RDS/IB: Implement RDMA ops using FMRs

Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 641 insertions, 0 deletions

diff --git a/net/rds/ib_rdma.c b/net/rds/ib_rdma.c
new file mode 100644
index 000000000000..69a6289ed672
--- /dev/null
+++ b/net/rds/ib_rdma.c
@@ -0,0 +1,641 @@
+/*
+ * Copyright (c) 2006 Oracle.  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 "rds.h"
+#include "rdma.h"
+#include "ib.h"
+
+
+/*
+ * This is stored as mr->r_trans_private.
+ */
+struct rds_ib_mr {
+        struct rds_ib_device    *device;
+        struct rds_ib_mr_pool   *pool;
+        struct ib_fmr           *fmr;
+        struct list_head        list;
+        unsigned int            remap_count;
+
+        struct scatterlist      *sg;
+        unsigned int            sg_len;
+        u64                     *dma;
+        int                     sg_dma_len;
+};
+
+/*
+ * Our own little FMR pool
+ */
+struct rds_ib_mr_pool {
+        struct mutex            flush_lock;             /* serialize fmr invalidate */
+        struct work_struct      flush_worker;           /* flush worker */
+
+        spinlock_t              list_lock;              /* protect variables below */
+        atomic_t                item_count;             /* total # of MRs */
+        atomic_t                dirty_count;            /* # dirty of MRs */
+        struct list_head        drop_list;              /* MRs that have reached their max_maps limit */
+        struct list_head        free_list;              /* unused MRs */
+        struct list_head        clean_list;             /* unused & unamapped MRs */
+        atomic_t                free_pinned;            /* memory pinned by free MRs */
+        unsigned long           max_items;
+        unsigned long           max_items_soft;
+        unsigned long           max_free_pinned;
+        struct ib_fmr_attr      fmr_attr;
+};
+
+static int rds_ib_flush_mr_pool(struct rds_ib_mr_pool *pool, int free_all);
+static void rds_ib_teardown_mr(struct rds_ib_mr *ibmr);
+static void rds_ib_mr_pool_flush_worker(struct work_struct *work);
+
+static struct rds_ib_device *rds_ib_get_device(__be32 ipaddr)
+{
+        struct rds_ib_device *rds_ibdev;
+        struct rds_ib_ipaddr *i_ipaddr;
+
+        list_for_each_entry(rds_ibdev, &rds_ib_devices, list) {
+                spin_lock_irq(&rds_ibdev->spinlock);
+                list_for_each_entry(i_ipaddr, &rds_ibdev->ipaddr_list, list) {
+                        if (i_ipaddr->ipaddr == ipaddr) {
+                                spin_unlock_irq(&rds_ibdev->spinlock);
+                                return rds_ibdev;
+                        }
+                }
+                spin_unlock_irq(&rds_ibdev->spinlock);
+        }
+
+        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(&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, *next;
+
+        spin_lock_irq(&rds_ibdev->spinlock);
+        list_for_each_entry_safe(i_ipaddr, next, &rds_ibdev->ipaddr_list, list) {
+                if (i_ipaddr->ipaddr == ipaddr) {
+                        list_del(&i_ipaddr->list);
+                        kfree(i_ipaddr);
+                        break;
+                }
+        }
+        spin_unlock_irq(&rds_ibdev->spinlock);
+}
+
+int rds_ib_update_ipaddr(struct rds_ib_device *rds_ibdev, __be32 ipaddr)
+{
+        struct rds_ib_device *rds_ibdev_old;
+
+        rds_ibdev_old = rds_ib_get_device(ipaddr);
+        if (rds_ibdev_old)
+                rds_ib_remove_ipaddr(rds_ibdev_old, ipaddr);
+
+        return rds_ib_add_ipaddr(rds_ibdev, ipaddr);
+}
+
+int 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_unlock_irq(&ib_nodev_conns_lock);
+
+        spin_lock_irq(&rds_ibdev->spinlock);
+        list_add_tail(&ic->ib_node, &rds_ibdev->conn_list);
+        spin_unlock_irq(&rds_ibdev->spinlock);
+
+        ic->rds_ibdev = rds_ibdev;
+
+        return 0;
+}
+
+void rds_ib_remove_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);
+        INIT_LIST_HEAD(&ib_nodev_conns);
+        spin_unlock_irq(&ib_nodev_conns_lock);
+
+        list_for_each_entry_safe(ic, _ic, &tmp_list, ib_node) {
+                if (ic->conn->c_passive)
+                        rds_conn_destroy(ic->conn->c_passive);
+                rds_conn_destroy(ic->conn);
+        }
+}
+
+void rds_ib_remove_conns(struct rds_ib_device *rds_ibdev)
+{
+        struct rds_ib_connection *ic, *_ic;
+        LIST_HEAD(tmp_list);
+
+        /* avoid calling conn_destroy with irqs off */
+        spin_lock_irq(&rds_ibdev->spinlock);
+        list_splice(&rds_ibdev->conn_list, &tmp_list);
+        INIT_LIST_HEAD(&rds_ibdev->conn_list);
+        spin_unlock_irq(&rds_ibdev->spinlock);
+
+        list_for_each_entry_safe(ic, _ic, &tmp_list, ib_node) {
+                if (ic->conn->c_passive)
+                        rds_conn_destroy(ic->conn->c_passive);
+                rds_conn_destroy(ic->conn);
+        }
+}
+
+struct rds_ib_mr_pool *rds_ib_create_mr_pool(struct rds_ib_device *rds_ibdev)
+{
+        struct rds_ib_mr_pool *pool;
+
+        pool = kzalloc(sizeof(*pool), GFP_KERNEL);
+        if (!pool)
+                return ERR_PTR(-ENOMEM);
+
+        INIT_LIST_HEAD(&pool->free_list);
+        INIT_LIST_HEAD(&pool->drop_list);
+        INIT_LIST_HEAD(&pool->clean_list);
+        mutex_init(&pool->flush_lock);
+        spin_lock_init(&pool->list_lock);
+        INIT_WORK(&pool->flush_worker, rds_ib_mr_pool_flush_worker);
+
+        pool->fmr_attr.max_pages = fmr_message_size;
+        pool->fmr_attr.max_maps = rds_ibdev->fmr_max_remaps;
+        pool->fmr_attr.page_shift = rds_ibdev->fmr_page_shift;
+        pool->max_free_pinned = rds_ibdev->max_fmrs * fmr_message_size / 4;
+
+        /* We never allow more than max_items MRs to be allocated.
+         * When we exceed more than max_items_soft, we start freeing
+         * items more aggressively.
+         * Make sure that max_items > max_items_soft > max_items / 2
+         */
+        pool->max_items_soft = rds_ibdev->max_fmrs * 3 / 4;
+        pool->max_items = rds_ibdev->max_fmrs;
+
+        return pool;
+}
+
+void rds_ib_get_mr_info(struct rds_ib_device *rds_ibdev, struct rds_info_rdma_connection *iinfo)
+{
+        struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;
+
+        iinfo->rdma_mr_max = pool->max_items;
+        iinfo->rdma_mr_size = pool->fmr_attr.max_pages;
+}
+
+void rds_ib_destroy_mr_pool(struct rds_ib_mr_pool *pool)
+{
+        flush_workqueue(rds_wq);
+        rds_ib_flush_mr_pool(pool, 1);
+        BUG_ON(atomic_read(&pool->item_count));
+        BUG_ON(atomic_read(&pool->free_pinned));
+        kfree(pool);
+}
+
+static inline struct rds_ib_mr *rds_ib_reuse_fmr(struct rds_ib_mr_pool *pool)
+{
+        struct rds_ib_mr *ibmr = NULL;
+        unsigned long flags;
+
+        spin_lock_irqsave(&pool->list_lock, flags);
+        if (!list_empty(&pool->clean_list)) {
+                ibmr = list_entry(pool->clean_list.next, struct rds_ib_mr, list);
+                list_del_init(&ibmr->list);
+        }
+        spin_unlock_irqrestore(&pool->list_lock, flags);
+
+        return ibmr;
+}
+
+static struct rds_ib_mr *rds_ib_alloc_fmr(struct rds_ib_device *rds_ibdev)
+{
+        struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;
+        struct rds_ib_mr *ibmr = NULL;
+        int err = 0, iter = 0;
+
+        while (1) {
+                ibmr = rds_ib_reuse_fmr(pool);
+                if (ibmr)
+                        return ibmr;
+
+                /* No clean MRs - now we have the choice of either
+                 * allocating a fresh MR up to the limit imposed by the
+                 * driver, or flush any dirty unused MRs.
+                 * We try to avoid stalling in the send path if possible,
+                 * so we allocate as long as we're allowed to.
+                 *
+                 * We're fussy with enforcing the FMR limit, though. If the driver
+                 * tells us we can't use more than N fmrs, we shouldn't start
+                 * arguing with it */
+                if (atomic_inc_return(&pool->item_count) <= pool->max_items)
+                        break;
+
+                atomic_dec(&pool->item_count);
+
+                if (++iter > 2) {
+                        rds_ib_stats_inc(s_ib_rdma_mr_pool_depleted);
+                        return ERR_PTR(-EAGAIN);
+                }
+
+                /* We do have some empty MRs. Flush them out. */
+                rds_ib_stats_inc(s_ib_rdma_mr_pool_wait);
+                rds_ib_flush_mr_pool(pool, 0);
+        }
+
+        ibmr = kzalloc(sizeof(*ibmr), GFP_KERNEL);
+        if (!ibmr) {
+                err = -ENOMEM;
+                goto out_no_cigar;
+        }
+
+        ibmr->fmr = ib_alloc_fmr(rds_ibdev->pd,
+                        (IB_ACCESS_LOCAL_WRITE |
+                         IB_ACCESS_REMOTE_READ |
+                         IB_ACCESS_REMOTE_WRITE),
+                        &pool->fmr_attr);
+        if (IS_ERR(ibmr->fmr)) {
+                err = PTR_ERR(ibmr->fmr);
+                ibmr->fmr = NULL;
+                printk(KERN_WARNING "RDS/IB: ib_alloc_fmr failed (err=%d)\n", err);
+                goto out_no_cigar;
+        }
+
+        rds_ib_stats_inc(s_ib_rdma_mr_alloc);
+        return ibmr;
+
+out_no_cigar:
+        if (ibmr) {
+                if (ibmr->fmr)
+                        ib_dealloc_fmr(ibmr->fmr);
+                kfree(ibmr);
+        }
+        atomic_dec(&pool->item_count);
+        return ERR_PTR(err);
+}
+
+static int rds_ib_map_fmr(struct rds_ib_device *rds_ibdev, struct rds_ib_mr *ibmr,
+               struct scatterlist *sg, unsigned int nents)
+{
+        struct ib_device *dev = rds_ibdev->dev;
+        struct scatterlist *scat = sg;
+        u64 io_addr = 0;
+        u64 *dma_pages;
+        u32 len;
+        int page_cnt, sg_dma_len;
+        int i, j;
+        int ret;
+
+        sg_dma_len = ib_dma_map_sg(dev, sg, nents,
+                                 DMA_BIDIRECTIONAL);
+        if (unlikely(!sg_dma_len)) {
+                printk(KERN_WARNING "RDS/IB: dma_map_sg failed!\n");
+                return -EBUSY;
+        }
+
+        len = 0;
+        page_cnt = 0;
+
+        for (i = 0; i < sg_dma_len; ++i) {
+                unsigned int dma_len = ib_sg_dma_len(dev, &scat[i]);
+                u64 dma_addr = ib_sg_dma_address(dev, &scat[i]);
+
+                if (dma_addr & ~rds_ibdev->fmr_page_mask) {
+                        if (i > 0)
+                                return -EINVAL;
+                        else
+                                ++page_cnt;
+                }
+                if ((dma_addr + dma_len) & ~rds_ibdev->fmr_page_mask) {
+                        if (i < sg_dma_len - 1)
+                                return -EINVAL;
+                        else
+                                ++page_cnt;
+                }
+
+                len += dma_len;
+        }
+
+        page_cnt += len >> rds_ibdev->fmr_page_shift;
+        if (page_cnt > fmr_message_size)
+                return -EINVAL;
+
+        dma_pages = kmalloc(sizeof(u64) * page_cnt, GFP_ATOMIC);
+        if (!dma_pages)
+                return -ENOMEM;
+
+        page_cnt = 0;
+        for (i = 0; i < sg_dma_len; ++i) {
+                unsigned int dma_len = ib_sg_dma_len(dev, &scat[i]);
+                u64 dma_addr = ib_sg_dma_address(dev, &scat[i]);
+
+                for (j = 0; j < dma_len; j += rds_ibdev->fmr_page_size)
+                        dma_pages[page_cnt++] =
+                                (dma_addr & rds_ibdev->fmr_page_mask) + j;
+        }
+
+        ret = ib_map_phys_fmr(ibmr->fmr,
+                                   dma_pages, page_cnt, io_addr);
+        if (ret)
+                goto out;
+
+        /* Success - we successfully remapped the MR, so we can
+         * safely tear down the old mapping. */
+        rds_ib_teardown_mr(ibmr);
+
+        ibmr->sg = scat;
+        ibmr->sg_len = nents;
+        ibmr->sg_dma_len = sg_dma_len;
+        ibmr->remap_count++;
+
+        rds_ib_stats_inc(s_ib_rdma_mr_used);
+        ret = 0;
+
+out:
+        kfree(dma_pages);
+
+        return ret;
+}
+
+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;
+        }
+}
+
+static 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 */
+                        set_page_dirty(page);
+                        put_page(page);
+                }
+                kfree(ibmr->sg);
+
+                ibmr->sg = NULL;
+                ibmr->sg_len = 0;
+        }
+}
+
+static 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_device *rds_ibdev = ibmr->device;
+                struct rds_ib_mr_pool *pool = rds_ibdev->mr_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;
+}
+
+/*
+ * 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.
+ */
+static int rds_ib_flush_mr_pool(struct rds_ib_mr_pool *pool, int free_all)
+{
+        struct rds_ib_mr *ibmr, *next;
+        LIST_HEAD(unmap_list);
+        LIST_HEAD(fmr_list);
+        unsigned long unpinned = 0;
+        unsigned long flags;
+        unsigned int nfreed = 0, ncleaned = 0, free_goal;
+        int ret = 0;
+
+        rds_ib_stats_inc(s_ib_rdma_mr_pool_flush);
+
+        mutex_lock(&pool->flush_lock);
+
+        spin_lock_irqsave(&pool->list_lock, flags);
+        /* Get the list of all MRs to be dropped. Ordering matters -
+         * we want to put drop_list ahead of free_list. */
+        list_splice_init(&pool->free_list, &unmap_list);
+        list_splice_init(&pool->drop_list, &unmap_list);
+        if (free_all)
+                list_splice_init(&pool->clean_list, &unmap_list);
+        spin_unlock_irqrestore(&pool->list_lock, flags);
+
+        free_goal = rds_ib_flush_goal(pool, free_all);
+
+        if (list_empty(&unmap_list))
+                goto out;
+
+        /* String all ib_mr's onto one list and hand them to ib_unmap_fmr */
+        list_for_each_entry(ibmr, &unmap_list, list)
+                list_add(&ibmr->fmr->list, &fmr_list);
+        ret = ib_unmap_fmr(&fmr_list);
+        if (ret)
+                printk(KERN_WARNING "RDS/IB: ib_unmap_fmr failed (err=%d)\n", ret);
+
+        /* Now we can destroy the DMA mapping and unpin any pages */
+        list_for_each_entry_safe(ibmr, next, &unmap_list, list) {
+                unpinned += ibmr->sg_len;
+                __rds_ib_teardown_mr(ibmr);
+                if (nfreed < free_goal || ibmr->remap_count >= pool->fmr_attr.max_maps) {
+                        rds_ib_stats_inc(s_ib_rdma_mr_free);
+                        list_del(&ibmr->list);
+                        ib_dealloc_fmr(ibmr->fmr);
+                        kfree(ibmr);
+                        nfreed++;
+                }
+                ncleaned++;
+        }
+
+        spin_lock_irqsave(&pool->list_lock, flags);
+        list_splice(&unmap_list, &pool->clean_list);
+        spin_unlock_irqrestore(&pool->list_lock, flags);
+
+        atomic_sub(unpinned, &pool->free_pinned);
+        atomic_sub(ncleaned, &pool->dirty_count);
+        atomic_sub(nfreed, &pool->item_count);
+
+out:
+        mutex_unlock(&pool->flush_lock);
+        return ret;
+}
+
+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);
+
+        rds_ib_flush_mr_pool(pool, 0);
+}
+
+void rds_ib_free_mr(void *trans_private, int invalidate)
+{
+        struct rds_ib_mr *ibmr = trans_private;
+        struct rds_ib_device *rds_ibdev = ibmr->device;
+        struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;
+        unsigned long flags;
+
+        rdsdebug("RDS/IB: free_mr nents %u\n", ibmr->sg_len);
+
+        /* Return it to the pool's free list */
+        spin_lock_irqsave(&pool->list_lock, flags);
+        if (ibmr->remap_count >= pool->fmr_attr.max_maps)
+                list_add(&ibmr->list, &pool->drop_list);
+        else
+                list_add(&ibmr->list, &pool->free_list);
+
+        atomic_add(ibmr->sg_len, &pool->free_pinned);
+        atomic_inc(&pool->dirty_count);
+        spin_unlock_irqrestore(&pool->list_lock, flags);
+
+        /* 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 / 10)
+                queue_work(rds_wq, &pool->flush_worker);
+
+        if (invalidate) {
+                if (likely(!in_interrupt())) {
+                        rds_ib_flush_mr_pool(pool, 0);
+                } else {
+                        /* We get here if the user created a MR marked
+                         * as use_once and invalidate at the same time. */
+                        queue_work(rds_wq, &pool->flush_worker);
+                }
+        }
+}
+
+void rds_ib_flush_mrs(void)
+{
+        struct rds_ib_device *rds_ibdev;
+
+        list_for_each_entry(rds_ibdev, &rds_ib_devices, list) {
+                struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;
+
+                if (pool)
+                        rds_ib_flush_mr_pool(pool, 0);
+        }
+}
+
+void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents,
+                    struct rds_sock *rs, u32 *key_ret)
+{
+        struct rds_ib_device *rds_ibdev;
+        struct rds_ib_mr *ibmr = NULL;
+        int ret;
+
+        rds_ibdev = rds_ib_get_device(rs->rs_bound_addr);
+        if (!rds_ibdev) {
+                ret = -ENODEV;
+                goto out;
+        }
+
+        if (!rds_ibdev->mr_pool) {
+                ret = -ENODEV;
+                goto out;
+        }
+
+        ibmr = rds_ib_alloc_fmr(rds_ibdev);
+        if (IS_ERR(ibmr))
+                return ibmr;
+
+        ret = rds_ib_map_fmr(rds_ibdev, ibmr, sg, nents);
+        if (ret == 0)
+                *key_ret = ibmr->fmr->rkey;
+        else
+                printk(KERN_WARNING "RDS/IB: map_fmr failed (errno=%d)\n", ret);
+
+        ibmr->device = rds_ibdev;
+
+ out:
+        if (ret) {
+                if (ibmr)
+                        rds_ib_free_mr(ibmr, 0);
+                ibmr = ERR_PTR(ret);
+        }
+        return ibmr;
+}