net/rds/recv.c - maze/linux - Git at Google

 /*
  * 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 <net/sock.h>
 #include <linux/in.h>
 #include <linux/export.h>

 #include "rds.h"

 void rds_inc_init(struct rds_incoming *inc, struct rds_connection *conn,
 		  __be32 saddr)
 {
 	atomic_set(&inc->i_refcount, 1);
 	INIT_LIST_HEAD(&inc->i_item);
 	inc->i_conn = conn;
 	inc->i_saddr = saddr;
 	inc->i_rdma_cookie = 0;
 }
 EXPORT_SYMBOL_GPL(rds_inc_init);

 static void rds_inc_addref(struct rds_incoming *inc)
 {
 	rdsdebug("addref inc %p ref %d\n", inc, atomic_read(&inc->i_refcount));
 	atomic_inc(&inc->i_refcount);
 }

 void rds_inc_put(struct rds_incoming *inc)
 {
 	rdsdebug("put inc %p ref %d\n", inc, atomic_read(&inc->i_refcount));
 	if (atomic_dec_and_test(&inc->i_refcount)) {
 		BUG_ON(!list_empty(&inc->i_item));

 		inc->i_conn->c_trans->inc_free(inc);
 	}
 }
 EXPORT_SYMBOL_GPL(rds_inc_put);

 static void rds_recv_rcvbuf_delta(struct rds_sock *rs, struct sock *sk,
 				  struct rds_cong_map *map,
 				  int delta, __be16 port)
 {
 	int now_congested;

 	if (delta == 0)
 		return;

 	rs->rs_rcv_bytes += delta;
 	now_congested = rs->rs_rcv_bytes > rds_sk_rcvbuf(rs);

 	rdsdebug("rs %p (%pI4:%u) recv bytes %d buf %d "
 	  "now_cong %d delta %d\n",
 	  rs, &rs->rs_bound_addr,
 	  ntohs(rs->rs_bound_port), rs->rs_rcv_bytes,
 	  rds_sk_rcvbuf(rs), now_congested, delta);

 	/* wasn't -> am congested */
 	if (!rs->rs_congested && now_congested) {
 		rs->rs_congested = 1;
 		rds_cong_set_bit(map, port);
 		rds_cong_queue_updates(map);
 	}
 	/* was -> aren't congested */
 	/* Require more free space before reporting uncongested to prevent
 	   bouncing cong/uncong state too often */
 	else if (rs->rs_congested && (rs->rs_rcv_bytes < (rds_sk_rcvbuf(rs)/2))) {
 		rs->rs_congested = 0;
 		rds_cong_clear_bit(map, port);
 		rds_cong_queue_updates(map);
 	}

 	/* do nothing if no change in cong state */
 }

 /*
  * Process all extension headers that come with this message.
  */
 static void rds_recv_incoming_exthdrs(struct rds_incoming *inc, struct rds_sock *rs)
 {
 	struct rds_header *hdr = &inc->i_hdr;
 	unsigned int pos = 0, type, len;
 	union {
 		struct rds_ext_header_version version;
 		struct rds_ext_header_rdma rdma;
 		struct rds_ext_header_rdma_dest rdma_dest;
 	} buffer;

 	while (1) {
 		len = sizeof(buffer);
 		type = rds_message_next_extension(hdr, &pos, &buffer, &len);
 		if (type == RDS_EXTHDR_NONE)
 			break;
 		/* Process extension header here */
 		switch (type) {
 		case RDS_EXTHDR_RDMA:
 			rds_rdma_unuse(rs, be32_to_cpu(buffer.rdma.h_rdma_rkey), 0);
 			break;

 		case RDS_EXTHDR_RDMA_DEST:
 			/* We ignore the size for now. We could stash it
 			 * somewhere and use it for error checking. */
 			inc->i_rdma_cookie = rds_rdma_make_cookie(
 					be32_to_cpu(buffer.rdma_dest.h_rdma_rkey),
 					be32_to_cpu(buffer.rdma_dest.h_rdma_offset));

 			break;
 		}
 	}
 }

 /*
  * The transport must make sure that this is serialized against other
  * rx and conn reset on this specific conn.
  *
  * We currently assert that only one fragmented message will be sent
  * down a connection at a time.  This lets us reassemble in the conn
  * instead of per-flow which means that we don't have to go digging through
  * flows to tear down partial reassembly progress on conn failure and
  * we save flow lookup and locking for each frag arrival.  It does mean
  * that small messages will wait behind large ones.  Fragmenting at all
  * is only to reduce the memory consumption of pre-posted buffers.
  *
  * The caller passes in saddr and daddr instead of us getting it from the
  * conn.  This lets loopback, who only has one conn for both directions,
  * tell us which roles the addrs in the conn are playing for this message.
  */
 void rds_recv_incoming(struct rds_connection *conn, __be32 saddr, __be32 daddr,
 		       struct rds_incoming *inc, gfp_t gfp)
 {
 	struct rds_sock *rs = NULL;
 	struct sock *sk;
 	unsigned long flags;

 	inc->i_conn = conn;
 	inc->i_rx_jiffies = jiffies;

 	rdsdebug("conn %p next %llu inc %p seq %llu len %u sport %u dport %u "
 		 "flags 0x%x rx_jiffies %lu\n", conn,
 		 (unsigned long long)conn->c_next_rx_seq,
 		 inc,
 		 (unsigned long long)be64_to_cpu(inc->i_hdr.h_sequence),
 		 be32_to_cpu(inc->i_hdr.h_len),
 		 be16_to_cpu(inc->i_hdr.h_sport),
 		 be16_to_cpu(inc->i_hdr.h_dport),
 		 inc->i_hdr.h_flags,
 		 inc->i_rx_jiffies);

 	/*
 	 * Sequence numbers should only increase.  Messages get their
 	 * sequence number as they're queued in a sending conn.  They
 	 * can be dropped, though, if the sending socket is closed before
 	 * they hit the wire.  So sequence numbers can skip forward
 	 * under normal operation.  They can also drop back in the conn
 	 * failover case as previously sent messages are resent down the
 	 * new instance of a conn.  We drop those, otherwise we have
 	 * to assume that the next valid seq does not come after a
 	 * hole in the fragment stream.
 	 *
 	 * The headers don't give us a way to realize if fragments of
 	 * a message have been dropped.  We assume that frags that arrive
 	 * to a flow are part of the current message on the flow that is
 	 * being reassembled.  This means that senders can't drop messages
 	 * from the sending conn until all their frags are sent.
 	 *
 	 * XXX we could spend more on the wire to get more robust failure
 	 * detection, arguably worth it to avoid data corruption.
 	 */
 	if (be64_to_cpu(inc->i_hdr.h_sequence) < conn->c_next_rx_seq &&
 	    (inc->i_hdr.h_flags & RDS_FLAG_RETRANSMITTED)) {
 		rds_stats_inc(s_recv_drop_old_seq);
 		goto out;
 	}
 	conn->c_next_rx_seq = be64_to_cpu(inc->i_hdr.h_sequence) + 1;

 	if (rds_sysctl_ping_enable && inc->i_hdr.h_dport == 0) {
 		rds_stats_inc(s_recv_ping);
 		rds_send_pong(conn, inc->i_hdr.h_sport);
 		goto out;
 	}

 	rs = rds_find_bound(daddr, inc->i_hdr.h_dport);
 	if (!rs) {
 		rds_stats_inc(s_recv_drop_no_sock);
 		goto out;
 	}

 	/* Process extension headers */
 	rds_recv_incoming_exthdrs(inc, rs);

 	/* We can be racing with rds_release() which marks the socket dead. */
 	sk = rds_rs_to_sk(rs);

 	/* serialize with rds_release -> sock_orphan */
 	write_lock_irqsave(&rs->rs_recv_lock, flags);
 	if (!sock_flag(sk, SOCK_DEAD)) {
 		rdsdebug("adding inc %p to rs %p's recv queue\n", inc, rs);
 		rds_stats_inc(s_recv_queued);
 		rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
 				      be32_to_cpu(inc->i_hdr.h_len),
 				      inc->i_hdr.h_dport);
 		rds_inc_addref(inc);
 		list_add_tail(&inc->i_item, &rs->rs_recv_queue);
 		__rds_wake_sk_sleep(sk);
 	} else {
 		rds_stats_inc(s_recv_drop_dead_sock);
 	}
 	write_unlock_irqrestore(&rs->rs_recv_lock, flags);

 out:
 	if (rs)
 		rds_sock_put(rs);
 }
 EXPORT_SYMBOL_GPL(rds_recv_incoming);

 /*
  * be very careful here.  This is being called as the condition in
  * wait_event_*() needs to cope with being called many times.
  */
 static int rds_next_incoming(struct rds_sock *rs, struct rds_incoming **inc)
 {
 	unsigned long flags;

 	if (!*inc) {
 		read_lock_irqsave(&rs->rs_recv_lock, flags);
 		if (!list_empty(&rs->rs_recv_queue)) {
 			*inc = list_entry(rs->rs_recv_queue.next,
 					  struct rds_incoming,
 					  i_item);
 			rds_inc_addref(*inc);
 		}
 		read_unlock_irqrestore(&rs->rs_recv_lock, flags);
 	}

 	return *inc != NULL;
 }

 static int rds_still_queued(struct rds_sock *rs, struct rds_incoming *inc,
 			    int drop)
 {
 	struct sock *sk = rds_rs_to_sk(rs);
 	int ret = 0;
 	unsigned long flags;

 	write_lock_irqsave(&rs->rs_recv_lock, flags);
 	if (!list_empty(&inc->i_item)) {
 		ret = 1;
 		if (drop) {
 			/* XXX make sure this i_conn is reliable */
 			rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
 					      -be32_to_cpu(inc->i_hdr.h_len),
 					      inc->i_hdr.h_dport);
 			list_del_init(&inc->i_item);
 			rds_inc_put(inc);
 		}
 	}
 	write_unlock_irqrestore(&rs->rs_recv_lock, flags);

 	rdsdebug("inc %p rs %p still %d dropped %d\n", inc, rs, ret, drop);
 	return ret;
 }

 /*
  * Pull errors off the error queue.
  * If msghdr is NULL, we will just purge the error queue.
  */
 int rds_notify_queue_get(struct rds_sock *rs, struct msghdr *msghdr)
 {
 	struct rds_notifier *notifier;
 	struct rds_rdma_notify cmsg = { 0 }; /* fill holes with zero */
 	unsigned int count = 0, max_messages = ~0U;
 	unsigned long flags;
 	LIST_HEAD(copy);
 	int err = 0;


 	/* put_cmsg copies to user space and thus may sleep. We can't do this
 	 * with rs_lock held, so first grab as many notifications as we can stuff
 	 * in the user provided cmsg buffer. We don't try to copy more, to avoid
 	 * losing notifications - except when the buffer is so small that it wouldn't
 	 * even hold a single notification. Then we give him as much of this single
 	 * msg as we can squeeze in, and set MSG_CTRUNC.
 	 */
 	if (msghdr) {
 		max_messages = msghdr->msg_controllen / CMSG_SPACE(sizeof(cmsg));
 		if (!max_messages)
 			max_messages = 1;
 	}

 	spin_lock_irqsave(&rs->rs_lock, flags);
 	while (!list_empty(&rs->rs_notify_queue) && count < max_messages) {
 		notifier = list_entry(rs->rs_notify_queue.next,
 				struct rds_notifier, n_list);
 		list_move(&notifier->n_list, &copy);
 		count++;
 	}
 	spin_unlock_irqrestore(&rs->rs_lock, flags);

 	if (!count)
 		return 0;

 	while (!list_empty(&copy)) {
 		notifier = list_entry(copy.next, struct rds_notifier, n_list);

 		if (msghdr) {
 			cmsg.user_token = notifier->n_user_token;
 			cmsg.status = notifier->n_status;

 			err = put_cmsg(msghdr, SOL_RDS, RDS_CMSG_RDMA_STATUS,
 				       sizeof(cmsg), &cmsg);
 			if (err)
 				break;
 		}

 		list_del_init(&notifier->n_list);
 		kfree(notifier);
 	}

 	/* If we bailed out because of an error in put_cmsg,
 	 * we may be left with one or more notifications that we
 	 * didn't process. Return them to the head of the list. */
 	if (!list_empty(&copy)) {
 		spin_lock_irqsave(&rs->rs_lock, flags);
 		list_splice(&copy, &rs->rs_notify_queue);
 		spin_unlock_irqrestore(&rs->rs_lock, flags);
 	}

 	return err;
 }

 /*
  * Queue a congestion notification
  */
 static int rds_notify_cong(struct rds_sock *rs, struct msghdr *msghdr)
 {
 	uint64_t notify = rs->rs_cong_notify;
 	unsigned long flags;
 	int err;

 	err = put_cmsg(msghdr, SOL_RDS, RDS_CMSG_CONG_UPDATE,
 			sizeof(notify), &notify);
 	if (err)
 		return err;

 	spin_lock_irqsave(&rs->rs_lock, flags);
 	rs->rs_cong_notify &= ~notify;
 	spin_unlock_irqrestore(&rs->rs_lock, flags);

 	return 0;
 }

 /*
  * Receive any control messages.
  */
 static int rds_cmsg_recv(struct rds_incoming *inc, struct msghdr *msg)
 {
 	int ret = 0;

 	if (inc->i_rdma_cookie) {
 		ret = put_cmsg(msg, SOL_RDS, RDS_CMSG_RDMA_DEST,
 				sizeof(inc->i_rdma_cookie), &inc->i_rdma_cookie);
 		if (ret)
 			return ret;
 	}

 	return 0;
 }

 int rds_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
 		size_t size, int msg_flags)
 {
 	struct sock *sk = sock->sk;
 	struct rds_sock *rs = rds_sk_to_rs(sk);
 	long timeo;
 	int ret = 0, nonblock = msg_flags & MSG_DONTWAIT;
 	struct sockaddr_in *sin;
 	struct rds_incoming *inc = NULL;

 	/* udp_recvmsg()->sock_recvtimeo() gets away without locking too.. */
 	timeo = sock_rcvtimeo(sk, nonblock);

 	rdsdebug("size %zu flags 0x%x timeo %ld\n", size, msg_flags, timeo);

 	if (msg_flags & MSG_OOB)
 		goto out;

 	while (1) {
 		/* If there are pending notifications, do those - and nothing else */
 		if (!list_empty(&rs->rs_notify_queue)) {
 			ret = rds_notify_queue_get(rs, msg);
 			break;
 		}

 		if (rs->rs_cong_notify) {
 			ret = rds_notify_cong(rs, msg);
 			break;
 		}

 		if (!rds_next_incoming(rs, &inc)) {
 			if (nonblock) {
 				ret = -EAGAIN;
 				break;
 			}

 			timeo = wait_event_interruptible_timeout(*sk_sleep(sk),
 					(!list_empty(&rs->rs_notify_queue) ||
 					 rs->rs_cong_notify ||
 					 rds_next_incoming(rs, &inc)), timeo);
 			rdsdebug("recvmsg woke inc %p timeo %ld\n", inc,
 				 timeo);
 			if (timeo > 0 || timeo == MAX_SCHEDULE_TIMEOUT)
 				continue;

 			ret = timeo;
 			if (ret == 0)
 				ret = -ETIMEDOUT;
 			break;
 		}

 		rdsdebug("copying inc %p from %pI4:%u to user\n", inc,
 			 &inc->i_conn->c_faddr,
 			 ntohs(inc->i_hdr.h_sport));
 		ret = inc->i_conn->c_trans->inc_copy_to_user(inc, msg->msg_iov,
 							     size);
 		if (ret < 0)
 			break;

 		/*
 		 * if the message we just copied isn't at the head of the
 		 * recv queue then someone else raced us to return it, try
 		 * to get the next message.
 		 */
 		if (!rds_still_queued(rs, inc, !(msg_flags & MSG_PEEK))) {
 			rds_inc_put(inc);
 			inc = NULL;
 			rds_stats_inc(s_recv_deliver_raced);
 			continue;
 		}

 		if (ret < be32_to_cpu(inc->i_hdr.h_len)) {
 			if (msg_flags & MSG_TRUNC)
 				ret = be32_to_cpu(inc->i_hdr.h_len);
 			msg->msg_flags |= MSG_TRUNC;
 		}

 		if (rds_cmsg_recv(inc, msg)) {
 			ret = -EFAULT;
 			goto out;
 		}

 		rds_stats_inc(s_recv_delivered);

 		sin = (struct sockaddr_in *)msg->msg_name;
 		if (sin) {
 			sin->sin_family = AF_INET;
 			sin->sin_port = inc->i_hdr.h_sport;
 			sin->sin_addr.s_addr = inc->i_saddr;
 			memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
 			msg->msg_namelen = sizeof(*sin);
 		}
 		break;
 	}

 	if (inc)
 		rds_inc_put(inc);

 out:
 	return ret;
 }

 /*
  * The socket is being shut down and we're asked to drop messages that were
  * queued for recvmsg.  The caller has unbound the socket so the receive path
  * won't queue any more incoming fragments or messages on the socket.
  */
 void rds_clear_recv_queue(struct rds_sock *rs)
 {
 	struct sock *sk = rds_rs_to_sk(rs);
 	struct rds_incoming *inc, *tmp;
 	unsigned long flags;

 	write_lock_irqsave(&rs->rs_recv_lock, flags);
 	list_for_each_entry_safe(inc, tmp, &rs->rs_recv_queue, i_item) {
 		rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
 				      -be32_to_cpu(inc->i_hdr.h_len),
 				      inc->i_hdr.h_dport);
 		list_del_init(&inc->i_item);
 		rds_inc_put(inc);
 	}
 	write_unlock_irqrestore(&rs->rs_recv_lock, flags);
 }

 /*
  * inc->i_saddr isn't used here because it is only set in the receive
  * path.
  */
 void rds_inc_info_copy(struct rds_incoming *inc,
 		       struct rds_info_iterator *iter,
 		       __be32 saddr, __be32 daddr, int flip)
 {
 	struct rds_info_message minfo;

 	minfo.seq = be64_to_cpu(inc->i_hdr.h_sequence);
 	minfo.len = be32_to_cpu(inc->i_hdr.h_len);

 	if (flip) {
 		minfo.laddr = daddr;
 		minfo.faddr = saddr;
 		minfo.lport = inc->i_hdr.h_dport;
 		minfo.fport = inc->i_hdr.h_sport;
 	} else {
 		minfo.laddr = saddr;
 		minfo.faddr = daddr;
 		minfo.lport = inc->i_hdr.h_sport;
 		minfo.fport = inc->i_hdr.h_dport;
 	}

 	rds_info_copy(iter, &minfo, sizeof(minfo));
 }
	/*
	* 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 <net/sock.h>
	#include <linux/in.h>
	#include <linux/export.h>

	#include "rds.h"

	void rds_inc_init(struct rds_incoming inc, struct rds_connection conn,
	__be32 saddr)
	{
	atomic_set(&inc->i_refcount, 1);
	INIT_LIST_HEAD(&inc->i_item);
	inc->i_conn = conn;
	inc->i_saddr = saddr;
	inc->i_rdma_cookie = 0;
	}
	EXPORT_SYMBOL_GPL(rds_inc_init);

	static void rds_inc_addref(struct rds_incoming *inc)
	{
	rdsdebug("addref inc %p ref %d\n", inc, atomic_read(&inc->i_refcount));
	atomic_inc(&inc->i_refcount);
	}

	void rds_inc_put(struct rds_incoming *inc)
	{
	rdsdebug("put inc %p ref %d\n", inc, atomic_read(&inc->i_refcount));
	if (atomic_dec_and_test(&inc->i_refcount)) {
	BUG_ON(!list_empty(&inc->i_item));

	inc->i_conn->c_trans->inc_free(inc);
	}
	}
	EXPORT_SYMBOL_GPL(rds_inc_put);

	static void rds_recv_rcvbuf_delta(struct rds_sock rs, struct sock sk,
	struct rds_cong_map *map,
	int delta, __be16 port)
	{
	int now_congested;

	if (delta == 0)
	return;

	rs->rs_rcv_bytes += delta;
	now_congested = rs->rs_rcv_bytes > rds_sk_rcvbuf(rs);

	rdsdebug("rs %p (%pI4:%u) recv bytes %d buf %d "
	"now_cong %d delta %d\n",
	rs, &rs->rs_bound_addr,
	ntohs(rs->rs_bound_port), rs->rs_rcv_bytes,
	rds_sk_rcvbuf(rs), now_congested, delta);

	/* wasn't -> am congested */
	if (!rs->rs_congested && now_congested) {
	rs->rs_congested = 1;
	rds_cong_set_bit(map, port);
	rds_cong_queue_updates(map);
	}
	/* was -> aren't congested */
	/* Require more free space before reporting uncongested to prevent
	bouncing cong/uncong state too often */
	else if (rs->rs_congested && (rs->rs_rcv_bytes < (rds_sk_rcvbuf(rs)/2))) {
	rs->rs_congested = 0;
	rds_cong_clear_bit(map, port);
	rds_cong_queue_updates(map);
	}

	/* do nothing if no change in cong state */
	}

	/*
	* Process all extension headers that come with this message.
	*/
	static void rds_recv_incoming_exthdrs(struct rds_incoming inc, struct rds_sock rs)
	{
	struct rds_header *hdr = &inc->i_hdr;
	unsigned int pos = 0, type, len;
	union {
	struct rds_ext_header_version version;
	struct rds_ext_header_rdma rdma;
	struct rds_ext_header_rdma_dest rdma_dest;
	} buffer;

	while (1) {
	len = sizeof(buffer);
	type = rds_message_next_extension(hdr, &pos, &buffer, &len);
	if (type == RDS_EXTHDR_NONE)
	break;
	/* Process extension header here */
	switch (type) {
	case RDS_EXTHDR_RDMA:
	rds_rdma_unuse(rs, be32_to_cpu(buffer.rdma.h_rdma_rkey), 0);
	break;

	case RDS_EXTHDR_RDMA_DEST:
	/* We ignore the size for now. We could stash it
	* somewhere and use it for error checking. */
	inc->i_rdma_cookie = rds_rdma_make_cookie(
	be32_to_cpu(buffer.rdma_dest.h_rdma_rkey),
	be32_to_cpu(buffer.rdma_dest.h_rdma_offset));

	break;
	}
	}
	}

	/*
	* The transport must make sure that this is serialized against other
	* rx and conn reset on this specific conn.
	*
	* We currently assert that only one fragmented message will be sent
	* down a connection at a time. This lets us reassemble in the conn
	* instead of per-flow which means that we don't have to go digging through
	* flows to tear down partial reassembly progress on conn failure and
	* we save flow lookup and locking for each frag arrival. It does mean
	* that small messages will wait behind large ones. Fragmenting at all
	* is only to reduce the memory consumption of pre-posted buffers.
	*
	* The caller passes in saddr and daddr instead of us getting it from the
	* conn. This lets loopback, who only has one conn for both directions,
	* tell us which roles the addrs in the conn are playing for this message.
	*/
	void rds_recv_incoming(struct rds_connection *conn, __be32 saddr, __be32 daddr,
	struct rds_incoming *inc, gfp_t gfp)
	{
	struct rds_sock *rs = NULL;
	struct sock *sk;
	unsigned long flags;

	inc->i_conn = conn;
	inc->i_rx_jiffies = jiffies;

	rdsdebug("conn %p next %llu inc %p seq %llu len %u sport %u dport %u "
	"flags 0x%x rx_jiffies %lu\n", conn,
	(unsigned long long)conn->c_next_rx_seq,
	inc,
	(unsigned long long)be64_to_cpu(inc->i_hdr.h_sequence),
	be32_to_cpu(inc->i_hdr.h_len),
	be16_to_cpu(inc->i_hdr.h_sport),
	be16_to_cpu(inc->i_hdr.h_dport),
	inc->i_hdr.h_flags,
	inc->i_rx_jiffies);

	/*
	* Sequence numbers should only increase. Messages get their
	* sequence number as they're queued in a sending conn. They
	* can be dropped, though, if the sending socket is closed before
	* they hit the wire. So sequence numbers can skip forward
	* under normal operation. They can also drop back in the conn
	* failover case as previously sent messages are resent down the
	* new instance of a conn. We drop those, otherwise we have
	* to assume that the next valid seq does not come after a
	* hole in the fragment stream.
	*
	* The headers don't give us a way to realize if fragments of
	* a message have been dropped. We assume that frags that arrive
	* to a flow are part of the current message on the flow that is
	* being reassembled. This means that senders can't drop messages
	* from the sending conn until all their frags are sent.
	*
	* XXX we could spend more on the wire to get more robust failure
	* detection, arguably worth it to avoid data corruption.
	*/
	if (be64_to_cpu(inc->i_hdr.h_sequence) < conn->c_next_rx_seq &&
	(inc->i_hdr.h_flags & RDS_FLAG_RETRANSMITTED)) {
	rds_stats_inc(s_recv_drop_old_seq);
	goto out;
	}
	conn->c_next_rx_seq = be64_to_cpu(inc->i_hdr.h_sequence) + 1;

	if (rds_sysctl_ping_enable && inc->i_hdr.h_dport == 0) {
	rds_stats_inc(s_recv_ping);
	rds_send_pong(conn, inc->i_hdr.h_sport);
	goto out;
	}

	rs = rds_find_bound(daddr, inc->i_hdr.h_dport);
	if (!rs) {
	rds_stats_inc(s_recv_drop_no_sock);
	goto out;
	}

	/* Process extension headers */
	rds_recv_incoming_exthdrs(inc, rs);

	/* We can be racing with rds_release() which marks the socket dead. */
	sk = rds_rs_to_sk(rs);

	/* serialize with rds_release -> sock_orphan */
	write_lock_irqsave(&rs->rs_recv_lock, flags);
	if (!sock_flag(sk, SOCK_DEAD)) {
	rdsdebug("adding inc %p to rs %p's recv queue\n", inc, rs);
	rds_stats_inc(s_recv_queued);
	rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
	be32_to_cpu(inc->i_hdr.h_len),
	inc->i_hdr.h_dport);
	rds_inc_addref(inc);
	list_add_tail(&inc->i_item, &rs->rs_recv_queue);
	__rds_wake_sk_sleep(sk);
	} else {
	rds_stats_inc(s_recv_drop_dead_sock);
	}
	write_unlock_irqrestore(&rs->rs_recv_lock, flags);

	out:
	if (rs)
	rds_sock_put(rs);
	}
	EXPORT_SYMBOL_GPL(rds_recv_incoming);

	/*
	* be very careful here. This is being called as the condition in
	* wait_event_*() needs to cope with being called many times.
	*/
	static int rds_next_incoming(struct rds_sock rs, struct rds_incoming *inc)
	{
	unsigned long flags;

	if (!*inc) {
	read_lock_irqsave(&rs->rs_recv_lock, flags);
	if (!list_empty(&rs->rs_recv_queue)) {
	*inc = list_entry(rs->rs_recv_queue.next,
	struct rds_incoming,
	i_item);
	rds_inc_addref(*inc);
	}
	read_unlock_irqrestore(&rs->rs_recv_lock, flags);
	}

	return *inc != NULL;
	}

	static int rds_still_queued(struct rds_sock rs, struct rds_incoming inc,
	int drop)
	{
	struct sock *sk = rds_rs_to_sk(rs);
	int ret = 0;
	unsigned long flags;

	write_lock_irqsave(&rs->rs_recv_lock, flags);
	if (!list_empty(&inc->i_item)) {
	ret = 1;
	if (drop) {
	/* XXX make sure this i_conn is reliable */
	rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
	-be32_to_cpu(inc->i_hdr.h_len),
	inc->i_hdr.h_dport);
	list_del_init(&inc->i_item);
	rds_inc_put(inc);
	}
	}
	write_unlock_irqrestore(&rs->rs_recv_lock, flags);

	rdsdebug("inc %p rs %p still %d dropped %d\n", inc, rs, ret, drop);
	return ret;
	}

	/*
	* Pull errors off the error queue.
	* If msghdr is NULL, we will just purge the error queue.
	*/
	int rds_notify_queue_get(struct rds_sock rs, struct msghdr msghdr)
	{
	struct rds_notifier *notifier;
	struct rds_rdma_notify cmsg = { 0 }; /* fill holes with zero */
	unsigned int count = 0, max_messages = ~0U;
	unsigned long flags;
	LIST_HEAD(copy);
	int err = 0;


	/* put_cmsg copies to user space and thus may sleep. We can't do this
	* with rs_lock held, so first grab as many notifications as we can stuff
	* in the user provided cmsg buffer. We don't try to copy more, to avoid
	* losing notifications - except when the buffer is so small that it wouldn't
	* even hold a single notification. Then we give him as much of this single
	* msg as we can squeeze in, and set MSG_CTRUNC.
	*/
	if (msghdr) {
	max_messages = msghdr->msg_controllen / CMSG_SPACE(sizeof(cmsg));
	if (!max_messages)
	max_messages = 1;
	}

	spin_lock_irqsave(&rs->rs_lock, flags);
	while (!list_empty(&rs->rs_notify_queue) && count < max_messages) {
	notifier = list_entry(rs->rs_notify_queue.next,
	struct rds_notifier, n_list);
	list_move(&notifier->n_list, &copy);
	count++;
	}
	spin_unlock_irqrestore(&rs->rs_lock, flags);

	if (!count)
	return 0;

	while (!list_empty(&copy)) {
	notifier = list_entry(copy.next, struct rds_notifier, n_list);

	if (msghdr) {
	cmsg.user_token = notifier->n_user_token;
	cmsg.status = notifier->n_status;

	err = put_cmsg(msghdr, SOL_RDS, RDS_CMSG_RDMA_STATUS,
	sizeof(cmsg), &cmsg);
	if (err)
	break;
	}

	list_del_init(&notifier->n_list);
	kfree(notifier);
	}

	/* If we bailed out because of an error in put_cmsg,
	* we may be left with one or more notifications that we
	* didn't process. Return them to the head of the list. */
	if (!list_empty(&copy)) {
	spin_lock_irqsave(&rs->rs_lock, flags);
	list_splice(&copy, &rs->rs_notify_queue);
	spin_unlock_irqrestore(&rs->rs_lock, flags);
	}

	return err;
	}

	/*
	* Queue a congestion notification
	*/
	static int rds_notify_cong(struct rds_sock rs, struct msghdr msghdr)
	{
	uint64_t notify = rs->rs_cong_notify;
	unsigned long flags;
	int err;

	err = put_cmsg(msghdr, SOL_RDS, RDS_CMSG_CONG_UPDATE,
	sizeof(notify), &notify);
	if (err)
	return err;

	spin_lock_irqsave(&rs->rs_lock, flags);
	rs->rs_cong_notify &= ~notify;
	spin_unlock_irqrestore(&rs->rs_lock, flags);

	return 0;
	}

	/*
	* Receive any control messages.
	*/
	static int rds_cmsg_recv(struct rds_incoming inc, struct msghdr msg)
	{
	int ret = 0;

	if (inc->i_rdma_cookie) {
	ret = put_cmsg(msg, SOL_RDS, RDS_CMSG_RDMA_DEST,
	sizeof(inc->i_rdma_cookie), &inc->i_rdma_cookie);
	if (ret)
	return ret;
	}

	return 0;
	}

	int rds_recvmsg(struct kiocb iocb, struct socket sock, struct msghdr *msg,
	size_t size, int msg_flags)
	{
	struct sock *sk = sock->sk;
	struct rds_sock *rs = rds_sk_to_rs(sk);
	long timeo;
	int ret = 0, nonblock = msg_flags & MSG_DONTWAIT;
	struct sockaddr_in *sin;
	struct rds_incoming *inc = NULL;

	/* udp_recvmsg()->sock_recvtimeo() gets away without locking too.. */
	timeo = sock_rcvtimeo(sk, nonblock);

	rdsdebug("size %zu flags 0x%x timeo %ld\n", size, msg_flags, timeo);

	if (msg_flags & MSG_OOB)
	goto out;

	while (1) {
	/* If there are pending notifications, do those - and nothing else */
	if (!list_empty(&rs->rs_notify_queue)) {
	ret = rds_notify_queue_get(rs, msg);
	break;
	}

	if (rs->rs_cong_notify) {
	ret = rds_notify_cong(rs, msg);
	break;
	}

	if (!rds_next_incoming(rs, &inc)) {
	if (nonblock) {
	ret = -EAGAIN;
	break;
	}

	timeo = wait_event_interruptible_timeout(*sk_sleep(sk),
	(!list_empty(&rs->rs_notify_queue) \|\|
	rs->rs_cong_notify \|\|
	rds_next_incoming(rs, &inc)), timeo);
	rdsdebug("recvmsg woke inc %p timeo %ld\n", inc,
	timeo);
	if (timeo > 0 \|\| timeo == MAX_SCHEDULE_TIMEOUT)
	continue;

	ret = timeo;
	if (ret == 0)
	ret = -ETIMEDOUT;
	break;
	}

	rdsdebug("copying inc %p from %pI4:%u to user\n", inc,
	&inc->i_conn->c_faddr,
	ntohs(inc->i_hdr.h_sport));
	ret = inc->i_conn->c_trans->inc_copy_to_user(inc, msg->msg_iov,
	size);
	if (ret < 0)
	break;

	/*
	* if the message we just copied isn't at the head of the
	* recv queue then someone else raced us to return it, try
	* to get the next message.
	*/
	if (!rds_still_queued(rs, inc, !(msg_flags & MSG_PEEK))) {
	rds_inc_put(inc);
	inc = NULL;
	rds_stats_inc(s_recv_deliver_raced);
	continue;
	}

	if (ret < be32_to_cpu(inc->i_hdr.h_len)) {
	if (msg_flags & MSG_TRUNC)
	ret = be32_to_cpu(inc->i_hdr.h_len);
	msg->msg_flags \|= MSG_TRUNC;
	}

	if (rds_cmsg_recv(inc, msg)) {
	ret = -EFAULT;
	goto out;
	}

	rds_stats_inc(s_recv_delivered);

	sin = (struct sockaddr_in *)msg->msg_name;
	if (sin) {
	sin->sin_family = AF_INET;
	sin->sin_port = inc->i_hdr.h_sport;
	sin->sin_addr.s_addr = inc->i_saddr;
	memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
	msg->msg_namelen = sizeof(*sin);
	}
	break;
	}

	if (inc)
	rds_inc_put(inc);

	out:
	return ret;
	}

	/*
	* The socket is being shut down and we're asked to drop messages that were
	* queued for recvmsg. The caller has unbound the socket so the receive path
	* won't queue any more incoming fragments or messages on the socket.
	*/
	void rds_clear_recv_queue(struct rds_sock *rs)
	{
	struct sock *sk = rds_rs_to_sk(rs);
	struct rds_incoming inc, tmp;
	unsigned long flags;

	write_lock_irqsave(&rs->rs_recv_lock, flags);
	list_for_each_entry_safe(inc, tmp, &rs->rs_recv_queue, i_item) {
	rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong,
	-be32_to_cpu(inc->i_hdr.h_len),
	inc->i_hdr.h_dport);
	list_del_init(&inc->i_item);
	rds_inc_put(inc);
	}
	write_unlock_irqrestore(&rs->rs_recv_lock, flags);
	}

	/*
	* inc->i_saddr isn't used here because it is only set in the receive
	* path.
	*/
	void rds_inc_info_copy(struct rds_incoming *inc,
	struct rds_info_iterator *iter,
	__be32 saddr, __be32 daddr, int flip)
	{
	struct rds_info_message minfo;

	minfo.seq = be64_to_cpu(inc->i_hdr.h_sequence);
	minfo.len = be32_to_cpu(inc->i_hdr.h_len);

	if (flip) {
	minfo.laddr = daddr;
	minfo.faddr = saddr;
	minfo.lport = inc->i_hdr.h_dport;
	minfo.fport = inc->i_hdr.h_sport;
	} else {
	minfo.laddr = saddr;
	minfo.faddr = daddr;
	minfo.lport = inc->i_hdr.h_sport;
	minfo.fport = inc->i_hdr.h_dport;
	}

	rds_info_copy(iter, &minfo, sizeof(minfo));
	}