xref: /openbmc/linux/drivers/infiniband/ulp/srp/ib_srp.c (revision e8f6f3b4)

/*
 * 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 <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	"1.0"
#define DRV_RELDATE	"July 1, 2013"

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

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;
static bool register_always;
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(SCSI_MAX_SG_CHAIN_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");

static 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);
static void srp_recv_completion(struct ib_cq *cq, void *ch_ptr);
static void srp_send_completion(struct ib_cq *cq, void *ch_ptr);
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;

	if (strncmp(val, "off", 3) != 0) {
		res = kstrtoint(val, 0, &tmo);
		if (res)
			goto out;
	} else {
		tmo = -1;
	}
	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 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 %d\n", 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_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->scsi_host->can_queue;
	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->frpl)
			ib_free_fast_reg_page_list(d->frpl);
		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;
	struct ib_fast_reg_page_list *frpl;
	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_fast_reg_mr(pd, max_page_list_len);
		if (IS_ERR(mr)) {
			ret = PTR_ERR(mr);
			goto destroy_pool;
		}
		d->mr = mr;
		frpl = ib_alloc_fast_reg_page_list(device, max_page_list_len);
		if (IS_ERR(frpl)) {
			ret = PTR_ERR(frpl);
			goto destroy_pool;
		}
		d->frpl = frpl;
		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->scsi_host->can_queue,
				  dev->max_pages_per_mr);
}

/**
 * srp_destroy_qp() - destroy an RDMA queue pair
 * @ch: SRP RDMA channel.
 *
 * Change a queue pair into the error state and wait until all receive
 * completions have been processed 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 srp_rdma_ch *ch)
{
	struct srp_target_port *target = ch->target;
	static struct ib_qp_attr attr = { .qp_state = IB_QPS_ERR };
	static struct ib_recv_wr wr = { .wr_id = SRP_LAST_WR_ID };
	struct ib_recv_wr *bad_wr;
	int ret;

	/* Destroying a QP and reusing ch->done is only safe if not connected */
	WARN_ON_ONCE(target->connected);

	ret = ib_modify_qp(ch->qp, &attr, IB_QP_STATE);
	WARN_ONCE(ret, "ib_cm_init_qp_attr() returned %d\n", ret);
	if (ret)
		goto out;

	init_completion(&ch->done);
	ret = ib_post_recv(ch->qp, &wr, &bad_wr);
	WARN_ONCE(ret, "ib_post_recv() returned %d\n", ret);
	if (ret == 0)
		wait_for_completion(&ch->done);

out:
	ib_destroy_qp(ch->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;
	int ret;

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

	/* + 1 for SRP_LAST_WR_ID */
	recv_cq = ib_create_cq(dev->dev, srp_recv_completion, NULL, ch,
			       target->queue_size + 1, ch->comp_vector);
	if (IS_ERR(recv_cq)) {
		ret = PTR_ERR(recv_cq);
		goto err;
	}

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

	ib_req_notify_cq(recv_cq, IB_CQ_NEXT_COMP);

	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 && dev->has_fr) {
		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;
		}
		if (ch->fr_pool)
			srp_destroy_fr_pool(ch->fr_pool);
		ch->fr_pool = fr_pool;
	} else if (!dev->use_fast_reg && dev->has_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->fmr_pool)
			ib_destroy_fmr_pool(ch->fmr_pool);
		ch->fmr_pool = fmr_pool;
	}

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

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

	kfree(init_attr);
	return 0;

err_qp:
	ib_destroy_qp(qp);

err_send_cq:
	ib_destroy_cq(send_cq);

err_recv_cq:
	ib_destroy_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 (ch->fmr_pool)
			ib_destroy_fmr_pool(ch->fmr_pool);
	}
	srp_destroy_qp(ch);
	ib_destroy_cq(ch->send_cq);
	ib_destroy_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",
			     (unsigned long long) 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 bool srp_change_conn_state(struct srp_target_port *target,
				  bool connected)
{
	bool changed = false;

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

	return changed;
}

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

	if (srp_change_conn_state(target, false)) {
		/* XXX should send SRP_I_LOGOUT request */

		for (i = 0; i < target->ch_count; i++) {
			ch = &target->ch[i];
			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->target || !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->cmd_sg_cnt * 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);
}

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 && target->connected);

	target->qp_in_error = false;

	ret = srp_lookup_path(ch);
	if (ret)
		return ret;

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

		/*
		 * 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.
		 */
		switch (ch->status) {
		case 0:
			srp_change_conn_state(target, true);
			return 0;

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

		case SRP_DLID_REDIRECT:
			break;

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

		default:
			return ch->status;
		}
	}
}

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

	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(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 {
		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 add request to the free request list.
 * @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];
		if (!ch->target)
			break;
		ret += srp_new_cm_id(ch);
	}
	for (i = 0; i < target->ch_count; i++) {
		ch = &target->ch[i];
		if (!ch->target)
			break;
		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];
		if (!ch->target)
			break;
		/*
		 * 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);
	}
	for (i = 0; i < target->ch_count; i++) {
		ch = &target->ch[i];
		if (ret || !ch->target) {
			if (i > 1)
				ret = 0;
			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;

	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 ib_pool_fmr *fmr;
	u64 io_addr = 0;

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

	*state->next_fmr++ = fmr;
	state->nmdesc++;

	srp_map_desc(state, 0, state->dma_len, fmr->fmr->rkey);

	return 0;
}

static int srp_map_finish_fr(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_send_wr *bad_wr;
	struct ib_send_wr wr;
	struct srp_fr_desc *desc;
	u32 rkey;

	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);

	memcpy(desc->frpl->page_list, state->pages,
	       sizeof(state->pages[0]) * state->npages);

	memset(&wr, 0, sizeof(wr));
	wr.opcode = IB_WR_FAST_REG_MR;
	wr.wr_id = FAST_REG_WR_ID_MASK;
	wr.wr.fast_reg.iova_start = state->base_dma_addr;
	wr.wr.fast_reg.page_list = desc->frpl;
	wr.wr.fast_reg.page_list_len = state->npages;
	wr.wr.fast_reg.page_shift = ilog2(dev->mr_page_size);
	wr.wr.fast_reg.length = state->dma_len;
	wr.wr.fast_reg.access_flags = (IB_ACCESS_LOCAL_WRITE |
				       IB_ACCESS_REMOTE_READ |
				       IB_ACCESS_REMOTE_WRITE);
	wr.wr.fast_reg.rkey = desc->mr->lkey;

	*state->next_fr++ = desc;
	state->nmdesc++;

	srp_map_desc(state, state->base_dma_addr, state->dma_len,
		     desc->mr->rkey);

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

static int srp_finish_mapping(struct srp_map_state *state,
			      struct srp_rdma_ch *ch)
{
	struct srp_target_port *target = ch->target;
	int ret = 0;

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

	if (state->npages == 1 && !register_always)
		srp_map_desc(state, state->base_dma_addr, state->dma_len,
			     target->rkey);
	else
		ret = target->srp_host->srp_dev->use_fast_reg ?
			srp_map_finish_fr(state, ch) :
			srp_map_finish_fmr(state, ch);

	if (ret == 0) {
		state->npages = 0;
		state->dma_len = 0;
	}

	return ret;
}

static void srp_map_update_start(struct srp_map_state *state,
				 struct scatterlist *sg, int sg_index,
				 dma_addr_t dma_addr)
{
	state->unmapped_sg = sg;
	state->unmapped_index = sg_index;
	state->unmapped_addr = dma_addr;
}

static int srp_map_sg_entry(struct srp_map_state *state,
			    struct srp_rdma_ch *ch,
			    struct scatterlist *sg, int sg_index,
			    bool use_mr)
{
	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;
	int ret;

	if (!dma_len)
		return 0;

	if (!use_mr) {
		/*
		 * Once we're in direct map mode for a request, we don't
		 * go back to FMR or FR mode, so no need to update anything
		 * other than the descriptor.
		 */
		srp_map_desc(state, dma_addr, dma_len, target->rkey);
		return 0;
	}

	/*
	 * Since not all RDMA HW drivers support non-zero page offsets for
	 * FMR, if we start at an offset into a page, don't merge into the
	 * current FMR mapping. Finish it out, and use the kernel's MR for
	 * this sg entry.
	 */
	if ((!dev->use_fast_reg && dma_addr & ~dev->mr_page_mask) ||
	    dma_len > dev->mr_max_size) {
		ret = srp_finish_mapping(state, ch);
		if (ret)
			return ret;

		srp_map_desc(state, dma_addr, dma_len, target->rkey);
		srp_map_update_start(state, NULL, 0, 0);
		return 0;
	}

	/*
	 * If this is the first sg that will be mapped via FMR or via FR, save
	 * our position. We need to know the first unmapped entry, its index,
	 * and the first unmapped address within that entry to be able to
	 * restart mapping after an error.
	 */
	if (!state->unmapped_sg)
		srp_map_update_start(state, sg, sg_index, dma_addr);

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

			srp_map_update_start(state, sg, sg_index, dma_addr);
		}

		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
	 * boundries.
	 */
	ret = 0;
	if (len != dev->mr_page_size) {
		ret = srp_finish_mapping(state, ch);
		if (!ret)
			srp_map_update_start(state, NULL, 0, 0);
	}
	return ret;
}

static int srp_map_sg(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 ib_device *ibdev = dev->dev;
	struct scatterlist *sg;
	int i;
	bool use_mr;

	state->desc	= req->indirect_desc;
	state->pages	= req->map_page;
	if (dev->use_fast_reg) {
		state->next_fr = req->fr_list;
		use_mr = !!ch->fr_pool;
	} else {
		state->next_fmr = req->fmr_list;
		use_mr = !!ch->fmr_pool;
	}

	for_each_sg(scat, sg, count, i) {
		if (srp_map_sg_entry(state, ch, sg, i, use_mr)) {
			/*
			 * Memory registration failed, so backtrack to the
			 * first unmapped entry and continue on without using
			 * memory registration.
			 */
			dma_addr_t dma_addr;
			unsigned int dma_len;

backtrack:
			sg = state->unmapped_sg;
			i = state->unmapped_index;

			dma_addr = ib_sg_dma_address(ibdev, sg);
			dma_len = ib_sg_dma_len(ibdev, sg);
			dma_len -= (state->unmapped_addr - dma_addr);
			dma_addr = state->unmapped_addr;
			use_mr = false;
			srp_map_desc(state, dma_addr, dma_len, target->rkey);
		}
	}

	if (use_mr && srp_finish_mapping(state, ch))
		goto backtrack;

	req->nmdesc = state->nmdesc;

	return 0;
}

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;
	struct srp_device *dev;
	struct ib_device *ibdev;
	struct srp_map_state state;
	struct srp_indirect_buf *indirect_hdr;
	u32 table_len;
	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 && !register_always) {
		/*
		 * 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->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));
	srp_map_sg(&state, ch, req, scat, count);

	/* 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");
		return -EIO;
	}

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

	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));

	indirect_hdr->table_desc.va = cpu_to_be64(req->indirect_dma_addr);
	indirect_hdr->table_desc.key = cpu_to_be32(target->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;
}

/*
 * 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;

	srp_send_completion(ch->send_cq, ch);

	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 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;

	wr.next       = NULL;
	wr.wr_id      = (uintptr_t) iu;
	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;

	wr.next     = NULL;
	wr.wr_id    = (uintptr_t) iu;
	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", be64_to_cpu(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_handle_recv(struct srp_rdma_ch *ch, struct ib_wc *wc)
{
	struct srp_target_port *target = ch->target;
	struct ib_device *dev = target->srp_host->srp_dev->dev;
	struct srp_iu *iu = (struct srp_iu *) (uintptr_t) wc->wr_id;
	int res;
	u8 opcode;

	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(u64 wr_id, enum ib_wc_status wc_status,
			      bool send_err, struct srp_rdma_ch *ch)
{
	struct srp_target_port *target = ch->target;

	if (wr_id == SRP_LAST_WR_ID) {
		complete(&ch->done);
		return;
	}

	if (target->connected && !target->qp_in_error) {
		if (wr_id & LOCAL_INV_WR_ID_MASK) {
			shost_printk(KERN_ERR, target->scsi_host, PFX
				     "LOCAL_INV failed with status %d\n",
				     wc_status);
		} else if (wr_id & FAST_REG_WR_ID_MASK) {
			shost_printk(KERN_ERR, target->scsi_host, PFX
				     "FAST_REG_MR failed status %d\n",
				     wc_status);
		} else {
			shost_printk(KERN_ERR, target->scsi_host,
				     PFX "failed %s status %d for iu %p\n",
				     send_err ? "send" : "receive",
				     wc_status, (void *)(uintptr_t)wr_id);
		}
		queue_work(system_long_wq, &target->tl_err_work);
	}
	target->qp_in_error = true;
}

static void srp_recv_completion(struct ib_cq *cq, void *ch_ptr)
{
	struct srp_rdma_ch *ch = ch_ptr;
	struct ib_wc wc;

	ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
	while (ib_poll_cq(cq, 1, &wc) > 0) {
		if (likely(wc.status == IB_WC_SUCCESS)) {
			srp_handle_recv(ch, &wc);
		} else {
			srp_handle_qp_err(wc.wr_id, wc.status, false, ch);
		}
	}
}

static void srp_send_completion(struct ib_cq *cq, void *ch_ptr)
{
	struct srp_rdma_ch *ch = ch_ptr;
	struct ib_wc wc;
	struct srp_iu *iu;

	while (ib_poll_cq(cq, 1, &wc) > 0) {
		if (likely(wc.status == IB_WC_SUCCESS)) {
			iu = (struct srp_iu *) (uintptr_t) wc.wr_id;
			list_add(&iu->list, &ch->free_tx);
		} else {
			srp_handle_qp_err(wc.wr_id, wc.status, true, ch);
		}
	}
}

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;
	cmd->lun    = cpu_to_be64((u64) scmnd->device->lun << 48);
	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,
			       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");
		srp_change_conn_state(target, 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,
			     unsigned int 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 (!target->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;
	tsk_mgmt->lun		= cpu_to_be64((u64) lun << 48);
	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_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",
		       (unsigned long long) 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",
		       (unsigned long long) 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",
		       (unsigned long long) 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_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,
	.use_blk_tags			= 1,
	.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;
}

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",
		 (unsigned long long) 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, 0);

	if (!target->connected || 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(PFX "%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,
	SRP_OPT_TL_RETRY_COUNT	= 1 << 13,
	SRP_OPT_QUEUE_SIZE	= 1 << 14,
	SRP_OPT_ALL		= (SRP_OPT_ID_EXT	|
				   SRP_OPT_IOC_GUID	|
				   SRP_OPT_DGID		|
				   SRP_OPT_PKEY		|
				   SRP_OPT_SERVICE_ID),
};

static const match_table_t srp_opt_tokens = {
	{ SRP_OPT_ID_EXT,		"id_ext=%s" 		},
	{ SRP_OPT_IOC_GUID,		"ioc_guid=%s" 		},
	{ SRP_OPT_DGID,			"dgid=%s" 		},
	{ SRP_OPT_PKEY,			"pkey=%x" 		},
	{ SRP_OPT_SERVICE_ID,		"service_id=%s"		},
	{ SRP_OPT_MAX_SECT,		"max_sect=%d" 		},
	{ SRP_OPT_MAX_CMD_PER_LUN,	"max_cmd_per_lun=%d" 	},
	{ SRP_OPT_IO_CLASS,		"io_class=%x"		},
	{ SRP_OPT_INITIATOR_EXT,	"initiator_ext=%s"	},
	{ SRP_OPT_CMD_SG_ENTRIES,	"cmd_sg_entries=%u"	},
	{ SRP_OPT_ALLOW_EXT_SG,		"allow_ext_sg=%u"	},
	{ SRP_OPT_SG_TABLESIZE,		"sg_tablesize=%u"	},
	{ SRP_OPT_COMP_VECTOR,		"comp_vector=%u"	},
	{ SRP_OPT_TL_RETRY_COUNT,	"tl_retry_count=%u"	},
	{ SRP_OPT_QUEUE_SIZE,		"queue_size=%d"		},
	{ SRP_OPT_ERR,			NULL 			}
};

static int srp_parse_options(const char *buf, struct srp_target_port *target)
{
	char *options, *sep_opt;
	char *p;
	char dgid[3];
	substring_t args[MAX_OPT_ARGS];
	int opt_mask = 0;
	int token;
	int ret = -EINVAL;
	int i;

	options = kstrdup(buf, GFP_KERNEL);
	if (!options)
		return -ENOMEM;

	sep_opt = options;
	while ((p = strsep(&sep_opt, ",\n")) != NULL) {
		if (!*p)
			continue;

		token = match_token(p, srp_opt_tokens, args);
		opt_mask |= token;

		switch (token) {
		case SRP_OPT_ID_EXT:
			p = match_strdup(args);
			if (!p) {
				ret = -ENOMEM;
				goto out;
			}
			target->id_ext = cpu_to_be64(simple_strtoull(p, NULL, 16));
			kfree(p);
			break;

		case SRP_OPT_IOC_GUID:
			p = match_strdup(args);
			if (!p) {
				ret = -ENOMEM;
				goto out;
			}
			target->ioc_guid = cpu_to_be64(simple_strtoull(p, NULL, 16));
			kfree(p);
			break;

		case SRP_OPT_DGID:
			p = match_strdup(args);
			if (!p) {
				ret = -ENOMEM;
				goto out;
			}
			if (strlen(p) != 32) {
				pr_warn("bad dest GID parameter '%s'\n", p);
				kfree(p);
				goto out;
			}

			for (i = 0; i < 16; ++i) {
				strlcpy(dgid, p + i * 2, sizeof(dgid));
				if (sscanf(dgid, "%hhx",
					   &target->orig_dgid.raw[i]) < 1) {
					ret = -EINVAL;
					kfree(p);
					goto out;
				}
			}
			kfree(p);
			break;

		case SRP_OPT_PKEY:
			if (match_hex(args, &token)) {
				pr_warn("bad P_Key parameter '%s'\n", p);
				goto out;
			}
			target->pkey = cpu_to_be16(token);
			break;

		case SRP_OPT_SERVICE_ID:
			p = match_strdup(args);
			if (!p) {
				ret = -ENOMEM;
				goto out;
			}
			target->service_id = cpu_to_be64(simple_strtoull(p, NULL, 16));
			kfree(p);
			break;

		case SRP_OPT_MAX_SECT:
			if (match_int(args, &token)) {
				pr_warn("bad max sect parameter '%s'\n", p);
				goto out;
			}
			target->scsi_host->max_sectors = token;
			break;

		case SRP_OPT_QUEUE_SIZE:
			if (match_int(args, &token) || token < 1) {
				pr_warn("bad queue_size parameter '%s'\n", p);
				goto out;
			}
			target->scsi_host->can_queue = token;
			target->queue_size = token + SRP_RSP_SQ_SIZE +
					     SRP_TSK_MGMT_SQ_SIZE;
			if (!(opt_mask & SRP_OPT_MAX_CMD_PER_LUN))
				target->scsi_host->cmd_per_lun = token;
			break;

		case SRP_OPT_MAX_CMD_PER_LUN:
			if (match_int(args, &token) || token < 1) {
				pr_warn("bad max cmd_per_lun parameter '%s'\n",
					p);
				goto out;
			}
			target->scsi_host->cmd_per_lun = token;
			break;

		case SRP_OPT_IO_CLASS:
			if (match_hex(args, &token)) {
				pr_warn("bad IO class parameter '%s'\n", p);
				goto out;
			}
			if (token != SRP_REV10_IB_IO_CLASS &&
			    token != SRP_REV16A_IB_IO_CLASS) {
				pr_warn("unknown IO class parameter value %x specified (use %x or %x).\n",
					token, SRP_REV10_IB_IO_CLASS,
					SRP_REV16A_IB_IO_CLASS);
				goto out;
			}
			target->io_class = token;
			break;

		case SRP_OPT_INITIATOR_EXT:
			p = match_strdup(args);
			if (!p) {
				ret = -ENOMEM;
				goto out;
			}
			target->initiator_ext = cpu_to_be64(simple_strtoull(p, NULL, 16));
			kfree(p);
			break;

		case SRP_OPT_CMD_SG_ENTRIES:
			if (match_int(args, &token) || token < 1 || token > 255) {
				pr_warn("bad max cmd_sg_entries parameter '%s'\n",
					p);
				goto out;
			}
			target->cmd_sg_cnt = token;
			break;

		case SRP_OPT_ALLOW_EXT_SG:
			if (match_int(args, &token)) {
				pr_warn("bad allow_ext_sg parameter '%s'\n", p);
				goto out;
			}
			target->allow_ext_sg = !!token;
			break;

		case SRP_OPT_SG_TABLESIZE:
			if (match_int(args, &token) || token < 1 ||
					token > SCSI_MAX_SG_CHAIN_SEGMENTS) {
				pr_warn("bad max sg_tablesize parameter '%s'\n",
					p);
				goto out;
			}
			target->sg_tablesize = token;
			break;

		case SRP_OPT_COMP_VECTOR:
			if (match_int(args, &token) || token < 0) {
				pr_warn("bad comp_vector parameter '%s'\n", p);
				goto out;
			}
			target->comp_vector = token;
			break;

		case SRP_OPT_TL_RETRY_COUNT:
			if (match_int(args, &token) || token < 2 || token > 7) {
				pr_warn("bad tl_retry_count parameter '%s' (must be a number between 2 and 7)\n",
					p);
				goto out;
			}
			target->tl_retry_count = token;
			break;

		default:
			pr_warn("unknown parameter or missing value '%s' in target creation request\n",
				p);
			goto out;
		}
	}

	if ((opt_mask & SRP_OPT_ALL) == SRP_OPT_ALL)
		ret = 0;
	else
		for (i = 0; i < ARRAY_SIZE(srp_opt_tokens); ++i)
			if ((srp_opt_tokens[i].token & SRP_OPT_ALL) &&
			    !(srp_opt_tokens[i].token & opt_mask))
				pr_warn("target creation request is missing parameter '%s'\n",
					srp_opt_tokens[i].pattern);

	if (target->scsi_host->cmd_per_lun > target->scsi_host->can_queue
	    && (opt_mask & SRP_OPT_MAX_CMD_PER_LUN))
		pr_warn("cmd_per_lun = %d > queue_size = %d\n",
			target->scsi_host->cmd_per_lun,
			target->scsi_host->can_queue);

out:
	kfree(options);
	return ret;
}

static ssize_t srp_create_target(struct device *dev,
				 struct device_attribute *attr,
				 const char *buf, size_t count)
{
	struct srp_host *host =
		container_of(dev, struct srp_host, dev);
	struct Scsi_Host *target_host;
	struct srp_target_port *target;
	struct srp_rdma_ch *ch;
	struct srp_device *srp_dev = host->srp_dev;
	struct ib_device *ibdev = srp_dev->dev;
	int ret, node_idx, node, cpu, i;
	bool multich = false;

	target_host = scsi_host_alloc(&srp_template,
				      sizeof (struct srp_target_port));
	if (!target_host)
		return -ENOMEM;

	target_host->transportt  = ib_srp_transport_template;
	target_host->max_channel = 0;
	target_host->max_id      = 1;
	target_host->max_lun     = SRP_MAX_LUN;
	target_host->max_cmd_len = sizeof ((struct srp_cmd *) (void *) 0L)->cdb;

	target = host_to_target(target_host);

	target->io_class	= SRP_REV16A_IB_IO_CLASS;
	target->scsi_host	= target_host;
	target->srp_host	= host;
	target->lkey		= host->srp_dev->mr->lkey;
	target->rkey		= host->srp_dev->mr->rkey;
	target->cmd_sg_cnt	= cmd_sg_entries;
	target->sg_tablesize	= indirect_sg_entries ? : cmd_sg_entries;
	target->allow_ext_sg	= allow_ext_sg;
	target->tl_retry_count	= 7;
	target->queue_size	= SRP_DEFAULT_QUEUE_SIZE;

	/*
	 * Avoid that the SCSI host can be removed by srp_remove_target()
	 * before this function returns.
	 */
	scsi_host_get(target->scsi_host);

	mutex_lock(&host->add_target_mutex);

	ret = srp_parse_options(buf, target);
	if (ret)
		goto err;

	ret = scsi_init_shared_tag_map(target_host, target_host->can_queue);
	if (ret)
		goto err;

	target->req_ring_size = target->queue_size - SRP_TSK_MGMT_SQ_SIZE;

	if (!srp_conn_unique(target->srp_host, target)) {
		shost_printk(KERN_INFO, target->scsi_host,
			     PFX "Already connected to target port with id_ext=%016llx;ioc_guid=%016llx;initiator_ext=%016llx\n",
			     be64_to_cpu(target->id_ext),
			     be64_to_cpu(target->ioc_guid),
			     be64_to_cpu(target->initiator_ext));
		ret = -EEXIST;
		goto err;
	}

	if (!srp_dev->has_fmr && !srp_dev->has_fr && !target->allow_ext_sg &&
	    target->cmd_sg_cnt < target->sg_tablesize) {
		pr_warn("No MR pool and no external indirect descriptors, limiting sg_tablesize to cmd_sg_cnt\n");
		target->sg_tablesize = target->cmd_sg_cnt;
	}

	target_host->sg_tablesize = target->sg_tablesize;
	target->indirect_size = target->sg_tablesize *
				sizeof (struct srp_direct_buf);
	target->max_iu_len = sizeof (struct srp_cmd) +
			     sizeof (struct srp_indirect_buf) +
			     target->cmd_sg_cnt * sizeof (struct srp_direct_buf);

	INIT_WORK(&target->tl_err_work, srp_tl_err_work);
	INIT_WORK(&target->remove_work, srp_remove_work);
	spin_lock_init(&target->lock);
	ret = ib_query_gid(ibdev, host->port, 0, &target->sgid);
	if (ret)
		goto err;

	ret = -ENOMEM;
	target->ch_count = max_t(unsigned, num_online_nodes(),
				 min(ch_count ? :
				     min(4 * num_online_nodes(),
					 ibdev->num_comp_vectors),
				     num_online_cpus()));
	target->ch = kcalloc(target->ch_count, sizeof(*target->ch),
			     GFP_KERNEL);
	if (!target->ch)
		goto err;

	node_idx = 0;
	for_each_online_node(node) {
		const int ch_start = (node_idx * target->ch_count /
				      num_online_nodes());
		const int ch_end = ((node_idx + 1) * target->ch_count /
				    num_online_nodes());
		const int cv_start = (node_idx * ibdev->num_comp_vectors /
				      num_online_nodes() + target->comp_vector)
				     % ibdev->num_comp_vectors;
		const int cv_end = ((node_idx + 1) * ibdev->num_comp_vectors /
				    num_online_nodes() + target->comp_vector)
				   % ibdev->num_comp_vectors;
		int cpu_idx = 0;

		for_each_online_cpu(cpu) {
			if (cpu_to_node(cpu) != node)
				continue;
			if (ch_start + cpu_idx >= ch_end)
				continue;
			ch = &target->ch[ch_start + cpu_idx];
			ch->target = target;
			ch->comp_vector = cv_start == cv_end ? cv_start :
				cv_start + cpu_idx % (cv_end - cv_start);
			spin_lock_init(&ch->lock);
			INIT_LIST_HEAD(&ch->free_tx);
			ret = srp_new_cm_id(ch);
			if (ret)
				goto err_disconnect;

			ret = srp_create_ch_ib(ch);
			if (ret)
				goto err_disconnect;

			ret = srp_alloc_req_data(ch);
			if (ret)
				goto err_disconnect;

			ret = srp_connect_ch(ch, multich);
			if (ret) {
				shost_printk(KERN_ERR, target->scsi_host,
					     PFX "Connection %d/%d failed\n",
					     ch_start + cpu_idx,
					     target->ch_count);
				if (node_idx == 0 && cpu_idx == 0) {
					goto err_disconnect;
				} else {
					srp_free_ch_ib(target, ch);
					srp_free_req_data(target, ch);
					target->ch_count = ch - target->ch;
					break;
				}
			}

			multich = true;
			cpu_idx++;
		}
		node_idx++;
	}

	target->scsi_host->nr_hw_queues = target->ch_count;

	ret = srp_add_target(host, target);
	if (ret)
		goto err_disconnect;

	if (target->state != SRP_TARGET_REMOVED) {
		shost_printk(KERN_DEBUG, target->scsi_host, PFX
			     "new target: id_ext %016llx ioc_guid %016llx pkey %04x service_id %016llx sgid %pI6 dgid %pI6\n",
			     be64_to_cpu(target->id_ext),
			     be64_to_cpu(target->ioc_guid),
			     be16_to_cpu(target->pkey),
			     be64_to_cpu(target->service_id),
			     target->sgid.raw, target->orig_dgid.raw);
	}

	ret = count;

out:
	mutex_unlock(&host->add_target_mutex);

	scsi_host_put(target->scsi_host);

	return ret;

err_disconnect:
	srp_disconnect_target(target);

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

	kfree(target->ch);

err:
	scsi_host_put(target_host);
	goto out;
}

static DEVICE_ATTR(add_target, S_IWUSR, NULL, srp_create_target);

static ssize_t show_ibdev(struct device *dev, struct device_attribute *attr,
			  char *buf)
{
	struct srp_host *host = container_of(dev, struct srp_host, dev);

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

static DEVICE_ATTR(ibdev, S_IRUGO, show_ibdev, NULL);

static ssize_t show_port(struct device *dev, struct device_attribute *attr,
			 char *buf)
{
	struct srp_host *host = container_of(dev, struct srp_host, dev);

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

static DEVICE_ATTR(port, S_IRUGO, show_port, NULL);

static struct srp_host *srp_add_port(struct srp_device *device, u8 port)
{
	struct srp_host *host;

	host = kzalloc(sizeof *host, GFP_KERNEL);
	if (!host)
		return NULL;

	INIT_LIST_HEAD(&host->target_list);
	spin_lock_init(&host->target_lock);
	init_completion(&host->released);
	mutex_init(&host->add_target_mutex);
	host->srp_dev = device;
	host->port = port;

	host->dev.class = &srp_class;
	host->dev.parent = device->dev->dma_device;
	dev_set_name(&host->dev, "srp-%s-%d", device->dev->name, port);

	if (device_register(&host->dev))
		goto free_host;
	if (device_create_file(&host->dev, &dev_attr_add_target))
		goto err_class;
	if (device_create_file(&host->dev, &dev_attr_ibdev))
		goto err_class;
	if (device_create_file(&host->dev, &dev_attr_port))
		goto err_class;

	return host;

err_class:
	device_unregister(&host->dev);

free_host:
	kfree(host);

	return NULL;
}

static void srp_add_one(struct ib_device *device)
{
	struct srp_device *srp_dev;
	struct ib_device_attr *dev_attr;
	struct srp_host *host;
	int mr_page_shift, s, e, p;
	u64 max_pages_per_mr;

	dev_attr = kmalloc(sizeof *dev_attr, GFP_KERNEL);
	if (!dev_attr)
		return;

	if (ib_query_device(device, dev_attr)) {
		pr_warn("Query device failed for %s\n", device->name);
		goto free_attr;
	}

	srp_dev = kmalloc(sizeof *srp_dev, GFP_KERNEL);
	if (!srp_dev)
		goto free_attr;

	srp_dev->has_fmr = (device->alloc_fmr && device->dealloc_fmr &&
			    device->map_phys_fmr && device->unmap_fmr);
	srp_dev->has_fr = (dev_attr->device_cap_flags &
			   IB_DEVICE_MEM_MGT_EXTENSIONS);
	if (!srp_dev->has_fmr && !srp_dev->has_fr)
		dev_warn(&device->dev, "neither FMR nor FR is supported\n");

	srp_dev->use_fast_reg = (srp_dev->has_fr &&
				 (!srp_dev->has_fmr || prefer_fr));

	/*
	 * Use the smallest page size supported by the HCA, down to a
	 * minimum of 4096 bytes. We're unlikely to build large sglists
	 * out of smaller entries.
	 */
	mr_page_shift		= max(12, ffs(dev_attr->page_size_cap) - 1);
	srp_dev->mr_page_size	= 1 << mr_page_shift;
	srp_dev->mr_page_mask	= ~((u64) srp_dev->mr_page_size - 1);
	max_pages_per_mr	= dev_attr->max_mr_size;
	do_div(max_pages_per_mr, srp_dev->mr_page_size);
	srp_dev->max_pages_per_mr = min_t(u64, SRP_MAX_PAGES_PER_MR,
					  max_pages_per_mr);
	if (srp_dev->use_fast_reg) {
		srp_dev->max_pages_per_mr =
			min_t(u32, srp_dev->max_pages_per_mr,
			      dev_attr->max_fast_reg_page_list_len);
	}
	srp_dev->mr_max_size	= srp_dev->mr_page_size *
				   srp_dev->max_pages_per_mr;
	pr_debug("%s: mr_page_shift = %d, dev_attr->max_mr_size = %#llx, dev_attr->max_fast_reg_page_list_len = %u, max_pages_per_mr = %d, mr_max_size = %#x\n",
		 device->name, mr_page_shift, dev_attr->max_mr_size,
		 dev_attr->max_fast_reg_page_list_len,
		 srp_dev->max_pages_per_mr, srp_dev->mr_max_size);

	INIT_LIST_HEAD(&srp_dev->dev_list);

	srp_dev->dev = device;
	srp_dev->pd  = ib_alloc_pd(device);
	if (IS_ERR(srp_dev->pd))
		goto free_dev;

	srp_dev->mr = ib_get_dma_mr(srp_dev->pd,
				    IB_ACCESS_LOCAL_WRITE |
				    IB_ACCESS_REMOTE_READ |
				    IB_ACCESS_REMOTE_WRITE);
	if (IS_ERR(srp_dev->mr))
		goto err_pd;

	if (device->node_type == RDMA_NODE_IB_SWITCH) {
		s = 0;
		e = 0;
	} else {
		s = 1;
		e = device->phys_port_cnt;
	}

	for (p = s; p <= e; ++p) {
		host = srp_add_port(srp_dev, p);
		if (host)
			list_add_tail(&host->list, &srp_dev->dev_list);
	}

	ib_set_client_data(device, &srp_client, srp_dev);

	goto free_attr;

err_pd:
	ib_dealloc_pd(srp_dev->pd);

free_dev:
	kfree(srp_dev);

free_attr:
	kfree(dev_attr);
}

static void srp_remove_one(struct ib_device *device)
{
	struct srp_device *srp_dev;
	struct srp_host *host, *tmp_host;
	struct srp_target_port *target;

	srp_dev = ib_get_client_data(device, &srp_client);
	if (!srp_dev)
		return;

	list_for_each_entry_safe(host, tmp_host, &srp_dev->dev_list, list) {
		device_unregister(&host->dev);
		/*
		 * Wait for the sysfs entry to go away, so that no new
		 * target ports can be created.
		 */
		wait_for_completion(&host->released);

		/*
		 * Remove all target ports.
		 */
		spin_lock(&host->target_lock);
		list_for_each_entry(target, &host->target_list, list)
			srp_queue_remove_work(target);
		spin_unlock(&host->target_lock);

		/*
		 * Wait for tl_err and target port removal tasks.
		 */
		flush_workqueue(system_long_wq);
		flush_workqueue(srp_remove_wq);

		kfree(host);
	}

	ib_dereg_mr(srp_dev->mr);
	ib_dealloc_pd(srp_dev->pd);

	kfree(srp_dev);
}

static struct srp_function_template ib_srp_transport_functions = {
	.has_rport_state	 = true,
	.reset_timer_if_blocked	 = true,
	.reconnect_delay	 = &srp_reconnect_delay,
	.fast_io_fail_tmo	 = &srp_fast_io_fail_tmo,
	.dev_loss_tmo		 = &srp_dev_loss_tmo,
	.reconnect		 = srp_rport_reconnect,
	.rport_delete		 = srp_rport_delete,
	.terminate_rport_io	 = srp_terminate_io,
};

static int __init srp_init_module(void)
{
	int ret;

	BUILD_BUG_ON(FIELD_SIZEOF(struct ib_wc, wr_id) < sizeof(void *));

	if (srp_sg_tablesize) {
		pr_warn("srp_sg_tablesize is deprecated, please use cmd_sg_entries\n");
		if (!cmd_sg_entries)
			cmd_sg_entries = srp_sg_tablesize;
	}

	if (!cmd_sg_entries)
		cmd_sg_entries = SRP_DEF_SG_TABLESIZE;

	if (cmd_sg_entries > 255) {
		pr_warn("Clamping cmd_sg_entries to 255\n");
		cmd_sg_entries = 255;
	}

	if (!indirect_sg_entries)
		indirect_sg_entries = cmd_sg_entries;
	else if (indirect_sg_entries < cmd_sg_entries) {
		pr_warn("Bumping up indirect_sg_entries to match cmd_sg_entries (%u)\n",
			cmd_sg_entries);
		indirect_sg_entries = cmd_sg_entries;
	}

	srp_remove_wq = create_workqueue("srp_remove");
	if (!srp_remove_wq) {
		ret = -ENOMEM;
		goto out;
	}

	ret = -ENOMEM;
	ib_srp_transport_template =
		srp_attach_transport(&ib_srp_transport_functions);
	if (!ib_srp_transport_template)
		goto destroy_wq;

	ret = class_register(&srp_class);
	if (ret) {
		pr_err("couldn't register class infiniband_srp\n");
		goto release_tr;
	}

	ib_sa_register_client(&srp_sa_client);

	ret = ib_register_client(&srp_client);
	if (ret) {
		pr_err("couldn't register IB client\n");
		goto unreg_sa;
	}

out:
	return ret;

unreg_sa:
	ib_sa_unregister_client(&srp_sa_client);
	class_unregister(&srp_class);

release_tr:
	srp_release_transport(ib_srp_transport_template);

destroy_wq:
	destroy_workqueue(srp_remove_wq);
	goto out;
}

static void __exit srp_cleanup_module(void)
{
	ib_unregister_client(&srp_client);
	ib_sa_unregister_client(&srp_sa_client);
	class_unregister(&srp_class);
	srp_release_transport(ib_srp_transport_template);
	destroy_workqueue(srp_remove_wq);
}

module_init(srp_init_module);
module_exit(srp_cleanup_module);