iwcm.c

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/*
 * Copyright (c) 2004, 2005 Intel Corporation.  All rights reserved.
 * Copyright (c) 2004 Topspin Corporation.  All rights reserved.
 * Copyright (c) 2004, 2005 Voltaire Corporation.  All rights reserved.
 * Copyright (c) 2005 Sun Microsystems, Inc. All rights reserved.
 * Copyright (c) 2005 Open Grid Computing, Inc. All rights reserved.
 * Copyright (c) 2005 Network Appliance, Inc. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <linux/dma-mapping.h>
#include <linux/err.h>
#include <linux/idr.h>
#include <linux/interrupt.h>
#include <linux/rbtree.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include <linux/completion.h>
#include <linux/slab.h>
#include <linux/module.h>

#include <rdma/iw_cm.h>
#include <rdma/ib_addr.h>

#include "iwcm.h"

MODULE_AUTHOR("Tom Tucker");
MODULE_DESCRIPTION("iWARP CM");
MODULE_LICENSE("Dual BSD/GPL");

static struct workqueue_struct *iwcm_wq;
struct iwcm_work {
    struct work_struct work;
    struct iwcm_id_private *cm_id;
    struct list_head list;
    struct iw_cm_event event;
    struct list_head free_list;
};

/*
 * The following services provide a mechanism for pre-allocating iwcm_work
 * elements.  The design pre-allocates them  based on the cm_id type:
 *  LISTENING IDS:  Get enough elements preallocated to handle the
 *          listen backlog.
 *  ACTIVE IDS: 4: CONNECT_REPLY, ESTABLISHED, DISCONNECT, CLOSE
 *  PASSIVE IDS:    3: ESTABLISHED, DISCONNECT, CLOSE
 *
 * Allocating them in connect and listen avoids having to deal
 * with allocation failures on the event upcall from the provider (which
 * is called in the interrupt context).
 *
 * One exception is when creating the cm_id for incoming connection requests.
 * There are two cases:
 * 1) in the event upcall, cm_event_handler(), for a listening cm_id.  If
 *    the backlog is exceeded, then no more connection request events will
 *    be processed.  cm_event_handler() returns -ENOMEM in this case.  Its up
 *    to the provider to reject the connection request.
 * 2) in the connection request workqueue handler, cm_conn_req_handler().
 *    If work elements cannot be allocated for the new connect request cm_id,
 *    then IWCM will call the provider reject method.  This is ok since
 *    cm_conn_req_handler() runs in the workqueue thread context.
 */

static struct iwcm_work *get_work(struct iwcm_id_private *cm_id_priv)
{
    struct iwcm_work *work;

    if (list_empty(&cm_id_priv->work_free_list))
        return NULL;
    work = list_entry(cm_id_priv->work_free_list.next, struct iwcm_work,
              free_list);
    list_del_init(&work->free_list);
    return work;
}

static void put_work(struct iwcm_work *work)
{
    list_add(&work->free_list, &work->cm_id->work_free_list);
}

static void dealloc_work_entries(struct iwcm_id_private *cm_id_priv)
{
    struct list_head *e, *tmp;

    list_for_each_safe(e, tmp, &cm_id_priv->work_free_list)
        kfree(list_entry(e, struct iwcm_work, free_list));
}

static int alloc_work_entries(struct iwcm_id_private *cm_id_priv, int count)
{
    struct iwcm_work *work;

    BUG_ON(!list_empty(&cm_id_priv->work_free_list));
    while (count--) {
        work = kmalloc(sizeof(struct iwcm_work), GFP_KERNEL);
        if (!work) {
            dealloc_work_entries(cm_id_priv);
            return -ENOMEM;
        }
        work->cm_id = cm_id_priv;
        INIT_LIST_HEAD(&work->list);
        put_work(work);
    }
    return 0;
}

/*
 * Save private data from incoming connection requests to
 * iw_cm_event, so the low level driver doesn't have to. Adjust
 * the event ptr to point to the local copy.
 */
static int copy_private_data(struct iw_cm_event *event)
{
    void *p;

    p = kmemdup(event->private_data, event->private_data_len, GFP_ATOMIC);
    if (!p)
        return -ENOMEM;
    event->private_data = p;
    return 0;
}

static void free_cm_id(struct iwcm_id_private *cm_id_priv)
{
    dealloc_work_entries(cm_id_priv);
    kfree(cm_id_priv);
}

/*
 * Release a reference on cm_id. If the last reference is being
 * released, enable the waiting thread (in iw_destroy_cm_id) to
 * get woken up, and return 1 if a thread is already waiting.
 */
static int iwcm_deref_id(struct iwcm_id_private *cm_id_priv)
{
    BUG_ON(atomic_read(&cm_id_priv->refcount)==0);
    if (atomic_dec_and_test(&cm_id_priv->refcount)) {
        BUG_ON(!list_empty(&cm_id_priv->work_list));
        complete(&cm_id_priv->destroy_comp);
        return 1;
    }

    return 0;
}

static void add_ref(struct iw_cm_id *cm_id)
{
    struct iwcm_id_private *cm_id_priv;
    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
    atomic_inc(&cm_id_priv->refcount);
}

static void rem_ref(struct iw_cm_id *cm_id)
{
    struct iwcm_id_private *cm_id_priv;
    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
    if (iwcm_deref_id(cm_id_priv) &&
        test_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags)) {
        BUG_ON(!list_empty(&cm_id_priv->work_list));
        free_cm_id(cm_id_priv);
    }
}

static int cm_event_handler(struct iw_cm_id *cm_id, struct iw_cm_event *event);

struct iw_cm_id *iw_create_cm_id(struct ib_device *device,
                 iw_cm_handler cm_handler,
                 void *context)
{
    struct iwcm_id_private *cm_id_priv;

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

    cm_id_priv->state = IW_CM_STATE_IDLE;
    cm_id_priv->id.device = device;
    cm_id_priv->id.cm_handler = cm_handler;
    cm_id_priv->id.context = context;
    cm_id_priv->id.event_handler = cm_event_handler;
    cm_id_priv->id.add_ref = add_ref;
    cm_id_priv->id.rem_ref = rem_ref;
    spin_lock_init(&cm_id_priv->lock);
    atomic_set(&cm_id_priv->refcount, 1);
    init_waitqueue_head(&cm_id_priv->connect_wait);
    init_completion(&cm_id_priv->destroy_comp);
    INIT_LIST_HEAD(&cm_id_priv->work_list);
    INIT_LIST_HEAD(&cm_id_priv->work_free_list);

    return &cm_id_priv->id;
}
EXPORT_SYMBOL(iw_create_cm_id);


static int iwcm_modify_qp_err(struct ib_qp *qp)
{
    struct ib_qp_attr qp_attr;

    if (!qp)
        return -EINVAL;

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

/*
 * This is really the RDMAC CLOSING state. It is most similar to the
 * IB SQD QP state.
 */
static int iwcm_modify_qp_sqd(struct ib_qp *qp)
{
    struct ib_qp_attr qp_attr;

    BUG_ON(qp == NULL);
    qp_attr.qp_state = IB_QPS_SQD;
    return ib_modify_qp(qp, &qp_attr, IB_QP_STATE);
}

/*
 * CM_ID <-- CLOSING
 *
 * Block if a passive or active connection is currently being processed. Then
 * process the event as follows:
 * - If we are ESTABLISHED, move to CLOSING and modify the QP state
 *   based on the abrupt flag
 * - If the connection is already in the CLOSING or IDLE state, the peer is
 *   disconnecting concurrently with us and we've already seen the
 *   DISCONNECT event -- ignore the request and return 0
 * - Disconnect on a listening endpoint returns -EINVAL
 */
int iw_cm_disconnect(struct iw_cm_id *cm_id, int abrupt)
{
    struct iwcm_id_private *cm_id_priv;
    unsigned long flags;
    int ret = 0;
    struct ib_qp *qp = NULL;

    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
    /* Wait if we're currently in a connect or accept downcall */
    wait_event(cm_id_priv->connect_wait,
           !test_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags));

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    switch (cm_id_priv->state) {
    case IW_CM_STATE_ESTABLISHED:
        cm_id_priv->state = IW_CM_STATE_CLOSING;

        /* QP could be <nul> for user-mode client */
        if (cm_id_priv->qp)
            qp = cm_id_priv->qp;
        else
            ret = -EINVAL;
        break;
    case IW_CM_STATE_LISTEN:
        ret = -EINVAL;
        break;
    case IW_CM_STATE_CLOSING:
        /* remote peer closed first */
    case IW_CM_STATE_IDLE:
        /* accept or connect returned !0 */
        break;
    case IW_CM_STATE_CONN_RECV:
        /*
         * App called disconnect before/without calling accept after
         * connect_request event delivered.
         */
        break;
    case IW_CM_STATE_CONN_SENT:
        /* Can only get here if wait above fails */
    default:
        BUG();
    }
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);

    if (qp) {
        if (abrupt)
            ret = iwcm_modify_qp_err(qp);
        else
            ret = iwcm_modify_qp_sqd(qp);

        /*
         * If both sides are disconnecting the QP could
         * already be in ERR or SQD states
         */
        ret = 0;
    }

    return ret;
}
EXPORT_SYMBOL(iw_cm_disconnect);

/*
 * CM_ID <-- DESTROYING
 *
 * Clean up all resources associated with the connection and release
 * the initial reference taken by iw_create_cm_id.
 */
static void destroy_cm_id(struct iw_cm_id *cm_id)
{
    struct iwcm_id_private *cm_id_priv;
    unsigned long flags;
    int ret;

    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
    /*
     * Wait if we're currently in a connect or accept downcall. A
     * listening endpoint should never block here.
     */
    wait_event(cm_id_priv->connect_wait,
           !test_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags));

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    switch (cm_id_priv->state) {
    case IW_CM_STATE_LISTEN:
        cm_id_priv->state = IW_CM_STATE_DESTROYING;
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        /* destroy the listening endpoint */
        ret = cm_id->device->iwcm->destroy_listen(cm_id);
        spin_lock_irqsave(&cm_id_priv->lock, flags);
        break;
    case IW_CM_STATE_ESTABLISHED:
        cm_id_priv->state = IW_CM_STATE_DESTROYING;
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        /* Abrupt close of the connection */
        (void)iwcm_modify_qp_err(cm_id_priv->qp);
        spin_lock_irqsave(&cm_id_priv->lock, flags);
        break;
    case IW_CM_STATE_IDLE:
    case IW_CM_STATE_CLOSING:
        cm_id_priv->state = IW_CM_STATE_DESTROYING;
        break;
    case IW_CM_STATE_CONN_RECV:
        /*
         * App called destroy before/without calling accept after
         * receiving connection request event notification or
         * returned non zero from the event callback function.
         * In either case, must tell the provider to reject.
         */
        cm_id_priv->state = IW_CM_STATE_DESTROYING;
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        cm_id->device->iwcm->reject(cm_id, NULL, 0);
        spin_lock_irqsave(&cm_id_priv->lock, flags);
        break;
    case IW_CM_STATE_CONN_SENT:
    case IW_CM_STATE_DESTROYING:
    default:
        BUG();
        break;
    }
    if (cm_id_priv->qp) {
        cm_id_priv->id.device->iwcm->rem_ref(cm_id_priv->qp);
        cm_id_priv->qp = NULL;
    }
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);

    (void)iwcm_deref_id(cm_id_priv);
}

/*
 * This function is only called by the application thread and cannot
 * be called by the event thread. The function will wait for all
 * references to be released on the cm_id and then kfree the cm_id
 * object.
 */
void iw_destroy_cm_id(struct iw_cm_id *cm_id)
{
    struct iwcm_id_private *cm_id_priv;

    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
    BUG_ON(test_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags));

    destroy_cm_id(cm_id);

    wait_for_completion(&cm_id_priv->destroy_comp);

    free_cm_id(cm_id_priv);
}
EXPORT_SYMBOL(iw_destroy_cm_id);

/*
 * CM_ID <-- LISTEN
 *
 * Start listening for connect requests. Generates one CONNECT_REQUEST
 * event for each inbound connect request.
 */
int iw_cm_listen(struct iw_cm_id *cm_id, int backlog)
{
    struct iwcm_id_private *cm_id_priv;
    unsigned long flags;
    int ret;

    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);

    ret = alloc_work_entries(cm_id_priv, backlog);
    if (ret)
        return ret;

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    switch (cm_id_priv->state) {
    case IW_CM_STATE_IDLE:
        cm_id_priv->state = IW_CM_STATE_LISTEN;
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        ret = cm_id->device->iwcm->create_listen(cm_id, backlog);
        if (ret)
            cm_id_priv->state = IW_CM_STATE_IDLE;
        spin_lock_irqsave(&cm_id_priv->lock, flags);
        break;
    default:
        ret = -EINVAL;
    }
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);

    return ret;
}
EXPORT_SYMBOL(iw_cm_listen);

/*
 * CM_ID <-- IDLE
 *
 * Rejects an inbound connection request. No events are generated.
 */
int iw_cm_reject(struct iw_cm_id *cm_id,
         const void *private_data,
         u8 private_data_len)
{
    struct iwcm_id_private *cm_id_priv;
    unsigned long flags;
    int ret;

    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
    set_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    if (cm_id_priv->state != IW_CM_STATE_CONN_RECV) {
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        clear_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
        wake_up_all(&cm_id_priv->connect_wait);
        return -EINVAL;
    }
    cm_id_priv->state = IW_CM_STATE_IDLE;
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);

    ret = cm_id->device->iwcm->reject(cm_id, private_data,
                      private_data_len);

    clear_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
    wake_up_all(&cm_id_priv->connect_wait);

    return ret;
}
EXPORT_SYMBOL(iw_cm_reject);

/*
 * CM_ID <-- ESTABLISHED
 *
 * Accepts an inbound connection request and generates an ESTABLISHED
 * event. Callers of iw_cm_disconnect and iw_destroy_cm_id will block
 * until the ESTABLISHED event is received from the provider.
 */
int iw_cm_accept(struct iw_cm_id *cm_id,
         struct iw_cm_conn_param *iw_param)
{
    struct iwcm_id_private *cm_id_priv;
    struct ib_qp *qp;
    unsigned long flags;
    int ret;

    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
    set_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    if (cm_id_priv->state != IW_CM_STATE_CONN_RECV) {
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        clear_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
        wake_up_all(&cm_id_priv->connect_wait);
        return -EINVAL;
    }
    /* Get the ib_qp given the QPN */
    qp = cm_id->device->iwcm->get_qp(cm_id->device, iw_param->qpn);
    if (!qp) {
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        clear_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
        wake_up_all(&cm_id_priv->connect_wait);
        return -EINVAL;
    }
    cm_id->device->iwcm->add_ref(qp);
    cm_id_priv->qp = qp;
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);

    ret = cm_id->device->iwcm->accept(cm_id, iw_param);
    if (ret) {
        /* An error on accept precludes provider events */
        BUG_ON(cm_id_priv->state != IW_CM_STATE_CONN_RECV);
        cm_id_priv->state = IW_CM_STATE_IDLE;
        spin_lock_irqsave(&cm_id_priv->lock, flags);
        if (cm_id_priv->qp) {
            cm_id->device->iwcm->rem_ref(qp);
            cm_id_priv->qp = NULL;
        }
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        clear_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
        wake_up_all(&cm_id_priv->connect_wait);
    }

    return ret;
}
EXPORT_SYMBOL(iw_cm_accept);

/*
 * Active Side: CM_ID <-- CONN_SENT
 *
 * If successful, results in the generation of a CONNECT_REPLY
 * event. iw_cm_disconnect and iw_cm_destroy will block until the
 * CONNECT_REPLY event is received from the provider.
 */
int iw_cm_connect(struct iw_cm_id *cm_id, struct iw_cm_conn_param *iw_param)
{
    struct iwcm_id_private *cm_id_priv;
    int ret;
    unsigned long flags;
    struct ib_qp *qp;

    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);

    ret = alloc_work_entries(cm_id_priv, 4);
    if (ret)
        return ret;

    set_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
    spin_lock_irqsave(&cm_id_priv->lock, flags);

    if (cm_id_priv->state != IW_CM_STATE_IDLE) {
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        clear_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
        wake_up_all(&cm_id_priv->connect_wait);
        return -EINVAL;
    }

    /* Get the ib_qp given the QPN */
    qp = cm_id->device->iwcm->get_qp(cm_id->device, iw_param->qpn);
    if (!qp) {
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        clear_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
        wake_up_all(&cm_id_priv->connect_wait);
        return -EINVAL;
    }
    cm_id->device->iwcm->add_ref(qp);
    cm_id_priv->qp = qp;
    cm_id_priv->state = IW_CM_STATE_CONN_SENT;
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);

    ret = cm_id->device->iwcm->connect(cm_id, iw_param);
    if (ret) {
        spin_lock_irqsave(&cm_id_priv->lock, flags);
        if (cm_id_priv->qp) {
            cm_id->device->iwcm->rem_ref(qp);
            cm_id_priv->qp = NULL;
        }
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        BUG_ON(cm_id_priv->state != IW_CM_STATE_CONN_SENT);
        cm_id_priv->state = IW_CM_STATE_IDLE;
        clear_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
        wake_up_all(&cm_id_priv->connect_wait);
    }

    return ret;
}
EXPORT_SYMBOL(iw_cm_connect);

/*
 * Passive Side: new CM_ID <-- CONN_RECV
 *
 * Handles an inbound connect request. The function creates a new
 * iw_cm_id to represent the new connection and inherits the client
 * callback function and other attributes from the listening parent.
 *
 * The work item contains a pointer to the listen_cm_id and the event. The
 * listen_cm_id contains the client cm_handler, context and
 * device. These are copied when the device is cloned. The event
 * contains the new four tuple.
 *
 * An error on the child should not affect the parent, so this
 * function does not return a value.
 */
static void cm_conn_req_handler(struct iwcm_id_private *listen_id_priv,
                struct iw_cm_event *iw_event)
{
    unsigned long flags;
    struct iw_cm_id *cm_id;
    struct iwcm_id_private *cm_id_priv;
    int ret;

    /*
     * The provider should never generate a connection request
     * event with a bad status.
     */
    BUG_ON(iw_event->status);

    cm_id = iw_create_cm_id(listen_id_priv->id.device,
                listen_id_priv->id.cm_handler,
                listen_id_priv->id.context);
    /* If the cm_id could not be created, ignore the request */
    if (IS_ERR(cm_id))
        goto out;

    cm_id->provider_data = iw_event->provider_data;
    cm_id->local_addr = iw_event->local_addr;
    cm_id->remote_addr = iw_event->remote_addr;

    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
    cm_id_priv->state = IW_CM_STATE_CONN_RECV;

    /*
     * We could be destroying the listening id. If so, ignore this
     * upcall.
     */
    spin_lock_irqsave(&listen_id_priv->lock, flags);
    if (listen_id_priv->state != IW_CM_STATE_LISTEN) {
        spin_unlock_irqrestore(&listen_id_priv->lock, flags);
        iw_cm_reject(cm_id, NULL, 0);
        iw_destroy_cm_id(cm_id);
        goto out;
    }
    spin_unlock_irqrestore(&listen_id_priv->lock, flags);

    ret = alloc_work_entries(cm_id_priv, 3);
    if (ret) {
        iw_cm_reject(cm_id, NULL, 0);
        iw_destroy_cm_id(cm_id);
        goto out;
    }

    /* Call the client CM handler */
    ret = cm_id->cm_handler(cm_id, iw_event);
    if (ret) {
        iw_cm_reject(cm_id, NULL, 0);
        set_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags);
        destroy_cm_id(cm_id);
        if (atomic_read(&cm_id_priv->refcount)==0)
            free_cm_id(cm_id_priv);
    }

out:
    if (iw_event->private_data_len)
        kfree(iw_event->private_data);
}

/*
 * Passive Side: CM_ID <-- ESTABLISHED
 *
 * The provider generated an ESTABLISHED event which means that
 * the MPA negotion has completed successfully and we are now in MPA
 * FPDU mode.
 *
 * This event can only be received in the CONN_RECV state. If the
 * remote peer closed, the ESTABLISHED event would be received followed
 * by the CLOSE event. If the app closes, it will block until we wake
 * it up after processing this event.
 */
static int cm_conn_est_handler(struct iwcm_id_private *cm_id_priv,
                   struct iw_cm_event *iw_event)
{
    unsigned long flags;
    int ret;

    spin_lock_irqsave(&cm_id_priv->lock, flags);

    /*
     * We clear the CONNECT_WAIT bit here to allow the callback
     * function to call iw_cm_disconnect. Calling iw_destroy_cm_id
     * from a callback handler is not allowed.
     */
    clear_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
    BUG_ON(cm_id_priv->state != IW_CM_STATE_CONN_RECV);
    cm_id_priv->state = IW_CM_STATE_ESTABLISHED;
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);
    ret = cm_id_priv->id.cm_handler(&cm_id_priv->id, iw_event);
    wake_up_all(&cm_id_priv->connect_wait);

    return ret;
}

/*
 * Active Side: CM_ID <-- ESTABLISHED
 *
 * The app has called connect and is waiting for the established event to
 * post it's requests to the server. This event will wake up anyone
 * blocked in iw_cm_disconnect or iw_destroy_id.
 */
static int cm_conn_rep_handler(struct iwcm_id_private *cm_id_priv,
                   struct iw_cm_event *iw_event)
{
    unsigned long flags;
    int ret;

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    /*
     * Clear the connect wait bit so a callback function calling
     * iw_cm_disconnect will not wait and deadlock this thread
     */
    clear_bit(IWCM_F_CONNECT_WAIT, &cm_id_priv->flags);
    BUG_ON(cm_id_priv->state != IW_CM_STATE_CONN_SENT);
    if (iw_event->status == 0) {
        cm_id_priv->id.local_addr = iw_event->local_addr;
        cm_id_priv->id.remote_addr = iw_event->remote_addr;
        cm_id_priv->state = IW_CM_STATE_ESTABLISHED;
    } else {
        /* REJECTED or RESET */
        cm_id_priv->id.device->iwcm->rem_ref(cm_id_priv->qp);
        cm_id_priv->qp = NULL;
        cm_id_priv->state = IW_CM_STATE_IDLE;
    }
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);
    ret = cm_id_priv->id.cm_handler(&cm_id_priv->id, iw_event);

    if (iw_event->private_data_len)
        kfree(iw_event->private_data);

    /* Wake up waiters on connect complete */
    wake_up_all(&cm_id_priv->connect_wait);

    return ret;
}

/*
 * CM_ID <-- CLOSING
 *
 * If in the ESTABLISHED state, move to CLOSING.
 */
static void cm_disconnect_handler(struct iwcm_id_private *cm_id_priv,
                  struct iw_cm_event *iw_event)
{
    unsigned long flags;

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    if (cm_id_priv->state == IW_CM_STATE_ESTABLISHED)
        cm_id_priv->state = IW_CM_STATE_CLOSING;
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);
}

/*
 * CM_ID <-- IDLE
 *
 * If in the ESTBLISHED or CLOSING states, the QP will have have been
 * moved by the provider to the ERR state. Disassociate the CM_ID from
 * the QP,  move to IDLE, and remove the 'connected' reference.
 *
 * If in some other state, the cm_id was destroyed asynchronously.
 * This is the last reference that will result in waking up
 * the app thread blocked in iw_destroy_cm_id.
 */
static int cm_close_handler(struct iwcm_id_private *cm_id_priv,
                  struct iw_cm_event *iw_event)
{
    unsigned long flags;
    int ret = 0;
    spin_lock_irqsave(&cm_id_priv->lock, flags);

    if (cm_id_priv->qp) {
        cm_id_priv->id.device->iwcm->rem_ref(cm_id_priv->qp);
        cm_id_priv->qp = NULL;
    }
    switch (cm_id_priv->state) {
    case IW_CM_STATE_ESTABLISHED:
    case IW_CM_STATE_CLOSING:
        cm_id_priv->state = IW_CM_STATE_IDLE;
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);
        ret = cm_id_priv->id.cm_handler(&cm_id_priv->id, iw_event);
        spin_lock_irqsave(&cm_id_priv->lock, flags);
        break;
    case IW_CM_STATE_DESTROYING:
        break;
    default:
        BUG();
    }
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);

    return ret;
}

static int process_event(struct iwcm_id_private *cm_id_priv,
             struct iw_cm_event *iw_event)
{
    int ret = 0;

    switch (iw_event->event) {
    case IW_CM_EVENT_CONNECT_REQUEST:
        cm_conn_req_handler(cm_id_priv, iw_event);
        break;
    case IW_CM_EVENT_CONNECT_REPLY:
        ret = cm_conn_rep_handler(cm_id_priv, iw_event);
        break;
    case IW_CM_EVENT_ESTABLISHED:
        ret = cm_conn_est_handler(cm_id_priv, iw_event);
        break;
    case IW_CM_EVENT_DISCONNECT:
        cm_disconnect_handler(cm_id_priv, iw_event);
        break;
    case IW_CM_EVENT_CLOSE:
        ret = cm_close_handler(cm_id_priv, iw_event);
        break;
    default:
        BUG();
    }

    return ret;
}

/*
 * Process events on the work_list for the cm_id. If the callback
 * function requests that the cm_id be deleted, a flag is set in the
 * cm_id flags to indicate that when the last reference is
 * removed, the cm_id is to be destroyed. This is necessary to
 * distinguish between an object that will be destroyed by the app
 * thread asleep on the destroy_comp list vs. an object destroyed
 * here synchronously when the last reference is removed.
 */
static void cm_work_handler(struct work_struct *_work)
{
    struct iwcm_work *work = container_of(_work, struct iwcm_work, work);
    struct iw_cm_event levent;
    struct iwcm_id_private *cm_id_priv = work->cm_id;
    unsigned long flags;
    int empty;
    int ret = 0;
    int destroy_id;

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    empty = list_empty(&cm_id_priv->work_list);
    while (!empty) {
        work = list_entry(cm_id_priv->work_list.next,
                  struct iwcm_work, list);
        list_del_init(&work->list);
        empty = list_empty(&cm_id_priv->work_list);
        levent = work->event;
        put_work(work);
        spin_unlock_irqrestore(&cm_id_priv->lock, flags);

        ret = process_event(cm_id_priv, &levent);
        if (ret) {
            set_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags);
            destroy_cm_id(&cm_id_priv->id);
        }
        BUG_ON(atomic_read(&cm_id_priv->refcount)==0);
        destroy_id = test_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags);
        if (iwcm_deref_id(cm_id_priv)) {
            if (destroy_id) {
                BUG_ON(!list_empty(&cm_id_priv->work_list));
                free_cm_id(cm_id_priv);
            }
            return;
        }
        spin_lock_irqsave(&cm_id_priv->lock, flags);
    }
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);
}

/*
 * This function is called on interrupt context. Schedule events on
 * the iwcm_wq thread to allow callback functions to downcall into
 * the CM and/or block.  Events are queued to a per-CM_ID
 * work_list. If this is the first event on the work_list, the work
 * element is also queued on the iwcm_wq thread.
 *
 * Each event holds a reference on the cm_id. Until the last posted
 * event has been delivered and processed, the cm_id cannot be
 * deleted.
 *
 * Returns:
 *        0 - the event was handled.
 *  -ENOMEM - the event was not handled due to lack of resources.
 */
static int cm_event_handler(struct iw_cm_id *cm_id,
                 struct iw_cm_event *iw_event)
{
    struct iwcm_work *work;
    struct iwcm_id_private *cm_id_priv;
    unsigned long flags;
    int ret = 0;

    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    work = get_work(cm_id_priv);
    if (!work) {
        ret = -ENOMEM;
        goto out;
    }

    INIT_WORK(&work->work, cm_work_handler);
    work->cm_id = cm_id_priv;
    work->event = *iw_event;

    if ((work->event.event == IW_CM_EVENT_CONNECT_REQUEST ||
         work->event.event == IW_CM_EVENT_CONNECT_REPLY) &&
        work->event.private_data_len) {
        ret = copy_private_data(&work->event);
        if (ret) {
            put_work(work);
            goto out;
        }
    }

    atomic_inc(&cm_id_priv->refcount);
    if (list_empty(&cm_id_priv->work_list)) {
        list_add_tail(&work->list, &cm_id_priv->work_list);
        queue_work(iwcm_wq, &work->work);
    } else
        list_add_tail(&work->list, &cm_id_priv->work_list);
out:
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);
    return ret;
}

static int iwcm_init_qp_init_attr(struct iwcm_id_private *cm_id_priv,
                  struct ib_qp_attr *qp_attr,
                  int *qp_attr_mask)
{
    unsigned long flags;
    int ret;

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    switch (cm_id_priv->state) {
    case IW_CM_STATE_IDLE:
    case IW_CM_STATE_CONN_SENT:
    case IW_CM_STATE_CONN_RECV:
    case IW_CM_STATE_ESTABLISHED:
        *qp_attr_mask = IB_QP_STATE | IB_QP_ACCESS_FLAGS;
        qp_attr->qp_access_flags = IB_ACCESS_REMOTE_WRITE|
                       IB_ACCESS_REMOTE_READ;
        ret = 0;
        break;
    default:
        ret = -EINVAL;
        break;
    }
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);
    return ret;
}

static int iwcm_init_qp_rts_attr(struct iwcm_id_private *cm_id_priv,
                  struct ib_qp_attr *qp_attr,
                  int *qp_attr_mask)
{
    unsigned long flags;
    int ret;

    spin_lock_irqsave(&cm_id_priv->lock, flags);
    switch (cm_id_priv->state) {
    case IW_CM_STATE_IDLE:
    case IW_CM_STATE_CONN_SENT:
    case IW_CM_STATE_CONN_RECV:
    case IW_CM_STATE_ESTABLISHED:
        *qp_attr_mask = 0;
        ret = 0;
        break;
    default:
        ret = -EINVAL;
        break;
    }
    spin_unlock_irqrestore(&cm_id_priv->lock, flags);
    return ret;
}

int iw_cm_init_qp_attr(struct iw_cm_id *cm_id,
               struct ib_qp_attr *qp_attr,
               int *qp_attr_mask)
{
    struct iwcm_id_private *cm_id_priv;
    int ret;

    cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
    switch (qp_attr->qp_state) {
    case IB_QPS_INIT:
    case IB_QPS_RTR:
        ret = iwcm_init_qp_init_attr(cm_id_priv,
                         qp_attr, qp_attr_mask);
        break;
    case IB_QPS_RTS:
        ret = iwcm_init_qp_rts_attr(cm_id_priv,
                        qp_attr, qp_attr_mask);
        break;
    default:
        ret = -EINVAL;
        break;
    }
    return ret;
}
EXPORT_SYMBOL(iw_cm_init_qp_attr);

static int __init iw_cm_init(void)
{
    iwcm_wq = create_singlethread_workqueue("iw_cm_wq");
    if (!iwcm_wq)
        return -ENOMEM;

    return 0;
}

static void __exit iw_cm_cleanup(void)
{
    destroy_workqueue(iwcm_wq);
}

module_init(iw_cm_init);
module_exit(iw_cm_cleanup);