/*
 * Copyright (c) 2005 Cisco Systems.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/parser.h>
#include <linux/random.h>
#include <linux/jiffies.h>
#include <rdma/ib_cache.h>

#include <linux/atomic.h>

#include <scsi/scsi.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_dbg.h>
#include <scsi/scsi_tcq.h>
#include <scsi/srp.h>
#include <scsi/scsi_transport_srp.h>

#include "ib_srp.h"

#define DRV_NAME        "ib_srp"
#define PFX             DRV_NAME ": "
#define DRV_VERSION     "2.0"
#define DRV_RELDATE     "July 26, 2015"

MODULE_AUTHOR("Roland Dreier");
MODULE_DESCRIPTION("InfiniBand SCSI RDMA Protocol initiator");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_VERSION(DRV_VERSION);
MODULE_INFO(release_date, DRV_RELDATE);

static unsigned int srp_sg_tablesize;
static unsigned int cmd_sg_entries;
static unsigned int indirect_sg_entries;
static bool allow_ext_sg;
static bool prefer_fr = true;
static bool register_always = true;
static bool never_register;
static int topspin_workarounds = 1;

module_param(srp_sg_tablesize, uint, 0444);
MODULE_PARM_DESC(srp_sg_tablesize, "Deprecated name for cmd_sg_entries");

module_param(cmd_sg_entries, uint, 0444);
MODULE_PARM_DESC(cmd_sg_entries,
                 "Default number of gather/scatter entries in the SRP command (default is 12, max 255)");

module_param(indirect_sg_entries, uint, 0444);
MODULE_PARM_DESC(indirect_sg_entries,
                 "Default max number of gather/scatter entries (default is 12, max is " __stringify(SG_MAX_SEGMENTS) ")");

module_param(allow_ext_sg, bool, 0444);
MODULE_PARM_DESC(allow_ext_sg,
                  "Default behavior when there are more than cmd_sg_entries S/G entries after mapping; fails the request when false (default false)");

module_param(topspin_workarounds, int, 0444);
MODULE_PARM_DESC(topspin_workarounds,
                 "Enable workarounds for Topspin/Cisco SRP target bugs if != 0");

module_param(prefer_fr, bool, 0444);
MODULE_PARM_DESC(prefer_fr,
"Whether to use fast registration if both FMR and fast registration are supported");

module_param(register_always, bool, 0444);
MODULE_PARM_DESC(register_always,
                 "Use memory registration even for contiguous memory regions");

module_param(never_register, bool, 0444);
MODULE_PARM_DESC(never_register, "Never register memory");

static const struct kernel_param_ops srp_tmo_ops;

static int srp_reconnect_delay = 10;
module_param_cb(reconnect_delay, &srp_tmo_ops, &srp_reconnect_delay,
                S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(reconnect_delay, "Time between successive reconnect attempts");

static int srp_fast_io_fail_tmo = 15;
module_param_cb(fast_io_fail_tmo, &srp_tmo_ops, &srp_fast_io_fail_tmo,
                S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(fast_io_fail_tmo,
                 "Number of seconds between the observation of a transport"
                 " layer error and failing all I/O. \"off\" means that this"
                 " functionality is disabled.");

static int srp_dev_loss_tmo = 600;
module_param_cb(dev_loss_tmo, &srp_tmo_ops, &srp_dev_loss_tmo,
                S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(dev_loss_tmo,
                 "Maximum number of seconds that the SRP transport should"
                 " insulate transport layer errors. After this time has been"
                 " exceeded the SCSI host is removed. Should be"
                 " between 1 and " __stringify(SCSI_DEVICE_BLOCK_MAX_TIMEOUT)
                 " if fast_io_fail_tmo has not been set. \"off\" means that"
                 " this functionality is disabled.");

static unsigned ch_count;
module_param(ch_count, uint, 0444);
MODULE_PARM_DESC(ch_count,
                 "Number of RDMA channels to use for communication with an SRP target. Using more than one channel improves performance if the HCA supports multiple completion vectors. The default value is the minimum of four times the number of online CPU sockets and the number of completion vectors supported by the HCA.");

static void srp_add_one(struct ib_device *device);
static void srp_remove_one(struct ib_device *device, void *client_data);
static void srp_recv_done(struct ib_cq *cq, struct ib_wc *wc);
static void srp_handle_qp_err(struct ib_cq *cq, struct ib_wc *wc,
                const char *opname);
static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event);

static struct scsi_transport_template *ib_srp_transport_template;
static struct workqueue_struct *srp_remove_wq;

static struct ib_client srp_client = {
        .name   = "srp",
        .add    = srp_add_one,
        .remove = srp_remove_one
};

static struct ib_sa_client srp_sa_client;

static int srp_tmo_get(char *buffer, const struct kernel_param *kp)
{
        int tmo = *(int *)kp->arg;

        if (tmo >= 0)
                return sprintf(buffer, "%d", tmo);
        else
                return sprintf(buffer, "off");
}

static int srp_tmo_set(const char *val, const struct kernel_param *kp)
{
        int tmo, res;

        res = srp_parse_tmo(&tmo, val);
        if (res)
                goto out;

        if (kp->arg == &srp_reconnect_delay)
                res = srp_tmo_valid(tmo, srp_fast_io_fail_tmo,
                                    srp_dev_loss_tmo);
        else if (kp->arg == &srp_fast_io_fail_tmo)
                res = srp_tmo_valid(srp_reconnect_delay, tmo, srp_dev_loss_tmo);
        else
                res = srp_tmo_valid(srp_reconnect_delay, srp_fast_io_fail_tmo,
                                    tmo);
        if (res)
                goto out;
        *(int *)kp->arg = tmo;

out:
        return res;
}

static const struct kernel_param_ops srp_tmo_ops = {
        .get = srp_tmo_get,
        .set = srp_tmo_set,
};

static inline struct srp_target_port *host_to_target(struct Scsi_Host *host)
{
        return (struct srp_target_port *) host->hostdata;
}

static const char *srp_target_info(struct Scsi_Host *host)
{
        return host_to_target(host)->target_name;
}

static int srp_target_is_topspin(struct srp_target_port *target)
{
        static const u8 topspin_oui[3] = { 0x00, 0x05, 0xad };
        static const u8 cisco_oui[3]   = { 0x00, 0x1b, 0x0d };

        return topspin_workarounds &&
                (!memcmp(&target->ioc_guid, topspin_oui, sizeof topspin_oui) ||
                 !memcmp(&target->ioc_guid, cisco_oui, sizeof cisco_oui));
}

static struct srp_iu *srp_alloc_iu(struct srp_host *host, size_t size,
                                   gfp_t gfp_mask,
                                   enum dma_data_direction direction)
{
        struct srp_iu *iu;

        iu = kmalloc(sizeof *iu, gfp_mask);
        if (!iu)
                goto out;

        iu->buf = kzalloc(size, gfp_mask);
        if (!iu->buf)
                goto out_free_iu;

        iu->dma = ib_dma_map_single(host->srp_dev->dev, iu->buf, size,
                                    direction);
        if (ib_dma_mapping_error(host->srp_dev->dev, iu->dma))
                goto out_free_buf;

        iu->size      = size;
        iu->direction = direction;

        return iu;

out_free_buf:
        kfree(iu->buf);
out_free_iu:
        kfree(iu);
out:
        return NULL;
}

static void srp_free_iu(struct srp_host *host, struct srp_iu *iu)
{
        if (!iu)
                return;

        ib_dma_unmap_single(host->srp_dev->dev, iu->dma, iu->size,
                            iu->direction);
        kfree(iu->buf);
        kfree(iu);
}

static void srp_qp_event(struct ib_event *event, void *context)
{
        pr_debug("QP event %s (%d)\n",
                 ib_event_msg(event->event), event->event);
}

static int srp_init_qp(struct srp_target_port *target,
                       struct ib_qp *qp)
{
        struct ib_qp_attr *attr;
        int ret;

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

        ret = ib_find_cached_pkey(target->srp_host->srp_dev->dev,
                                  target->srp_host->port,
                                  be16_to_cpu(target->pkey),
                                  &attr->pkey_index);
        if (ret)
                goto out;

        attr->qp_state        = IB_QPS_INIT;
        attr->qp_access_flags = (IB_ACCESS_REMOTE_READ |
                                    IB_ACCESS_REMOTE_WRITE);
        attr->port_num        = target->srp_host->port;

        ret = ib_modify_qp(qp, attr,
                           IB_QP_STATE          |
                           IB_QP_PKEY_INDEX     |
                           IB_QP_ACCESS_FLAGS   |
                           IB_QP_PORT);

out:
        kfree(attr);
        return ret;
}

static int srp_new_cm_id(struct srp_rdma_ch *ch)
{
        struct srp_target_port *target = ch->target;
        struct ib_cm_id *new_cm_id;

        new_cm_id = ib_create_cm_id(target->srp_host->srp_dev->dev,
                                    srp_cm_handler, ch);
        if (IS_ERR(new_cm_id))
                return PTR_ERR(new_cm_id);

        if (ch->cm_id)
                ib_destroy_cm_id(ch->cm_id);
        ch->cm_id = new_cm_id;
        ch->path.sgid = target->sgid;
        ch->path.dgid = target->orig_dgid;
        ch->path.pkey = target->pkey;
        ch->path.service_id = target->service_id;

        return 0;
}

static struct ib_fmr_pool *srp_alloc_fmr_pool(struct srp_target_port *target)
{
        struct srp_device *dev = target->srp_host->srp_dev;
        struct ib_fmr_pool_param fmr_param;

        memset(&fmr_param, 0, sizeof(fmr_param));
        fmr_param.pool_size         = target->mr_pool_size;
        fmr_param.dirty_watermark   = fmr_param.pool_size / 4;
        fmr_param.cache             = 1;
        fmr_param.max_pages_per_fmr = dev->max_pages_per_mr;
        fmr_param.page_shift        = ilog2(dev->mr_page_size);
        fmr_param.access            = (IB_ACCESS_LOCAL_WRITE |
                                       IB_ACCESS_REMOTE_WRITE |
                                       IB_ACCESS_REMOTE_READ);

        return ib_create_fmr_pool(dev->pd, &fmr_param);
}

/**
 * srp_destroy_fr_pool() - free the resources owned by a pool
 * @pool: Fast registration pool to be destroyed.
 */
static void srp_destroy_fr_pool(struct srp_fr_pool *pool)
{
        int i;
        struct srp_fr_desc *d;

        if (!pool)
                return;

        for (i = 0, d = &pool->desc[0]; i < pool->size; i++, d++) {
                if (d->mr)
                        ib_dereg_mr(d->mr);
        }
        kfree(pool);
}

/**
 * srp_create_fr_pool() - allocate and initialize a pool for fast registration
 * @device:            IB device to allocate fast registration descriptors for.
 * @pd:                Protection domain associated with the FR descriptors.
 * @pool_size:         Number of descriptors to allocate.
 * @max_page_list_len: Maximum fast registration work request page list length.
 */
static struct srp_fr_pool *srp_create_fr_pool(struct ib_device *device,
                                              struct ib_pd *pd, int pool_size,
                                              int max_page_list_len)
{
        struct srp_fr_pool *pool;
        struct srp_fr_desc *d;
        struct ib_mr *mr;
        int i, ret = -EINVAL;

        if (pool_size <= 0)
                goto err;
        ret = -ENOMEM;
        pool = kzalloc(sizeof(struct srp_fr_pool) +
                       pool_size * sizeof(struct srp_fr_desc), GFP_KERNEL);
        if (!pool)
                goto err;
        pool->size = pool_size;
        pool->max_page_list_len = max_page_list_len;
        spin_lock_init(&pool->lock);
        INIT_LIST_HEAD(&pool->free_list);

        for (i = 0, d = &pool->desc[0]; i < pool->size; i++, d++) {
                mr = ib_alloc_mr(pd, IB_MR_TYPE_MEM_REG,
                                 max_page_list_len);
                if (IS_ERR(mr)) {
                        ret = PTR_ERR(mr);
                        goto destroy_pool;
                }
                d->mr = mr;
                list_add_tail(&d->entry, &pool->free_list);
        }

out:
        return pool;

destroy_pool:
        srp_destroy_fr_pool(pool);

err:
        pool = ERR_PTR(ret);
        goto out;
}

/**
 * srp_fr_pool_get() - obtain a descriptor suitable for fast registration
 * @pool: Pool to obtain descriptor from.
 */
static struct srp_fr_desc *srp_fr_pool_get(struct srp_fr_pool *pool)
{
        struct srp_fr_desc *d = NULL;
        unsigned long flags;

        spin_lock_irqsave(&pool->lock, flags);
        if (!list_empty(&pool->free_list)) {
                d = list_first_entry(&pool->free_list, typeof(*d), entry);
                list_del(&d->entry);
        }
        spin_unlock_irqrestore(&pool->lock, flags);

        return d;
}

/**
 * srp_fr_pool_put() - put an FR descriptor back in the free list
 * @pool: Pool the descriptor was allocated from.
 * @desc: Pointer to an array of fast registration descriptor pointers.
 * @n:    Number of descriptors to put back.
 *
 * Note: The caller must already have queued an invalidation request for
 * desc->mr->rkey before calling this function.
 */
static void srp_fr_pool_put(struct srp_fr_pool *pool, struct srp_fr_desc **desc,
                            int n)
{
        unsigned long flags;
        int i;

        spin_lock_irqsave(&pool->lock, flags);
        for (i = 0; i < n; i++)
                list_add(&desc[i]->entry, &pool->free_list);
        spin_unlock_irqrestore(&pool->lock, flags);
}

static struct srp_fr_pool *srp_alloc_fr_pool(struct srp_target_port *target)
{
        struct srp_device *dev = target->srp_host->srp_dev;

        return srp_create_fr_pool(dev->dev, dev->pd, target->mr_pool_size,
                                  dev->max_pages_per_mr);
}

/**
 * srp_destroy_qp() - destroy an RDMA queue pair
 * @qp: RDMA queue pair.
 *
 * Drain the qp before destroying it.  This avoids that the receive
 * completion handler can access the queue pair while it is
 * being destroyed.
 */
static void srp_destroy_qp(struct ib_qp *qp)
{
        ib_drain_rq(qp);
        ib_destroy_qp(qp);
}

static int srp_create_ch_ib(struct srp_rdma_ch *ch)
{
        struct srp_target_port *target = ch->target;
        struct srp_device *dev = target->srp_host->srp_dev;
        struct ib_qp_init_attr *init_attr;
        struct ib_cq *recv_cq, *send_cq;
        struct ib_qp *qp;
        struct ib_fmr_pool *fmr_pool = NULL;
        struct srp_fr_pool *fr_pool = NULL;
        const int m = 1 + dev->use_fast_reg * target->mr_per_cmd * 2;
        int ret;

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

        /* queue_size + 1 for ib_drain_rq() */
        recv_cq = ib_alloc_cq(dev->dev, ch, target->queue_size + 1,
                                ch->comp_vector, IB_POLL_SOFTIRQ);
        if (IS_ERR(recv_cq)) {
                ret = PTR_ERR(recv_cq);
                goto err;
        }

        send_cq = ib_alloc_cq(dev->dev, ch, m * target->queue_size,
                                ch->comp_vector, IB_POLL_DIRECT);
        if (IS_ERR(send_cq)) {
                ret = PTR_ERR(send_cq);
                goto err_recv_cq;
        }

        init_attr->event_handler       = srp_qp_event;
        init_attr->cap.max_send_wr     = m * target->queue_size;
        init_attr->cap.max_recv_wr     = target->queue_size + 1;
        init_attr->cap.max_recv_sge    = 1;
        init_attr->cap.max_send_sge    = 1;
        init_attr->sq_sig_type         = IB_SIGNAL_REQ_WR;
        init_attr->qp_type             = IB_QPT_RC;
        init_attr->send_cq             = send_cq;
        init_attr->recv_cq             = recv_cq;

        qp = ib_create_qp(dev->pd, init_attr);
        if (IS_ERR(qp)) {
                ret = PTR_ERR(qp);
                goto err_send_cq;
        }

        ret = srp_init_qp(target, qp);
        if (ret)
                goto err_qp;

        if (dev->use_fast_reg) {
                fr_pool = srp_alloc_fr_pool(target);
                if (IS_ERR(fr_pool)) {
                        ret = PTR_ERR(fr_pool);
                        shost_printk(KERN_WARNING, target->scsi_host, PFX
                                     "FR pool allocation failed (%d)\n", ret);
                        goto err_qp;
                }
        } else if (dev->use_fmr) {
                fmr_pool = srp_alloc_fmr_pool(target);
                if (IS_ERR(fmr_pool)) {
                        ret = PTR_ERR(fmr_pool);
                        shost_printk(KERN_WARNING, target->scsi_host, PFX
                                     "FMR pool allocation failed (%d)\n", ret);
                        goto err_qp;
                }
        }

        if (ch->qp)
                srp_destroy_qp(ch->qp);
        if (ch->recv_cq)
                ib_free_cq(ch->recv_cq);
        if (ch->send_cq)
                ib_free_cq(ch->send_cq);

        ch->qp = qp;
        ch->recv_cq = recv_cq;
        ch->send_cq = send_cq;

        if (dev->use_fast_reg) {
                if (ch->fr_pool)
                        srp_destroy_fr_pool(ch->fr_pool);
                ch->fr_pool = fr_pool;
        } else if (dev->use_fmr) {
                if (ch->fmr_pool)
                        ib_destroy_fmr_pool(ch->fmr_pool);
                ch->fmr_pool = fmr_pool;
        }

        kfree(init_attr);
        return 0;

err_qp:
        srp_destroy_qp(qp);

err_send_cq:
        ib_free_cq(send_cq);

err_recv_cq:
        ib_free_cq(recv_cq);

err:
        kfree(init_attr);
        return ret;
}

/*
 * Note: this function may be called without srp_alloc_iu_bufs() having been
 * invoked. Hence the ch->[rt]x_ring checks.
 */
static void srp_free_ch_ib(struct srp_target_port *target,
                           struct srp_rdma_ch *ch)
{
        struct srp_device *dev = target->srp_host->srp_dev;
        int i;

        if (!ch->target)
                return;

        if (ch->cm_id) {
                ib_destroy_cm_id(ch->cm_id);
                ch->cm_id = NULL;
        }

        /* If srp_new_cm_id() succeeded but srp_create_ch_ib() not, return. */
        if (!ch->qp)
                return;

        if (dev->use_fast_reg) {
                if (ch->fr_pool)
                        srp_destroy_fr_pool(ch->fr_pool);
        } else if (dev->use_fmr) {
                if (ch->fmr_pool)
                        ib_destroy_fmr_pool(ch->fmr_pool);
        }

        srp_destroy_qp(ch->qp);
        ib_free_cq(ch->send_cq);
        ib_free_cq(ch->recv_cq);

        /*
         * Avoid that the SCSI error handler tries to use this channel after
         * it has been freed. The SCSI error handler can namely continue
         * trying to perform recovery actions after scsi_remove_host()
         * returned.
         */
        ch->target = NULL;

        ch->qp = NULL;
        ch->send_cq = ch->recv_cq = NULL;

        if (ch->rx_ring) {
                for (i = 0; i < target->queue_size; ++i)
                        srp_free_iu(target->srp_host, ch->rx_ring[i]);
                kfree(ch->rx_ring);
                ch->rx_ring = NULL;
        }
        if (ch->tx_ring) {
                for (i = 0; i < target->queue_size; ++i)
                        srp_free_iu(target->srp_host, ch->tx_ring[i]);
                kfree(ch->tx_ring);
                ch->tx_ring = NULL;
        }
}

static void srp_path_rec_completion(int status,
                                    struct ib_sa_path_rec *pathrec,
                                    void *ch_ptr)
{
        struct srp_rdma_ch *ch = ch_ptr;
        struct srp_target_port *target = ch->target;

        ch->status = status;
        if (status)
                shost_printk(KERN_ERR, target->scsi_host,
                             PFX "Got failed path rec status %d\n", status);
        else
                ch->path = *pathrec;
        complete(&ch->done);
}

static int srp_lookup_path(struct srp_rdma_ch *ch)
{
        struct srp_target_port *target = ch->target;
        int ret;

        ch->path.numb_path = 1;

        init_completion(&ch->done);

        ch->path_query_id = ib_sa_path_rec_get(&srp_sa_client,
                                               target->srp_host->srp_dev->dev,
                                               target->srp_host->port,
                                               &ch->path,
                                               IB_SA_PATH_REC_SERVICE_ID |
                                               IB_SA_PATH_REC_DGID       |
                                               IB_SA_PATH_REC_SGID       |
                                               IB_SA_PATH_REC_NUMB_PATH  |
                                               IB_SA_PATH_REC_PKEY,
                                               SRP_PATH_REC_TIMEOUT_MS,
                                               GFP_KERNEL,
                                               srp_path_rec_completion,
                                               ch, &ch->path_query);
        if (ch->path_query_id < 0)
                return ch->path_query_id;

        ret = wait_for_completion_interruptible(&ch->done);
        if (ret < 0)
                return ret;

        if (ch->status < 0)
                shost_printk(KERN_WARNING, target->scsi_host,
                             PFX "Path record query failed\n");

        return ch->status;
}

static int srp_send_req(struct srp_rdma_ch *ch, bool multich)
{
        struct srp_target_port *target = ch->target;
        struct {
                struct ib_cm_req_param param;
                struct srp_login_req   priv;
        } *req = NULL;
        int status;

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

        req->param.primary_path               = &ch->path;
        req->param.alternate_path             = NULL;
        req->param.service_id                 = target->service_id;
        req->param.qp_num                     = ch->qp->qp_num;
        req->param.qp_type                    = ch->qp->qp_type;
        req->param.private_data               = &req->priv;
        req->param.private_data_len           = sizeof req->priv;
        req->param.flow_control               = 1;

        get_random_bytes(&req->param.starting_psn, 4);
        req->param.starting_psn              &= 0xffffff;

        /*
         * Pick some arbitrary defaults here; we could make these
         * module parameters if anyone cared about setting them.
         */
        req->param.responder_resources        = 4;
        req->param.remote_cm_response_timeout = 20;
        req->param.local_cm_response_timeout  = 20;
        req->param.retry_count                = target->tl_retry_count;
        req->param.rnr_retry_count            = 7;
        req->param.max_cm_retries             = 15;

        req->priv.opcode        = SRP_LOGIN_REQ;
        req->priv.tag           = 0;
        req->priv.req_it_iu_len = cpu_to_be32(target->max_iu_len);
        req->priv.req_buf_fmt   = cpu_to_be16(SRP_BUF_FORMAT_DIRECT |
                                              SRP_BUF_FORMAT_INDIRECT);
        req->priv.req_flags     = (multich ? SRP_MULTICHAN_MULTI :
                                   SRP_MULTICHAN_SINGLE);
        /*
         * In the published SRP specification (draft rev. 16a), the
         * port identifier format is 8 bytes of ID extension followed
         * by 8 bytes of GUID.  Older drafts put the two halves in the
         * opposite order, so that the GUID comes first.
         *
         * Targets conforming to these obsolete drafts can be
         * recognized by the I/O Class they report.
         */
        if (target->io_class == SRP_REV10_IB_IO_CLASS) {
                memcpy(req->priv.initiator_port_id,
                       &target->sgid.global.interface_id, 8);
                memcpy(req->priv.initiator_port_id + 8,
                       &target->initiator_ext, 8);
                memcpy(req->priv.target_port_id,     &target->ioc_guid, 8);
                memcpy(req->priv.target_port_id + 8, &target->id_ext, 8);
        } else {
                memcpy(req->priv.initiator_port_id,
                       &target->initiator_ext, 8);
                memcpy(req->priv.initiator_port_id + 8,
                       &target->sgid.global.interface_id, 8);
                memcpy(req->priv.target_port_id,     &target->id_ext, 8);
                memcpy(req->priv.target_port_id + 8, &target->ioc_guid, 8);
        }

        /*
         * Topspin/Cisco SRP targets will reject our login unless we
         * zero out the first 8 bytes of our initiator port ID and set
         * the second 8 bytes to the local node GUID.
         */
        if (srp_target_is_topspin(target)) {
                shost_printk(KERN_DEBUG, target->scsi_host,
                             PFX "Topspin/Cisco initiator port ID workaround "
                             "activated for target GUID %016llx\n",
                             be64_to_cpu(target->ioc_guid));
                memset(req->priv.initiator_port_id, 0, 8);
                memcpy(req->priv.initiator_port_id + 8,
                       &target->srp_host->srp_dev->dev->node_guid, 8);
        }

        status = ib_send_cm_req(ch->cm_id, &req->param);

        kfree(req);

        return status;
}

static bool srp_queue_remove_work(struct srp_target_port *target)
{
        bool changed = false;

        spin_lock_irq(&target->lock);
        if (target->state != SRP_TARGET_REMOVED) {
                target->state = SRP_TARGET_REMOVED;
                changed = true;
        }
        spin_unlock_irq(&target->lock);

        if (changed)
                queue_work(srp_remove_wq, &target->remove_work);

        return changed;
}

static void srp_disconnect_target(struct srp_target_port *target)
{
        struct srp_rdma_ch *ch;
        int i;

        /* XXX should send SRP_I_LOGOUT request */

        for (i = 0; i < target->ch_count; i++) {
                ch = &target->ch[i];
                ch->connected = false;
                if (ch->cm_id && ib_send_cm_dreq(ch->cm_id, NULL, 0)) {
                        shost_printk(KERN_DEBUG, target->scsi_host,
                                     PFX "Sending CM DREQ failed\n");
                }
        }
}

static void srp_free_req_data(struct srp_target_port *target,
                              struct srp_rdma_ch *ch)
{
        struct srp_device *dev = target->srp_host->srp_dev;
        struct ib_device *ibdev = dev->dev;
        struct srp_request *req;
        int i;

        if (!ch->req_ring)
                return;

        for (i = 0; i < target->req_ring_size; ++i) {
                req = &ch->req_ring[i];
                if (dev->use_fast_reg) {
                        kfree(req->fr_list);
                } else {
                        kfree(req->fmr_list);
                        kfree(req->map_page);
                }
                if (req->indirect_dma_addr) {
                        ib_dma_unmap_single(ibdev, req->indirect_dma_addr,
                                            target->indirect_size,
                                            DMA_TO_DEVICE);
                }
                kfree(req->indirect_desc);
        }

        kfree(ch->req_ring);
        ch->req_ring = NULL;
}

static int srp_alloc_req_data(struct srp_rdma_ch *ch)
{
        struct srp_target_port *target = ch->target;
        struct srp_device *srp_dev = target->srp_host->srp_dev;
        struct ib_device *ibdev = srp_dev->dev;
        struct srp_request *req;
        void *mr_list;
        dma_addr_t dma_addr;
        int i, ret = -ENOMEM;

        ch->req_ring = kcalloc(target->req_ring_size, sizeof(*ch->req_ring),
                               GFP_KERNEL);
        if (!ch->req_ring)
                goto out;

        for (i = 0; i < target->req_ring_size; ++i) {
                req = &ch->req_ring[i];
                mr_list = kmalloc(target->mr_per_cmd * sizeof(void *),
                                  GFP_KERNEL);
                if (!mr_list)
                        goto out;
                if (srp_dev->use_fast_reg) {
                        req->fr_list = mr_list;
                } else {
                        req->fmr_list = mr_list;
                        req->map_page = kmalloc(srp_dev->max_pages_per_mr *
                                                sizeof(void *), GFP_KERNEL);
                        if (!req->map_page)
                                goto out;
                }
                req->indirect_desc = kmalloc(target->indirect_size, GFP_KERNEL);
                if (!req->indirect_desc)
                        goto out;

                dma_addr = ib_dma_map_single(ibdev, req->indirect_desc,
                                             target->indirect_size,
                                             DMA_TO_DEVICE);
                if (ib_dma_mapping_error(ibdev, dma_addr))
                        goto out;

                req->indirect_dma_addr = dma_addr;
        }
        ret = 0;

out:
        return ret;
}

/**
 * srp_del_scsi_host_attr() - Remove attributes defined in the host template.
 * @shost: SCSI host whose attributes to remove from sysfs.
 *
 * Note: Any attributes defined in the host template and that did not exist
 * before invocation of this function will be ignored.
 */
static void srp_del_scsi_host_attr(struct Scsi_Host *shost)
{
        struct device_attribute **attr;

        for (attr = shost->hostt->shost_attrs; attr && *attr; ++attr)
                device_remove_file(&shost->shost_dev, *attr);
}

static void srp_remove_target(struct srp_target_port *target)
{
        struct srp_rdma_ch *ch;
        int i;

        WARN_ON_ONCE(target->state != SRP_TARGET_REMOVED);

        srp_del_scsi_host_attr(target->scsi_host);
        srp_rport_get(target->rport);
        srp_remove_host(target->scsi_host);
        scsi_remove_host(target->scsi_host);
        srp_stop_rport_timers(target->rport);
        srp_disconnect_target(target);
        for (i = 0; i < target->ch_count; i++) {
                ch = &target->ch[i];
                srp_free_ch_ib(target, ch);
        }
        cancel_work_sync(&target->tl_err_work);
        srp_rport_put(target->rport);
        for (i = 0; i < target->ch_count; i++) {
                ch = &target->ch[i];
                srp_free_req_data(target, ch);
        }
        kfree(target->ch);
        target->ch = NULL;

        spin_lock(&target->srp_host->target_lock);
        list_del(&target->list);
        spin_unlock(&target->srp_host->target_lock);

        scsi_host_put(target->scsi_host);
}

static void srp_remove_work(struct work_struct *work)
{
        struct srp_target_port *target =
                container_of(work, struct srp_target_port, remove_work);

        WARN_ON_ONCE(target->state != SRP_TARGET_REMOVED);

        srp_remove_target(target);
}

static void srp_rport_delete(struct srp_rport *rport)
{
        struct srp_target_port *target = rport->lld_data;

        srp_queue_remove_work(target);
}

/**
 * srp_connected_ch() - number of connected channels
 * @target: SRP target port.
 */
static int srp_connected_ch(struct srp_target_port *target)
{
        int i, c = 0;

        for (i = 0; i < target->ch_count; i++)
                c += target->ch[i].connected;

        return c;
}

static int srp_connect_ch(struct srp_rdma_ch *ch, bool multich)
{
        struct srp_target_port *target = ch->target;
        int ret;

        WARN_ON_ONCE(!multich && srp_connected_ch(target) > 0);

        ret = srp_lookup_path(ch);
        if (ret)
                goto out;

        while (1) {
                init_completion(&ch->done);
                ret = srp_send_req(ch, multich);
                if (ret)
                        goto out;
                ret = wait_for_completion_interruptible(&ch->done);
                if (ret < 0)
                        goto out;

                /*
                 * The CM event handling code will set status to
                 * SRP_PORT_REDIRECT if we get a port redirect REJ
                 * back, or SRP_DLID_REDIRECT if we get a lid/qp
                 * redirect REJ back.
                 */
                ret = ch->status;
                switch (ret) {
                case 0:
                        ch->connected = true;
                        goto out;

                case SRP_PORT_REDIRECT:
                        ret = srp_lookup_path(ch);
                        if (ret)

                                goto out;
                        break;

                case SRP_DLID_REDIRECT:
                        break;

                case SRP_STALE_CONN:
                        shost_printk(KERN_ERR, target->scsi_host, PFX
                                     "giving up on stale connection\n");
                        ret = -ECONNRESET;
                        goto out;

                default:
                        goto out;
                }
        }

out:
        return ret <= 0 ? ret : -ENODEV;
}

static void srp_inv_rkey_err_done(struct ib_cq *cq, struct ib_wc *wc)
{
        srp_handle_qp_err(cq, wc, "INV RKEY");
}

static int srp_inv_rkey(struct srp_request *req, struct srp_rdma_ch *ch,
                u32 rkey)
{
        struct ib_send_wr *bad_wr;
        struct ib_send_wr wr = {
                .opcode             = IB_WR_LOCAL_INV,
                .next               = NULL,
                .num_sge            = 0,
                .send_flags         = 0,
                .ex.invalidate_rkey = rkey,
        };

        wr.wr_cqe = &req->reg_cqe;
        req->reg_cqe.done = srp_inv_rkey_err_done;
        return ib_post_send(ch->qp, &wr, &bad_wr);
}

static void srp_unmap_data(struct scsi_cmnd *scmnd,
                           struct srp_rdma_ch *ch,
                           struct srp_request *req)
{
        struct srp_target_port *target = ch->target;
        struct srp_device *dev = target->srp_host->srp_dev;
        struct ib_device *ibdev = dev->dev;
        int i, res;

        if (!scsi_sglist(scmnd) ||
            (scmnd->sc_data_direction != DMA_TO_DEVICE &&
             scmnd->sc_data_direction != DMA_FROM_DEVICE))
                return;

        if (dev->use_fast_reg) {
                struct srp_fr_desc **pfr;

                for (i = req->nmdesc, pfr = req->fr_list; i > 0; i--, pfr++) {
                        res = srp_inv_rkey(req, ch, (*pfr)->mr->rkey);
                        if (res < 0) {
                                shost_printk(KERN_ERR, target->scsi_host, PFX
                                  "Queueing INV WR for rkey %#x failed (%d)\n",
                                  (*pfr)->mr->rkey, res);
                                queue_work(system_long_wq,
                                           &target->tl_err_work);
                        }
                }
                if (req->nmdesc)
                        srp_fr_pool_put(ch->fr_pool, req->fr_list,
                                        req->nmdesc);
        } else if (dev->use_fmr) {
                struct ib_pool_fmr **pfmr;

                for (i = req->nmdesc, pfmr = req->fmr_list; i > 0; i--, pfmr++)
                        ib_fmr_pool_unmap(*pfmr);
        }

        ib_dma_unmap_sg(ibdev, scsi_sglist(scmnd), scsi_sg_count(scmnd),
                        scmnd->sc_data_direction);
}

/**
 * srp_claim_req - Take ownership of the scmnd associated with a request.
 * @ch: SRP RDMA channel.
 * @req: SRP request.
 * @sdev: If not NULL, only take ownership for this SCSI device.
 * @scmnd: If NULL, take ownership of @req->scmnd. If not NULL, only take
 *         ownership of @req->scmnd if it equals @scmnd.
 *
 * Return value:
 * Either NULL or a pointer to the SCSI command the caller became owner of.
 */
static struct scsi_cmnd *srp_claim_req(struct srp_rdma_ch *ch,
                                       struct srp_request *req,
                                       struct scsi_device *sdev,
                                       struct scsi_cmnd *scmnd)
{
        unsigned long flags;

        spin_lock_irqsave(&ch->lock, flags);
        if (req->scmnd &&
            (!sdev || req->scmnd->device == sdev) &&
            (!scmnd || req->scmnd == scmnd)) {
                scmnd = req->scmnd;
                req->scmnd = NULL;
        } else {
                scmnd = NULL;
        }
        spin_unlock_irqrestore(&ch->lock, flags);

        return scmnd;
}

/**
 * srp_free_req() - Unmap data and adjust ch->req_lim.
 * @ch:     SRP RDMA channel.
 * @req:    Request to be freed.
 * @scmnd:  SCSI command associated with @req.
 * @req_lim_delta: Amount to be added to @target->req_lim.
 */
static void srp_free_req(struct srp_rdma_ch *ch, struct srp_request *req,
                         struct scsi_cmnd *scmnd, s32 req_lim_delta)
{
        unsigned long flags;

        srp_unmap_data(scmnd, ch, req);

        spin_lock_irqsave(&ch->lock, flags);
        ch->req_lim += req_lim_delta;
        spin_unlock_irqrestore(&ch->lock, flags);
}

static void srp_finish_req(struct srp_rdma_ch *ch, struct srp_request *req,
                           struct scsi_device *sdev, int result)
{
        struct scsi_cmnd *scmnd = srp_claim_req(ch, req, sdev, NULL);

        if (scmnd) {
                srp_free_req(ch, req, scmnd, 0);
                scmnd->result = result;
                scmnd->scsi_done(scmnd);
        }
}

static void srp_terminate_io(struct srp_rport *rport)
{
        struct srp_target_port *target = rport->lld_data;
        struct srp_rdma_ch *ch;
        struct Scsi_Host *shost = target->scsi_host;
        struct scsi_device *sdev;
        int i, j;

        /*
         * Invoking srp_terminate_io() while srp_queuecommand() is running
         * is not safe. Hence the warning statement below.
         */
        shost_for_each_device(sdev, shost)
                WARN_ON_ONCE(sdev->request_queue->request_fn_active);

        for (i = 0; i < target->ch_count; i++) {
                ch = &target->ch[i];

                for (j = 0; j < target->req_ring_size; ++j) {
                        struct srp_request *req = &ch->req_ring[j];

                        srp_finish_req(ch, req, NULL,
                                       DID_TRANSPORT_FAILFAST << 16);
                }
        }
}

/*
 * It is up to the caller to ensure that srp_rport_reconnect() calls are
 * serialized and that no concurrent srp_queuecommand(), srp_abort(),
 * srp_reset_device() or srp_reset_host() calls will occur while this function
 * is in progress. One way to realize that is not to call this function
 * directly but to call srp_reconnect_rport() instead since that last function
 * serializes calls of this function via rport->mutex and also blocks
 * srp_queuecommand() calls before invoking this function.
 */
static int srp_rport_reconnect(struct srp_rport *rport)
{
        struct srp_target_port *target = rport->lld_data;
        struct srp_rdma_ch *ch;
        int i, j, ret = 0;
        bool multich = false;

        srp_disconnect_target(target);

        if (target->state == SRP_TARGET_SCANNING)
                return -ENODEV;

        /*
         * Now get a new local CM ID so that we avoid confusing the target in
         * case things are really fouled up. Doing so also ensures that all CM
         * callbacks will have finished before a new QP is allocated.
         */
        for (i = 0; i < target->ch_count; i++) {
                ch = &target->ch[i];
                ret += srp_new_cm_id(ch);
        }
        for (i = 0; i < target->ch_count; i++) {
                ch = &target->ch[i];
                for (j = 0; j < target->req_ring_size; ++j) {
                        struct srp_request *req = &ch->req_ring[j];

                        srp_finish_req(ch, req, NULL, DID_RESET << 16);
                }
        }
        for (i = 0; i < target->ch_count; i++) {
                ch = &target->ch[i];
                /*
                 * Whether or not creating a new CM ID succeeded, create a new
                 * QP. This guarantees that all completion callback function
                 * invocations have finished before request resetting starts.
                 */
                ret += srp_create_ch_ib(ch);

                INIT_LIST_HEAD(&ch->free_tx);
                for (j = 0; j < target->queue_size; ++j)
                        list_add(&ch->tx_ring[j]->list, &ch->free_tx);
        }

        target->qp_in_error = false;

        for (i = 0; i < target->ch_count; i++) {
                ch = &target->ch[i];
                if (ret)
                        break;
                ret = srp_connect_ch(ch, multich);
                multich = true;
        }

        if (ret == 0)
                shost_printk(KERN_INFO, target->scsi_host,
                             PFX "reconnect succeeded\n");

        return ret;
}

static void srp_map_desc(struct srp_map_state *state, dma_addr_t dma_addr,
                         unsigned int dma_len, u32 rkey)
{
        struct srp_direct_buf *desc = state->desc;

        WARN_ON_ONCE(!dma_len);

        desc->va = cpu_to_be64(dma_addr);
        desc->key = cpu_to_be32(rkey);
        desc->len = cpu_to_be32(dma_len);

        state->total_len += dma_len;
        state->desc++;
        state->ndesc++;
}

static int srp_map_finish_fmr(struct srp_map_state *state,
                              struct srp_rdma_ch *ch)
{
        struct srp_target_port *target = ch->target;
        struct srp_device *dev = target->srp_host->srp_dev;
        struct ib_pool_fmr *fmr;
        u64 io_addr = 0;

        if (state->fmr.next >= state->fmr.end)
                return -ENOMEM;

        WARN_ON_ONCE(!dev->use_fmr);

        if (state->npages == 0)
                return 0;

        if (state->npages == 1 && target->global_mr) {
                srp_map_desc(state, state->base_dma_addr, state->dma_len,
                             target->global_mr->rkey);
                goto reset_state;
        }

        fmr = ib_fmr_pool_map_phys(ch->fmr_pool, state->pages,
                                   state->npages, io_addr);
        if (IS_ERR(fmr))
                return PTR_ERR(fmr);

        *state->fmr.next++ = fmr;
        state->nmdesc++;

        srp_map_desc(state, state->base_dma_addr & ~dev->mr_page_mask,
                     state->dma_len, fmr->fmr->rkey);

reset_state:
        state->npages = 0;
        state->dma_len = 0;

        return 0;
}

static void srp_reg_mr_err_done(struct ib_cq *cq, struct ib_wc *wc)
{
        srp_handle_qp_err(cq, wc, "FAST REG");
}

/*
 * Map up to sg_nents elements of state->sg where *sg_offset_p is the offset
 * where to start in the first element. If sg_offset_p != NULL then
 * *sg_offset_p is updated to the offset in state->sg[retval] of the first
 * byte that has not yet been mapped.
 */
static int srp_map_finish_fr(struct srp_map_state *state,
                             struct srp_request *req,
                             struct srp_rdma_ch *ch, int sg_nents,
                             unsigned int *sg_offset_p)
{
        struct srp_target_port *target = ch->target;
        struct srp_device *dev = target->srp_host->srp_dev;
        struct ib_send_wr *bad_wr;
        struct ib_reg_wr wr;
        struct srp_fr_desc *desc;
        u32 rkey;
        int n, err;

        if (state->fr.next >= state->fr.end)
                return -ENOMEM;

        WARN_ON_ONCE(!dev->use_fast_reg);

        if (sg_nents == 1 && target->global_mr) {
                unsigned int sg_offset = sg_offset_p ? *sg_offset_p : 0;

                srp_map_desc(state, sg_dma_address(state->sg) + sg_offset,
                             sg_dma_len(state->sg) - sg_offset,
                             target->global_mr->rkey);
                if (sg_offset_p)
                        *sg_offset_p = 0;
                return 1;
        }

        desc = srp_fr_pool_get(ch->fr_pool);
        if (!desc)
                return -ENOMEM;

        rkey = ib_inc_rkey(desc->mr->rkey);
        ib_update_fast_reg_key(desc->mr, rkey);

        n = ib_map_mr_sg(desc->mr, state->sg, sg_nents, sg_offset_p,
                         dev->mr_page_size);
        if (unlikely(n < 0)) {
                srp_fr_pool_put(ch->fr_pool, &desc, 1);
                pr_debug("%s: ib_map_mr_sg(%d, %d) returned %d.\n",
                         dev_name(&req->scmnd->device->sdev_gendev), sg_nents,
                         sg_offset_p ? *sg_offset_p : -1, n);
                return n;
        }

        WARN_ON_ONCE(desc->mr->length == 0);

        req->reg_cqe.done = srp_reg_mr_err_done;

        wr.wr.next = NULL;
        wr.wr.opcode = IB_WR_REG_MR;
        wr.wr.wr_cqe = &req->reg_cqe;
        wr.wr.num_sge = 0;
        wr.wr.send_flags = 0;
        wr.mr = desc->mr;
        wr.key = desc->mr->rkey;
        wr.access = (IB_ACCESS_LOCAL_WRITE |
                     IB_ACCESS_REMOTE_READ |
                     IB_ACCESS_REMOTE_WRITE);

        *state->fr.next++ = desc;
        state->nmdesc++;

        srp_map_desc(state, desc->mr->iova,
                     desc->mr->length, desc->mr->rkey);

        err = ib_post_send(ch->qp, &wr.wr, &bad_wr);
        if (unlikely(err)) {
                WARN_ON_ONCE(err == -ENOMEM);
                return err;
        }

        return n;
}

static int srp_map_sg_entry(struct srp_map_state *state,
                            struct srp_rdma_ch *ch,
                            struct scatterlist *sg, int sg_index)
{
        struct srp_target_port *target = ch->target;
        struct srp_device *dev = target->srp_host->srp_dev;
        struct ib_device *ibdev = dev->dev;
        dma_addr_t dma_addr = ib_sg_dma_address(ibdev, sg);
        unsigned int dma_len = ib_sg_dma_len(ibdev, sg);
        unsigned int len = 0;
        int ret;

        WARN_ON_ONCE(!dma_len);

        while (dma_len) {
                unsigned offset = dma_addr & ~dev->mr_page_mask;
                if (state->npages == dev->max_pages_per_mr || offset != 0) {
                        ret = srp_map_finish_fmr(state, ch);
                        if (ret)
                                return ret;
                }

                len = min_t(unsigned int, dma_len, dev->mr_page_size - offset);

                if (!state->npages)
                        state->base_dma_addr = dma_addr;
                state->pages[state->npages++] = dma_addr & dev->mr_page_mask;
                state->dma_len += len;
                dma_addr += len;
                dma_len -= len;
        }

        /*
         * If the last entry of the MR wasn't a full page, then we need to
         * close it out and start a new one -- we can only merge at page
         * boundaries.
         */
        ret = 0;
        if (len != dev->mr_page_size)
                ret = srp_map_finish_fmr(state, ch);
        return ret;
}

static int srp_map_sg_fmr(struct srp_map_state *state, struct srp_rdma_ch *ch,
                          struct srp_request *req, struct scatterlist *scat,
                          int count)
{
        struct scatterlist *sg;
        int i, ret;

        state->pages = req->map_page;
        state->fmr.next = req->fmr_list;
        state->fmr.end = req->fmr_list + ch->target->mr_per_cmd;

        for_each_sg(scat, sg, count, i) {
                ret = srp_map_sg_entry(state, ch, sg, i);
                if (ret)
                        return ret;
        }

        ret = srp_map_finish_fmr(state, ch);
        if (ret)
                return ret;

        return 0;
}

static int srp_map_sg_fr(struct srp_map_state *state, struct srp_rdma_ch *ch,
                         struct srp_request *req, struct scatterlist *scat,
                         int count)
{
        unsigned int sg_offset = 0;

        state->fr.next = req->fr_list;
        state->fr.end = req->fr_list + ch->target->mr_per_cmd;
        state->sg = scat;

        if (count == 0)
                return 0;

        while (count) {
                int i, n;

                n = srp_map_finish_fr(state, req, ch, count, &sg_offset);
                if (unlikely(n < 0))
                        return n;

                count -= n;
                for (i = 0; i < n; i++)
                        state->sg = sg_next(state->sg);
        }

        return 0;
}

static int srp_map_sg_dma(struct srp_map_state *state, struct srp_rdma_ch *ch,
                          struct srp_request *req, struct scatterlist *scat,
                          int count)
{
        struct srp_target_port *target = ch->target;
        struct srp_device *dev = target->srp_host->srp_dev;
        struct scatterlist *sg;
        int i;

        for_each_sg(scat, sg, count, i) {
                srp_map_desc(state, ib_sg_dma_address(dev->dev, sg),
                             ib_sg_dma_len(dev->dev, sg),
                             target->global_mr->rkey);
        }

        return 0;
}

/*
 * Register the indirect data buffer descriptor with the HCA.
 *
 * Note: since the indirect data buffer descriptor has been allocated with
 * kmalloc() it is guaranteed that this buffer is a physically contiguous
 * memory buffer.
 */
static int srp_map_idb(struct srp_rdma_ch *ch, struct srp_request *req,
                       void **next_mr, void **end_mr, u32 idb_len,
                       __be32 *idb_rkey)
{
        struct srp_target_port *target = ch->target;
        struct srp_device *dev = target->srp_host->srp_dev;
        struct srp_map_state state;
        struct srp_direct_buf idb_desc;
        u64 idb_pages[1];
        struct scatterlist idb_sg[1];
        int ret;

        memset(&state, 0, sizeof(state));
        memset(&idb_desc, 0, sizeof(idb_desc));
        state.gen.next = next_mr;
        state.gen.end = end_mr;
        state.desc = &idb_desc;
        state.base_dma_addr = req->indirect_dma_addr;
        state.dma_len = idb_len;

        if (dev->use_fast_reg) {
                state.sg = idb_sg;
                sg_init_one(idb_sg, req->indirect_desc, idb_len);
                idb_sg->dma_address = req->indirect_dma_addr; /* hack! */
#ifdef CONFIG_NEED_SG_DMA_LENGTH
                idb_sg->dma_length = idb_sg->length;          /* hack^2 */
#endif
                ret = srp_map_finish_fr(&state, req, ch, 1, NULL);
                if (ret < 0)
                        return ret;
                WARN_ON_ONCE(ret < 1);
        } else if (dev->use_fmr) {
                state.pages = idb_pages;
                state.pages[0] = (req->indirect_dma_addr &
                                  dev->mr_page_mask);
                state.npages = 1;
                ret = srp_map_finish_fmr(&state, ch);
                if (ret < 0)
                        return ret;
        } else {
                return -EINVAL;
        }

        *idb_rkey = idb_desc.key;

        return 0;
}

#if defined(DYNAMIC_DATA_DEBUG)
static void srp_check_mapping(struct srp_map_state *state,
                              struct srp_rdma_ch *ch, struct srp_request *req,
                              struct scatterlist *scat, int count)
{
        struct srp_device *dev = ch->target->srp_host->srp_dev;
        struct srp_fr_desc **pfr;
        u64 desc_len = 0, mr_len = 0;
        int i;

        for (i = 0; i < state->ndesc; i++)
                desc_len += be32_to_cpu(req->indirect_desc[i].len);
        if (dev->use_fast_reg)
                for (i = 0, pfr = req->fr_list; i < state->nmdesc; i++, pfr++)
                        mr_len += (*pfr)->mr->length;
        else if (dev->use_fmr)
                for (i = 0; i < state->nmdesc; i++)
                        mr_len += be32_to_cpu(req->indirect_desc[i].len);
        if (desc_len != scsi_bufflen(req->scmnd) ||
            mr_len > scsi_bufflen(req->scmnd))
                pr_err("Inconsistent: scsi len %d <> desc len %lld <> mr len %lld; ndesc %d; nmdesc = %d\n",
                       scsi_bufflen(req->scmnd), desc_len, mr_len,
                       state->ndesc, state->nmdesc);
}
#endif

/**
 * srp_map_data() - map SCSI data buffer onto an SRP request
 * @scmnd: SCSI command to map
 * @ch: SRP RDMA channel
 * @req: SRP request
 *
 * Returns the length in bytes of the SRP_CMD IU or a negative value if
 * mapping failed.
 */
static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_rdma_ch *ch,
                        struct srp_request *req)
{
        struct srp_target_port *target = ch->target;
        struct scatterlist *scat;
        struct srp_cmd *cmd = req->cmd->buf;
        int len, nents, count, ret;
        struct srp_device *dev;
        struct ib_device *ibdev;
        struct srp_map_state state;
        struct srp_indirect_buf *indirect_hdr;
        u32 idb_len, table_len;
        __be32 idb_rkey;
        u8 fmt;

        if (!scsi_sglist(scmnd) || scmnd->sc_data_direction == DMA_NONE)
                return sizeof (struct srp_cmd);

        if (scmnd->sc_data_direction != DMA_FROM_DEVICE &&
            scmnd->sc_data_direction != DMA_TO_DEVICE) {
                shost_printk(KERN_WARNING, target->scsi_host,
                             PFX "Unhandled data direction %d\n",
                             scmnd->sc_data_direction);
                return -EINVAL;
        }

        nents = scsi_sg_count(scmnd);
        scat  = scsi_sglist(scmnd);

        dev = target->srp_host->srp_dev;
        ibdev = dev->dev;

        count = ib_dma_map_sg(ibdev, scat, nents, scmnd->sc_data_direction);
        if (unlikely(count == 0))
                return -EIO;

        fmt = SRP_DATA_DESC_DIRECT;
        len = sizeof (struct srp_cmd) + sizeof (struct srp_direct_buf);

        if (count == 1 && target->global_mr) {
                /*
                 * The midlayer only generated a single gather/scatter
                 * entry, or DMA mapping coalesced everything to a
                 * single entry.  So a direct descriptor along with
                 * the DMA MR suffices.
                 */
                struct srp_direct_buf *buf = (void *) cmd->add_data;

                buf->va  = cpu_to_be64(ib_sg_dma_address(ibdev, scat));
                buf->key = cpu_to_be32(target->global_mr->rkey);
                buf->len = cpu_to_be32(ib_sg_dma_len(ibdev, scat));

                req->nmdesc = 0;
                goto map_complete;
        }

        /*
         * We have more than one scatter/gather entry, so build our indirect
         * descriptor table, trying to merge as many entries as we can.
         */
        indirect_hdr = (void *) cmd->add_data;

        ib_dma_sync_single_for_cpu(ibdev, req->indirect_dma_addr,
                                   target->indirect_size, DMA_TO_DEVICE);

        memset(&state, 0, sizeof(state));
        state.desc = req->indirect_desc;
        if (dev->use_fast_reg)
                ret = srp_map_sg_fr(&state, ch, req, scat, count);
        else if (dev->use_fmr)
                ret = srp_map_sg_fmr(&state, ch, req, scat, count);
        else
                ret = srp_map_sg_dma(&state, ch, req, scat, count);
        req->nmdesc = state.nmdesc;
        if (ret < 0)
                goto unmap;

#if defined(DYNAMIC_DEBUG)
        {
                DEFINE_DYNAMIC_DEBUG_METADATA(ddm,
                        "Memory mapping consistency check");
                if (unlikely(ddm.flags & _DPRINTK_FLAGS_PRINT))
                        srp_check_mapping(&state, ch, req, scat, count);
        }
#endif

        /* We've mapped the request, now pull as much of the indirect
         * descriptor table as we can into the command buffer. If this
         * target is not using an external indirect table, we are
         * guaranteed to fit into the command, as the SCSI layer won't
         * give us more S/G entries than we allow.
         */
        if (state.ndesc == 1) {
                /*
                 * Memory registration collapsed the sg-list into one entry,
                 * so use a direct descriptor.
                 */
                struct srp_direct_buf *buf = (void *) cmd->add_data;

                *buf = req->indirect_desc[0];
                goto map_complete;
        }

        if (unlikely(target->cmd_sg_cnt < state.ndesc &&
                                                !target->allow_ext_sg)) {
                shost_printk(KERN_ERR, target->scsi_host,
                             "Could not fit S/G list into SRP_CMD\n");
                ret = -EIO;
                goto unmap;
        }

        count = min(state.ndesc, target->cmd_sg_cnt);
        table_len = state.ndesc * sizeof (struct srp_direct_buf);
        idb_len = sizeof(struct srp_indirect_buf) + table_len;

        fmt = SRP_DATA_DESC_INDIRECT;
        len = sizeof(struct srp_cmd) + sizeof (struct srp_indirect_buf);
        len += count * sizeof (struct srp_direct_buf);

        memcpy(indirect_hdr->desc_list, req->indirect_desc,
               count * sizeof (struct srp_direct_buf));

        if (!target->global_mr) {
                ret = srp_map_idb(ch, req, state.gen.next, state.gen.end,
                                  idb_len, &idb_rkey);
                if (ret < 0)
                        goto unmap;
                req->nmdesc++;
        } else {
                idb_rkey = cpu_to_be32(target->global_mr->rkey);
        }

        indirect_hdr->table_desc.va = cpu_to_be64(req->indirect_dma_addr);
        indirect_hdr->table_desc.key = idb_rkey;
        indirect_hdr->table_desc.len = cpu_to_be32(table_len);
        indirect_hdr->len = cpu_to_be32(state.total_len);

        if (scmnd->sc_data_direction == DMA_TO_DEVICE)
                cmd->data_out_desc_cnt = count;
        else
                cmd->data_in_desc_cnt = count;

        ib_dma_sync_single_for_device(ibdev, req->indirect_dma_addr, table_len,
                                      DMA_TO_DEVICE);

map_complete:
        if (scmnd->sc_data_direction == DMA_TO_DEVICE)
                cmd->buf_fmt = fmt << 4;
        else
                cmd->buf_fmt = fmt;

        return len;

unmap:
        srp_unmap_data(scmnd, ch, req);
        if (ret == -ENOMEM && req->nmdesc >= target->mr_pool_size)
                ret = -E2BIG;
        return ret;
}

/*
 * Return an IU and possible credit to the free pool
 */
static void srp_put_tx_iu(struct srp_rdma_ch *ch, struct srp_iu *iu,
                          enum srp_iu_type iu_type)
{
        unsigned long flags;

        spin_lock_irqsave(&ch->lock, flags);
        list_add(&iu->list, &ch->free_tx);
        if (iu_type != SRP_IU_RSP)
                ++ch->req_lim;
        spin_unlock_irqrestore(&ch->lock, flags);
}

/*
 * Must be called with ch->lock held to protect req_lim and free_tx.
 * If IU is not sent, it must be returned using srp_put_tx_iu().
 *
 * Note:
 * An upper limit for the number of allocated information units for each
 * request type is:
 * - SRP_IU_CMD: SRP_CMD_SQ_SIZE, since the SCSI mid-layer never queues
 *   more than Scsi_Host.can_queue requests.
 * - SRP_IU_TSK_MGMT: SRP_TSK_MGMT_SQ_SIZE.
 * - SRP_IU_RSP: 1, since a conforming SRP target never sends more than
 *   one unanswered SRP request to an initiator.
 */
static struct srp_iu *__srp_get_tx_iu(struct srp_rdma_ch *ch,
                                      enum srp_iu_type iu_type)
{
        struct srp_target_port *target = ch->target;
        s32 rsv = (iu_type == SRP_IU_TSK_MGMT) ? 0 : SRP_TSK_MGMT_SQ_SIZE;
        struct srp_iu *iu;

        ib_process_cq_direct(ch->send_cq, -1);

        if (list_empty(&ch->free_tx))
                return NULL;

        /* Initiator responses to target requests do not consume credits */
        if (iu_type != SRP_IU_RSP) {
                if (ch->req_lim <= rsv) {
                        ++target->zero_req_lim;
                        return NULL;
                }

                --ch->req_lim;
        }

        iu = list_first_entry(&ch->free_tx, struct srp_iu, list);
        list_del(&iu->list);
        return iu;
}

static void srp_send_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct srp_iu *iu = container_of(wc->wr_cqe, struct srp_iu, cqe);
        struct srp_rdma_ch *ch = cq->cq_context;

        if (unlikely(wc->status != IB_WC_SUCCESS)) {
                srp_handle_qp_err(cq, wc, "SEND");
                return;
        }

        list_add(&iu->list, &ch->free_tx);
}

static int srp_post_send(struct srp_rdma_ch *ch, struct srp_iu *iu, int len)
{
        struct srp_target_port *target = ch->target;
        struct ib_sge list;
        struct ib_send_wr wr, *bad_wr;

        list.addr   = iu->dma;
        list.length = len;
        list.lkey   = target->lkey;

        iu->cqe.done = srp_send_done;

        wr.next       = NULL;
        wr.wr_cqe     = &iu->cqe;
        wr.sg_list    = &list;
        wr.num_sge    = 1;
        wr.opcode     = IB_WR_SEND;
        wr.send_flags = IB_SEND_SIGNALED;

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

static int srp_post_recv(struct srp_rdma_ch *ch, struct srp_iu *iu)
{
        struct srp_target_port *target = ch->target;
        struct ib_recv_wr wr, *bad_wr;
        struct ib_sge list;

        list.addr   = iu->dma;
        list.length = iu->size;
        list.lkey   = target->lkey;

        iu->cqe.done = srp_recv_done;

        wr.next     = NULL;
        wr.wr_cqe   = &iu->cqe;
        wr.sg_list  = &list;
        wr.num_sge  = 1;

        return ib_post_recv(ch->qp, &wr, &bad_wr);
}

static void srp_process_rsp(struct srp_rdma_ch *ch, struct srp_rsp *rsp)
{
        struct srp_target_port *target = ch->target;
        struct srp_request *req;
        struct scsi_cmnd *scmnd;
        unsigned long flags;

        if (unlikely(rsp->tag & SRP_TAG_TSK_MGMT)) {
                spin_lock_irqsave(&ch->lock, flags);
                ch->req_lim += be32_to_cpu(rsp->req_lim_delta);
                spin_unlock_irqrestore(&ch->lock, flags);

                ch->tsk_mgmt_status = -1;
                if (be32_to_cpu(rsp->resp_data_len) >= 4)
                        ch->tsk_mgmt_status = rsp->data[3];
                complete(&ch->tsk_mgmt_done);
        } else {
                scmnd = scsi_host_find_tag(target->scsi_host, rsp->tag);
                if (scmnd) {
                        req = (void *)scmnd->host_scribble;
                        scmnd = srp_claim_req(ch, req, NULL, scmnd);
                }
                if (!scmnd) {
                        shost_printk(KERN_ERR, target->scsi_host,
                                     "Null scmnd for RSP w/tag %#016llx received on ch %td / QP %#x\n",
                                     rsp->tag, ch - target->ch, ch->qp->qp_num);

                        spin_lock_irqsave(&ch->lock, flags);
                        ch->req_lim += be32_to_cpu(rsp->req_lim_delta);
                        spin_unlock_irqrestore(&ch->lock, flags);

                        return;
                }
                scmnd->result = rsp->status;

                if (rsp->flags & SRP_RSP_FLAG_SNSVALID) {
                        memcpy(scmnd->sense_buffer, rsp->data +
                               be32_to_cpu(rsp->resp_data_len),
                               min_t(int, be32_to_cpu(rsp->sense_data_len),
                                     SCSI_SENSE_BUFFERSIZE));
                }

                if (unlikely(rsp->flags & SRP_RSP_FLAG_DIUNDER))
                        scsi_set_resid(scmnd, be32_to_cpu(rsp->data_in_res_cnt));
                else if (unlikely(rsp->flags & SRP_RSP_FLAG_DIOVER))
                        scsi_set_resid(scmnd, -be32_to_cpu(rsp->data_in_res_cnt));
                else if (unlikely(rsp->flags & SRP_RSP_FLAG_DOUNDER))
                        scsi_set_resid(scmnd, be32_to_cpu(rsp->data_out_res_cnt));
                else if (unlikely(rsp->flags & SRP_RSP_FLAG_DOOVER))
                        scsi_set_resid(scmnd, -be32_to_cpu(rsp->data_out_res_cnt));

                srp_free_req(ch, req, scmnd,
                             be32_to_cpu(rsp->req_lim_delta));

                scmnd->host_scribble = NULL;
                scmnd->scsi_done(scmnd);
        }
}

static int srp_response_common(struct srp_rdma_ch *ch, s32 req_delta,
                               void *rsp, int len)
{
        struct srp_target_port *target = ch->target;
        struct ib_device *dev = target->srp_host->srp_dev->dev;
        unsigned long flags;
        struct srp_iu *iu;
        int err;

        spin_lock_irqsave(&ch->lock, flags);
        ch->req_lim += req_delta;
        iu = __srp_get_tx_iu(ch, SRP_IU_RSP);
        spin_unlock_irqrestore(&ch->lock, flags);

        if (!iu) {
                shost_printk(KERN_ERR, target->scsi_host, PFX
                             "no IU available to send response\n");
                return 1;
        }

        ib_dma_sync_single_for_cpu(dev, iu->dma, len, DMA_TO_DEVICE);
        memcpy(iu->buf, rsp, len);
        ib_dma_sync_single_for_device(dev, iu->dma, len, DMA_TO_DEVICE);

        err = srp_post_send(ch, iu, len);
        if (err) {
                shost_printk(KERN_ERR, target->scsi_host, PFX
                             "unable to post response: %d\n", err);
                srp_put_tx_iu(ch, iu, SRP_IU_RSP);
        }

        return err;
}

static void srp_process_cred_req(struct srp_rdma_ch *ch,
                                 struct srp_cred_req *req)
{
        struct srp_cred_rsp rsp = {
                .opcode = SRP_CRED_RSP,
                .tag = req->tag,
        };
        s32 delta = be32_to_cpu(req->req_lim_delta);

        if (srp_response_common(ch, delta, &rsp, sizeof(rsp)))
                shost_printk(KERN_ERR, ch->target->scsi_host, PFX
                             "problems processing SRP_CRED_REQ\n");
}

static void srp_process_aer_req(struct srp_rdma_ch *ch,
                                struct srp_aer_req *req)
{
        struct srp_target_port *target = ch->target;
        struct srp_aer_rsp rsp = {
                .opcode = SRP_AER_RSP,
                .tag = req->tag,
        };
        s32 delta = be32_to_cpu(req->req_lim_delta);

        shost_printk(KERN_ERR, target->scsi_host, PFX
                     "ignoring AER for LUN %llu\n", scsilun_to_int(&req->lun));

        if (srp_response_common(ch, delta, &rsp, sizeof(rsp)))
                shost_printk(KERN_ERR, target->scsi_host, PFX
                             "problems processing SRP_AER_REQ\n");
}

static void srp_recv_done(struct ib_cq *cq, struct ib_wc *wc)
{
        struct srp_iu *iu = container_of(wc->wr_cqe, struct srp_iu, cqe);
        struct srp_rdma_ch *ch = cq->cq_context;
        struct srp_target_port *target = ch->target;
        struct ib_device *dev = target->srp_host->srp_dev->dev;
        int res;
        u8 opcode;

        if (unlikely(wc->status != IB_WC_SUCCESS)) {
                srp_handle_qp_err(cq, wc, "RECV");
                return;
        }

        ib_dma_sync_single_for_cpu(dev, iu->dma, ch->max_ti_iu_len,
                                   DMA_FROM_DEVICE);

        opcode = *(u8 *) iu->buf;

        if (0) {
                shost_printk(KERN_ERR, target->scsi_host,
                             PFX "recv completion, opcode 0x%02x\n", opcode);
                print_hex_dump(KERN_ERR, "", DUMP_PREFIX_OFFSET, 8, 1,
                               iu->buf, wc->byte_len, true);
        }

        switch (opcode) {
        case SRP_RSP:
                srp_process_rsp(ch, iu->buf);
                break;

        case SRP_CRED_REQ:
                srp_process_cred_req(ch, iu->buf);
                break;

        case SRP_AER_REQ:
                srp_process_aer_req(ch, iu->buf);
                break;

        case SRP_T_LOGOUT:
                /* XXX Handle target logout */
                shost_printk(KERN_WARNING, target->scsi_host,
                             PFX "Got target logout request\n");
                break;

        default:
                shost_printk(KERN_WARNING, target->scsi_host,
                             PFX "Unhandled SRP opcode 0x%02x\n", opcode);
                break;
        }

        ib_dma_sync_single_for_device(dev, iu->dma, ch->max_ti_iu_len,
                                      DMA_FROM_DEVICE);

        res = srp_post_recv(ch, iu);
        if (res != 0)
                shost_printk(KERN_ERR, target->scsi_host,
                             PFX "Recv failed with error code %d\n", res);
}

/**
 * srp_tl_err_work() - handle a transport layer error
 * @work: Work structure embedded in an SRP target port.
 *
 * Note: This function may get invoked before the rport has been created,
 * hence the target->rport test.
 */
static void srp_tl_err_work(struct work_struct *work)
{
        struct srp_target_port *target;

        target = container_of(work, struct srp_target_port, tl_err_work);
        if (target->rport)
                srp_start_tl_fail_timers(target->rport);
}

static void srp_handle_qp_err(struct ib_cq *cq, struct ib_wc *wc,
                const char *opname)
{
        struct srp_rdma_ch *ch = cq->cq_context;
        struct srp_target_port *target = ch->target;

        if (ch->connected && !target->qp_in_error) {
                shost_printk(KERN_ERR, target->scsi_host,
                             PFX "failed %s status %s (%d) for CQE %p\n",
                             opname, ib_wc_status_msg(wc->status), wc->status,
                             wc->wr_cqe);
                queue_work(system_long_wq, &target->tl_err_work);
        }
        target->qp_in_error = true;
}

static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd)
{
        struct srp_target_port *target = host_to_target(shost);
        struct srp_rport *rport = target->rport;
        struct srp_rdma_ch *ch;
        struct srp_request *req;
        struct srp_iu *iu;
        struct srp_cmd *cmd;
        struct ib_device *dev;
        unsigned long flags;
        u32 tag;
        u16 idx;
        int len, ret;
        const bool in_scsi_eh = !in_interrupt() && current == shost->ehandler;

        /*
         * The SCSI EH thread is the only context from which srp_queuecommand()
         * can get invoked for blocked devices (SDEV_BLOCK /
         * SDEV_CREATED_BLOCK). Avoid racing with srp_reconnect_rport() by
         * locking the rport mutex if invoked from inside the SCSI EH.
         */
        if (in_scsi_eh)
                mutex_lock(&rport->mutex);

        scmnd->result = srp_chkready(target->rport);
        if (unlikely(scmnd->result))
                goto err;

        WARN_ON_ONCE(scmnd->request->tag < 0);
        tag = blk_mq_unique_tag(scmnd->request);
        ch = &target->ch[blk_mq_unique_tag_to_hwq(tag)];
        idx = blk_mq_unique_tag_to_tag(tag);
        WARN_ONCE(idx >= target->req_ring_size, "%s: tag %#x: idx %d >= %d\n",
                  dev_name(&shost->shost_gendev), tag, idx,
                  target->req_ring_size);

        spin_lock_irqsave(&ch->lock, flags);
        iu = __srp_get_tx_iu(ch, SRP_IU_CMD);
        spin_unlock_irqrestore(&ch->lock, flags);

        if (!iu)
                goto err;

        req = &ch->req_ring[idx];
        dev = target->srp_host->srp_dev->dev;
        ib_dma_sync_single_for_cpu(dev, iu->dma, target->max_iu_len,
                                   DMA_TO_DEVICE);

        scmnd->host_scribble = (void *) req;

        cmd = iu->buf;
        memset(cmd, 0, sizeof *cmd);

        cmd->opcode = SRP_CMD;
        int_to_scsilun(scmnd->device->lun, &cmd->lun);
        cmd->tag    = tag;
        memcpy(cmd->cdb, scmnd->cmnd, scmnd->cmd_len);

        req->scmnd    = scmnd;
        req->cmd      = iu;

        len = srp_map_data(scmnd, ch, req);
        if (len < 0) {
                shost_printk(KERN_ERR, target->scsi_host,
                             PFX "Failed to map data (%d)\n", len);
                /*
                 * If we ran out of memory descriptors (-ENOMEM) because an
                 * application is queuing many requests with more than
                 * max_pages_per_mr sg-list elements, tell the SCSI mid-layer
                 * to reduce queue depth temporarily.
                 */
                scmnd->result = len == -ENOMEM ?
                        DID_OK << 16 | QUEUE_FULL << 1 : DID_ERROR << 16;
                goto err_iu;
        }

        ib_dma_sync_single_for_device(dev, iu->dma, target->max_iu_len,
                                      DMA_TO_DEVICE);

        if (srp_post_send(ch, iu, len)) {
                shost_printk(KERN_ERR, target->scsi_host, PFX "Send failed\n");
                goto err_unmap;
        }

        ret = 0;

unlock_rport:
        if (in_scsi_eh)
                mutex_unlock(&rport->mutex);

        return ret;

err_unmap:
        srp_unmap_data(scmnd, ch, req);

err_iu:
        srp_put_tx_iu(ch, iu, SRP_IU_CMD);

        /*
         * Avoid that the loops that iterate over the request ring can
         * encounter a dangling SCSI command pointer.
         */
        req->scmnd = NULL;

err:
        if (scmnd->result) {
                scmnd->scsi_done(scmnd);
                ret = 0;
        } else {
                ret = SCSI_MLQUEUE_HOST_BUSY;
        }

        goto unlock_rport;
}

/*
 * Note: the resources allocated in this function are freed in
 * srp_free_ch_ib().
 */
static int srp_alloc_iu_bufs(struct srp_rdma_ch *ch)
{
        struct srp_target_port *target = ch->target;
        int i;

        ch->rx_ring = kcalloc(target->queue_size, sizeof(*ch->rx_ring),
                              GFP_KERNEL);
        if (!ch->rx_ring)
                goto err_no_ring;
        ch->tx_ring = kcalloc(target->queue_size, sizeof(*ch->tx_ring),
                              GFP_KERNEL);
        if (!ch->tx_ring)
                goto err_no_ring;

        for (i = 0; i < target->queue_size; ++i) {
                ch->rx_ring[i] = srp_alloc_iu(target->srp_host,
                                              ch->max_ti_iu_len,
                                              GFP_KERNEL, DMA_FROM_DEVICE);
                if (!ch->rx_ring[i])
                        goto err;
        }

        for (i = 0; i < target->queue_size; ++i) {
                ch->tx_ring[i] = srp_alloc_iu(target->srp_host,
                                              target->max_iu_len,
                                              GFP_KERNEL, DMA_TO_DEVICE);
                if (!ch->tx_ring[i])
                        goto err;

                list_add(&ch->tx_ring[i]->list, &ch->free_tx);
        }

        return 0;

err:
        for (i = 0; i < target->queue_size; ++i) {
                srp_free_iu(target->srp_host, ch->rx_ring[i]);
                srp_free_iu(target->srp_host, ch->tx_ring[i]);
        }


err_no_ring:
        kfree(ch->tx_ring);
        ch->tx_ring = NULL;
        kfree(ch->rx_ring);
        ch->rx_ring = NULL;

        return -ENOMEM;
}

static uint32_t srp_compute_rq_tmo(struct ib_qp_attr *qp_attr, int attr_mask)
{
        uint64_t T_tr_ns, max_compl_time_ms;
        uint32_t rq_tmo_jiffies;

        /*
         * According to section 11.2.4.2 in the IBTA spec (Modify Queue Pair,
         * table 91), both the QP timeout and the retry count have to be set
         * for RC QP's during the RTR to RTS transition.
         */
        WARN_ON_ONCE((attr_mask & (IB_QP_TIMEOUT | IB_QP_RETRY_CNT)) !=
                     (IB_QP_TIMEOUT | IB_QP_RETRY_CNT));

        /*
         * Set target->rq_tmo_jiffies to one second more than the largest time
         * it can take before an error completion is generated. See also
         * C9-140..142 in the IBTA spec for more information about how to
         * convert the QP Local ACK Timeout value to nanoseconds.
         */
        T_tr_ns = 4096 * (1ULL << qp_attr->timeout);
        max_compl_time_ms = qp_attr->retry_cnt * 4 * T_tr_ns;
        do_div(max_compl_time_ms, NSEC_PER_MSEC);
        rq_tmo_jiffies = msecs_to_jiffies(max_compl_time_ms + 1000);

        return rq_tmo_jiffies;
}

static void srp_cm_rep_handler(struct ib_cm_id *cm_id,
                               const struct srp_login_rsp *lrsp,
                               struct srp_rdma_ch *ch)
{
        struct srp_target_port *target = ch->target;
        struct ib_qp_attr *qp_attr = NULL;
        int attr_mask = 0;
        int ret;
        int i;

        if (lrsp->opcode == SRP_LOGIN_RSP) {
                ch->max_ti_iu_len = be32_to_cpu(lrsp->max_ti_iu_len);
                ch->req_lim       = be32_to_cpu(lrsp->req_lim_delta);

                /*
                 * Reserve credits for task management so we don't
                 * bounce requests back to the SCSI mid-layer.
                 */
                target->scsi_host->can_queue
                        = min(ch->req_lim - SRP_TSK_MGMT_SQ_SIZE,
                              target->scsi_host->can_queue);
                target->scsi_host->cmd_per_lun
                        = min_t(int, target->scsi_host->can_queue,
                                target->scsi_host->cmd_per_lun);
        } else {
                shost_printk(KERN_WARNING, target->scsi_host,
                             PFX "Unhandled RSP opcode %#x\n", lrsp->opcode);
                ret = -ECONNRESET;
                goto error;
        }

        if (!ch->rx_ring) {
                ret = srp_alloc_iu_bufs(ch);
                if (ret)
                        goto error;
        }

        ret = -ENOMEM;
        qp_attr = kmalloc(sizeof *qp_attr, GFP_KERNEL);
        if (!qp_attr)
                goto error;

        qp_attr->qp_state = IB_QPS_RTR;
        ret = ib_cm_init_qp_attr(cm_id, qp_attr, &attr_mask);
        if (ret)
                goto error_free;

        ret = ib_modify_qp(ch->qp, qp_attr, attr_mask);
        if (ret)
                goto error_free;

        for (i = 0; i < target->queue_size; i++) {
                struct srp_iu *iu = ch->rx_ring[i];

                ret = srp_post_recv(ch, iu);
                if (ret)
                        goto error_free;
        }

        qp_attr->qp_state = IB_QPS_RTS;
        ret = ib_cm_init_qp_attr(cm_id, qp_attr, &attr_mask);
        if (ret)
                goto error_free;

        target->rq_tmo_jiffies = srp_compute_rq_tmo(qp_attr, attr_mask);

        ret = ib_modify_qp(ch->qp, qp_attr, attr_mask);
        if (ret)
                goto error_free;

        ret = ib_send_cm_rtu(cm_id, NULL, 0);

error_free:
        kfree(qp_attr);

error:
        ch->status = ret;
}

static void srp_cm_rej_handler(struct ib_cm_id *cm_id,
                               struct ib_cm_event *event,
                               struct srp_rdma_ch *ch)
{
        struct srp_target_port *target = ch->target;
        struct Scsi_Host *shost = target->scsi_host;
        struct ib_class_port_info *cpi;
        int opcode;

        switch (event->param.rej_rcvd.reason) {
        case IB_CM_REJ_PORT_CM_REDIRECT:
                cpi = event->param.rej_rcvd.ari;
                ch->path.dlid = cpi->redirect_lid;
                ch->path.pkey = cpi->redirect_pkey;
                cm_id->remote_cm_qpn = be32_to_cpu(cpi->redirect_qp) & 0x00ffffff;
                memcpy(ch->path.dgid.raw, cpi->redirect_gid, 16);

                ch->status = ch->path.dlid ?
                        SRP_DLID_REDIRECT : SRP_PORT_REDIRECT;
                break;

        case IB_CM_REJ_PORT_REDIRECT:
                if (srp_target_is_topspin(target)) {
                        /*
                         * Topspin/Cisco SRP gateways incorrectly send
                         * reject reason code 25 when they mean 24
                         * (port redirect).
                         */
                        memcpy(ch->path.dgid.raw,
                               event->param.rej_rcvd.ari, 16);

                        shost_printk(KERN_DEBUG, shost,
                                     PFX "Topspin/Cisco redirect to target port GID %016llx%016llx\n",
                                     be64_to_cpu(ch->path.dgid.global.subnet_prefix),
                                     be64_to_cpu(ch->path.dgid.global.interface_id));

                        ch->status = SRP_PORT_REDIRECT;
                } else {
                        shost_printk(KERN_WARNING, shost,
                                     "  REJ reason: IB_CM_REJ_PORT_REDIRECT\n");
                        ch->status = -ECONNRESET;
                }
                break;

        case IB_CM_REJ_DUPLICATE_LOCAL_COMM_ID:
                shost_printk(KERN_WARNING, shost,
                            "  REJ reason: IB_CM_REJ_DUPLICATE_LOCAL_COMM_ID\n");
                ch->status = -ECONNRESET;
                break;

        case IB_CM_REJ_CONSUMER_DEFINED:
                opcode = *(u8 *) event->private_data;
                if (opcode == SRP_LOGIN_REJ) {
                        struct srp_login_rej *rej = event->private_data;
                        u32 reason = be32_to_cpu(rej->reason);

                        if (reason == SRP_LOGIN_REJ_REQ_IT_IU_LENGTH_TOO_LARGE)
                                shost_printk(KERN_WARNING, shost,
                                             PFX "SRP_LOGIN_REJ: requested max_it_iu_len too large\n");
                        else
                                shost_printk(KERN_WARNING, shost, PFX
                                             "SRP LOGIN from %pI6 to %pI6 REJECTED, reason 0x%08x\n",
                                             target->sgid.raw,
                                             target->orig_dgid.raw, reason);
                } else
                        shost_printk(KERN_WARNING, shost,
                                     "  REJ reason: IB_CM_REJ_CONSUMER_DEFINED,"
                                     " opcode 0x%02x\n", opcode);
                ch->status = -ECONNRESET;
                break;

        case IB_CM_REJ_STALE_CONN:
                shost_printk(KERN_WARNING, shost, "  REJ reason: stale connection\n");
                ch->status = SRP_STALE_CONN;
                break;

        default:
                shost_printk(KERN_WARNING, shost, "  REJ reason 0x%x\n",
                             event->param.rej_rcvd.reason);
                ch->status = -ECONNRESET;
        }
}

static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event)
{
        struct srp_rdma_ch *ch = cm_id->context;
        struct srp_target_port *target = ch->target;
        int comp = 0;

        switch (event->event) {
        case IB_CM_REQ_ERROR:
                shost_printk(KERN_DEBUG, target->scsi_host,
                             PFX "Sending CM REQ failed\n");
                comp = 1;
                ch->status = -ECONNRESET;
                break;

        case IB_CM_REP_RECEIVED:
                comp = 1;
                srp_cm_rep_handler(cm_id, event->private_data, ch);
                break;

        case IB_CM_REJ_RECEIVED:
                shost_printk(KERN_DEBUG, target->scsi_host, PFX "REJ received\n");
                comp = 1;

                srp_cm_rej_handler(cm_id, event, ch);
                break;

        case IB_CM_DREQ_RECEIVED:
                shost_printk(KERN_WARNING, target->scsi_host,
                             PFX "DREQ received - connection closed\n");
                ch->connected = false;
                if (ib_send_cm_drep(cm_id, NULL, 0))
                        shost_printk(KERN_ERR, target->scsi_host,
                                     PFX "Sending CM DREP failed\n");
                queue_work(system_long_wq, &target->tl_err_work);
                break;

        case IB_CM_TIMEWAIT_EXIT:
                shost_printk(KERN_ERR, target->scsi_host,
                             PFX "connection closed\n");
                comp = 1;

                ch->status = 0;
                break;

        case IB_CM_MRA_RECEIVED:
        case IB_CM_DREQ_ERROR:
        case IB_CM_DREP_RECEIVED:
                break;

        default:
                shost_printk(KERN_WARNING, target->scsi_host,
                             PFX "Unhandled CM event %d\n", event->event);
                break;
        }

        if (comp)
                complete(&ch->done);

        return 0;
}

/**
 * srp_change_queue_depth - setting device queue depth
 * @sdev: scsi device struct
 * @qdepth: requested queue depth
 *
 * Returns queue depth.
 */
static int
srp_change_queue_depth(struct scsi_device *sdev, int qdepth)
{
        if (!sdev->tagged_supported)
                qdepth = 1;
        return scsi_change_queue_depth(sdev, qdepth);
}

static int srp_send_tsk_mgmt(struct srp_rdma_ch *ch, u64 req_tag, u64 lun,
                             u8 func)
{
        struct srp_target_port *target = ch->target;
        struct srp_rport *rport = target->rport;
        struct ib_device *dev = target->srp_host->srp_dev->dev;
        struct srp_iu *iu;
        struct srp_tsk_mgmt *tsk_mgmt;

        if (!ch->connected || target->qp_in_error)
                return -1;

        init_completion(&ch->tsk_mgmt_done);

        /*
         * Lock the rport mutex to avoid that srp_create_ch_ib() is
         * invoked while a task management function is being sent.
         */
        mutex_lock(&rport->mutex);
        spin_lock_irq(&ch->lock);
        iu = __srp_get_tx_iu(ch, SRP_IU_TSK_MGMT);
        spin_unlock_irq(&ch->lock);

        if (!iu) {
                mutex_unlock(&rport->mutex);

                return -1;
        }

        ib_dma_sync_single_for_cpu(dev, iu->dma, sizeof *tsk_mgmt,
                                   DMA_TO_DEVICE);
        tsk_mgmt = iu->buf;
        memset(tsk_mgmt, 0, sizeof *tsk_mgmt);

        tsk_mgmt->opcode        = SRP_TSK_MGMT;
        int_to_scsilun(lun, &tsk_mgmt->lun);
        tsk_mgmt->tag           = req_tag | SRP_TAG_TSK_MGMT;
        tsk_mgmt->tsk_mgmt_func = func;
        tsk_mgmt->task_tag      = req_tag;

        ib_dma_sync_single_for_device(dev, iu->dma, sizeof *tsk_mgmt,
                                      DMA_TO_DEVICE);
        if (srp_post_send(ch, iu, sizeof(*tsk_mgmt))) {
                srp_put_tx_iu(ch, iu, SRP_IU_TSK_MGMT);
                mutex_unlock(&rport->mutex);

                return -1;
        }
        mutex_unlock(&rport->mutex);

        if (!wait_for_completion_timeout(&ch->tsk_mgmt_done,
                                         msecs_to_jiffies(SRP_ABORT_TIMEOUT_MS)))
                return -1;

        return 0;
}

static int srp_abort(struct scsi_cmnd *scmnd)
{
        struct srp_target_port *target = host_to_target(scmnd->device->host);
        struct srp_request *req = (struct srp_request *) scmnd->host_scribble;
        u32 tag;
        u16 ch_idx;
        struct srp_rdma_ch *ch;
        int ret;

        shost_printk(KERN_ERR, target->scsi_host, "SRP abort called\n");

        if (!req)
                return SUCCESS;
        tag = blk_mq_unique_tag(scmnd->request);
        ch_idx = blk_mq_unique_tag_to_hwq(tag);
        if (WARN_ON_ONCE(ch_idx >= target->ch_count))
                return SUCCESS;
        ch = &target->ch[ch_idx];
        if (!srp_claim_req(ch, req, NULL, scmnd))
                return SUCCESS;
        shost_printk(KERN_ERR, target->scsi_host,
                     "Sending SRP abort for tag %#x\n", tag);
        if (srp_send_tsk_mgmt(ch, tag, scmnd->device->lun,
                              SRP_TSK_ABORT_TASK) == 0)
                ret = SUCCESS;
        else if (target->rport->state == SRP_RPORT_LOST)
                ret = FAST_IO_FAIL;
        else
                ret = FAILED;
        srp_free_req(ch, req, scmnd, 0);
        scmnd->result = DID_ABORT << 16;
        scmnd->scsi_done(scmnd);

        return ret;
}

static int srp_reset_device(struct scsi_cmnd *scmnd)
{
        struct srp_target_port *target = host_to_target(scmnd->device->host);
        struct srp_rdma_ch *ch;
        int i;

        shost_printk(KERN_ERR, target->scsi_host, "SRP reset_device called\n");

        ch = &target->ch[0];
        if (srp_send_tsk_mgmt(ch, SRP_TAG_NO_REQ, scmnd->device->lun,
                              SRP_TSK_LUN_RESET))
                return FAILED;
        if (ch->tsk_mgmt_status)
                return FAILED;

        for (i = 0; i < target->ch_count; i++) {
                ch = &target->ch[i];
                for (i = 0; i < target->req_ring_size; ++i) {
                        struct srp_request *req = &ch->req_ring[i];

                        srp_finish_req(ch, req, scmnd->device, DID_RESET << 16);
                }
        }

        return SUCCESS;
}

static int srp_reset_host(struct scsi_cmnd *scmnd)
{
        struct srp_target_port *target = host_to_target(scmnd->device->host);

        shost_printk(KERN_ERR, target->scsi_host, PFX "SRP reset_host called\n");

        return srp_reconnect_rport(target->rport) == 0 ? SUCCESS : FAILED;
}

static int srp_slave_alloc(struct scsi_device *sdev)
{
        struct Scsi_Host *shost = sdev->host;
        struct srp_target_port *target = host_to_target(shost);
        struct srp_device *srp_dev = target->srp_host->srp_dev;
        struct ib_device *ibdev = srp_dev->dev;

        if (!(ibdev->attrs.device_cap_flags & IB_DEVICE_SG_GAPS_REG))
                blk_queue_virt_boundary(sdev->request_queue,
                                        ~srp_dev->mr_page_mask);

        return 0;
}

static int srp_slave_configure(struct scsi_device *sdev)
{
        struct Scsi_Host *shost = sdev->host;
        struct srp_target_port *target = host_to_target(shost);
        struct request_queue *q = sdev->request_queue;
        unsigned long timeout;

        if (sdev->type == TYPE_DISK) {
                timeout = max_t(unsigned, 30 * HZ, target->rq_tmo_jiffies);
                blk_queue_rq_timeout(q, timeout);
        }

        return 0;
}

static ssize_t show_id_ext(struct device *dev, struct device_attribute *attr,
                           char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "0x%016llx\n", be64_to_cpu(target->id_ext));
}

static ssize_t show_ioc_guid(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "0x%016llx\n", be64_to_cpu(target->ioc_guid));
}

static ssize_t show_service_id(struct device *dev,
                               struct device_attribute *attr, char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "0x%016llx\n", be64_to_cpu(target->service_id));
}

static ssize_t show_pkey(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "0x%04x\n", be16_to_cpu(target->pkey));
}

static ssize_t show_sgid(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "%pI6\n", target->sgid.raw);
}

static ssize_t show_dgid(struct device *dev, struct device_attribute *attr,
                         char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));
        struct srp_rdma_ch *ch = &target->ch[0];

        return sprintf(buf, "%pI6\n", ch->path.dgid.raw);
}

static ssize_t show_orig_dgid(struct device *dev,
                              struct device_attribute *attr, char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "%pI6\n", target->orig_dgid.raw);
}

static ssize_t show_req_lim(struct device *dev,
                            struct device_attribute *attr, char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));
        struct srp_rdma_ch *ch;
        int i, req_lim = INT_MAX;

        for (i = 0; i < target->ch_count; i++) {
                ch = &target->ch[i];
                req_lim = min(req_lim, ch->req_lim);
        }
        return sprintf(buf, "%d\n", req_lim);
}

static ssize_t show_zero_req_lim(struct device *dev,
                                 struct device_attribute *attr, char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "%d\n", target->zero_req_lim);
}

static ssize_t show_local_ib_port(struct device *dev,
                                  struct device_attribute *attr, char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "%d\n", target->srp_host->port);
}

static ssize_t show_local_ib_device(struct device *dev,
                                    struct device_attribute *attr, char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "%s\n", target->srp_host->srp_dev->dev->name);
}

static ssize_t show_ch_count(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "%d\n", target->ch_count);
}

static ssize_t show_comp_vector(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "%d\n", target->comp_vector);
}

static ssize_t show_tl_retry_count(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "%d\n", target->tl_retry_count);
}

static ssize_t show_cmd_sg_entries(struct device *dev,
                                   struct device_attribute *attr, char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "%u\n", target->cmd_sg_cnt);
}

static ssize_t show_allow_ext_sg(struct device *dev,
                                 struct device_attribute *attr, char *buf)
{
        struct srp_target_port *target = host_to_target(class_to_shost(dev));

        return sprintf(buf, "%s\n", target->allow_ext_sg ? "true" : "false");
}

static DEVICE_ATTR(id_ext,          S_IRUGO, show_id_ext,          NULL);
static DEVICE_ATTR(ioc_guid,        S_IRUGO, show_ioc_guid,        NULL);
static DEVICE_ATTR(service_id,      S_IRUGO, show_service_id,      NULL);
static DEVICE_ATTR(pkey,            S_IRUGO, show_pkey,            NULL);
static DEVICE_ATTR(sgid,            S_IRUGO, show_sgid,            NULL);
static DEVICE_ATTR(dgid,            S_IRUGO, show_dgid,            NULL);
static DEVICE_ATTR(orig_dgid,       S_IRUGO, show_orig_dgid,       NULL);
static DEVICE_ATTR(req_lim,         S_IRUGO, show_req_lim,         NULL);
static DEVICE_ATTR(zero_req_lim,    S_IRUGO, show_zero_req_lim,    NULL);
static DEVICE_ATTR(local_ib_port,   S_IRUGO, show_local_ib_port,   NULL);
static DEVICE_ATTR(local_ib_device, S_IRUGO, show_local_ib_device, NULL);
static DEVICE_ATTR(ch_count,        S_IRUGO, show_ch_count,        NULL);
static DEVICE_ATTR(comp_vector,     S_IRUGO, show_comp_vector,     NULL);
static DEVICE_ATTR(tl_retry_count,  S_IRUGO, show_tl_retry_count,  NULL);
static DEVICE_ATTR(cmd_sg_entries,  S_IRUGO, show_cmd_sg_entries,  NULL);
static DEVICE_ATTR(allow_ext_sg,    S_IRUGO, show_allow_ext_sg,    NULL);

static struct device_attribute *srp_host_attrs[] = {
        &dev_attr_id_ext,
        &dev_attr_ioc_guid,
        &dev_attr_service_id,
        &dev_attr_pkey,
        &dev_attr_sgid,
        &dev_attr_dgid,
        &dev_attr_orig_dgid,
        &dev_attr_req_lim,
        &dev_attr_zero_req_lim,
        &dev_attr_local_ib_port,
        &dev_attr_local_ib_device,
        &dev_attr_ch_count,
        &dev_attr_comp_vector,
        &dev_attr_tl_retry_count,
        &dev_attr_cmd_sg_entries,
        &dev_attr_allow_ext_sg,
        NULL
};

static struct scsi_host_template srp_template = {
        .module                         = THIS_MODULE,
        .name                           = "InfiniBand SRP initiator",
        .proc_name                      = DRV_NAME,
        .slave_alloc                    = srp_slave_alloc,
        .slave_configure                = srp_slave_configure,
        .info                           = srp_target_info,
        .queuecommand                   = srp_queuecommand,
        .change_queue_depth             = srp_change_queue_depth,
        .eh_abort_handler               = srp_abort,
        .eh_device_reset_handler        = srp_reset_device,
        .eh_host_reset_handler          = srp_reset_host,
        .skip_settle_delay              = true,
        .sg_tablesize                   = SRP_DEF_SG_TABLESIZE,
        .can_queue                      = SRP_DEFAULT_CMD_SQ_SIZE,
        .this_id                        = -1,
        .cmd_per_lun                    = SRP_DEFAULT_CMD_SQ_SIZE,
        .use_clustering                 = ENABLE_CLUSTERING,
        .shost_attrs                    = srp_host_attrs,
        .track_queue_depth              = 1,
};

static int srp_sdev_count(struct Scsi_Host *host)
{
        struct scsi_device *sdev;
        int c = 0;

        shost_for_each_device(sdev, host)
                c++;

        return c;
}

/*
 * Return values:
 * < 0 upon failure. Caller is responsible for SRP target port cleanup.
 * 0 and target->state == SRP_TARGET_REMOVED if asynchronous target port
 *    removal has been scheduled.
 * 0 and target->state != SRP_TARGET_REMOVED upon success.
 */
static int srp_add_target(struct srp_host *host, struct srp_target_port *target)
{
        struct srp_rport_identifiers ids;
        struct srp_rport *rport;

        target->state = SRP_TARGET_SCANNING;
        sprintf(target->target_name, "SRP.T10:%016llX",
                be64_to_cpu(target->id_ext));

        if (scsi_add_host(target->scsi_host, host->srp_dev->dev->dma_device))
                return -ENODEV;

        memcpy(ids.port_id, &target->id_ext, 8);
        memcpy(ids.port_id + 8, &target->ioc_guid, 8);
        ids.roles = SRP_RPORT_ROLE_TARGET;
        rport = srp_rport_add(target->scsi_host, &ids);
        if (IS_ERR(rport)) {
                scsi_remove_host(target->scsi_host);
                return PTR_ERR(rport);
        }

        rport->lld_data = target;
        target->rport = rport;

        spin_lock(&host->target_lock);
        list_add_tail(&target->list, &host->target_list);
        spin_unlock(&host->target_lock);

        scsi_scan_target(&target->scsi_host->shost_gendev,
                         0, target->scsi_id, SCAN_WILD_CARD, SCSI_SCAN_INITIAL);

        if (srp_connected_ch(target) < target->ch_count ||
            target->qp_in_error) {
                shost_printk(KERN_INFO, target->scsi_host,
                             PFX "SCSI scan failed - removing SCSI host\n");
                srp_queue_remove_work(target);
                goto out;
        }

        pr_debug("%s: SCSI scan succeeded - detected %d LUNs\n",
                 dev_name(&target->scsi_host->shost_gendev),
                 srp_sdev_count(target->scsi_host));

        spin_lock_irq(&target->lock);
        if (target->state == SRP_TARGET_SCANNING)
                target->state = SRP_TARGET_LIVE;
        spin_unlock_irq(&target->lock);

out:
        return 0;
}

static void srp_release_dev(struct device *dev)
{
        struct srp_host *host =
                container_of(dev, struct srp_host, dev);

        complete(&host->released);
}

static struct class srp_class = {
        .name    = "infiniband_srp",
        .dev_release = srp_release_dev
};

/**
 * srp_conn_unique() - check whether the connection to a target is unique
 * @host:   SRP host.
 * @target: SRP target port.
 */
static bool srp_conn_unique(struct srp_host *host,
                            struct srp_target_port *target)
{
        struct srp_target_port *t;
        bool ret = false;

        if (target->state == SRP_TARGET_REMOVED)
                goto out;

        ret = true;

        spin_lock(&host->target_lock);
        list_for_each_entry(t, &host->target_list, list) {
                if (t != target &&
                    target->id_ext == t->id_ext &&
                    target->ioc_guid == t->ioc_guid &&
                    target->initiator_ext == t->initiator_ext) {
                        ret = false;
                        break;
                }
        }
        spin_unlock(&host->target_lock);

out:
        return ret;
}

/*
 * Target ports are added by writing
 *
 *     id_ext=<SRP ID ext>,ioc_guid=<SRP IOC GUID>,dgid=<dest GID>,
 *     pkey=<P_Key>,service_id=<service ID>
 *
 * to the add_target sysfs attribute.
 */
enum {
        SRP_OPT_ERR             = 0,
        SRP_OPT_ID_EXT          = 1 << 0,
        SRP_OPT_IOC_GUID        = 1 << 1,
        SRP_OPT_DGID            = 1 << 2,
        SRP_OPT_PKEY            = 1 << 3,
        SRP_OPT_SERVICE_ID      = 1 << 4,
        SRP_OPT_MAX_SECT        = 1 << 5,
        SRP_OPT_MAX_CMD_PER_LUN = 1 << 6,
        SRP_OPT_IO_CLASS        = 1 << 7,
        SRP_OPT_INITIATOR_EXT   = 1 << 8,
        SRP_OPT_CMD_SG_ENTRIES  = 1 << 9,
        SRP_OPT_ALLOW_EXT_SG    = 1 << 10,
        SRP_OPT_SG_TABLESIZE    = 1 << 11,
        SRP_OPT_COMP_VECTOR     = 1 << 12,