq->cq_context;
        struct srpt_recv_ioctx *ioctx =
                container_of(wc->wr_cqe, struct srpt_recv_ioctx, ioctx.cqe);

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

                req_lim = atomic_dec_return(&ch->req_lim);
                if (unlikely(req_lim < 0))
                        pr_err("req_lim = %d < 0\n", req_lim);
                ioctx->byte_len = wc->byte_len;
                srpt_handle_new_iu(ch, ioctx);
        } else {
                pr_info_ratelimited("receiving failed for ioctx %p with status %d\n",
                                    ioctx, wc->status);
        }
}

/*
 * This function must be called from the context in which RDMA completions are
 * processed because it accesses the wait list without protection against
 * access from other threads.
 */
static void srpt_process_wait_list(struct srpt_rdma_ch *ch)
{
        struct srpt_recv_ioctx *recv_ioctx, *tmp;

        WARN_ON_ONCE(ch->state == CH_CONNECTING);

        if (list_empty(&ch->cmd_wait_list))
                return;

        WARN_ON_ONCE(ch->processing_wait_list);
        ch->processing_wait_list = true;
        list_for_each_entry_safe(recv_ioctx, tmp, &ch->cmd_wait_list,
                                 wait_list) {
                if (!srpt_handle_new_iu(ch, recv_ioctx))
                        break;
        }
        ch->processing_wait_list = false;
}

/**
 * srpt_send_done - send completion callback
 * @cq: Completion queue.
 * @wc: Work 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_send_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct srpt_rdma_ch *ch = cq->cq_context;
        struct srpt_send_ioctx *ioctx =
                container_of(wc->wr_cqe, struct srpt_send_ioctx, ioctx.cqe);
        enum srpt_command_state state;

        state = srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);

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

        atomic_add(1 + ioctx->n_rdma, &ch->sq_wr_avail);

        if (wc->status != IB_WC_SUCCESS)
                pr_info("sending response for ioctx 0x%p failed with status %d\n",
                        ioctx, wc->status);

        if (state != SRPT_STATE_DONE) {
                transport_generic_free_cmd(&ioctx->cmd, 0);
        } else {
                pr_err("IB completion has been received too late for wr_id = %u.\n",
                       ioctx->ioctx.index);
        }

        srpt_process_wait_list(ch);
}

/**
 * srpt_create_ch_ib - create receive and send completion queues
 * @ch: SRPT RDMA channel.
 */
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;
        const struct ib_device_attr *attrs = &sdev->device->attrs;
        int sq_size = sport->port_attrib.srp_sq_size;
        int i, ret;

        WARN_ON(ch->rq_size < 1);

        ret = -ENOMEM;
        qp_init = kzalloc(sizeof(*qp_init), GFP_KERNEL);
        if (!qp_init)
                goto out;

retry:
        ch->cq = ib_alloc_cq_any(sdev->device, ch, ch->rq_size + sq_size,
                                 IB_POLL_WORKQUEUE);
        if (IS_ERR(ch->cq)) {
                ret = PTR_ERR(ch->cq);
                pr_err("failed to create CQ cqe= %d ret= %d\n",
                       ch->rq_size + 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->sq_sig_type = IB_SIGNAL_REQ_WR;
        qp_init->qp_type = IB_QPT_RC;
        /*
         * We divide up our send queue size into half SEND WRs to send the
         * completions, and half R/W contexts to actually do the RDMA
         * READ/WRITE transfers.  Note that we need to allocate CQ slots for
         * both both, as RDMA contexts will also post completions for the
         * RDMA READ case.
         */
        qp_init->cap.max_send_wr = min(sq_size / 2, attrs->max_qp_wr);
        qp_init->cap.max_rdma_ctxs = sq_size / 2;
        qp_init->cap.max_send_sge = min(attrs->max_send_sge,
                                        SRPT_MAX_SG_PER_WQE);
        qp_init->cap.max_recv_sge = min(attrs->max_recv_sge,
                                        SRPT_MAX_SG_PER_WQE);
        qp_init->port_num = ch->sport->port;
        if (sdev->use_srq) {
                qp_init->srq = sdev->srq;
        } else {
                qp_init->cap.max_recv_wr = ch->rq_size;
                qp_init->cap.max_recv_sge = min(attrs->max_recv_sge,
                                                SRPT_MAX_SG_PER_WQE);
        }

        if (ch->using_rdma_cm) {
                ret = rdma_create_qp(ch->rdma_cm.cm_id, sdev->pd, qp_init);
                ch->qp = ch->rdma_cm.cm_id->qp;
        } else {
                ch->qp = ib_create_qp(sdev->pd, qp_init);
                if (!IS_ERR(ch->qp)) {
                        ret = srpt_init_ch_qp(ch, ch->qp);
                        if (ret)
                                ib_destroy_qp(ch->qp);
                } else {
                        ret = PTR_ERR(ch->qp);
                }
        }
        if (ret) {
                bool retry = sq_size > MIN_SRPT_SQ_SIZE;

                if (retry) {
                        pr_debug("failed to create queue pair with sq_size = %d (%d) - retrying\n",
                                 sq_size, ret);
                        ib_free_cq(ch->cq);
                        sq_size = max(sq_size / 2, MIN_SRPT_SQ_SIZE);
                        goto retry;
                } else {
                        pr_err("failed to create queue pair with sq_size = %d (%d)\n",
                               sq_size, 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 ch= %p\n",
                 __func__, ch->cq->cqe, qp_init->cap.max_send_sge,
                 qp_init->cap.max_send_wr, ch);

        if (!sdev->use_srq)
                for (i = 0; i < ch->rq_size; i++)
                        srpt_post_recv(sdev, ch, ch->ioctx_recv_ring[i]);

out:
        kfree(qp_init);
        return ret;

err_destroy_cq:
        ch->qp = NULL;
        ib_free_cq(ch->cq);
        goto out;
}

static void srpt_destroy_ch_ib(struct srpt_rdma_ch *ch)
{
        ib_destroy_qp(ch->qp);
        ib_free_cq(ch->cq);
}

/**
 * srpt_close_ch - close a RDMA channel
 * @ch: SRPT RDMA channel.
 *
 * Make sure all resources associated with the channel will be deallocated at
 * an appropriate time.
 *
 * Returns true if and only if the channel state has been modified into
 * CH_DRAINING.
 */
static bool srpt_close_ch(struct srpt_rdma_ch *ch)
{
        int ret;

        if (!srpt_set_ch_state(ch, CH_DRAINING)) {
                pr_debug("%s: already closed\n", ch->sess_name);
                return false;
        }

        kref_get(&ch->kref);

        ret = srpt_ch_qp_err(ch);
        if (ret < 0)
                pr_err("%s-%d: changing queue pair into error state failed: %d\n",
                       ch->sess_name, ch->qp->qp_num, ret);

        ret = srpt_zerolength_write(ch);
        if (ret < 0) {
                pr_err("%s-%d: queuing zero-length write failed: %d\n",
                       ch->sess_name, ch->qp->qp_num, ret);
                if (srpt_set_ch_state(ch, CH_DISCONNECTED))
                        schedule_work(&ch->release_work);
                else
                        WARN_ON_ONCE(true);
        }

        kref_put(&ch->kref, srpt_free_ch);

        return true;
}

/*
 * Change the channel state into CH_DISCONNECTING. If a channel has not yet
 * reached the connected state, close it. If a channel is in the connected
 * state, send a DREQ. If a DREQ has been received, send a DREP. Note: it is
 * the responsibility of the caller to ensure that this function is not
 * invoked concurrently with the code that accepts a connection. This means
 * that this function must either be invoked from inside a CM callback
 * function or that it must be invoked with the srpt_port.mutex held.
 */
static int srpt_disconnect_ch(struct srpt_rdma_ch *ch)
{
        int ret;

        if (!srpt_set_ch_state(ch, CH_DISCONNECTING))
                return -ENOTCONN;

        if (ch->using_rdma_cm) {
                ret = rdma_disconnect(ch->rdma_cm.cm_id);
        } else {
                ret = ib_send_cm_dreq(ch->ib_cm.cm_id, NULL, 0);
                if (ret < 0)
                        ret = ib_send_cm_drep(ch->ib_cm.cm_id, NULL, 0);
        }

        if (ret < 0 && srpt_close_ch(ch))
                ret = 0;

        return ret;
}

/* Send DREQ and wait for DREP. */
static void srpt_disconnect_ch_sync(struct srpt_rdma_ch *ch)
{
        DECLARE_COMPLETION_ONSTACK(closed);
        struct srpt_port *sport = ch->sport;

        pr_debug("ch %s-%d state %d\n", ch->sess_name, ch->qp->qp_num,
                 ch->state);

        ch->closed = &closed;

        mutex_lock(&sport->mutex);
        srpt_disconnect_ch(ch);
        mutex_unlock(&sport->mutex);

        while (wait_for_completion_timeout(&closed, 5 * HZ) == 0)
                pr_info("%s(%s-%d state %d): still waiting ...\n", __func__,
                        ch->sess_name, ch->qp->qp_num, ch->state);

}

static void __srpt_close_all_ch(struct srpt_port *sport)
{
        struct srpt_nexus *nexus;
        struct srpt_rdma_ch *ch;

        lockdep_assert_held(&sport->mutex);

        list_for_each_entry(nexus, &sport->nexus_list, entry) {
                list_for_each_entry(ch, &nexus->ch_list, list) {
                        if (srpt_disconnect_ch(ch) >= 0)
                                pr_info("Closing channel %s because target %s_%d has been disabled\n",
                                        ch->sess_name,
                                        dev_name(&sport->sdev->device->dev),
                                        sport->port);
                        srpt_close_ch(ch);
                }
        }
}

/*
 * Look up (i_port_id, t_port_id) in sport->nexus_list. Create an entry if
 * it does not yet exist.
 */
static struct srpt_nexus *srpt_get_nexus(struct srpt_port *sport,

                                         const u8 i_port_id[16],
                                         const u8 t_port_id[16])
{
        struct srpt_nexus *nexus = NULL, *tmp_nexus = NULL, *n;

        for (;;) {
                mutex_lock(&sport->mutex);
                list_for_each_entry(n, &sport->nexus_list, entry) {
                        if (memcmp(n->i_port_id, i_port_id, 16) == 0 &&
                            memcmp(n->t_port_id, t_port_id, 16) == 0) {
                                nexus = n;
                                break;
                        }
                }
                if (!nexus && tmp_nexus) {
                        list_add_tail_rcu(&tmp_nexus->entry,
                                          &sport->nexus_list);
                        swap(nexus, tmp_nexus);
                }
                mutex_unlock(&sport->mutex);

                if (nexus)
                        break;
                tmp_nexus = kzalloc(sizeof(*nexus), GFP_KERNEL);
                if (!tmp_nexus) {
                        nexus = ERR_PTR(-ENOMEM);
                        break;
                }
                INIT_LIST_HEAD(&tmp_nexus->ch_list);
                memcpy(tmp_nexus->i_port_id, i_port_id, 16);
                memcpy(tmp_nexus->t_port_id, t_port_id, 16);
        }

        kfree(tmp_nexus);

        return nexus;
}

static void srpt_set_enabled(struct srpt_port *sport, bool enabled)
        __must_hold(&sport->mutex)
{
        lockdep_assert_held(&sport->mutex);

        if (sport->enabled == enabled)
                return;
        sport->enabled = enabled;
        if (!enabled)
                __srpt_close_all_ch(sport);
}

static void srpt_drop_sport_ref(struct srpt_port *sport)
{
        if (atomic_dec_return(&sport->refcount) == 0 && sport->freed_channels)
                complete(sport->freed_channels);
}

static void srpt_free_ch(struct kref *kref)
{
        struct srpt_rdma_ch *ch = container_of(kref, struct srpt_rdma_ch, kref);

        srpt_drop_sport_ref(ch->sport);
        kfree_rcu(ch, rcu);
}

/*
 * Shut down the SCSI target session, tell the connection manager to
 * disconnect the associated RDMA channel, transition the QP to the error
 * state and remove the channel from the channel list. This function is
 * typically called from inside srpt_zerolength_write_done(). Concurrent
 * srpt_zerolength_write() calls from inside srpt_close_ch() are possible
 * as long as the channel is on sport->nexus_list.
 */
static void srpt_release_channel_work(struct work_struct *w)
{
        struct srpt_rdma_ch *ch;
        struct srpt_device *sdev;
        struct srpt_port *sport;
        struct se_session *se_sess;

        ch = container_of(w, struct srpt_rdma_ch, release_work);
        pr_debug("%s-%d\n", ch->sess_name, ch->qp->qp_num);

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

        se_sess = ch->sess;
        BUG_ON(!se_sess);

        target_sess_cmd_list_set_waiting(se_sess);
        target_wait_for_sess_cmds(se_sess);

        target_remove_session(se_sess);
        ch->sess = NULL;

        if (ch->using_rdma_cm)
                rdma_destroy_id(ch->rdma_cm.cm_id);
        else
                ib_destroy_cm_id(ch->ib_cm.cm_id);

        sport = ch->sport;
        mutex_lock(&sport->mutex);
        list_del_rcu(&ch->list);
        mutex_unlock(&sport->mutex);

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

        srpt_destroy_ch_ib(ch);

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

        kmem_cache_destroy(ch->rsp_buf_cache);

        srpt_free_ioctx_ring((struct srpt_ioctx **)ch->ioctx_recv_ring,
                             sdev, ch->rq_size,
                             ch->req_buf_cache, DMA_FROM_DEVICE);

        kmem_cache_destroy(ch->req_buf_cache);

        kref_put(&ch->kref, srpt_free_ch);
}

/**
 * srpt_cm_req_recv - process the event IB_CM_REQ_RECEIVED
 * @sdev: HCA through which the login request was received.
 * @ib_cm_id: IB/CM connection identifier in case of IB/CM.
 * @rdma_cm_id: RDMA/CM connection identifier in case of RDMA/CM.
 * @port_num: Port through which the REQ message was received.
 * @pkey: P_Key of the incoming connection.
 * @req: SRP login request.
 * @src_addr: GID (IB/CM) or IP address (RDMA/CM) of the port that submitted
 * the login request.
 *
 * Ownership of the cm_id is transferred to the target session if this
 * function returns zero. Otherwise the caller remains the owner of cm_id.
 */
static int srpt_cm_req_recv(struct srpt_device *const sdev,
                            struct ib_cm_id *ib_cm_id,
                            struct rdma_cm_id *rdma_cm_id,
                            u8 port_num, __be16 pkey,
                            const struct srp_login_req *req,
                            const char *src_addr)
{
        struct srpt_port *sport = &sdev->port[port_num - 1];
        struct srpt_nexus *nexus;
        struct srp_login_rsp *rsp = NULL;
        struct srp_login_rej *rej = NULL;
        union {
                struct rdma_conn_param rdma_cm;
                struct ib_cm_rep_param ib_cm;
        } *rep_param = NULL;
        struct srpt_rdma_ch *ch = NULL;
        char i_port_id[36];
        u32 it_iu_len;
        int i, tag_num, tag_size, ret;
        struct srpt_tpg *stpg;

        WARN_ON_ONCE(irqs_disabled());

        if (WARN_ON(!sdev || !req))
                return -EINVAL;

        it_iu_len = be32_to_cpu(req->req_it_iu_len);

        pr_info("Received SRP_LOGIN_REQ with i_port_id %pI6, t_port_id %pI6 and it_iu_len %d on port %d (guid=%pI6); pkey %#04x\n",
                req->initiator_port_id, req->target_port_id, it_iu_len,
                port_num, &sport->gid, be16_to_cpu(pkey));

        nexus = srpt_get_nexus(sport, req->initiator_port_id,
                               req->target_port_id);
        if (IS_ERR(nexus)) {
                ret = PTR_ERR(nexus);
                goto out;
        }

        ret = -ENOMEM;
        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)
                goto out;

        ret = -EINVAL;
        if (it_iu_len > srp_max_req_size || it_iu_len < 64) {
                rej->reason = cpu_to_be32(
                                SRP_LOGIN_REJ_REQ_IT_IU_LENGTH_TOO_LARGE);
                pr_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 = cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                pr_info("rejected SRP_LOGIN_REQ because target port %s_%d has not yet been enabled\n",
                        dev_name(&sport->sdev->device->dev), port_num);
                goto reject;
        }

        if (*(__be64 *)req->target_port_id != cpu_to_be64(srpt_service_guid)
            || *(__be64 *)(req->target_port_id + 8) !=
               cpu_to_be64(srpt_service_guid)) {
                rej->reason = cpu_to_be32(
                                SRP_LOGIN_REJ_UNABLE_ASSOCIATE_CHANNEL);
                pr_err("rejected SRP_LOGIN_REQ because it has an invalid target port identifier.\n");
                goto reject;
        }

        ret = -ENOMEM;
        ch = kzalloc(sizeof(*ch), GFP_KERNEL);
        if (!ch) {
                rej->reason = cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                pr_err("rejected SRP_LOGIN_REQ because out of memory.\n");
                goto reject;
        }

        kref_init(&ch->kref);
        ch->pkey = be16_to_cpu(pkey);
        ch->nexus = nexus;
        ch->zw_cqe.done = srpt_zerolength_write_done;
        INIT_WORK(&ch->release_work, srpt_release_channel_work);
        ch->sport = sport;
        if (ib_cm_id) {
                ch->ib_cm.cm_id = ib_cm_id;
                ib_cm_id->context = ch;
        } else {
                ch->using_rdma_cm = true;
                ch->rdma_cm.cm_id = rdma_cm_id;
                rdma_cm_id->context = ch;
        }
        /*
         * ch->rq_size should be at least as large as the initiator queue
         * depth to avoid that the initiator driver has to report QUEUE_FULL
         * to the SCSI mid-layer.
         */
        ch->rq_size = min(MAX_SRPT_RQ_SIZE, sdev->device->attrs.max_qp_wr);
        spin_lock_init(&ch->spinlock);
        ch->state = CH_CONNECTING;
        INIT_LIST_HEAD(&ch->cmd_wait_list);
        ch->max_rsp_size = ch->sport->port_attrib.srp_max_rsp_size;

        ch->rsp_buf_cache = kmem_cache_create("srpt-rsp-buf", ch->max_rsp_size,
                                              512, 0, NULL);
        if (!ch->rsp_buf_cache)
                goto free_ch;

        ch->ioctx_ring = (struct srpt_send_ioctx **)
                srpt_alloc_ioctx_ring(ch->sport->sdev, ch->rq_size,
                                      sizeof(*ch->ioctx_ring[0]),
                                      ch->rsp_buf_cache, 0, DMA_TO_DEVICE);
        if (!ch->ioctx_ring) {
                pr_err("rejected SRP_LOGIN_REQ because creating a new QP SQ ring failed.\n");
                rej->reason = cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                goto free_rsp_cache;
        }

        for (i = 0; i < ch->rq_size; i++)
                ch->ioctx_ring[i]->ch = ch;
        if (!sdev->use_srq) {
                u16 imm_data_offset = req->req_flags & SRP_IMMED_REQUESTED ?
                        be16_to_cpu(req->imm_data_offset) : 0;
                u16 alignment_offset;
                u32 req_sz;

                if (req->req_flags & SRP_IMMED_REQUESTED)
                        pr_debug("imm_data_offset = %d\n",
                                 be16_to_cpu(req->imm_data_offset));
                if (imm_data_offset >= sizeof(struct srp_cmd)) {
                        ch->imm_data_offset = imm_data_offset;
                        rsp->rsp_flags |= SRP_LOGIN_RSP_IMMED_SUPP;
                } else {
                        ch->imm_data_offset = 0;
                }
                alignment_offset = round_up(imm_data_offset, 512) -
                        imm_data_offset;
                req_sz = alignment_offset + imm_data_offset + srp_max_req_size;
                ch->req_buf_cache = kmem_cache_create("srpt-req-buf", req_sz,
                                                      512, 0, NULL);
                if (!ch->req_buf_cache)
                        goto free_rsp_ring;

                ch->ioctx_recv_ring = (struct srpt_recv_ioctx **)
                        srpt_alloc_ioctx_ring(ch->sport->sdev, ch->rq_size,
                                              sizeof(*ch->ioctx_recv_ring[0]),
                                              ch->req_buf_cache,
                                              alignment_offset,
                                              DMA_FROM_DEVICE);
                if (!ch->ioctx_recv_ring) {
                        pr_err("rejected SRP_LOGIN_REQ because creating a new QP RQ ring failed.\n");
                        rej->reason =
                            cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                        goto free_recv_cache;
                }
                for (i = 0; i < ch->rq_size; i++)
                        INIT_LIST_HEAD(&ch->ioctx_recv_ring[i]->wait_list);
        }

        ret = srpt_create_ch_ib(ch);
        if (ret) {
                rej->reason = cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                pr_err("rejected SRP_LOGIN_REQ because creating a new RDMA channel failed.\n");
                goto free_recv_ring;
        }

        strlcpy(ch->sess_name, src_addr, sizeof(ch->sess_name));
        snprintf(i_port_id, sizeof(i_port_id), "0x%016llx%016llx",
                        be64_to_cpu(*(__be64 *)nexus->i_port_id),
                        be64_to_cpu(*(__be64 *)(nexus->i_port_id + 8)));

        pr_debug("registering src addr %s or i_port_id %s\n", ch->sess_name,
                 i_port_id);

        tag_num = ch->rq_size;
        tag_size = 1; /* ib_srpt does not use se_sess->sess_cmd_map */

        mutex_lock(&sport->port_guid_id.mutex);
        list_for_each_entry(stpg, &sport->port_guid_id.tpg_list, entry) {
                if (!IS_ERR_OR_NULL(ch->sess))
                        break;
                ch->sess = target_setup_session(&stpg->tpg, tag_num,
                                                tag_size, TARGET_PROT_NORMAL,
                                                ch->sess_name, ch, NULL);
        }
        mutex_unlock(&sport->port_guid_id.mutex);

        mutex_lock(&sport->port_gid_id.mutex);
        list_for_each_entry(stpg, &sport->port_gid_id.tpg_list, entry) {
                if (!IS_ERR_OR_NULL(ch->sess))
                        break;
                ch->sess = target_setup_session(&stpg->tpg, tag_num,
                                        tag_size, TARGET_PROT_NORMAL, i_port_id,
                                        ch, NULL);
                if (!IS_ERR_OR_NULL(ch->sess))
                        break;
                /* Retry without leading "0x" */
                ch->sess = target_setup_session(&stpg->tpg, tag_num,
                                                tag_size, TARGET_PROT_NORMAL,
                                                i_port_id + 2, ch, NULL);
        }
        mutex_unlock(&sport->port_gid_id.mutex);

        if (IS_ERR_OR_NULL(ch->sess)) {
                WARN_ON_ONCE(ch->sess == NULL);
                ret = PTR_ERR(ch->sess);
                ch->sess = NULL;
                pr_info("Rejected login for initiator %s: ret = %d.\n",
                        ch->sess_name, ret);
                rej->reason = cpu_to_be32(ret == -ENOMEM ?
                                SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES :
                                SRP_LOGIN_REJ_CHANNEL_LIMIT_REACHED);
                goto destroy_ib;
        }

        /*
         * Once a session has been created destruction of srpt_rdma_ch objects
         * will decrement sport->refcount. Hence increment sport->refcount now.
         */
        atomic_inc(&sport->refcount);

        mutex_lock(&sport->mutex);

        if ((req->req_flags & SRP_MTCH_ACTION) == SRP_MULTICHAN_SINGLE) {
                struct srpt_rdma_ch *ch2;

                list_for_each_entry(ch2, &nexus->ch_list, list) {
                        if (srpt_disconnect_ch(ch2) < 0)
                                continue;
                        pr_info("Relogin - closed existing channel %s\n",
                                ch2->sess_name);
                        rsp->rsp_flags |= SRP_LOGIN_RSP_MULTICHAN_TERMINATED;
                }
        } else {
                rsp->rsp_flags |= SRP_LOGIN_RSP_MULTICHAN_MAINTAINED;
        }

        list_add_tail_rcu(&ch->list, &nexus->ch_list);

        if (!sport->enabled) {
                rej->reason = cpu_to_be32(
                                SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                pr_info("rejected SRP_LOGIN_REQ because target %s_%d is not enabled\n",
                        dev_name(&sdev->device->dev), port_num);
                mutex_unlock(&sport->mutex);
                goto reject;
        }

        mutex_unlock(&sport->mutex);

        ret = ch->using_rdma_cm ? 0 : srpt_ch_qp_rtr(ch, ch->qp);
        if (ret) {
                rej->reason = cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                pr_err("rejected SRP_LOGIN_REQ because enabling RTR failed (error code = %d)\n",
                       ret);
                goto reject;
        }

        pr_debug("Establish connection sess=%p name=%s ch=%p\n", ch->sess,
                 ch->sess_name, ch);

        /* create srp_login_response */
        rsp->opcode = SRP_LOGIN_RSP;
        rsp->tag = req->tag;
        rsp->max_it_iu_len = cpu_to_be32(srp_max_req_size);
        rsp->max_ti_iu_len = req->req_it_iu_len;
        ch->max_ti_iu_len = it_iu_len;
        rsp->buf_fmt = cpu_to_be16(SRP_BUF_FORMAT_DIRECT |
                                   SRP_BUF_FORMAT_INDIRECT);
        rsp->req_lim_delta = cpu_to_be32(ch->rq_size);
        atomic_set(&ch->req_lim, ch->rq_size);
        atomic_set(&ch->req_lim_delta, 0);

        /* create cm reply */
        if (ch->using_rdma_cm) {
                rep_param->rdma_cm.private_data = (void *)rsp;
                rep_param->rdma_cm.private_data_len = sizeof(*rsp);
                rep_param->rdma_cm.rnr_retry_count = 7;
                rep_param->rdma_cm.flow_control = 1;
                rep_param->rdma_cm.responder_resources = 4;
                rep_param->rdma_cm.initiator_depth = 4;
        } else {
                rep_param->ib_cm.qp_num = ch->qp->qp_num;
                rep_param->ib_cm.private_data = (void *)rsp;
                rep_param->ib_cm.private_data_len = sizeof(*rsp);
                rep_param->ib_cm.rnr_retry_count = 7;
                rep_param->ib_cm.flow_control = 1;
                rep_param->ib_cm.failover_accepted = 0;
                rep_param->ib_cm.srq = 1;
                rep_param->ib_cm.responder_resources = 4;
                rep_param->ib_cm.initiator_depth = 4;
        }

        /*
         * Hold the sport mutex while accepting a connection to avoid that
         * srpt_disconnect_ch() is invoked concurrently with this code.
         */
        mutex_lock(&sport->mutex);
        if (sport->enabled && ch->state == CH_CONNECTING) {
                if (ch->using_rdma_cm)
                        ret = rdma_accept(rdma_cm_id, &rep_param->rdma_cm);
                else
                        ret = ib_send_cm_rep(ib_cm_id, &rep_param->ib_cm);
        } else {
                ret = -EINVAL;
        }
        mutex_unlock(&sport->mutex);

        switch (ret) {
        case 0:
                break;
        case -EINVAL:
                goto reject;
        default:
                rej->reason = cpu_to_be32(SRP_LOGIN_REJ_INSUFFICIENT_RESOURCES);
                pr_err("sending SRP_LOGIN_REQ response failed (error code = %d)\n",
                       ret);
                goto reject;
        }

        goto out;

destroy_ib:
        srpt_destroy_ch_ib(ch);

free_recv_ring:
        srpt_free_ioctx_ring((struct srpt_ioctx **)ch->ioctx_recv_ring,
                             ch->sport->sdev, ch->rq_size,
                             ch->req_buf_cache, DMA_FROM_DEVICE);

free_recv_cache:
        kmem_cache_destroy(ch->req_buf_cache);

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

free_rsp_cache:
        kmem_cache_destroy(ch->rsp_buf_cache);

free_ch:
        if (rdma_cm_id)
                rdma_cm_id->context = NULL;
        else
                ib_cm_id->context = NULL;
        kfree(ch);
        ch = NULL;

        WARN_ON_ONCE(ret == 0);

reject:
        pr_info("Rejecting login with reason %#x\n", be32_to_cpu(rej->reason));
        rej->opcode = SRP_LOGIN_REJ;
        rej->tag = req->tag;
        rej->buf_fmt = cpu_to_be16(SRP_BUF_FORMAT_DIRECT |
                                   SRP_BUF_FORMAT_INDIRECT);

        if (rdma_cm_id)
                rdma_reject(rdma_cm_id, rej, sizeof(*rej));
        else
                ib_send_cm_rej(ib_cm_id, IB_CM_REJ_CONSUMER_DEFINED, NULL, 0,
                               rej, sizeof(*rej));

        if (ch && ch->sess) {
                srpt_close_ch(ch);
                /*
                 * Tell the caller not to free cm_id since
                 * srpt_release_channel_work() will do that.
                 */
                ret = 0;
        }

out:
        kfree(rep_param);
        kfree(rsp);
        kfree(rej);

        return ret;
}

static int srpt_ib_cm_req_recv(struct ib_cm_id *cm_id,
                               const struct ib_cm_req_event_param *param,
                               void *private_data)
{
        char sguid[40];

        srpt_format_guid(sguid, sizeof(sguid),
                         &param->primary_path->dgid.global.interface_id);

        return srpt_cm_req_recv(cm_id->context, cm_id, NULL, param->port,
                                param->primary_path->pkey,
                                private_data, sguid);
}

static int srpt_rdma_cm_req_recv(struct rdma_cm_id *cm_id,
                                 struct rdma_cm_event *event)
{
        struct srpt_device *sdev;
        struct srp_login_req req;
        const struct srp_login_req_rdma *req_rdma;
        struct sa_path_rec *path_rec = cm_id->route.path_rec;
        char src_addr[40];

        sdev = ib_get_client_data(cm_id->device, &srpt_client);
        if (!sdev)
                return -ECONNREFUSED;

        if (event->param.conn.private_data_len < sizeof(*req_rdma))
                return -EINVAL;

        /* Transform srp_login_req_rdma into srp_login_req. */
        req_rdma = event->param.conn.private_data;
        memset(&req, 0, sizeof(req));
        req.opcode              = req_rdma->opcode;
        req.tag                 = req_rdma->tag;
        req.req_it_iu_len       = req_rdma->req_it_iu_len;
        req.req_buf_fmt         = req_rdma->req_buf_fmt;
        req.req_flags           = req_rdma->req_flags;
        memcpy(req.initiator_port_id, req_rdma->initiator_port_id, 16);
        memcpy(req.target_port_id, req_rdma->target_port_id, 16);
        req.imm_data_offset     = req_rdma->imm_data_offset;

        snprintf(src_addr, sizeof(src_addr), "%pIS",
                 &cm_id->route.addr.src_addr);

        return srpt_cm_req_recv(sdev, NULL, cm_id, cm_id->port_num,
                                path_rec ? path_rec->pkey : 0, &req, src_addr);
}

static void srpt_cm_rej_recv(struct srpt_rdma_ch *ch,
                             enum ib_cm_rej_reason reason,
                             const u8 *private_data,
                             u8 private_data_len)
{
        char *priv = NULL;
        int i;

        if (private_data_len && (priv = kmalloc(private_data_len * 3 + 1,
                                                GFP_KERNEL))) {
                for (i = 0; i < private_data_len; i++)
                        sprintf(priv + 3 * i, " %02x", private_data[i]);
        }
        pr_info("Received CM REJ for ch %s-%d; reason %d%s%s.\n",
                ch->sess_name, ch->qp->qp_num, reason, private_data_len ?
                "; private data" : "", priv ? priv : " (?)");
        kfree(priv);
}

/**
 * srpt_cm_rtu_recv - process an IB_CM_RTU_RECEIVED or USER_ESTABLISHED event
 * @ch: SRPT RDMA channel.
 *
 * An RTU (ready to use) message indicates that the connection has been
 * established and that the recipient may begin transmitting.
 */
static void srpt_cm_rtu_recv(struct srpt_rdma_ch *ch)
{
        int ret;

        ret = ch->using_rdma_cm ? 0 : srpt_ch_qp_rts(ch, ch->qp);
        if (ret < 0) {
                pr_err("%s-%d: QP transition to RTS failed\n", ch->sess_name,
                       ch->qp->qp_num);
                srpt_close_ch(ch);
                return;
        }

        /*
         * Note: calling srpt_close_ch() if the transition to the LIVE state
         * fails is not necessary since that means that that function has
         * already been invoked from another thread.
         */
        if (!srpt_set_ch_state(ch, CH_LIVE)) {
                pr_err("%s-%d: channel transition to LIVE state failed\n",
                       ch->sess_name, ch->qp->qp_num);
                return;
        }

        /* Trigger wait list processing. */
        ret = srpt_zerolength_write(ch);
        WARN_ONCE(ret < 0, "%d\n", ret);
}

/**
 * srpt_cm_handler - IB connection manager callback function
 * @cm_id: IB/CM connection identifier.
 * @event: IB/CM event.
 *
 * 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,
                           const struct ib_cm_event *event)
{
        struct srpt_rdma_ch *ch = cm_id->context;
        int ret;

        ret = 0;
        switch (event->event) {
        case IB_CM_REQ_RECEIVED:
                ret = srpt_ib_cm_req_recv(cm_id, &event->param.req_rcvd,
                                          event->private_data);
                break;
        case IB_CM_REJ_RECEIVED:
                srpt_cm_rej_recv(ch, event->param.rej_rcvd.reason,
                                 event->private_data,
                                 IB_CM_REJ_PRIVATE_DATA_SIZE);
                break;
        case IB_CM_RTU_RECEIVED:
        case IB_CM_USER_ESTABLISHED:
                srpt_cm_rtu_recv(ch);
                break;
        case IB_CM_DREQ_RECEIVED:
                srpt_disconnect_ch(ch);
                break;
        case IB_CM_DREP_RECEIVED:
                pr_info("Received CM DREP message for ch %s-%d.\n",
                        ch->sess_name, ch->qp->qp_num);
                srpt_close_ch(ch);
                break;
        case IB_CM_TIMEWAIT_EXIT:
                pr_info("Received CM TimeWait exit for ch %s-%d.\n",
                        ch->sess_name, ch->qp->qp_num);
                srpt_close_ch(ch);
                break;
        case IB_CM_REP_ERROR:
                pr_info("Received CM REP error for ch %s-%d.\n", ch->sess_name,
                        ch->qp->qp_num);
                break;
        case IB_CM_DREQ_ERROR:
                pr_info("Received CM DREQ ERROR event.\n");
                break;
        case IB_CM_MRA_RECEIVED:
                pr_info("Received CM MRA event\n");
                break;
        default:
                pr_err("received unrecognized CM event %d\n", event->event);
                break;
        }

        return ret;
}

static int srpt_rdma_cm_handler(struct rdma_cm_id *cm_id,
                                struct rdma_cm_event *event)
{
        struct srpt_rdma_ch *ch = cm_id->context;
        int ret = 0;

        switch (event->event) {
        case RDMA_CM_EVENT_CONNECT_REQUEST:
                ret = srpt_rdma_cm_req_recv(cm_id, event);
                break;
        case RDMA_CM_EVENT_REJECTED:
                srpt_cm_rej_recv(ch, event->status,
                                 event->param.conn.private_data,
                                 event->param.conn.private_data_len);
                break;
        case RDMA_CM_EVENT_ESTABLISHED:
                srpt_cm_rtu_recv(ch);
                break;
        case RDMA_CM_EVENT_DISCONNECTED:
                if (ch->state < CH_DISCONNECTING)
                        srpt_disconnect_ch(ch);
                else
                        srpt_close_ch(ch);
                break;
        case RDMA_CM_EVENT_TIMEWAIT_EXIT:
                srpt_close_ch(ch);
                break;
        case RDMA_CM_EVENT_UNREACHABLE:
                pr_info("Received CM REP error for ch %s-%d.\n", ch->sess_name,
                        ch->qp->qp_num);
                break;
        case RDMA_CM_EVENT_DEVICE_REMOVAL:
        case RDMA_CM_EVENT_ADDR_CHANGE:
                break;
        default:
                pr_err("received unrecognized RDMA CM event %d\n",
                       event->event);
                break;
        }

        return ret;
}

/*
 * srpt_write_pending - Start data transfer from initiator to target (write).
 */
static int srpt_write_pending(struct se_cmd *se_cmd)
{
        struct srpt_send_ioctx *ioctx =
                container_of(se_cmd, struct srpt_send_ioctx, cmd);
        struct srpt_rdma_ch *ch = ioctx->ch;
        struct ib_send_wr *first_wr = NULL;
        struct ib_cqe *cqe = &ioctx->rdma_cqe;
        enum srpt_command_state new_state;
        int ret, i;

        if (ioctx->recv_ioctx) {
                srpt_set_cmd_state(ioctx, SRPT_STATE_DATA_IN);
                target_execute_cmd(&ioctx->cmd);
                return 0;
        }

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

        if (atomic_sub_return(ioctx->n_rdma, &ch->sq_wr_avail) < 0) {
                pr_warn("%s: IB send queue full (needed %d)\n",
                                __func__, ioctx->n_rdma);
                ret = -ENOMEM;
                goto out_undo;
        }

        cqe->done = srpt_rdma_read_done;
        for (i = ioctx->n_rw_ctx - 1; i >= 0; i--) {
                struct srpt_rw_ctx *ctx = &ioctx->rw_ctxs[i];

                first_wr = rdma_rw_ctx_wrs(&ctx->rw, ch->qp, ch->sport->port,
                                cqe, first_wr);
                cqe = NULL;
        }

        ret = ib_post_send(ch->qp, first_wr, NULL);
        if (ret) {
                pr_err("%s: ib_post_send() returned %d for %d (avail: %d)\n",
                         __func__, ret, ioctx->n_rdma,
                         atomic_read(&ch->sq_wr_avail));
                goto out_undo;
        }

        return 0;
out_undo:
        atomic_add(ioctx->n_rdma, &ch->sq_wr_avail);
        return ret;
}

static u8 tcm_to_srp_tsk_mgmt_status(const int tcm_mgmt_status)
{
        switch (tcm_mgmt_status) {
        case TMR_FUNCTION_COMPLETE:
                return SRP_TSK_MGMT_SUCCESS;
        case TMR_FUNCTION_REJECTED:
                return SRP_TSK_MGMT_FUNC_NOT_SUPP;
        }
        return SRP_TSK_MGMT_FAILED;
}

/**
 * srpt_queue_response - transmit the response to a SCSI command
 * @cmd: SCSI target command.
 *
 * Callback function called by the TCM core. Must not block since it can be
 * invoked on the context of the IB completion handler.
 */
static void srpt_queue_response(struct se_cmd *cmd)
{
        struct srpt_send_ioctx *ioctx =
                container_of(cmd, struct srpt_send_ioctx, cmd);
        struct srpt_rdma_ch *ch = ioctx->ch;
        struct srpt_device *sdev = ch->sport->sdev;
        struct ib_send_wr send_wr, *first_wr = &send_wr;
        struct ib_sge sge;
        enum srpt_command_state state;
        int resp_len, ret, i;
        u8 srp_tm_status;

        state = ioctx->state;
        switch (state) {
        case SRPT_STATE_NEW:
        case SRPT_STATE_DATA_IN:
                ioctx->state = SRPT_STATE_CMD_RSP_SENT;
                break;
        case SRPT_STATE_MGMT:
                ioctx->state = SRPT_STATE_MGMT_RSP_SENT;
                break;
        default:
                WARN(true, "ch %p; cmd %d: unexpected command state %d\n",
                        ch, ioctx->ioctx.index, ioctx->state);
                break;
        }

        if (WARN_ON_ONCE(state == SRPT_STATE_CMD_RSP_SENT))
                return;

        /* For read commands, transfer the data to the initiator. */
        if (ioctx->cmd.data_direction == DMA_FROM_DEVICE &&
            ioctx->cmd.data_length &&
            !ioctx->queue_status_only) {
                for (i = ioctx->n_rw_ctx - 1; i >= 0; i--) {
                        struct srpt_rw_ctx *ctx = &ioctx->rw_ctxs[i];

                        first_wr = rdma_rw_ctx_wrs(&ctx->rw, ch->qp,
                                        ch->sport->port, NULL, first_wr);
                }
        }

        if (state != SRPT_STATE_MGMT)
                resp_len = srpt_build_cmd_rsp(ch, ioctx, ioctx->cmd.tag,
                                              cmd->scsi_status);
        else {
                srp_tm_status
                        = tcm_to_srp_tsk_mgmt_status(cmd->se_tmr_req->response);
                resp_len = srpt_build_tskmgmt_rsp(ch, ioctx, srp_tm_status,
                                                 ioctx->cmd.tag);
        }

        atomic_inc(&ch->req_lim);

        if (unlikely(atomic_sub_return(1 + ioctx->n_rdma,
                        &ch->sq_wr_avail) < 0)) {
                pr_warn("%s: IB send queue full (needed %d)\n",
                                __func__, ioctx->n_rdma);
                ret = -ENOMEM;
                goto out;
        }

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

        sge.addr = ioctx->ioctx.dma;
        sge.length = resp_len;
        sge.lkey = sdev->lkey;

        ioctx->ioctx.cqe.done = srpt_send_done;
        send_wr.next = NULL;
        send_wr.wr_cqe = &ioctx->ioctx.cqe;
        send_wr.sg_list = &sge;
        send_wr.num_sge = 1;
        send_wr.opcode = IB_WR_SEND;
        send_wr.send_flags = IB_SEND_SIGNALED;

        ret = ib_post_send(ch->qp, first_wr, NULL);
        if (ret < 0) {
                pr_err("%s: sending cmd response failed for tag %llu (%d)\n",
                        __func__, ioctx->cmd.tag, ret);
                goto out;
        }

        return;

out:
        atomic_add(1 + ioctx->n_rdma, &ch->sq_wr_avail);
        atomic_dec(&ch->req_lim);
        srpt_set_cmd_state(ioctx, SRPT_STATE_DONE);
        target_put_sess_cmd(&ioctx->cmd);
}

static int srpt_queue_data_in(struct se_cmd *cmd)
{
        srpt_queue_response(cmd);
        return 0;
}

static void srpt_queue_tm_rsp(struct se_cmd *cmd)
{
        srpt_queue_response(cmd);
}

/*
 * This function is called for aborted commands if no response is sent to the
 * initiator. Make sure that the credits freed by aborting a command are
 * returned to the initiator the next time a response is sent by incrementing
 * ch->req_lim_delta.
 */
static void srpt_aborted_task(struct se_cmd *cmd)
{
        struct srpt_send_ioctx *ioctx = container_of(cmd,
                                struct srpt_send_ioctx, cmd);
        struct srpt_rdma_ch *ch = ioctx->ch;

        atomic_inc(&ch->req_lim_delta);
}

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

        ioctx = container_of(cmd, struct srpt_send_ioctx, cmd);
        BUG_ON(ioctx->sense_data != cmd->sense_buffer);
        if (cmd->se_cmd_flags &
            (SCF_TRANSPORT_TASK_SENSE | SCF_EMULATED_TASK_SENSE))
                WARN_ON(cmd->scsi_status != SAM_STAT_CHECK_CONDITION);
        ioctx->queue_status_only = true;
        srpt_queue_response(cmd);
        return 0;
}

static void srpt_refresh_port_work(struct work_struct *work)
{
        struct srpt_port *sport = container_of(work, struct srpt_port, work);

        srpt_refresh_port(sport);
}

/**
 * srpt_release_sport - disable login and wait for associated channels
 * @sport: SRPT HCA port.
 */
static int srpt_release_sport(struct srpt_port *sport)
{
        DECLARE_COMPLETION_ONSTACK(c);
        struct srpt_nexus *nexus, *next_n;
        struct srpt_rdma_ch *ch;

        WARN_ON_ONCE(irqs_disabled());

        sport->freed_channels = &c;

        mutex_lock(&sport->mutex);
        srpt_set_enabled(sport, false);
        mutex_unlock(&sport->mutex);

        while (atomic_read(&sport->refcount) > 0 &&
               wait_for_completion_timeout(&c, 5 * HZ) <= 0) {
                pr_info("%s_%d: waiting for unregistration of %d sessions ...\n",
                        dev_name(&sport->sdev->device->dev), sport->port,
                        atomic_read(&sport->refcount));
                rcu_read_lock();
                list_for_each_entry(nexus, &sport->nexus_list, entry) {
                        list_for_each_entry(ch, &nexus->ch_list, list) {
                                pr_info("%s-%d: state %s\n",
                                        ch->sess_name, ch->qp->qp_num,
                                        get_ch_state_name(ch->state));
                        }
                }
                rcu_read_unlock();
        }

        mutex_lock(&sport->mutex);
        list_for_each_entry_safe(nexus, next_n, &sport->nexus_list, entry) {
                list_del(&nexus->entry);
                kfree_rcu(nexus, rcu);
        }
        mutex_unlock(&sport->mutex);

        return 0;
}

static struct se_wwn *__srpt_lookup_wwn(const char *name)
{
        struct ib_device *dev;
        struct srpt_device *sdev;
        struct srpt_port *sport;
        int i;

        list_for_each_entry(sdev, &srpt_dev_list, list) {
                dev = sdev->device;
                if (!dev)
                        continue;

                for (i = 0; i < dev->phys_port_cnt; i++) {
                        sport = &sdev->port[i];

                        if (strcmp(sport->port_guid_id.name, name) == 0)