ib_recv.c

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/*
 * 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/pci.h>
#include <linux/dma-mapping.h>
#include <rdma/rdma_cm.h>

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

static struct kmem_cache *rds_ib_incoming_slab;
static struct kmem_cache *rds_ib_frag_slab;
static atomic_t rds_ib_allocation = ATOMIC_INIT(0);

void rds_ib_recv_init_ring(struct rds_ib_connection *ic)
{
    struct rds_ib_recv_work *recv;
    u32 i;

    for (i = 0, recv = ic->i_recvs; i < ic->i_recv_ring.w_nr; i++, recv++) {
        struct ib_sge *sge;

        recv->r_ibinc = NULL;
        recv->r_frag = NULL;

        recv->r_wr.next = NULL;
        recv->r_wr.wr_id = i;
        recv->r_wr.sg_list = recv->r_sge;
        recv->r_wr.num_sge = RDS_IB_RECV_SGE;

        sge = &recv->r_sge[0];
        sge->addr = ic->i_recv_hdrs_dma + (i * sizeof(struct rds_header));
        sge->length = sizeof(struct rds_header);
        sge->lkey = ic->i_mr->lkey;

        sge = &recv->r_sge[1];
        sge->addr = 0;
        sge->length = RDS_FRAG_SIZE;
        sge->lkey = ic->i_mr->lkey;
    }
}

/*
 * The entire 'from' list, including the from element itself, is put on
 * to the tail of the 'to' list.
 */
static void list_splice_entire_tail(struct list_head *from,
                    struct list_head *to)
{
    struct list_head *from_last = from->prev;

    list_splice_tail(from_last, to);
    list_add_tail(from_last, to);
}

static void rds_ib_cache_xfer_to_ready(struct rds_ib_refill_cache *cache)
{
    struct list_head *tmp;

    tmp = xchg(&cache->xfer, NULL);
    if (tmp) {
        if (cache->ready)
            list_splice_entire_tail(tmp, cache->ready);
        else
            cache->ready = tmp;
    }
}

static int rds_ib_recv_alloc_cache(struct rds_ib_refill_cache *cache)
{
    struct rds_ib_cache_head *head;
    int cpu;

    cache->percpu = alloc_percpu(struct rds_ib_cache_head);
    if (!cache->percpu)
           return -ENOMEM;

    for_each_possible_cpu(cpu) {
        head = per_cpu_ptr(cache->percpu, cpu);
        head->first = NULL;
        head->count = 0;
    }
    cache->xfer = NULL;
    cache->ready = NULL;

    return 0;
}

int rds_ib_recv_alloc_caches(struct rds_ib_connection *ic)
{
    int ret;

    ret = rds_ib_recv_alloc_cache(&ic->i_cache_incs);
    if (!ret) {
        ret = rds_ib_recv_alloc_cache(&ic->i_cache_frags);
        if (ret)
            free_percpu(ic->i_cache_incs.percpu);
    }

    return ret;
}

static void rds_ib_cache_splice_all_lists(struct rds_ib_refill_cache *cache,
                      struct list_head *caller_list)
{
    struct rds_ib_cache_head *head;
    int cpu;

    for_each_possible_cpu(cpu) {
        head = per_cpu_ptr(cache->percpu, cpu);
        if (head->first) {
            list_splice_entire_tail(head->first, caller_list);
            head->first = NULL;
        }
    }

    if (cache->ready) {
        list_splice_entire_tail(cache->ready, caller_list);
        cache->ready = NULL;
    }
}

void rds_ib_recv_free_caches(struct rds_ib_connection *ic)
{
    struct rds_ib_incoming *inc;
    struct rds_ib_incoming *inc_tmp;
    struct rds_page_frag *frag;
    struct rds_page_frag *frag_tmp;
    LIST_HEAD(list);

    rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
    rds_ib_cache_splice_all_lists(&ic->i_cache_incs, &list);
    free_percpu(ic->i_cache_incs.percpu);

    list_for_each_entry_safe(inc, inc_tmp, &list, ii_cache_entry) {
        list_del(&inc->ii_cache_entry);
        WARN_ON(!list_empty(&inc->ii_frags));
        kmem_cache_free(rds_ib_incoming_slab, inc);
    }

    rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);
    rds_ib_cache_splice_all_lists(&ic->i_cache_frags, &list);
    free_percpu(ic->i_cache_frags.percpu);

    list_for_each_entry_safe(frag, frag_tmp, &list, f_cache_entry) {
        list_del(&frag->f_cache_entry);
        WARN_ON(!list_empty(&frag->f_item));
        kmem_cache_free(rds_ib_frag_slab, frag);
    }
}

/* fwd decl */
static void rds_ib_recv_cache_put(struct list_head *new_item,
                  struct rds_ib_refill_cache *cache);
static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache);


/* Recycle frag and attached recv buffer f_sg */
static void rds_ib_frag_free(struct rds_ib_connection *ic,
                 struct rds_page_frag *frag)
{
    rdsdebug("frag %p page %p\n", frag, sg_page(&frag->f_sg));

    rds_ib_recv_cache_put(&frag->f_cache_entry, &ic->i_cache_frags);
}

/* Recycle inc after freeing attached frags */
void rds_ib_inc_free(struct rds_incoming *inc)
{
    struct rds_ib_incoming *ibinc;
    struct rds_page_frag *frag;
    struct rds_page_frag *pos;
    struct rds_ib_connection *ic = inc->i_conn->c_transport_data;

    ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);

    /* Free attached frags */
    list_for_each_entry_safe(frag, pos, &ibinc->ii_frags, f_item) {
        list_del_init(&frag->f_item);
        rds_ib_frag_free(ic, frag);
    }
    BUG_ON(!list_empty(&ibinc->ii_frags));

    rdsdebug("freeing ibinc %p inc %p\n", ibinc, inc);
    rds_ib_recv_cache_put(&ibinc->ii_cache_entry, &ic->i_cache_incs);
}

static void rds_ib_recv_clear_one(struct rds_ib_connection *ic,
                  struct rds_ib_recv_work *recv)
{
    if (recv->r_ibinc) {
        rds_inc_put(&recv->r_ibinc->ii_inc);
        recv->r_ibinc = NULL;
    }
    if (recv->r_frag) {
        ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);
        rds_ib_frag_free(ic, recv->r_frag);
        recv->r_frag = NULL;
    }
}

void rds_ib_recv_clear_ring(struct rds_ib_connection *ic)
{
    u32 i;

    for (i = 0; i < ic->i_recv_ring.w_nr; i++)
        rds_ib_recv_clear_one(ic, &ic->i_recvs[i]);
}

static struct rds_ib_incoming *rds_ib_refill_one_inc(struct rds_ib_connection *ic,
                             gfp_t slab_mask)
{
    struct rds_ib_incoming *ibinc;
    struct list_head *cache_item;
    int avail_allocs;

    cache_item = rds_ib_recv_cache_get(&ic->i_cache_incs);
    if (cache_item) {
        ibinc = container_of(cache_item, struct rds_ib_incoming, ii_cache_entry);
    } else {
        avail_allocs = atomic_add_unless(&rds_ib_allocation,
                         1, rds_ib_sysctl_max_recv_allocation);
        if (!avail_allocs) {
            rds_ib_stats_inc(s_ib_rx_alloc_limit);
            return NULL;
        }
        ibinc = kmem_cache_alloc(rds_ib_incoming_slab, slab_mask);
        if (!ibinc) {
            atomic_dec(&rds_ib_allocation);
            return NULL;
        }
    }
    INIT_LIST_HEAD(&ibinc->ii_frags);
    rds_inc_init(&ibinc->ii_inc, ic->conn, ic->conn->c_faddr);

    return ibinc;
}

static struct rds_page_frag *rds_ib_refill_one_frag(struct rds_ib_connection *ic,
                            gfp_t slab_mask, gfp_t page_mask)
{
    struct rds_page_frag *frag;
    struct list_head *cache_item;
    int ret;

    cache_item = rds_ib_recv_cache_get(&ic->i_cache_frags);
    if (cache_item) {
        frag = container_of(cache_item, struct rds_page_frag, f_cache_entry);
    } else {
        frag = kmem_cache_alloc(rds_ib_frag_slab, slab_mask);
        if (!frag)
            return NULL;

        sg_init_table(&frag->f_sg, 1);
        ret = rds_page_remainder_alloc(&frag->f_sg,
                           RDS_FRAG_SIZE, page_mask);
        if (ret) {
            kmem_cache_free(rds_ib_frag_slab, frag);
            return NULL;
        }
    }

    INIT_LIST_HEAD(&frag->f_item);

    return frag;
}

static int rds_ib_recv_refill_one(struct rds_connection *conn,
                  struct rds_ib_recv_work *recv, int prefill)
{
    struct rds_ib_connection *ic = conn->c_transport_data;
    struct ib_sge *sge;
    int ret = -ENOMEM;
    gfp_t slab_mask = GFP_NOWAIT;
    gfp_t page_mask = GFP_NOWAIT;

    if (prefill) {
        slab_mask = GFP_KERNEL;
        page_mask = GFP_HIGHUSER;
    }

    if (!ic->i_cache_incs.ready)
        rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
    if (!ic->i_cache_frags.ready)
        rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);

    /*
     * ibinc was taken from recv if recv contained the start of a message.
     * recvs that were continuations will still have this allocated.
     */
    if (!recv->r_ibinc) {
        recv->r_ibinc = rds_ib_refill_one_inc(ic, slab_mask);
        if (!recv->r_ibinc)
            goto out;
    }

    WARN_ON(recv->r_frag); /* leak! */
    recv->r_frag = rds_ib_refill_one_frag(ic, slab_mask, page_mask);
    if (!recv->r_frag)
        goto out;

    ret = ib_dma_map_sg(ic->i_cm_id->device, &recv->r_frag->f_sg,
                1, DMA_FROM_DEVICE);
    WARN_ON(ret != 1);

    sge = &recv->r_sge[0];
    sge->addr = ic->i_recv_hdrs_dma + (recv - ic->i_recvs) * sizeof(struct rds_header);
    sge->length = sizeof(struct rds_header);

    sge = &recv->r_sge[1];
    sge->addr = sg_dma_address(&recv->r_frag->f_sg);
    sge->length = sg_dma_len(&recv->r_frag->f_sg);

    ret = 0;
out:
    return ret;
}

/*
 * This tries to allocate and post unused work requests after making sure that
 * they have all the allocations they need to queue received fragments into
 * sockets.
 *
 * -1 is returned if posting fails due to temporary resource exhaustion.
 */
void rds_ib_recv_refill(struct rds_connection *conn, int prefill)
{
    struct rds_ib_connection *ic = conn->c_transport_data;
    struct rds_ib_recv_work *recv;
    struct ib_recv_wr *failed_wr;
    unsigned int posted = 0;
    int ret = 0;
    u32 pos;

    while ((prefill || rds_conn_up(conn)) &&
           rds_ib_ring_alloc(&ic->i_recv_ring, 1, &pos)) {
        if (pos >= ic->i_recv_ring.w_nr) {
            printk(KERN_NOTICE "Argh - ring alloc returned pos=%u\n",
                    pos);
            break;
        }

        recv = &ic->i_recvs[pos];
        ret = rds_ib_recv_refill_one(conn, recv, prefill);
        if (ret) {
            break;
        }

        /* XXX when can this fail? */
        ret = ib_post_recv(ic->i_cm_id->qp, &recv->r_wr, &failed_wr);
        rdsdebug("recv %p ibinc %p page %p addr %lu ret %d\n", recv,
             recv->r_ibinc, sg_page(&recv->r_frag->f_sg),
             (long) sg_dma_address(&recv->r_frag->f_sg), ret);
        if (ret) {
            rds_ib_conn_error(conn, "recv post on "
                   "%pI4 returned %d, disconnecting and "
                   "reconnecting\n", &conn->c_faddr,
                   ret);
            break;
        }

        posted++;
    }

    /* We're doing flow control - update the window. */
    if (ic->i_flowctl && posted)
        rds_ib_advertise_credits(conn, posted);

    if (ret)
        rds_ib_ring_unalloc(&ic->i_recv_ring, 1);
}

/*
 * We want to recycle several types of recv allocations, like incs and frags.
 * To use this, the *_free() function passes in the ptr to a list_head within
 * the recyclee, as well as the cache to put it on.
 *
 * First, we put the memory on a percpu list. When this reaches a certain size,
 * We move it to an intermediate non-percpu list in a lockless manner, with some
 * xchg/compxchg wizardry.
 *
 * N.B. Instead of a list_head as the anchor, we use a single pointer, which can
 * be NULL and xchg'd. The list is actually empty when the pointer is NULL, and
 * list_empty() will return true with one element is actually present.
 */
static void rds_ib_recv_cache_put(struct list_head *new_item,
                 struct rds_ib_refill_cache *cache)
{
    unsigned long flags;
    struct rds_ib_cache_head *chp;
    struct list_head *old;

    local_irq_save(flags);

    chp = per_cpu_ptr(cache->percpu, smp_processor_id());
    if (!chp->first)
        INIT_LIST_HEAD(new_item);
    else /* put on front */
        list_add_tail(new_item, chp->first);
    chp->first = new_item;
    chp->count++;

    if (chp->count < RDS_IB_RECYCLE_BATCH_COUNT)
        goto end;

    /*
     * Return our per-cpu first list to the cache's xfer by atomically
     * grabbing the current xfer list, appending it to our per-cpu list,
     * and then atomically returning that entire list back to the
     * cache's xfer list as long as it's still empty.
     */
    do {
        old = xchg(&cache->xfer, NULL);
        if (old)
            list_splice_entire_tail(old, chp->first);
        old = cmpxchg(&cache->xfer, NULL, chp->first);
    } while (old);

    chp->first = NULL;
    chp->count = 0;
end:
    local_irq_restore(flags);
}

static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache)
{
    struct list_head *head = cache->ready;

    if (head) {
        if (!list_empty(head)) {
            cache->ready = head->next;
            list_del_init(head);
        } else
            cache->ready = NULL;
    }

    return head;
}

int rds_ib_inc_copy_to_user(struct rds_incoming *inc, struct iovec *first_iov,
                size_t size)
{
    struct rds_ib_incoming *ibinc;
    struct rds_page_frag *frag;
    struct iovec *iov = first_iov;
    unsigned long to_copy;
    unsigned long frag_off = 0;
    unsigned long iov_off = 0;
    int copied = 0;
    int ret;
    u32 len;

    ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
    frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
    len = be32_to_cpu(inc->i_hdr.h_len);

    while (copied < size && copied < len) {
        if (frag_off == RDS_FRAG_SIZE) {
            frag = list_entry(frag->f_item.next,
                      struct rds_page_frag, f_item);
            frag_off = 0;
        }
        while (iov_off == iov->iov_len) {
            iov_off = 0;
            iov++;
        }

        to_copy = min(iov->iov_len - iov_off, RDS_FRAG_SIZE - frag_off);
        to_copy = min_t(size_t, to_copy, size - copied);
        to_copy = min_t(unsigned long, to_copy, len - copied);

        rdsdebug("%lu bytes to user [%p, %zu] + %lu from frag "
             "[%p, %u] + %lu\n",
             to_copy, iov->iov_base, iov->iov_len, iov_off,
             sg_page(&frag->f_sg), frag->f_sg.offset, frag_off);

        /* XXX needs + offset for multiple recvs per page */
        ret = rds_page_copy_to_user(sg_page(&frag->f_sg),
                        frag->f_sg.offset + frag_off,
                        iov->iov_base + iov_off,
                        to_copy);
        if (ret) {
            copied = ret;
            break;
        }

        iov_off += to_copy;
        frag_off += to_copy;
        copied += to_copy;
    }

    return copied;
}

/* ic starts out kzalloc()ed */
void rds_ib_recv_init_ack(struct rds_ib_connection *ic)
{
    struct ib_send_wr *wr = &ic->i_ack_wr;
    struct ib_sge *sge = &ic->i_ack_sge;

    sge->addr = ic->i_ack_dma;
    sge->length = sizeof(struct rds_header);
    sge->lkey = ic->i_mr->lkey;

    wr->sg_list = sge;
    wr->num_sge = 1;
    wr->opcode = IB_WR_SEND;
    wr->wr_id = RDS_IB_ACK_WR_ID;
    wr->send_flags = IB_SEND_SIGNALED | IB_SEND_SOLICITED;
}

/*
 * You'd think that with reliable IB connections you wouldn't need to ack
 * messages that have been received.  The problem is that IB hardware generates
 * an ack message before it has DMAed the message into memory.  This creates a
 * potential message loss if the HCA is disabled for any reason between when it
 * sends the ack and before the message is DMAed and processed.  This is only a
 * potential issue if another HCA is available for fail-over.
 *
 * When the remote host receives our ack they'll free the sent message from
 * their send queue.  To decrease the latency of this we always send an ack
 * immediately after we've received messages.
 *
 * For simplicity, we only have one ack in flight at a time.  This puts
 * pressure on senders to have deep enough send queues to absorb the latency of
 * a single ack frame being in flight.  This might not be good enough.
 *
 * This is implemented by have a long-lived send_wr and sge which point to a
 * statically allocated ack frame.  This ack wr does not fall under the ring
 * accounting that the tx and rx wrs do.  The QP attribute specifically makes
 * room for it beyond the ring size.  Send completion notices its special
 * wr_id and avoids working with the ring in that case.
 */
#ifndef KERNEL_HAS_ATOMIC64
static void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
                int ack_required)
{
    unsigned long flags;

    spin_lock_irqsave(&ic->i_ack_lock, flags);
    ic->i_ack_next = seq;
    if (ack_required)
        set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
    spin_unlock_irqrestore(&ic->i_ack_lock, flags);
}

static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
{
    unsigned long flags;
    u64 seq;

    clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);

    spin_lock_irqsave(&ic->i_ack_lock, flags);
    seq = ic->i_ack_next;
    spin_unlock_irqrestore(&ic->i_ack_lock, flags);

    return seq;
}
#else
static void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
                int ack_required)
{
    atomic64_set(&ic->i_ack_next, seq);
    if (ack_required) {
        smp_mb__before_clear_bit();
        set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
    }
}

static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
{
    clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
    smp_mb__after_clear_bit();

    return atomic64_read(&ic->i_ack_next);
}
#endif


static void rds_ib_send_ack(struct rds_ib_connection *ic, unsigned int adv_credits)
{
    struct rds_header *hdr = ic->i_ack;
    struct ib_send_wr *failed_wr;
    u64 seq;
    int ret;

    seq = rds_ib_get_ack(ic);

    rdsdebug("send_ack: ic %p ack %llu\n", ic, (unsigned long long) seq);
    rds_message_populate_header(hdr, 0, 0, 0);
    hdr->h_ack = cpu_to_be64(seq);
    hdr->h_credit = adv_credits;
    rds_message_make_checksum(hdr);
    ic->i_ack_queued = jiffies;

    ret = ib_post_send(ic->i_cm_id->qp, &ic->i_ack_wr, &failed_wr);
    if (unlikely(ret)) {
        /* Failed to send. Release the WR, and
         * force another ACK.
         */
        clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
        set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);

        rds_ib_stats_inc(s_ib_ack_send_failure);

        rds_ib_conn_error(ic->conn, "sending ack failed\n");
    } else
        rds_ib_stats_inc(s_ib_ack_sent);
}

/*
 * There are 3 ways of getting acknowledgements to the peer:
 *  1.  We call rds_ib_attempt_ack from the recv completion handler
 *  to send an ACK-only frame.
 *  However, there can be only one such frame in the send queue
 *  at any time, so we may have to postpone it.
 *  2.  When another (data) packet is transmitted while there's
 *  an ACK in the queue, we piggyback the ACK sequence number
 *  on the data packet.
 *  3.  If the ACK WR is done sending, we get called from the
 *  send queue completion handler, and check whether there's
 *  another ACK pending (postponed because the WR was on the
 *  queue). If so, we transmit it.
 *
 * We maintain 2 variables:
 *  -   i_ack_flags, which keeps track of whether the ACK WR
 *  is currently in the send queue or not (IB_ACK_IN_FLIGHT)
 *  -   i_ack_next, which is the last sequence number we received
 *
 * Potentially, send queue and receive queue handlers can run concurrently.
 * It would be nice to not have to use a spinlock to synchronize things,
 * but the one problem that rules this out is that 64bit updates are
 * not atomic on all platforms. Things would be a lot simpler if
 * we had atomic64 or maybe cmpxchg64 everywhere.
 *
 * Reconnecting complicates this picture just slightly. When we
 * reconnect, we may be seeing duplicate packets. The peer
 * is retransmitting them, because it hasn't seen an ACK for
 * them. It is important that we ACK these.
 *
 * ACK mitigation adds a header flag "ACK_REQUIRED"; any packet with
 * this flag set *MUST* be acknowledged immediately.
 */

/*
 * When we get here, we're called from the recv queue handler.
 * Check whether we ought to transmit an ACK.
 */
void rds_ib_attempt_ack(struct rds_ib_connection *ic)
{
    unsigned int adv_credits;

    if (!test_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
        return;

    if (test_and_set_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags)) {
        rds_ib_stats_inc(s_ib_ack_send_delayed);
        return;
    }

    /* Can we get a send credit? */
    if (!rds_ib_send_grab_credits(ic, 1, &adv_credits, 0, RDS_MAX_ADV_CREDIT)) {
        rds_ib_stats_inc(s_ib_tx_throttle);
        clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
        return;
    }

    clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
    rds_ib_send_ack(ic, adv_credits);
}

/*
 * We get here from the send completion handler, when the
 * adapter tells us the ACK frame was sent.
 */
void rds_ib_ack_send_complete(struct rds_ib_connection *ic)
{
    clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
    rds_ib_attempt_ack(ic);
}

/*
 * This is called by the regular xmit code when it wants to piggyback
 * an ACK on an outgoing frame.
 */
u64 rds_ib_piggyb_ack(struct rds_ib_connection *ic)
{
    if (test_and_clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
        rds_ib_stats_inc(s_ib_ack_send_piggybacked);
    return rds_ib_get_ack(ic);
}

/*
 * It's kind of lame that we're copying from the posted receive pages into
 * long-lived bitmaps.  We could have posted the bitmaps and rdma written into
 * them.  But receiving new congestion bitmaps should be a *rare* event, so
 * hopefully we won't need to invest that complexity in making it more
 * efficient.  By copying we can share a simpler core with TCP which has to
 * copy.
 */
static void rds_ib_cong_recv(struct rds_connection *conn,
                  struct rds_ib_incoming *ibinc)
{
    struct rds_cong_map *map;
    unsigned int map_off;
    unsigned int map_page;
    struct rds_page_frag *frag;
    unsigned long frag_off;
    unsigned long to_copy;
    unsigned long copied;
    uint64_t uncongested = 0;
    void *addr;

    /* catch completely corrupt packets */
    if (be32_to_cpu(ibinc->ii_inc.i_hdr.h_len) != RDS_CONG_MAP_BYTES)
        return;

    map = conn->c_fcong;
    map_page = 0;
    map_off = 0;

    frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
    frag_off = 0;

    copied = 0;

    while (copied < RDS_CONG_MAP_BYTES) {
        uint64_t *src, *dst;
        unsigned int k;

        to_copy = min(RDS_FRAG_SIZE - frag_off, PAGE_SIZE - map_off);
        BUG_ON(to_copy & 7); /* Must be 64bit aligned. */

        addr = kmap_atomic(sg_page(&frag->f_sg));

        src = addr + frag_off;
        dst = (void *)map->m_page_addrs[map_page] + map_off;
        for (k = 0; k < to_copy; k += 8) {
            /* Record ports that became uncongested, ie
             * bits that changed from 0 to 1. */
            uncongested |= ~(*src) & *dst;
            *dst++ = *src++;
        }
        kunmap_atomic(addr);

        copied += to_copy;

        map_off += to_copy;
        if (map_off == PAGE_SIZE) {
            map_off = 0;
            map_page++;
        }

        frag_off += to_copy;
        if (frag_off == RDS_FRAG_SIZE) {
            frag = list_entry(frag->f_item.next,
                      struct rds_page_frag, f_item);
            frag_off = 0;
        }
    }

    /* the congestion map is in little endian order */
    uncongested = le64_to_cpu(uncongested);

    rds_cong_map_updated(map, uncongested);
}

/*
 * Rings are posted with all the allocations they'll need to queue the
 * incoming message to the receiving socket so this can't fail.
 * All fragments start with a header, so we can make sure we're not receiving
 * garbage, and we can tell a small 8 byte fragment from an ACK frame.
 */
struct rds_ib_ack_state {
    u64     ack_next;
    u64     ack_recv;
    unsigned int    ack_required:1;
    unsigned int    ack_next_valid:1;
    unsigned int    ack_recv_valid:1;
};

static void rds_ib_process_recv(struct rds_connection *conn,
                struct rds_ib_recv_work *recv, u32 data_len,
                struct rds_ib_ack_state *state)
{
    struct rds_ib_connection *ic = conn->c_transport_data;
    struct rds_ib_incoming *ibinc = ic->i_ibinc;
    struct rds_header *ihdr, *hdr;

    /* XXX shut down the connection if port 0,0 are seen? */

    rdsdebug("ic %p ibinc %p recv %p byte len %u\n", ic, ibinc, recv,
         data_len);

    if (data_len < sizeof(struct rds_header)) {
        rds_ib_conn_error(conn, "incoming message "
               "from %pI4 didn't include a "
               "header, disconnecting and "
               "reconnecting\n",
               &conn->c_faddr);
        return;
    }
    data_len -= sizeof(struct rds_header);

    ihdr = &ic->i_recv_hdrs[recv - ic->i_recvs];

    /* Validate the checksum. */
    if (!rds_message_verify_checksum(ihdr)) {
        rds_ib_conn_error(conn, "incoming message "
               "from %pI4 has corrupted header - "
               "forcing a reconnect\n",
               &conn->c_faddr);
        rds_stats_inc(s_recv_drop_bad_checksum);
        return;
    }

    /* Process the ACK sequence which comes with every packet */
    state->ack_recv = be64_to_cpu(ihdr->h_ack);
    state->ack_recv_valid = 1;

    /* Process the credits update if there was one */
    if (ihdr->h_credit)
        rds_ib_send_add_credits(conn, ihdr->h_credit);

    if (ihdr->h_sport == 0 && ihdr->h_dport == 0 && data_len == 0) {
        /* This is an ACK-only packet. The fact that it gets
         * special treatment here is that historically, ACKs
         * were rather special beasts.
         */
        rds_ib_stats_inc(s_ib_ack_received);

        /*
         * Usually the frags make their way on to incs and are then freed as
         * the inc is freed.  We don't go that route, so we have to drop the
         * page ref ourselves.  We can't just leave the page on the recv
         * because that confuses the dma mapping of pages and each recv's use
         * of a partial page.
         *
         * FIXME: Fold this into the code path below.
         */
        rds_ib_frag_free(ic, recv->r_frag);
        recv->r_frag = NULL;
        return;
    }

    /*
     * If we don't already have an inc on the connection then this
     * fragment has a header and starts a message.. copy its header
     * into the inc and save the inc so we can hang upcoming fragments
     * off its list.
     */
    if (!ibinc) {
        ibinc = recv->r_ibinc;
        recv->r_ibinc = NULL;
        ic->i_ibinc = ibinc;

        hdr = &ibinc->ii_inc.i_hdr;
        memcpy(hdr, ihdr, sizeof(*hdr));
        ic->i_recv_data_rem = be32_to_cpu(hdr->h_len);

        rdsdebug("ic %p ibinc %p rem %u flag 0x%x\n", ic, ibinc,
             ic->i_recv_data_rem, hdr->h_flags);
    } else {
        hdr = &ibinc->ii_inc.i_hdr;
        /* We can't just use memcmp here; fragments of a
         * single message may carry different ACKs */
        if (hdr->h_sequence != ihdr->h_sequence ||
            hdr->h_len != ihdr->h_len ||
            hdr->h_sport != ihdr->h_sport ||
            hdr->h_dport != ihdr->h_dport) {
            rds_ib_conn_error(conn,
                "fragment header mismatch; forcing reconnect\n");
            return;
        }
    }

    list_add_tail(&recv->r_frag->f_item, &ibinc->ii_frags);
    recv->r_frag = NULL;

    if (ic->i_recv_data_rem > RDS_FRAG_SIZE)
        ic->i_recv_data_rem -= RDS_FRAG_SIZE;
    else {
        ic->i_recv_data_rem = 0;
        ic->i_ibinc = NULL;

        if (ibinc->ii_inc.i_hdr.h_flags == RDS_FLAG_CONG_BITMAP)
            rds_ib_cong_recv(conn, ibinc);
        else {
            rds_recv_incoming(conn, conn->c_faddr, conn->c_laddr,
                      &ibinc->ii_inc, GFP_ATOMIC);
            state->ack_next = be64_to_cpu(hdr->h_sequence);
            state->ack_next_valid = 1;
        }

        /* Evaluate the ACK_REQUIRED flag *after* we received
         * the complete frame, and after bumping the next_rx
         * sequence. */
        if (hdr->h_flags & RDS_FLAG_ACK_REQUIRED) {
            rds_stats_inc(s_recv_ack_required);
            state->ack_required = 1;
        }

        rds_inc_put(&ibinc->ii_inc);
    }
}

/*
 * Plucking the oldest entry from the ring can be done concurrently with
 * the thread refilling the ring.  Each ring operation is protected by
 * spinlocks and the transient state of refilling doesn't change the
 * recording of which entry is oldest.
 *
 * This relies on IB only calling one cq comp_handler for each cq so that
 * there will only be one caller of rds_recv_incoming() per RDS connection.
 */
void rds_ib_recv_cq_comp_handler(struct ib_cq *cq, void *context)
{
    struct rds_connection *conn = context;
    struct rds_ib_connection *ic = conn->c_transport_data;

    rdsdebug("conn %p cq %p\n", conn, cq);

    rds_ib_stats_inc(s_ib_rx_cq_call);

    tasklet_schedule(&ic->i_recv_tasklet);
}

static inline void rds_poll_cq(struct rds_ib_connection *ic,
                   struct rds_ib_ack_state *state)
{
    struct rds_connection *conn = ic->conn;
    struct ib_wc wc;
    struct rds_ib_recv_work *recv;

    while (ib_poll_cq(ic->i_recv_cq, 1, &wc) > 0) {
        rdsdebug("wc wr_id 0x%llx status %u (%s) byte_len %u imm_data %u\n",
             (unsigned long long)wc.wr_id, wc.status,
             rds_ib_wc_status_str(wc.status), wc.byte_len,
             be32_to_cpu(wc.ex.imm_data));
        rds_ib_stats_inc(s_ib_rx_cq_event);

        recv = &ic->i_recvs[rds_ib_ring_oldest(&ic->i_recv_ring)];

        ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);

        /*
         * Also process recvs in connecting state because it is possible
         * to get a recv completion _before_ the rdmacm ESTABLISHED
         * event is processed.
         */
        if (wc.status == IB_WC_SUCCESS) {
            rds_ib_process_recv(conn, recv, wc.byte_len, state);
        } else {
            /* We expect errors as the qp is drained during shutdown */
            if (rds_conn_up(conn) || rds_conn_connecting(conn))
                rds_ib_conn_error(conn, "recv completion on %pI4 had "
                          "status %u (%s), disconnecting and "
                          "reconnecting\n", &conn->c_faddr,
                          wc.status,
                          rds_ib_wc_status_str(wc.status));
        }

        /*
         * It's very important that we only free this ring entry if we've truly
         * freed the resources allocated to the entry.  The refilling path can
         * leak if we don't.
         */
        rds_ib_ring_free(&ic->i_recv_ring, 1);
    }
}

void rds_ib_recv_tasklet_fn(unsigned long data)
{
    struct rds_ib_connection *ic = (struct rds_ib_connection *) data;
    struct rds_connection *conn = ic->conn;
    struct rds_ib_ack_state state = { 0, };

    rds_poll_cq(ic, &state);
    ib_req_notify_cq(ic->i_recv_cq, IB_CQ_SOLICITED);
    rds_poll_cq(ic, &state);

    if (state.ack_next_valid)
        rds_ib_set_ack(ic, state.ack_next, state.ack_required);
    if (state.ack_recv_valid && state.ack_recv > ic->i_ack_recv) {
        rds_send_drop_acked(conn, state.ack_recv, NULL);
        ic->i_ack_recv = state.ack_recv;
    }
    if (rds_conn_up(conn))
        rds_ib_attempt_ack(ic);

    /* If we ever end up with a really empty receive ring, we're
     * in deep trouble, as the sender will definitely see RNR
     * timeouts. */
    if (rds_ib_ring_empty(&ic->i_recv_ring))
        rds_ib_stats_inc(s_ib_rx_ring_empty);

    if (rds_ib_ring_low(&ic->i_recv_ring))
        rds_ib_recv_refill(conn, 0);
}

int rds_ib_recv(struct rds_connection *conn)
{
    struct rds_ib_connection *ic = conn->c_transport_data;
    int ret = 0;

    rdsdebug("conn %p\n", conn);
    if (rds_conn_up(conn))
        rds_ib_attempt_ack(ic);

    return ret;
}

int rds_ib_recv_init(void)
{
    struct sysinfo si;
    int ret = -ENOMEM;

    /* Default to 30% of all available RAM for recv memory */
    si_meminfo(&si);
    rds_ib_sysctl_max_recv_allocation = si.totalram / 3 * PAGE_SIZE / RDS_FRAG_SIZE;

    rds_ib_incoming_slab = kmem_cache_create("rds_ib_incoming",
                    sizeof(struct rds_ib_incoming),
                    0, SLAB_HWCACHE_ALIGN, NULL);
    if (!rds_ib_incoming_slab)
        goto out;

    rds_ib_frag_slab = kmem_cache_create("rds_ib_frag",
                    sizeof(struct rds_page_frag),
                    0, SLAB_HWCACHE_ALIGN, NULL);
    if (!rds_ib_frag_slab)
        kmem_cache_destroy(rds_ib_incoming_slab);
    else
        ret = 0;
out:
    return ret;
}

void rds_ib_recv_exit(void)
{
    kmem_cache_destroy(rds_ib_incoming_slab);
    kmem_cache_destroy(rds_ib_frag_slab);
}