text: /*
   * 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/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);
  
  static void rds_ib_frag_drop_page(struct rds_page_frag *frag)
  {
  	rdsdebug("frag %p page %p\n", frag, frag->f_page);
  	__free_page(frag->f_page);
  	frag->f_page = NULL;
  }
  
  static void rds_ib_frag_free(struct rds_page_frag *frag)
  {
  	rdsdebug("frag %p page %p\n", frag, frag->f_page);
  	BUG_ON(frag->f_page != NULL);
  	kmem_cache_free(rds_ib_frag_slab, frag);
  }
  
  /*
   * We map a page at a time.  Its fragments are posted in order.  This
   * is called in fragment order as the fragments get send completion events.
   * Only the last frag in the page performs the unmapping.
   *
   * It's OK for ring cleanup to call this in whatever order it likes because
   * DMA is not in flight and so we can unmap while other ring entries still
   * hold page references in their frags.
   */
  static void rds_ib_recv_unmap_page(struct rds_ib_connection *ic,
  				   struct rds_ib_recv_work *recv)
  {
  	struct rds_page_frag *frag = recv->r_frag;
  
  	rdsdebug("recv %p frag %p page %p\n", recv, frag, frag->f_page);
  	if (frag->f_mapped)
  		ib_dma_unmap_page(ic->i_cm_id->device,
  			       frag->f_mapped,
  			       RDS_FRAG_SIZE, DMA_FROM_DEVICE);
  	frag->f_mapped = 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 = rds_ib_data_sge(ic, recv->r_sge);
  		sge->addr = 0;
  		sge->length = RDS_FRAG_SIZE;
  		sge->lkey = ic->i_mr->lkey;
  
  		sge = rds_ib_header_sge(ic, recv->r_sge);
  		sge->addr = ic->i_recv_hdrs_dma + (i * sizeof(struct rds_header));
  		sge->length = sizeof(struct rds_header);
  		sge->lkey = ic->i_mr->lkey;
  	}
  }
  
  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) {
  		rds_ib_recv_unmap_page(ic, recv);
  		if (recv->r_frag->f_page)
  			rds_ib_frag_drop_page(recv->r_frag);
  		rds_ib_frag_free(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]);
  
  	if (ic->i_frag.f_page)
  		rds_ib_frag_drop_page(&ic->i_frag);
  }
  
  static int rds_ib_recv_refill_one(struct rds_connection *conn,
  				  struct rds_ib_recv_work *recv,
  				  gfp_t kptr_gfp, gfp_t page_gfp)
  {
  	struct rds_ib_connection *ic = conn->c_transport_data;
  	dma_addr_t dma_addr;
  	struct ib_sge *sge;
  	int ret = -ENOMEM;
  
  	if (recv->r_ibinc == NULL) {
  		if (atomic_read(&rds_ib_allocation) >= rds_ib_sysctl_max_recv_allocation) {
  			rds_ib_stats_inc(s_ib_rx_alloc_limit);
  			goto out;
  		}
  		recv->r_ibinc = kmem_cache_alloc(rds_ib_incoming_slab,
  						 kptr_gfp);
  		if (recv->r_ibinc == NULL)
  			goto out;
  		atomic_inc(&rds_ib_allocation);
  		INIT_LIST_HEAD(&recv->r_ibinc->ii_frags);
  		rds_inc_init(&recv->r_ibinc->ii_inc, conn, conn->c_faddr);
  	}
  
  	if (recv->r_frag == NULL) {
  		recv->r_frag = kmem_cache_alloc(rds_ib_frag_slab, kptr_gfp);
  		if (recv->r_frag == NULL)
  			goto out;
  		INIT_LIST_HEAD(&recv->r_frag->f_item);
  		recv->r_frag->f_page = NULL;
  	}
  
  	if (ic->i_frag.f_page == NULL) {
  		ic->i_frag.f_page = alloc_page(page_gfp);
  		if (ic->i_frag.f_page == NULL)
  			goto out;
  		ic->i_frag.f_offset = 0;
  	}
  
  	dma_addr = ib_dma_map_page(ic->i_cm_id->device,
  				  ic->i_frag.f_page,
  				  ic->i_frag.f_offset,
  				  RDS_FRAG_SIZE,
  				  DMA_FROM_DEVICE);
  	if (ib_dma_mapping_error(ic->i_cm_id->device, dma_addr))
  		goto out;
  
  	/*
  	 * Once we get the RDS_PAGE_LAST_OFF frag then rds_ib_frag_unmap()
  	 * must be called on this recv.  This happens as completions hit
  	 * in order or on connection shutdown.
  	 */
  	recv->r_frag->f_page = ic->i_frag.f_page;
  	recv->r_frag->f_offset = ic->i_frag.f_offset;
  	recv->r_frag->f_mapped = dma_addr;
  
  	sge = rds_ib_data_sge(ic, recv->r_sge);
  	sge->addr = dma_addr;
  	sge->length = RDS_FRAG_SIZE;
  
  	sge = rds_ib_header_sge(ic, recv->r_sge);
  	sge->addr = ic->i_recv_hdrs_dma + (recv - ic->i_recvs) * sizeof(struct rds_header);
  	sge->length = sizeof(struct rds_header);
  
  	get_page(recv->r_frag->f_page);
  
  	if (ic->i_frag.f_offset < RDS_PAGE_LAST_OFF) {
  		ic->i_frag.f_offset += RDS_FRAG_SIZE;
  	} else {
  		put_page(ic->i_frag.f_page);
  		ic->i_frag.f_page = NULL;
  		ic->i_frag.f_offset = 0;
  	}
  
  	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.  The i_recv_mutex is held here so that ring_alloc and _unalloc
   * pairs don't go unmatched.
   *
   * -1 is returned if posting fails due to temporary resource exhaustion.
   */
  int rds_ib_recv_refill(struct rds_connection *conn, gfp_t kptr_gfp,
  		       gfp_t page_gfp, 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);
  			ret = -EINVAL;
  			break;
  		}
  
  		recv = &ic->i_recvs[pos];
  		ret = rds_ib_recv_refill_one(conn, recv, kptr_gfp, page_gfp);
  		if (ret) {
  			ret = -1;
  			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, recv->r_frag->f_page,
  			 (long) recv->r_frag->f_mapped, ret);
  		if (ret) {
  			rds_ib_conn_error(conn, "recv post on "
  			       "%pI4 returned %d, disconnecting and "
  			       "reconnecting\n", &conn->c_faddr,
  			       ret);
  			ret = -1;
  			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);
  	return ret;
  }
  
  void rds_ib_inc_purge(struct rds_incoming *inc)
  {
  	struct rds_ib_incoming *ibinc;
  	struct rds_page_frag *frag;
  	struct rds_page_frag *pos;
  
  	ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
  	rdsdebug("purging ibinc %p inc %p\n", ibinc, inc);
  
  	list_for_each_entry_safe(frag, pos, &ibinc->ii_frags, f_item) {
  		list_del_init(&frag->f_item);
  		rds_ib_frag_drop_page(frag);
  		rds_ib_frag_free(frag);
  	}
  }
  
  void rds_ib_inc_free(struct rds_incoming *inc)
  {
  	struct rds_ib_incoming *ibinc;
  
  	ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
  
  	rds_ib_inc_purge(inc);
  	rdsdebug("freeing ibinc %p inc %p\n", ibinc, inc);
  	BUG_ON(!list_empty(&ibinc->ii_frags));
  	kmem_cache_free(rds_ib_incoming_slab, ibinc);
  	atomic_dec(&rds_ib_allocation);
  	BUG_ON(atomic_read(&rds_ib_allocation) < 0);
  }
  
  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, %lu] + %lu\n",
  			 to_copy, iov->iov_base, iov->iov_len, iov_off,
  			 frag->f_page, frag->f_offset, frag_off);
  
  		/* XXX needs + offset for multiple recvs per page */
  		ret = rds_page_copy_to_user(frag->f_page,
  					    frag->f_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);
  		/* Need to finesse this later. */
  		BUG();
  	} 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);
  }
  
  static struct rds_header *rds_ib_get_header(struct rds_connection *conn,
  					    struct rds_ib_recv_work *recv,
  					    u32 data_len)
  {
  	struct rds_ib_connection *ic = conn->c_transport_data;
  	void *hdr_buff = &ic->i_recv_hdrs[recv - ic->i_recvs];
  	void *addr;
  	u32 misplaced_hdr_bytes;
  
  	/*
  	 * Support header at the front (RDS 3.1+) as well as header-at-end.
  	 *
  	 * Cases:
  	 * 1) header all in header buff (great!)
  	 * 2) header all in data page (copy all to header buff)
  	 * 3) header split across hdr buf + data page
  	 *    (move bit in hdr buff to end before copying other bit from data page)
  	 */
  	if (conn->c_version > RDS_PROTOCOL_3_0 || data_len == RDS_FRAG_SIZE)
  	        return hdr_buff;
  
  	if (data_len <= (RDS_FRAG_SIZE - sizeof(struct rds_header))) {
  		addr = kmap_atomic(recv->r_frag->f_page, KM_SOFTIRQ0);
  		memcpy(hdr_buff,
  		       addr + recv->r_frag->f_offset + data_len,
  		       sizeof(struct rds_header));
  		kunmap_atomic(addr, KM_SOFTIRQ0);
  		return hdr_buff;
  	}
  
  	misplaced_hdr_bytes = (sizeof(struct rds_header) - (RDS_FRAG_SIZE - data_len));
  
  	memmove(hdr_buff + misplaced_hdr_bytes, hdr_buff, misplaced_hdr_bytes);
  
  	addr = kmap_atomic(recv->r_frag->f_page, KM_SOFTIRQ0);
  	memcpy(hdr_buff, addr + recv->r_frag->f_offset + data_len,
  	       sizeof(struct rds_header) - misplaced_hdr_bytes);
  	kunmap_atomic(addr, KM_SOFTIRQ0);
  	return hdr_buff;
  }
  
  /*
   * 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(frag->f_page, KM_SOFTIRQ0);
  
  		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, KM_SOFTIRQ0);
  
  		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 inclue a "
  		       "header, disconnecting and "
  		       "reconnecting\n",
  		       &conn->c_faddr);
  		return;
  	}
  	data_len -= sizeof(struct rds_header);
  
  	ihdr = rds_ib_get_header(conn, recv, data_len);
  
  	/* 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.  We can leave the frag, though, it will be
  		 * reused.
  		 *
  		 * FIXME: Fold this into the code path below.
  		 */
  		rds_ib_frag_drop_page(recv->r_frag);
  		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 == NULL) {
  		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,
  					  KM_SOFTIRQ0);
  			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;
  	struct ib_wc wc;
  	struct rds_ib_ack_state state = { 0, };
  	struct rds_ib_recv_work *recv;
  
  	rdsdebug("conn %p cq %p\n", conn, cq);
  
  	rds_ib_stats_inc(s_ib_rx_cq_call);
  
  	ib_req_notify_cq(cq, IB_CQ_SOLICITED);
  
  	while (ib_poll_cq(cq, 1, &wc) > 0) {
  		rdsdebug("wc wr_id 0x%llx status %u byte_len %u imm_data %u\n",
  			 (unsigned long long)wc.wr_id, 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)];
  
  		rds_ib_recv_unmap_page(ic, recv);
  
  		/*
  		 * Also process recvs in connecting state because it is possible
  		 * to get a recv completion _before_ the rdmacm ESTABLISHED
  		 * event is processed.
  		 */
  		if (rds_conn_up(conn) || rds_conn_connecting(conn)) {
  			/* We expect errors as the qp is drained during shutdown */
  			if (wc.status == IB_WC_SUCCESS) {
  				rds_ib_process_recv(conn, recv, wc.byte_len, &state);
  			} else {
  				rds_ib_conn_error(conn, "recv completion on "
  				       "%pI4 had status %u, disconnecting and "
  				       "reconnecting\n", &conn->c_faddr,
  				       wc.status);
  			}
  		}
  
  		rds_ib_ring_free(&ic->i_recv_ring, 1);
  	}
  
  	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 the ring is running low, then schedule the thread to refill.
  	 */
  	if (rds_ib_ring_low(&ic->i_recv_ring))
  		queue_delayed_work(rds_wq, &conn->c_recv_w, 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 we get a temporary posting failure in this context then
  	 * we're really low and we want the caller to back off for a bit.
  	 */
  	mutex_lock(&ic->i_recv_mutex);
  	if (rds_ib_recv_refill(conn, GFP_KERNEL, GFP_HIGHUSER, 0))
  		ret = -ENOMEM;
  	else
  		rds_ib_stats_inc(s_ib_rx_refill_from_thread);
  	mutex_unlock(&ic->i_recv_mutex);
  
  	if (rds_conn_up(conn))
  		rds_ib_attempt_ack(ic);
  
  	return ret;
  }
  
  int __init 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, 0, NULL);
  	if (rds_ib_incoming_slab == NULL)
  		goto out;
  
  	rds_ib_frag_slab = kmem_cache_create("rds_ib_frag",
  					sizeof(struct rds_page_frag),
  					0, 0, NULL);
  	if (rds_ib_frag_slab == NULL)
  		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);
  }
  