powerpc: gup_hugepte() support THP based tail recounting

[linux-2.6.git] / net / rds / ib_rdma.c

/*
 * 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 <linux/slab.h>
#include <linux/rculist.h>
#include <linux/llist.h>

#include "rds.h"
#include "ib.h"

static DEFINE_PER_CPU(unsigned long, clean_list_grace);
#define CLEAN_LIST_BUSY_BIT 0

/*
 * 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 llist_node       llnode;

        /* unmap_list is for freeing */
        struct list_head        unmap_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 delayed_work     flush_worker;           /* flush worker */

        atomic_t                item_count;             /* total # of MRs */
        atomic_t                dirty_count;            /* # dirty of MRs */

        struct llist_head       drop_list;              /* MRs that have reached their max_maps limit */
        struct llist_head       free_list;              /* unused MRs */
        struct llist_head       clean_list;             /* global unused & unamapped MRs */
        wait_queue_head_t       flush_wait;

        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, struct rds_ib_mr **);
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;

        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) {
                                atomic_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) {
                synchronize_rcu();
                kfree(to_free);
        }
}

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);
                rds_ib_dev_put(rds_ibdev_old);
        }

        return rds_ib_add_ipaddr(rds_ibdev, ipaddr);
}

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;
        atomic_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);
}

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_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);

        pool->fmr_attr.max_pages = fmr_message_size;
        pool->fmr_attr.max_maps = rds_ibdev->fmr_max_remaps;
        pool->fmr_attr.page_shift = 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)
{
        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);
}

static inline struct rds_ib_mr *rds_ib_reuse_fmr(struct rds_ib_mr_pool *pool)
{
        struct rds_ib_mr *ibmr = NULL;
        struct llist_node *ret;
        unsigned long *flag;

        preempt_disable();
        flag = &__get_cpu_var(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);

        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();
        }
}

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;

        if (atomic_read(&pool->dirty_count) >= pool->max_items / 10)
                schedule_delayed_work(&pool->flush_worker, 10);

        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);
                if (ibmr)
                        return ibmr;
        }

        ibmr = kzalloc_node(sizeof(*ibmr), GFP_KERNEL, rdsibdev_to_node(rds_ibdev));
        if (!ibmr) {
                err = -ENOMEM;
                goto out_no_cigar;
        }

        memset(ibmr, 0, sizeof(*ibmr));

        ibmr->fmr = ib_alloc_fmr(rds_ibdev->pd,
                        (IB_ACCESS_LOCAL_WRITE |
                         IB_ACCESS_REMOTE_READ |
                         IB_ACCESS_REMOTE_WRITE|
                         IB_ACCESS_REMOTE_ATOMIC),
                        &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 & ~PAGE_MASK) {
                        if (i > 0)
                                return -EINVAL;
                        else
                                ++page_cnt;
                }
                if ((dma_addr + dma_len) & ~PAGE_MASK) {
                        if (i < sg_dma_len - 1)
                                return -EINVAL;
                        else
                                ++page_cnt;
                }

                len += dma_len;
        }

        page_cnt += len >> PAGE_SHIFT;
        if (page_cnt > fmr_message_size)
                return -EINVAL;

        dma_pages = kmalloc_node(sizeof(u64) * page_cnt, GFP_ATOMIC,
                                 rdsibdev_to_node(rds_ibdev));
        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 += PAGE_SIZE)
                        dma_pages[page_cnt++] =
                                (dma_addr & 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 */
                        BUG_ON(irqs_disabled());
                        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;
}

/*
 * given an llist of mrs, put them all into the list_head for more processing
 */
static void 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;

        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;
        }
}

/*
 * 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.
 */
static 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, *next;
        struct llist_node *clean_nodes;
        struct llist_node *clean_tail;
        LIST_HEAD(unmap_list);
        LIST_HEAD(fmr_list);
        unsigned long unpinned = 0;
        unsigned int nfreed = 0, ncleaned = 0, free_goal;
        int ret = 0;

        rds_ib_stats_inc(s_ib_rdma_mr_pool_flush);

        if (ibmr_ret) {
                DEFINE_WAIT(wait);
                while(!mutex_trylock(&pool->flush_lock)) {
                        ibmr = rds_ib_reuse_fmr(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_fmr(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_fmr(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.
         */
        llist_append_to_list(&pool->drop_list, &unmap_list);
        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;

        /* String all ib_mr's onto one list and hand them to ib_unmap_fmr */
        list_for_each_entry(ibmr, &unmap_list, unmap_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, unmap_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->unmap_list);
                        ib_dealloc_fmr(ibmr->fmr);
                        kfree(ibmr);
                        nfreed++;
                }
                ncleaned++;
        }

        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);

                /* more than one entry in llist nodes */
                if (clean_nodes->next)
                        llist_add_batch(clean_nodes->next, clean_tail, &pool->clean_list);

        }

        atomic_sub(unpinned, &pool->free_pinned);
        atomic_sub(ncleaned, &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 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.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_device *rds_ibdev = ibmr->device;
        struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;

        rdsdebug("RDS/IB: free_mr nents %u\n", ibmr->sg_len);

        /* Return it to the pool's free list */
        if (ibmr->remap_count >= pool->fmr_attr.max_maps)
                llist_add(&ibmr->llnode, &pool->drop_list);
        else
                llist_add(&ibmr->llnode, &pool->free_list);

        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 / 10)
                schedule_delayed_work(&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. */
                        schedule_delayed_work(&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) {
                struct rds_ib_mr_pool *pool = rds_ibdev->mr_pool;

                if (pool)
                        rds_ib_flush_mr_pool(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_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;
        rds_ibdev = NULL;

 out:
        if (ret) {
                if (ibmr)
                        rds_ib_free_mr(ibmr, 0);
                ibmr = ERR_PTR(ret);
        }
        if (rds_ibdev)
                rds_ib_dev_put(rds_ibdev);
        return ibmr;
}