drivers/infiniband/sw/rdmavt/mcast.c - linux - Git at Google

 /*
  * Copyright(c) 2016 Intel Corporation.
  *
  * This file is provided under a dual BSD/GPLv2 license.  When using or
  * redistributing this file, you may do so under either license.
  *
  * GPL LICENSE SUMMARY
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of version 2 of the GNU General Public License as
  * published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful, but
  * WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License for more details.
  *
  * BSD LICENSE
  *
  * 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.
  *  - Neither the name of Intel Corporation nor the names of its
  *    contributors may be used to endorse or promote products derived
  *    from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */

 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/rculist.h>
 #include <rdma/rdma_vt.h>
 #include <rdma/rdmavt_qp.h>

 #include "mcast.h"

 /**
  * rvt_driver_mcast - init resources for multicast
  * @rdi: rvt dev struct
  *
  * This is per device that registers with rdmavt
  */
 void rvt_driver_mcast_init(struct rvt_dev_info *rdi)
 {
 	/*
 	 * Anything that needs setup for multicast on a per driver or per rdi
 	 * basis should be done in here.
 	 */
 	spin_lock_init(&rdi->n_mcast_grps_lock);
 }

 /**
  * mcast_qp_alloc - alloc a struct to link a QP to mcast GID struct
  * @qp: the QP to link
  */
 static struct rvt_mcast_qp *rvt_mcast_qp_alloc(struct rvt_qp *qp)
 {
 	struct rvt_mcast_qp *mqp;

 	mqp = kmalloc(sizeof(*mqp), GFP_KERNEL);
 	if (!mqp)
 		goto bail;

 	mqp->qp = qp;
 	rvt_get_qp(qp);

 bail:
 	return mqp;
 }

 static void rvt_mcast_qp_free(struct rvt_mcast_qp *mqp)
 {
 	struct rvt_qp *qp = mqp->qp;

 	/* Notify hfi1_destroy_qp() if it is waiting. */
 	rvt_put_qp(qp);

 	kfree(mqp);
 }

 /**
  * mcast_alloc - allocate the multicast GID structure
  * @mgid: the multicast GID
  * @lid: the muilticast LID (host order)
  *
  * A list of QPs will be attached to this structure.
  */
 static struct rvt_mcast *rvt_mcast_alloc(union ib_gid *mgid, u16 lid)
 {
 	struct rvt_mcast *mcast;

 	mcast = kzalloc(sizeof(*mcast), GFP_KERNEL);
 	if (!mcast)
 		goto bail;

 	mcast->mcast_addr.mgid = *mgid;
 	mcast->mcast_addr.lid = lid;

 	INIT_LIST_HEAD(&mcast->qp_list);
 	init_waitqueue_head(&mcast->wait);
 	atomic_set(&mcast->refcount, 0);

 bail:
 	return mcast;
 }

 static void rvt_mcast_free(struct rvt_mcast *mcast)
 {
 	struct rvt_mcast_qp *p, *tmp;

 	list_for_each_entry_safe(p, tmp, &mcast->qp_list, list)
 		rvt_mcast_qp_free(p);

 	kfree(mcast);
 }

 /**
  * rvt_mcast_find - search the global table for the given multicast GID/LID
  * NOTE: It is valid to have 1 MLID with multiple MGIDs.  It is not valid
  * to have 1 MGID with multiple MLIDs.
  * @ibp: the IB port structure
  * @mgid: the multicast GID to search for
  * @lid: the multicast LID portion of the multicast address (host order)
  *
  * The caller is responsible for decrementing the reference count if found.
  *
  * Return: NULL if not found.
  */
 struct rvt_mcast *rvt_mcast_find(struct rvt_ibport *ibp, union ib_gid *mgid,
 				 u16 lid)
 {
 	struct rb_node *n;
 	unsigned long flags;
 	struct rvt_mcast *found = NULL;

 	spin_lock_irqsave(&ibp->lock, flags);
 	n = ibp->mcast_tree.rb_node;
 	while (n) {
 		int ret;
 		struct rvt_mcast *mcast;

 		mcast = rb_entry(n, struct rvt_mcast, rb_node);

 		ret = memcmp(mgid->raw, mcast->mcast_addr.mgid.raw,
 			     sizeof(*mgid));
 		if (ret < 0) {
 			n = n->rb_left;
 		} else if (ret > 0) {
 			n = n->rb_right;
 		} else {
 			/* MGID/MLID must match */
 			if (mcast->mcast_addr.lid == lid) {
 				atomic_inc(&mcast->refcount);
 				found = mcast;
 			}
 			break;
 		}
 	}
 	spin_unlock_irqrestore(&ibp->lock, flags);
 	return found;
 }
 EXPORT_SYMBOL(rvt_mcast_find);

 /**
  * mcast_add - insert mcast GID into table and attach QP struct
  * @mcast: the mcast GID table
  * @mqp: the QP to attach
  *
  * Return: zero if both were added.  Return EEXIST if the GID was already in
  * the table but the QP was added.  Return ESRCH if the QP was already
  * attached and neither structure was added. Return EINVAL if the MGID was
  * found, but the MLID did NOT match.
  */
 static int rvt_mcast_add(struct rvt_dev_info *rdi, struct rvt_ibport *ibp,
 			 struct rvt_mcast *mcast, struct rvt_mcast_qp *mqp)
 {
 	struct rb_node **n = &ibp->mcast_tree.rb_node;
 	struct rb_node *pn = NULL;
 	int ret;

 	spin_lock_irq(&ibp->lock);

 	while (*n) {
 		struct rvt_mcast *tmcast;
 		struct rvt_mcast_qp *p;

 		pn = *n;
 		tmcast = rb_entry(pn, struct rvt_mcast, rb_node);

 		ret = memcmp(mcast->mcast_addr.mgid.raw,
 			     tmcast->mcast_addr.mgid.raw,
 			     sizeof(mcast->mcast_addr.mgid));
 		if (ret < 0) {
 			n = &pn->rb_left;
 			continue;
 		}
 		if (ret > 0) {
 			n = &pn->rb_right;
 			continue;
 		}

 		if (tmcast->mcast_addr.lid != mcast->mcast_addr.lid) {
 			ret = EINVAL;
 			goto bail;
 		}

 		/* Search the QP list to see if this is already there. */
 		list_for_each_entry_rcu(p, &tmcast->qp_list, list) {
 			if (p->qp == mqp->qp) {
 				ret = ESRCH;
 				goto bail;
 			}
 		}
 		if (tmcast->n_attached ==
 		    rdi->dparms.props.max_mcast_qp_attach) {
 			ret = ENOMEM;
 			goto bail;
 		}

 		tmcast->n_attached++;

 		list_add_tail_rcu(&mqp->list, &tmcast->qp_list);
 		ret = EEXIST;
 		goto bail;
 	}

 	spin_lock(&rdi->n_mcast_grps_lock);
 	if (rdi->n_mcast_grps_allocated == rdi->dparms.props.max_mcast_grp) {
 		spin_unlock(&rdi->n_mcast_grps_lock);
 		ret = ENOMEM;
 		goto bail;
 	}

 	rdi->n_mcast_grps_allocated++;
 	spin_unlock(&rdi->n_mcast_grps_lock);

 	mcast->n_attached++;

 	list_add_tail_rcu(&mqp->list, &mcast->qp_list);

 	atomic_inc(&mcast->refcount);
 	rb_link_node(&mcast->rb_node, pn, n);
 	rb_insert_color(&mcast->rb_node, &ibp->mcast_tree);

 	ret = 0;

 bail:
 	spin_unlock_irq(&ibp->lock);

 	return ret;
 }

 /**
  * rvt_attach_mcast - attach a qp to a multicast group
  * @ibqp: Infiniband qp
  * @gid: multicast guid
  * @lid: multicast lid
  *
  * Return: 0 on success
  */
 int rvt_attach_mcast(struct ib_qp *ibqp, union ib_gid *gid, u16 lid)
 {
 	struct rvt_qp *qp = ibqp_to_rvtqp(ibqp);
 	struct rvt_dev_info *rdi = ib_to_rvt(ibqp->device);
 	struct rvt_ibport *ibp = rdi->ports[qp->port_num - 1];
 	struct rvt_mcast *mcast;
 	struct rvt_mcast_qp *mqp;
 	int ret = -ENOMEM;

 	if (ibqp->qp_num <= 1 || qp->state == IB_QPS_RESET)
 		return -EINVAL;

 	/*
 	 * Allocate data structures since its better to do this outside of
 	 * spin locks and it will most likely be needed.
 	 */
 	mcast = rvt_mcast_alloc(gid, lid);
 	if (!mcast)
 		return -ENOMEM;

 	mqp = rvt_mcast_qp_alloc(qp);
 	if (!mqp)
 		goto bail_mcast;

 	switch (rvt_mcast_add(rdi, ibp, mcast, mqp)) {
 	case ESRCH:
 		/* Neither was used: OK to attach the same QP twice. */
 		ret = 0;
 		goto bail_mqp;
 	case EEXIST: /* The mcast wasn't used */
 		ret = 0;
 		goto bail_mcast;
 	case ENOMEM:
 		/* Exceeded the maximum number of mcast groups. */
 		ret = -ENOMEM;
 		goto bail_mqp;
 	case EINVAL:
 		/* Invalid MGID/MLID pair */
 		ret = -EINVAL;
 		goto bail_mqp;
 	default:
 		break;
 	}

 	return 0;

 bail_mqp:
 	rvt_mcast_qp_free(mqp);

 bail_mcast:
 	rvt_mcast_free(mcast);

 	return ret;
 }

 /**
  * rvt_detach_mcast - remove a qp from a multicast group
  * @ibqp: Infiniband qp
  * @gid: multicast guid
  * @lid: multicast lid
  *
  * Return: 0 on success
  */
 int rvt_detach_mcast(struct ib_qp *ibqp, union ib_gid *gid, u16 lid)
 {
 	struct rvt_qp *qp = ibqp_to_rvtqp(ibqp);
 	struct rvt_dev_info *rdi = ib_to_rvt(ibqp->device);
 	struct rvt_ibport *ibp = rdi->ports[qp->port_num - 1];
 	struct rvt_mcast *mcast = NULL;
 	struct rvt_mcast_qp *p, *tmp, *delp = NULL;
 	struct rb_node *n;
 	int last = 0;
 	int ret = 0;

 	if (ibqp->qp_num <= 1)
 		return -EINVAL;

 	spin_lock_irq(&ibp->lock);

 	/* Find the GID in the mcast table. */
 	n = ibp->mcast_tree.rb_node;
 	while (1) {
 		if (!n) {
 			spin_unlock_irq(&ibp->lock);
 			return -EINVAL;
 		}

 		mcast = rb_entry(n, struct rvt_mcast, rb_node);
 		ret = memcmp(gid->raw, mcast->mcast_addr.mgid.raw,
 			     sizeof(*gid));
 		if (ret < 0) {
 			n = n->rb_left;
 		} else if (ret > 0) {
 			n = n->rb_right;
 		} else {
 			/* MGID/MLID must match */
 			if (mcast->mcast_addr.lid != lid) {
 				spin_unlock_irq(&ibp->lock);
 				return -EINVAL;
 			}
 			break;
 		}
 	}

 	/* Search the QP list. */
 	list_for_each_entry_safe(p, tmp, &mcast->qp_list, list) {
 		if (p->qp != qp)
 			continue;
 		/*
 		 * We found it, so remove it, but don't poison the forward
 		 * link until we are sure there are no list walkers.
 		 */
 		list_del_rcu(&p->list);
 		mcast->n_attached--;
 		delp = p;

 		/* If this was the last attached QP, remove the GID too. */
 		if (list_empty(&mcast->qp_list)) {
 			rb_erase(&mcast->rb_node, &ibp->mcast_tree);
 			last = 1;
 		}
 		break;
 	}

 	spin_unlock_irq(&ibp->lock);
 	/* QP not attached */
 	if (!delp)
 		return -EINVAL;

 	/*
 	 * Wait for any list walkers to finish before freeing the
 	 * list element.
 	 */
 	wait_event(mcast->wait, atomic_read(&mcast->refcount) <= 1);
 	rvt_mcast_qp_free(delp);

 	if (last) {
 		atomic_dec(&mcast->refcount);
 		wait_event(mcast->wait, !atomic_read(&mcast->refcount));
 		rvt_mcast_free(mcast);
 		spin_lock_irq(&rdi->n_mcast_grps_lock);
 		rdi->n_mcast_grps_allocated--;
 		spin_unlock_irq(&rdi->n_mcast_grps_lock);
 	}

 	return 0;
 }

 /**
  *rvt_mast_tree_empty - determine if any qps are attached to any mcast group
  *@rdi: rvt dev struct
  *
  * Return: in use count
  */
 int rvt_mcast_tree_empty(struct rvt_dev_info *rdi)
 {
 	int i;
 	int in_use = 0;

 	for (i = 0; i < rdi->dparms.nports; i++)
 		if (rdi->ports[i]->mcast_tree.rb_node)
 			in_use++;
 	return in_use;
 }
	/*
	* Copyright(c) 2016 Intel Corporation.
	*
	* This file is provided under a dual BSD/GPLv2 license. When using or
	* redistributing this file, you may do so under either license.
	*
	* GPL LICENSE SUMMARY
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of version 2 of the GNU General Public License as
	* published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful, but
	* WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* General Public License for more details.
	*
	* BSD LICENSE
	*
	* 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.
	* - Neither the name of Intel Corporation nor the names of its
	* contributors may be used to endorse or promote products derived
	* from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*
	*/

	#include <linux/slab.h>
	#include <linux/sched.h>
	#include <linux/rculist.h>
	#include <rdma/rdma_vt.h>
	#include <rdma/rdmavt_qp.h>

	#include "mcast.h"

	/**
	* rvt_driver_mcast - init resources for multicast
	* @rdi: rvt dev struct
	*
	* This is per device that registers with rdmavt
	*/
	void rvt_driver_mcast_init(struct rvt_dev_info *rdi)
	{
	/*
	* Anything that needs setup for multicast on a per driver or per rdi
	* basis should be done in here.
	*/
	spin_lock_init(&rdi->n_mcast_grps_lock);
	}

	/**
	* mcast_qp_alloc - alloc a struct to link a QP to mcast GID struct
	* @qp: the QP to link
	*/
	static struct rvt_mcast_qp rvt_mcast_qp_alloc(struct rvt_qp qp)
	{
	struct rvt_mcast_qp *mqp;

	mqp = kmalloc(sizeof(*mqp), GFP_KERNEL);
	if (!mqp)
	goto bail;

	mqp->qp = qp;
	rvt_get_qp(qp);

	bail:
	return mqp;
	}

	static void rvt_mcast_qp_free(struct rvt_mcast_qp *mqp)
	{
	struct rvt_qp *qp = mqp->qp;

	/* Notify hfi1_destroy_qp() if it is waiting. */
	rvt_put_qp(qp);

	kfree(mqp);
	}

	/**
	* mcast_alloc - allocate the multicast GID structure
	* @mgid: the multicast GID
	* @lid: the muilticast LID (host order)
	*
	* A list of QPs will be attached to this structure.
	*/
	static struct rvt_mcast rvt_mcast_alloc(union ib_gid mgid, u16 lid)
	{
	struct rvt_mcast *mcast;

	mcast = kzalloc(sizeof(*mcast), GFP_KERNEL);
	if (!mcast)
	goto bail;

	mcast->mcast_addr.mgid = *mgid;
	mcast->mcast_addr.lid = lid;

	INIT_LIST_HEAD(&mcast->qp_list);
	init_waitqueue_head(&mcast->wait);
	atomic_set(&mcast->refcount, 0);

	bail:
	return mcast;
	}

	static void rvt_mcast_free(struct rvt_mcast *mcast)
	{
	struct rvt_mcast_qp p, tmp;

	list_for_each_entry_safe(p, tmp, &mcast->qp_list, list)
	rvt_mcast_qp_free(p);

	kfree(mcast);
	}

	/**
	* rvt_mcast_find - search the global table for the given multicast GID/LID
	* NOTE: It is valid to have 1 MLID with multiple MGIDs. It is not valid
	* to have 1 MGID with multiple MLIDs.
	* @ibp: the IB port structure
	* @mgid: the multicast GID to search for
	* @lid: the multicast LID portion of the multicast address (host order)
	*
	* The caller is responsible for decrementing the reference count if found.
	*
	* Return: NULL if not found.
	*/
	struct rvt_mcast rvt_mcast_find(struct rvt_ibport ibp, union ib_gid *mgid,
	u16 lid)
	{
	struct rb_node *n;
	unsigned long flags;
	struct rvt_mcast *found = NULL;

	spin_lock_irqsave(&ibp->lock, flags);
	n = ibp->mcast_tree.rb_node;
	while (n) {
	int ret;
	struct rvt_mcast *mcast;

	mcast = rb_entry(n, struct rvt_mcast, rb_node);

	ret = memcmp(mgid->raw, mcast->mcast_addr.mgid.raw,
	sizeof(*mgid));
	if (ret < 0) {
	n = n->rb_left;
	} else if (ret > 0) {
	n = n->rb_right;
	} else {
	/* MGID/MLID must match */
	if (mcast->mcast_addr.lid == lid) {
	atomic_inc(&mcast->refcount);
	found = mcast;
	}
	break;
	}
	}
	spin_unlock_irqrestore(&ibp->lock, flags);
	return found;
	}
	EXPORT_SYMBOL(rvt_mcast_find);

	/**
	* mcast_add - insert mcast GID into table and attach QP struct
	* @mcast: the mcast GID table
	* @mqp: the QP to attach
	*
	* Return: zero if both were added. Return EEXIST if the GID was already in
	* the table but the QP was added. Return ESRCH if the QP was already
	* attached and neither structure was added. Return EINVAL if the MGID was
	* found, but the MLID did NOT match.
	*/
	static int rvt_mcast_add(struct rvt_dev_info rdi, struct rvt_ibport ibp,
	struct rvt_mcast mcast, struct rvt_mcast_qp mqp)
	{
	struct rb_node **n = &ibp->mcast_tree.rb_node;
	struct rb_node *pn = NULL;
	int ret;

	spin_lock_irq(&ibp->lock);

	while (*n) {
	struct rvt_mcast *tmcast;
	struct rvt_mcast_qp *p;

	pn = *n;
	tmcast = rb_entry(pn, struct rvt_mcast, rb_node);

	ret = memcmp(mcast->mcast_addr.mgid.raw,
	tmcast->mcast_addr.mgid.raw,
	sizeof(mcast->mcast_addr.mgid));
	if (ret < 0) {
	n = &pn->rb_left;
	continue;
	}
	if (ret > 0) {
	n = &pn->rb_right;
	continue;
	}

	if (tmcast->mcast_addr.lid != mcast->mcast_addr.lid) {
	ret = EINVAL;
	goto bail;
	}

	/* Search the QP list to see if this is already there. */
	list_for_each_entry_rcu(p, &tmcast->qp_list, list) {
	if (p->qp == mqp->qp) {
	ret = ESRCH;
	goto bail;
	}
	}
	if (tmcast->n_attached ==
	rdi->dparms.props.max_mcast_qp_attach) {
	ret = ENOMEM;
	goto bail;
	}

	tmcast->n_attached++;

	list_add_tail_rcu(&mqp->list, &tmcast->qp_list);
	ret = EEXIST;
	goto bail;
	}

	spin_lock(&rdi->n_mcast_grps_lock);
	if (rdi->n_mcast_grps_allocated == rdi->dparms.props.max_mcast_grp) {
	spin_unlock(&rdi->n_mcast_grps_lock);
	ret = ENOMEM;
	goto bail;
	}

	rdi->n_mcast_grps_allocated++;
	spin_unlock(&rdi->n_mcast_grps_lock);

	mcast->n_attached++;

	list_add_tail_rcu(&mqp->list, &mcast->qp_list);

	atomic_inc(&mcast->refcount);
	rb_link_node(&mcast->rb_node, pn, n);
	rb_insert_color(&mcast->rb_node, &ibp->mcast_tree);

	ret = 0;

	bail:
	spin_unlock_irq(&ibp->lock);

	return ret;
	}

	/**
	* rvt_attach_mcast - attach a qp to a multicast group
	* @ibqp: Infiniband qp
	* @gid: multicast guid
	* @lid: multicast lid
	*
	* Return: 0 on success
	*/
	int rvt_attach_mcast(struct ib_qp ibqp, union ib_gid gid, u16 lid)
	{
	struct rvt_qp *qp = ibqp_to_rvtqp(ibqp);
	struct rvt_dev_info *rdi = ib_to_rvt(ibqp->device);
	struct rvt_ibport *ibp = rdi->ports[qp->port_num - 1];
	struct rvt_mcast *mcast;
	struct rvt_mcast_qp *mqp;
	int ret = -ENOMEM;

	if (ibqp->qp_num <= 1 \|\| qp->state == IB_QPS_RESET)
	return -EINVAL;

	/*
	* Allocate data structures since its better to do this outside of
	* spin locks and it will most likely be needed.
	*/
	mcast = rvt_mcast_alloc(gid, lid);
	if (!mcast)
	return -ENOMEM;

	mqp = rvt_mcast_qp_alloc(qp);
	if (!mqp)
	goto bail_mcast;

	switch (rvt_mcast_add(rdi, ibp, mcast, mqp)) {
	case ESRCH:
	/* Neither was used: OK to attach the same QP twice. */
	ret = 0;
	goto bail_mqp;
	case EEXIST: /* The mcast wasn't used */
	ret = 0;
	goto bail_mcast;
	case ENOMEM:
	/* Exceeded the maximum number of mcast groups. */
	ret = -ENOMEM;
	goto bail_mqp;
	case EINVAL:
	/* Invalid MGID/MLID pair */
	ret = -EINVAL;
	goto bail_mqp;
	default:
	break;
	}

	return 0;

	bail_mqp:
	rvt_mcast_qp_free(mqp);

	bail_mcast:
	rvt_mcast_free(mcast);

	return ret;
	}

	/**
	* rvt_detach_mcast - remove a qp from a multicast group
	* @ibqp: Infiniband qp
	* @gid: multicast guid
	* @lid: multicast lid
	*
	* Return: 0 on success
	*/
	int rvt_detach_mcast(struct ib_qp ibqp, union ib_gid gid, u16 lid)
	{
	struct rvt_qp *qp = ibqp_to_rvtqp(ibqp);
	struct rvt_dev_info *rdi = ib_to_rvt(ibqp->device);
	struct rvt_ibport *ibp = rdi->ports[qp->port_num - 1];
	struct rvt_mcast *mcast = NULL;
	struct rvt_mcast_qp p, tmp, *delp = NULL;
	struct rb_node *n;
	int last = 0;
	int ret = 0;

	if (ibqp->qp_num <= 1)
	return -EINVAL;

	spin_lock_irq(&ibp->lock);

	/* Find the GID in the mcast table. */
	n = ibp->mcast_tree.rb_node;
	while (1) {
	if (!n) {
	spin_unlock_irq(&ibp->lock);
	return -EINVAL;
	}

	mcast = rb_entry(n, struct rvt_mcast, rb_node);
	ret = memcmp(gid->raw, mcast->mcast_addr.mgid.raw,
	sizeof(*gid));
	if (ret < 0) {
	n = n->rb_left;
	} else if (ret > 0) {
	n = n->rb_right;
	} else {
	/* MGID/MLID must match */
	if (mcast->mcast_addr.lid != lid) {
	spin_unlock_irq(&ibp->lock);
	return -EINVAL;
	}
	break;
	}
	}

	/* Search the QP list. */
	list_for_each_entry_safe(p, tmp, &mcast->qp_list, list) {
	if (p->qp != qp)
	continue;
	/*
	* We found it, so remove it, but don't poison the forward
	* link until we are sure there are no list walkers.
	*/
	list_del_rcu(&p->list);
	mcast->n_attached--;
	delp = p;

	/* If this was the last attached QP, remove the GID too. */
	if (list_empty(&mcast->qp_list)) {
	rb_erase(&mcast->rb_node, &ibp->mcast_tree);
	last = 1;
	}
	break;
	}

	spin_unlock_irq(&ibp->lock);
	/* QP not attached */
	if (!delp)
	return -EINVAL;

	/*
	* Wait for any list walkers to finish before freeing the
	* list element.
	*/
	wait_event(mcast->wait, atomic_read(&mcast->refcount) <= 1);
	rvt_mcast_qp_free(delp);

	if (last) {
	atomic_dec(&mcast->refcount);
	wait_event(mcast->wait, !atomic_read(&mcast->refcount));
	rvt_mcast_free(mcast);
	spin_lock_irq(&rdi->n_mcast_grps_lock);
	rdi->n_mcast_grps_allocated--;
	spin_unlock_irq(&rdi->n_mcast_grps_lock);
	}

	return 0;
	}

	/**
	*rvt_mast_tree_empty - determine if any qps are attached to any mcast group
	*@rdi: rvt dev struct
	*
	* Return: in use count
	*/
	int rvt_mcast_tree_empty(struct rvt_dev_info *rdi)
	{
	int i;
	int in_use = 0;

	for (i = 0; i < rdi->dparms.nports; i++)
	if (rdi->ports[i]->mcast_tree.rb_node)
	in_use++;
	return in_use;
	}