1 files changed, 651 insertions, 0 deletions

diff --git a/net/rds/ib_rdma.c b/net/rds/ib_rdma.c
new file mode 100644
index 000000000..0b347f46b
--- /dev/null
+++ b/net/rds/ib_rdma.c
@@ -0,0 +1,651 @@
+/*
+ * Copyright (c) 2006, 2018 Oracle and/or its affiliates. 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/kernel.h>
+#include <linux/slab.h>
+#include <linux/rculist.h>
+#include <linux/llist.h>
+
+#include "rds_single_path.h"
+#include "ib_mr.h"
+
+struct workqueue_struct *rds_ib_mr_wq;
+
+static DEFINE_PER_CPU(unsigned long, clean_list_grace);
+#define CLEAN_LIST_BUSY_BIT 0
+
+static struct rds_ib_device *rds_ib_get_device(__be32 ipaddr)
+{
+	struct rds_ib_device *rds_ibdev;
+	struct rds_ib_ipaddr *i_ipaddr;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(rds_ibdev, &rds_ib_devices, list) {
+		list_for_each_entry_rcu(i_ipaddr, &rds_ibdev->ipaddr_list, list) {
+			if (i_ipaddr->ipaddr == ipaddr) {
+				refcount_inc(&rds_ibdev->refcount);
+				rcu_read_unlock();
+				return rds_ibdev;
+			}
+		}
+	}
+	rcu_read_unlock();
+
+	return NULL;
+}
+
+static int rds_ib_add_ipaddr(struct rds_ib_device *rds_ibdev, __be32 ipaddr)
+{
+	struct rds_ib_ipaddr *i_ipaddr;
+
+	i_ipaddr = kmalloc(sizeof *i_ipaddr, GFP_KERNEL);
+	if (!i_ipaddr)
+		return -ENOMEM;
+
+	i_ipaddr->ipaddr = ipaddr;
+
+	spin_lock_irq(&rds_ibdev->spinlock);
+	list_add_tail_rcu(&i_ipaddr->list, &rds_ibdev->ipaddr_list);
+	spin_unlock_irq(&rds_ibdev->spinlock);
+
+	return 0;
+}
+
+static void rds_ib_remove_ipaddr(struct rds_ib_device *rds_ibdev, __be32 ipaddr)
+{
+	struct rds_ib_ipaddr *i_ipaddr;
+	struct rds_ib_ipaddr *to_free = NULL;
+
+
+	spin_lock_irq(&rds_ibdev->spinlock);
+	list_for_each_entry_rcu(i_ipaddr, &rds_ibdev->ipaddr_list, list) {
+		if (i_ipaddr->ipaddr == ipaddr) {
+			list_del_rcu(&i_ipaddr->list);
+			to_free = i_ipaddr;
+			break;
+		}
+	}
+	spin_unlock_irq(&rds_ibdev->spinlock);
+
+	if (to_free)
+		kfree_rcu(to_free, rcu);
+}
+
+int rds_ib_update_ipaddr(struct rds_ib_device *rds_ibdev,
+			 struct in6_addr *ipaddr)
+{
+	struct rds_ib_device *rds_ibdev_old;
+
+	rds_ibdev_old = rds_ib_get_device(ipaddr->s6_addr32[3]);
+	if (!rds_ibdev_old)
+		return rds_ib_add_ipaddr(rds_ibdev, ipaddr->s6_addr32[3]);
+
+	if (rds_ibdev_old != rds_ibdev) {
+		rds_ib_remove_ipaddr(rds_ibdev_old, ipaddr->s6_addr32[3]);
+		rds_ib_dev_put(rds_ibdev_old);
+		return rds_ib_add_ipaddr(rds_ibdev, ipaddr->s6_addr32[3]);
+	}
+	rds_ib_dev_put(rds_ibdev_old);
+
+	return 0;
+}
+
+void rds_ib_add_conn(struct rds_ib_device *rds_ibdev, struct rds_connection *conn)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	/* conn was previously on the nodev_conns_list */
+	spin_lock_irq(&ib_nodev_conns_lock);
+	BUG_ON(list_empty(&ib_nodev_conns));
+	BUG_ON(list_empty(&ic->ib_node));
+	list_del(&ic->ib_node);
+
+	spin_lock(&rds_ibdev->spinlock);
+	list_add_tail(&ic->ib_node, &rds_ibdev->conn_list);
+	spin_unlock(&rds_ibdev->spinlock);
+	spin_unlock_irq(&ib_nodev_conns_lock);
+
+	ic->rds_ibdev = rds_ibdev;
+	refcount_inc(&rds_ibdev->refcount);
+}
+
+void rds_ib_remove_conn(struct rds_ib_device *rds_ibdev, struct rds_connection *conn)
+{
+	struct rds_ib_connection *ic = conn->c_transport_data;
+
+	/* place conn on nodev_conns_list */
+	spin_lock(&ib_nodev_conns_lock);
+
+	spin_lock_irq(&rds_ibdev->spinlock);
+	BUG_ON(list_empty(&ic->ib_node));
+	list_del(&ic->ib_node);
+	spin_unlock_irq(&rds_ibdev->spinlock);
+
+	list_add_tail(&ic->ib_node, &ib_nodev_conns);
+
+	spin_unlock(&ib_nodev_conns_lock);
+
+	ic->rds_ibdev = NULL;
+	rds_ib_dev_put(rds_ibdev);
+}
+
+void rds_ib_destroy_nodev_conns(void)
+{
+	struct rds_ib_connection *ic, *_ic;
+	LIST_HEAD(tmp_list);
+
+	/* avoid calling conn_destroy with irqs off */
+	spin_lock_irq(&ib_nodev_conns_lock);
+	list_splice(&ib_nodev_conns, &tmp_list);
+	spin_unlock_irq(&ib_nodev_conns_lock);
+
+	list_for_each_entry_safe(ic, _ic, &tmp_list, ib_node)
+		rds_conn_destroy(ic->conn);
+}
+
+void rds_ib_get_mr_info(struct rds_ib_device *rds_ibdev, struct rds_info_rdma_connection *iinfo)
+{
+	struct rds_ib_mr_pool *pool_1m = rds_ibdev->mr_1m_pool;
+
+	iinfo->rdma_mr_max = pool_1m->max_items;
+	iinfo->rdma_mr_size = pool_1m->fmr_attr.max_pages;
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+void rds6_ib_get_mr_info(struct rds_ib_device *rds_ibdev,
+			 struct rds6_info_rdma_connection *iinfo6)
+{
+	struct rds_ib_mr_pool *pool_1m = rds_ibdev->mr_1m_pool;
+
+	iinfo6->rdma_mr_max = pool_1m->max_items;
+	iinfo6->rdma_mr_size = pool_1m->fmr_attr.max_pages;
+}
+#endif
+
+struct rds_ib_mr *rds_ib_reuse_mr(struct rds_ib_mr_pool *pool)
+{
+	struct rds_ib_mr *ibmr = NULL;
+	struct llist_node *ret;
+	unsigned long *flag;
+
+	preempt_disable();
+	flag = this_cpu_ptr(&clean_list_grace);
+	set_bit(CLEAN_LIST_BUSY_BIT, flag);
+	ret = llist_del_first(&pool->clean_list);
+	if (ret) {
+		ibmr = llist_entry(ret, struct rds_ib_mr, llnode);
+		if (pool->pool_type == RDS_IB_MR_8K_POOL)
+			rds_ib_stats_inc(s_ib_rdma_mr_8k_reused);
+		else
+			rds_ib_stats_inc(s_ib_rdma_mr_1m_reused);
+	}
+
+	clear_bit(CLEAN_LIST_BUSY_BIT, flag);
+	preempt_enable();
+	return ibmr;
+}
+
+static inline void wait_clean_list_grace(void)
+{
+	int cpu;
+	unsigned long *flag;
+
+	for_each_online_cpu(cpu) {
+		flag = &per_cpu(clean_list_grace, cpu);
+		while (test_bit(CLEAN_LIST_BUSY_BIT, flag))
+			cpu_relax();
+	}
+}
+
+void rds_ib_sync_mr(void *trans_private, int direction)
+{
+	struct rds_ib_mr *ibmr = trans_private;
+	struct rds_ib_device *rds_ibdev = ibmr->device;
+
+	switch (direction) {
+	case DMA_FROM_DEVICE:
+		ib_dma_sync_sg_for_cpu(rds_ibdev->dev, ibmr->sg,
+			ibmr->sg_dma_len, DMA_BIDIRECTIONAL);
+		break;
+	case DMA_TO_DEVICE:
+		ib_dma_sync_sg_for_device(rds_ibdev->dev, ibmr->sg,
+			ibmr->sg_dma_len, DMA_BIDIRECTIONAL);
+		break;
+	}
+}
+
+void __rds_ib_teardown_mr(struct rds_ib_mr *ibmr)
+{
+	struct rds_ib_device *rds_ibdev = ibmr->device;
+
+	if (ibmr->sg_dma_len) {
+		ib_dma_unmap_sg(rds_ibdev->dev,
+				ibmr->sg, ibmr->sg_len,
+				DMA_BIDIRECTIONAL);
+		ibmr->sg_dma_len = 0;
+	}
+
+	/* Release the s/g list */
+	if (ibmr->sg_len) {
+		unsigned int i;
+
+		for (i = 0; i < ibmr->sg_len; ++i) {
+			struct page *page = sg_page(&ibmr->sg[i]);
+
+			/* FIXME we need a way to tell a r/w MR
+			 * from a r/o MR */
+			WARN_ON(!page->mapping && irqs_disabled());
+			set_page_dirty(page);
+			put_page(page);
+		}
+		kfree(ibmr->sg);
+
+		ibmr->sg = NULL;
+		ibmr->sg_len = 0;
+	}
+}
+
+void rds_ib_teardown_mr(struct rds_ib_mr *ibmr)
+{
+	unsigned int pinned = ibmr->sg_len;
+
+	__rds_ib_teardown_mr(ibmr);
+	if (pinned) {
+		struct rds_ib_mr_pool *pool = ibmr->pool;
+
+		atomic_sub(pinned, &pool->free_pinned);
+	}
+}
+
+static inline unsigned int rds_ib_flush_goal(struct rds_ib_mr_pool *pool, int free_all)
+{
+	unsigned int item_count;
+
+	item_count = atomic_read(&pool->item_count);
+	if (free_all)
+		return item_count;
+
+	return 0;
+}
+
+/*
+ * given an llist of mrs, put them all into the list_head for more processing
+ */
+static unsigned int llist_append_to_list(struct llist_head *llist,
+					 struct list_head *list)
+{
+	struct rds_ib_mr *ibmr;
+	struct llist_node *node;
+	struct llist_node *next;
+	unsigned int count = 0;
+
+	node = llist_del_all(llist);
+	while (node) {
+		next = node->next;
+		ibmr = llist_entry(node, struct rds_ib_mr, llnode);
+		list_add_tail(&ibmr->unmap_list, list);
+		node = next;
+		count++;
+	}
+	return count;
+}
+
+/*
+ * this takes a list head of mrs and turns it into linked llist nodes
+ * of clusters.  Each cluster has linked llist nodes of
+ * MR_CLUSTER_SIZE mrs that are ready for reuse.
+ */
+static void list_to_llist_nodes(struct rds_ib_mr_pool *pool,
+				struct list_head *list,
+				struct llist_node **nodes_head,
+				struct llist_node **nodes_tail)
+{
+	struct rds_ib_mr *ibmr;
+	struct llist_node *cur = NULL;
+	struct llist_node **next = nodes_head;
+
+	list_for_each_entry(ibmr, list, unmap_list) {
+		cur = &ibmr->llnode;
+		*next = cur;
+		next = &cur->next;
+	}
+	*next = NULL;
+	*nodes_tail = cur;
+}
+
+/*
+ * Flush our pool of MRs.
+ * At a minimum, all currently unused MRs are unmapped.
+ * If the number of MRs allocated exceeds the limit, we also try
+ * to free as many MRs as needed to get back to this limit.
+ */
+int rds_ib_flush_mr_pool(struct rds_ib_mr_pool *pool,
+			 int free_all, struct rds_ib_mr **ibmr_ret)
+{
+	struct rds_ib_mr *ibmr;
+	struct llist_node *clean_nodes;
+	struct llist_node *clean_tail;
+	LIST_HEAD(unmap_list);
+	unsigned long unpinned = 0;
+	unsigned int nfreed = 0, dirty_to_clean = 0, free_goal;
+
+	if (pool->pool_type == RDS_IB_MR_8K_POOL)
+		rds_ib_stats_inc(s_ib_rdma_mr_8k_pool_flush);
+	else
+		rds_ib_stats_inc(s_ib_rdma_mr_1m_pool_flush);
+
+	if (ibmr_ret) {
+		DEFINE_WAIT(wait);
+		while (!mutex_trylock(&pool->flush_lock)) {
+			ibmr = rds_ib_reuse_mr(pool);
+			if (ibmr) {
+				*ibmr_ret = ibmr;
+				finish_wait(&pool->flush_wait, &wait);
+				goto out_nolock;
+			}
+
+			prepare_to_wait(&pool->flush_wait, &wait,
+					TASK_UNINTERRUPTIBLE);
+			if (llist_empty(&pool->clean_list))
+				schedule();
+
+			ibmr = rds_ib_reuse_mr(pool);
+			if (ibmr) {
+				*ibmr_ret = ibmr;
+				finish_wait(&pool->flush_wait, &wait);
+				goto out_nolock;
+			}
+		}
+		finish_wait(&pool->flush_wait, &wait);
+	} else
+		mutex_lock(&pool->flush_lock);
+
+	if (ibmr_ret) {
+		ibmr = rds_ib_reuse_mr(pool);
+		if (ibmr) {
+			*ibmr_ret = ibmr;
+			goto out;
+		}
+	}
+
+	/* Get the list of all MRs to be dropped. Ordering matters -
+	 * we want to put drop_list ahead of free_list.
+	 */
+	dirty_to_clean = llist_append_to_list(&pool->drop_list, &unmap_list);
+	dirty_to_clean += llist_append_to_list(&pool->free_list, &unmap_list);
+	if (free_all)
+		llist_append_to_list(&pool->clean_list, &unmap_list);
+
+	free_goal = rds_ib_flush_goal(pool, free_all);
+
+	if (list_empty(&unmap_list))
+		goto out;
+
+	if (pool->use_fastreg)
+		rds_ib_unreg_frmr(&unmap_list, &nfreed, &unpinned, free_goal);
+	else
+		rds_ib_unreg_fmr(&unmap_list, &nfreed, &unpinned, free_goal);
+
+	if (!list_empty(&unmap_list)) {
+		/* we have to make sure that none of the things we're about
+		 * to put on the clean list would race with other cpus trying
+		 * to pull items off.  The llist would explode if we managed to
+		 * remove something from the clean list and then add it back again
+		 * while another CPU was spinning on that same item in llist_del_first.
+		 *
+		 * This is pretty unlikely, but just in case  wait for an llist grace period
+		 * here before adding anything back into the clean list.
+		 */
+		wait_clean_list_grace();
+
+		list_to_llist_nodes(pool, &unmap_list, &clean_nodes, &clean_tail);
+		if (ibmr_ret) {
+			*ibmr_ret = llist_entry(clean_nodes, struct rds_ib_mr, llnode);
+			clean_nodes = clean_nodes->next;
+		}
+		/* more than one entry in llist nodes */
+		if (clean_nodes)
+			llist_add_batch(clean_nodes, clean_tail,
+					&pool->clean_list);
+
+	}
+
+	atomic_sub(unpinned, &pool->free_pinned);
+	atomic_sub(dirty_to_clean, &pool->dirty_count);
+	atomic_sub(nfreed, &pool->item_count);
+
+out:
+	mutex_unlock(&pool->flush_lock);
+	if (waitqueue_active(&pool->flush_wait))
+		wake_up(&pool->flush_wait);
+out_nolock:
+	return 0;
+}
+
+struct rds_ib_mr *rds_ib_try_reuse_ibmr(struct rds_ib_mr_pool *pool)
+{
+	struct rds_ib_mr *ibmr = NULL;
+	int iter = 0;
+
+	while (1) {
+		ibmr = rds_ib_reuse_mr(pool);
+		if (ibmr)
+			return ibmr;
+
+		if (atomic_inc_return(&pool->item_count) <= pool->max_items)
+			break;
+
+		atomic_dec(&pool->item_count);
+
+		if (++iter > 2) {
+			if (pool->pool_type == RDS_IB_MR_8K_POOL)
+				rds_ib_stats_inc(s_ib_rdma_mr_8k_pool_depleted);
+			else
+				rds_ib_stats_inc(s_ib_rdma_mr_1m_pool_depleted);
+			return ERR_PTR(-EAGAIN);
+		}
+
+		/* We do have some empty MRs. Flush them out. */
+		if (pool->pool_type == RDS_IB_MR_8K_POOL)
+			rds_ib_stats_inc(s_ib_rdma_mr_8k_pool_wait);
+		else
+			rds_ib_stats_inc(s_ib_rdma_mr_1m_pool_wait);
+
+		rds_ib_flush_mr_pool(pool, 0, &ibmr);
+		if (ibmr)
+			return ibmr;
+	}
+
+	return ibmr;
+}
+
+static void rds_ib_mr_pool_flush_worker(struct work_struct *work)
+{
+	struct rds_ib_mr_pool *pool = container_of(work, struct rds_ib_mr_pool, flush_worker.work);
+
+	rds_ib_flush_mr_pool(pool, 0, NULL);
+}
+
+void rds_ib_free_mr(void *trans_private, int invalidate)
+{
+	struct rds_ib_mr *ibmr = trans_private;
+	struct rds_ib_mr_pool *pool = ibmr->pool;
+	struct rds_ib_device *rds_ibdev = ibmr->device;
+
+	rdsdebug("RDS/IB: free_mr nents %u\n", ibmr->sg_len);
+
+	/* Return it to the pool's free list */
+	if (rds_ibdev->use_fastreg)
+		rds_ib_free_frmr_list(ibmr);
+	else
+		rds_ib_free_fmr_list(ibmr);
+
+	atomic_add(ibmr->sg_len, &pool->free_pinned);
+	atomic_inc(&pool->dirty_count);
+
+	/* If we've pinned too many pages, request a flush */
+	if (atomic_read(&pool->free_pinned) >= pool->max_free_pinned ||
+	    atomic_read(&pool->dirty_count) >= pool->max_items / 5)
+		queue_delayed_work(rds_ib_mr_wq, &pool->flush_worker, 10);
+
+	if (invalidate) {
+		if (likely(!in_interrupt())) {
+			rds_ib_flush_mr_pool(pool, 0, NULL);
+		} else {
+			/* We get here if the user created a MR marked
+			 * as use_once and invalidate at the same time.
+			 */
+			queue_delayed_work(rds_ib_mr_wq,
+					   &pool->flush_worker, 10);
+		}
+	}
+
+	rds_ib_dev_put(rds_ibdev);
+}
+
+void rds_ib_flush_mrs(void)
+{
+	struct rds_ib_device *rds_ibdev;
+
+	down_read(&rds_ib_devices_lock);
+	list_for_each_entry(rds_ibdev, &rds_ib_devices, list) {
+		if (rds_ibdev->mr_8k_pool)
+			rds_ib_flush_mr_pool(rds_ibdev->mr_8k_pool, 0, NULL);
+
+		if (rds_ibdev->mr_1m_pool)
+			rds_ib_flush_mr_pool(rds_ibdev->mr_1m_pool, 0, NULL);
+	}
+	up_read(&rds_ib_devices_lock);
+}
+
+void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents,
+		    struct rds_sock *rs, u32 *key_ret,
+		    struct rds_connection *conn)
+{
+	struct rds_ib_device *rds_ibdev;
+	struct rds_ib_mr *ibmr = NULL;
+	struct rds_ib_connection *ic = NULL;
+	int ret;
+
+	rds_ibdev = rds_ib_get_device(rs->rs_bound_addr.s6_addr32[3]);
+	if (!rds_ibdev) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (conn)
+		ic = conn->c_transport_data;
+
+	if (!rds_ibdev->mr_8k_pool || !rds_ibdev->mr_1m_pool) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (rds_ibdev->use_fastreg)
+		ibmr = rds_ib_reg_frmr(rds_ibdev, ic, sg, nents, key_ret);
+	else
+		ibmr = rds_ib_reg_fmr(rds_ibdev, sg, nents, key_ret);
+	if (IS_ERR(ibmr)) {
+		ret = PTR_ERR(ibmr);
+		pr_warn("RDS/IB: rds_ib_get_mr failed (errno=%d)\n", ret);
+	} else {
+		return ibmr;
+	}
+
+ out:
+	if (rds_ibdev)
+		rds_ib_dev_put(rds_ibdev);
+
+	return ERR_PTR(ret);
+}
+
+void rds_ib_destroy_mr_pool(struct rds_ib_mr_pool *pool)
+{
+	cancel_delayed_work_sync(&pool->flush_worker);
+	rds_ib_flush_mr_pool(pool, 1, NULL);
+	WARN_ON(atomic_read(&pool->item_count));
+	WARN_ON(atomic_read(&pool->free_pinned));
+	kfree(pool);
+}
+
+struct rds_ib_mr_pool *rds_ib_create_mr_pool(struct rds_ib_device *rds_ibdev,
+					     int pool_type)
+{
+	struct rds_ib_mr_pool *pool;
+
+	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
+	if (!pool)
+		return ERR_PTR(-ENOMEM);
+
+	pool->pool_type = pool_type;
+	init_llist_head(&pool->free_list);
+	init_llist_head(&pool->drop_list);
+	init_llist_head(&pool->clean_list);
+	mutex_init(&pool->flush_lock);
+	init_waitqueue_head(&pool->flush_wait);
+	INIT_DELAYED_WORK(&pool->flush_worker, rds_ib_mr_pool_flush_worker);
+
+	if (pool_type == RDS_IB_MR_1M_POOL) {
+		/* +1 allows for unaligned MRs */
+		pool->fmr_attr.max_pages = RDS_MR_1M_MSG_SIZE + 1;
+		pool->max_items = rds_ibdev->max_1m_mrs;
+	} else {
+		/* pool_type == RDS_IB_MR_8K_POOL */
+		pool->fmr_attr.max_pages = RDS_MR_8K_MSG_SIZE + 1;
+		pool->max_items = rds_ibdev->max_8k_mrs;
+	}
+
+	pool->max_free_pinned = pool->max_items * pool->fmr_attr.max_pages / 4;
+	pool->fmr_attr.max_maps = rds_ibdev->fmr_max_remaps;
+	pool->fmr_attr.page_shift = PAGE_SHIFT;
+	pool->max_items_soft = rds_ibdev->max_mrs * 3 / 4;
+	pool->use_fastreg = rds_ibdev->use_fastreg;
+
+	return pool;
+}
+
+int rds_ib_mr_init(void)
+{
+	rds_ib_mr_wq = alloc_workqueue("rds_mr_flushd", WQ_MEM_RECLAIM, 0);
+	if (!rds_ib_mr_wq)
+		return -ENOMEM;
+	return 0;
+}
+
+/* By the time this is called all the IB devices should have been torn down and
+ * had their pools freed.  As each pool is freed its work struct is waited on,
+ * so the pool flushing work queue should be idle by the time we get here.
+ */
+void rds_ib_mr_exit(void)
+{
+	destroy_workqueue(rds_ib_mr_wq);
+}