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/moduleparam.h>
  #include <linux/gfp.h>
  #include <net/sock.h>
  #include <linux/in.h>
  #include <linux/list.h>
  #include <linux/ratelimit.h>
  #include <linux/export.h>
  
  #include "rds.h"
  
  /* When transmitting messages in rds_send_xmit, we need to emerge from
   * time to time and briefly release the CPU. Otherwise the softlock watchdog
   * will kick our shin.
   * Also, it seems fairer to not let one busy connection stall all the
   * others.
   *
   * send_batch_count is the number of times we'll loop in send_xmit. Setting
   * it to 0 will restore the old behavior (where we looped until we had
   * drained the queue).
   */
  static int send_batch_count = 64;
  module_param(send_batch_count, int, 0444);
  MODULE_PARM_DESC(send_batch_count, " batch factor when working the send queue");
  
  static void rds_send_remove_from_sock(struct list_head *messages, int status);
  
  /*
   * Reset the send state.  Callers must ensure that this doesn't race with
   * rds_send_xmit().
   */
  void rds_send_reset(struct rds_connection *conn)
  {
  	struct rds_message *rm, *tmp;
  	unsigned long flags;
  
  	if (conn->c_xmit_rm) {
  		rm = conn->c_xmit_rm;
  		conn->c_xmit_rm = NULL;
  		/* Tell the user the RDMA op is no longer mapped by the
  		 * transport. This isn't entirely true (it's flushed out
  		 * independently) but as the connection is down, there's
  		 * no ongoing RDMA to/from that memory */
  		rds_message_unmapped(rm);
  		rds_message_put(rm);
  	}
  
  	conn->c_xmit_sg = 0;
  	conn->c_xmit_hdr_off = 0;
  	conn->c_xmit_data_off = 0;
  	conn->c_xmit_atomic_sent = 0;
  	conn->c_xmit_rdma_sent = 0;
  	conn->c_xmit_data_sent = 0;
  
  	conn->c_map_queued = 0;
  
  	conn->c_unacked_packets = rds_sysctl_max_unacked_packets;
  	conn->c_unacked_bytes = rds_sysctl_max_unacked_bytes;
  
  	/* Mark messages as retransmissions, and move them to the send q */
  	spin_lock_irqsave(&conn->c_lock, flags);
  	list_for_each_entry_safe(rm, tmp, &conn->c_retrans, m_conn_item) {
  		set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
  		set_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags);
  	}
  	list_splice_init(&conn->c_retrans, &conn->c_send_queue);
  	spin_unlock_irqrestore(&conn->c_lock, flags);
  }
  
  static int acquire_in_xmit(struct rds_connection *conn)
  {
  	return test_and_set_bit(RDS_IN_XMIT, &conn->c_flags) == 0;
  }
  
  static void release_in_xmit(struct rds_connection *conn)
  {
  	clear_bit(RDS_IN_XMIT, &conn->c_flags);
  	smp_mb__after_clear_bit();
  	/*
  	 * We don't use wait_on_bit()/wake_up_bit() because our waking is in a
  	 * hot path and finding waiters is very rare.  We don't want to walk
  	 * the system-wide hashed waitqueue buckets in the fast path only to
  	 * almost never find waiters.
  	 */
  	if (waitqueue_active(&conn->c_waitq))
  		wake_up_all(&conn->c_waitq);
  }
  
  /*
   * We're making the conscious trade-off here to only send one message
   * down the connection at a time.
   *   Pro:
   *      - tx queueing is a simple fifo list
   *   	- reassembly is optional and easily done by transports per conn
   *      - no per flow rx lookup at all, straight to the socket
   *   	- less per-frag memory and wire overhead
   *   Con:
   *      - queued acks can be delayed behind large messages
   *   Depends:
   *      - small message latency is higher behind queued large messages
   *      - large message latency isn't starved by intervening small sends
   */
  int rds_send_xmit(struct rds_connection *conn)
  {
  	struct rds_message *rm;
  	unsigned long flags;
  	unsigned int tmp;
  	struct scatterlist *sg;
  	int ret = 0;
  	LIST_HEAD(to_be_dropped);
  
  restart:
  
  	/*
  	 * sendmsg calls here after having queued its message on the send
  	 * queue.  We only have one task feeding the connection at a time.  If
  	 * another thread is already feeding the queue then we back off.  This
  	 * avoids blocking the caller and trading per-connection data between
  	 * caches per message.
  	 */
  	if (!acquire_in_xmit(conn)) {
  		rds_stats_inc(s_send_lock_contention);
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	/*
  	 * rds_conn_shutdown() sets the conn state and then tests RDS_IN_XMIT,
  	 * we do the opposite to avoid races.
  	 */
  	if (!rds_conn_up(conn)) {
  		release_in_xmit(conn);
  		ret = 0;
  		goto out;
  	}
  
  	if (conn->c_trans->xmit_prepare)
  		conn->c_trans->xmit_prepare(conn);
  
  	/*
  	 * spin trying to push headers and data down the connection until
  	 * the connection doesn't make forward progress.
  	 */
  	while (1) {
  
  		rm = conn->c_xmit_rm;
  
  		/*
  		 * If between sending messages, we can send a pending congestion
  		 * map update.
  		 */
  		if (!rm && test_and_clear_bit(0, &conn->c_map_queued)) {
  			rm = rds_cong_update_alloc(conn);
  			if (IS_ERR(rm)) {
  				ret = PTR_ERR(rm);
  				break;
  			}
  			rm->data.op_active = 1;
  
  			conn->c_xmit_rm = rm;
  		}
  
  		/*
  		 * If not already working on one, grab the next message.
  		 *
  		 * c_xmit_rm holds a ref while we're sending this message down
  		 * the connction.  We can use this ref while holding the
  		 * send_sem.. rds_send_reset() is serialized with it.
  		 */
  		if (!rm) {
  			unsigned int len;
  
  			spin_lock_irqsave(&conn->c_lock, flags);
  
  			if (!list_empty(&conn->c_send_queue)) {
  				rm = list_entry(conn->c_send_queue.next,
  						struct rds_message,
  						m_conn_item);
  				rds_message_addref(rm);
  
  				/*
  				 * Move the message from the send queue to the retransmit
  				 * list right away.
  				 */
  				list_move_tail(&rm->m_conn_item, &conn->c_retrans);
  			}
  
  			spin_unlock_irqrestore(&conn->c_lock, flags);
  
  			if (!rm)
  				break;
  
  			/* Unfortunately, the way Infiniband deals with
  			 * RDMA to a bad MR key is by moving the entire
  			 * queue pair to error state. We cold possibly
  			 * recover from that, but right now we drop the
  			 * connection.
  			 * Therefore, we never retransmit messages with RDMA ops.
  			 */
  			if (rm->rdma.op_active &&
  			    test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags)) {
  				spin_lock_irqsave(&conn->c_lock, flags);
  				if (test_and_clear_bit(RDS_MSG_ON_CONN, &rm->m_flags))
  					list_move(&rm->m_conn_item, &to_be_dropped);
  				spin_unlock_irqrestore(&conn->c_lock, flags);
  				continue;
  			}
  
  			/* Require an ACK every once in a while */
  			len = ntohl(rm->m_inc.i_hdr.h_len);
  			if (conn->c_unacked_packets == 0 ||
  			    conn->c_unacked_bytes < len) {
  				__set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
  
  				conn->c_unacked_packets = rds_sysctl_max_unacked_packets;
  				conn->c_unacked_bytes = rds_sysctl_max_unacked_bytes;
  				rds_stats_inc(s_send_ack_required);
  			} else {
  				conn->c_unacked_bytes -= len;
  				conn->c_unacked_packets--;
  			}
  
  			conn->c_xmit_rm = rm;
  		}
  
  		/* The transport either sends the whole rdma or none of it */
  		if (rm->rdma.op_active && !conn->c_xmit_rdma_sent) {
  			rm->m_final_op = &rm->rdma;
  			ret = conn->c_trans->xmit_rdma(conn, &rm->rdma);
  			if (ret)
  				break;
  			conn->c_xmit_rdma_sent = 1;
  
  			/* The transport owns the mapped memory for now.
  			 * You can't unmap it while it's on the send queue */
  			set_bit(RDS_MSG_MAPPED, &rm->m_flags);
  		}
  
  		if (rm->atomic.op_active && !conn->c_xmit_atomic_sent) {
  			rm->m_final_op = &rm->atomic;
  			ret = conn->c_trans->xmit_atomic(conn, &rm->atomic);
  			if (ret)
  				break;
  			conn->c_xmit_atomic_sent = 1;
  
  			/* The transport owns the mapped memory for now.
  			 * You can't unmap it while it's on the send queue */
  			set_bit(RDS_MSG_MAPPED, &rm->m_flags);
  		}
  
  		/*
  		 * A number of cases require an RDS header to be sent
  		 * even if there is no data.
  		 * We permit 0-byte sends; rds-ping depends on this.
  		 * However, if there are exclusively attached silent ops,
  		 * we skip the hdr/data send, to enable silent operation.
  		 */
  		if (rm->data.op_nents == 0) {
  			int ops_present;
  			int all_ops_are_silent = 1;
  
  			ops_present = (rm->atomic.op_active || rm->rdma.op_active);
  			if (rm->atomic.op_active && !rm->atomic.op_silent)
  				all_ops_are_silent = 0;
  			if (rm->rdma.op_active && !rm->rdma.op_silent)
  				all_ops_are_silent = 0;
  
  			if (ops_present && all_ops_are_silent
  			    && !rm->m_rdma_cookie)
  				rm->data.op_active = 0;
  		}
  
  		if (rm->data.op_active && !conn->c_xmit_data_sent) {
  			rm->m_final_op = &rm->data;
  			ret = conn->c_trans->xmit(conn, rm,
  						  conn->c_xmit_hdr_off,
  						  conn->c_xmit_sg,
  						  conn->c_xmit_data_off);
  			if (ret <= 0)
  				break;
  
  			if (conn->c_xmit_hdr_off < sizeof(struct rds_header)) {
  				tmp = min_t(int, ret,
  					    sizeof(struct rds_header) -
  					    conn->c_xmit_hdr_off);
  				conn->c_xmit_hdr_off += tmp;
  				ret -= tmp;
  			}
  
  			sg = &rm->data.op_sg[conn->c_xmit_sg];
  			while (ret) {
  				tmp = min_t(int, ret, sg->length -
  						      conn->c_xmit_data_off);
  				conn->c_xmit_data_off += tmp;
  				ret -= tmp;
  				if (conn->c_xmit_data_off == sg->length) {
  					conn->c_xmit_data_off = 0;
  					sg++;
  					conn->c_xmit_sg++;
  					BUG_ON(ret != 0 &&
  					       conn->c_xmit_sg == rm->data.op_nents);
  				}
  			}
  
  			if (conn->c_xmit_hdr_off == sizeof(struct rds_header) &&
  			    (conn->c_xmit_sg == rm->data.op_nents))
  				conn->c_xmit_data_sent = 1;
  		}
  
  		/*
  		 * A rm will only take multiple times through this loop
  		 * if there is a data op. Thus, if the data is sent (or there was
  		 * none), then we're done with the rm.
  		 */
  		if (!rm->data.op_active || conn->c_xmit_data_sent) {
  			conn->c_xmit_rm = NULL;
  			conn->c_xmit_sg = 0;
  			conn->c_xmit_hdr_off = 0;
  			conn->c_xmit_data_off = 0;
  			conn->c_xmit_rdma_sent = 0;
  			conn->c_xmit_atomic_sent = 0;
  			conn->c_xmit_data_sent = 0;
  
  			rds_message_put(rm);
  		}
  	}
  
  	if (conn->c_trans->xmit_complete)
  		conn->c_trans->xmit_complete(conn);
  
  	release_in_xmit(conn);
  
  	/* Nuke any messages we decided not to retransmit. */
  	if (!list_empty(&to_be_dropped)) {
  		/* irqs on here, so we can put(), unlike above */
  		list_for_each_entry(rm, &to_be_dropped, m_conn_item)
  			rds_message_put(rm);
  		rds_send_remove_from_sock(&to_be_dropped, RDS_RDMA_DROPPED);
  	}
  
  	/*
  	 * Other senders can queue a message after we last test the send queue
  	 * but before we clear RDS_IN_XMIT.  In that case they'd back off and
  	 * not try and send their newly queued message.  We need to check the
  	 * send queue after having cleared RDS_IN_XMIT so that their message
  	 * doesn't get stuck on the send queue.
  	 *
  	 * If the transport cannot continue (i.e ret != 0), then it must
  	 * call us when more room is available, such as from the tx
  	 * completion handler.
  	 */
  	if (ret == 0) {
  		smp_mb();
  		if (!list_empty(&conn->c_send_queue)) {
  			rds_stats_inc(s_send_lock_queue_raced);
  			goto restart;
  		}
  	}
  out:
  	return ret;
  }
  
  static void rds_send_sndbuf_remove(struct rds_sock *rs, struct rds_message *rm)
  {
  	u32 len = be32_to_cpu(rm->m_inc.i_hdr.h_len);
  
  	assert_spin_locked(&rs->rs_lock);
  
  	BUG_ON(rs->rs_snd_bytes < len);
  	rs->rs_snd_bytes -= len;
  
  	if (rs->rs_snd_bytes == 0)
  		rds_stats_inc(s_send_queue_empty);
  }
  
  static inline int rds_send_is_acked(struct rds_message *rm, u64 ack,
  				    is_acked_func is_acked)
  {
  	if (is_acked)
  		return is_acked(rm, ack);
  	return be64_to_cpu(rm->m_inc.i_hdr.h_sequence) <= ack;
  }
  
  /*
   * This is pretty similar to what happens below in the ACK
   * handling code - except that we call here as soon as we get
   * the IB send completion on the RDMA op and the accompanying
   * message.
   */
  void rds_rdma_send_complete(struct rds_message *rm, int status)
  {
  	struct rds_sock *rs = NULL;
  	struct rm_rdma_op *ro;
  	struct rds_notifier *notifier;
  	unsigned long flags;
  
  	spin_lock_irqsave(&rm->m_rs_lock, flags);
  
  	ro = &rm->rdma;
  	if (test_bit(RDS_MSG_ON_SOCK, &rm->m_flags) &&
  	    ro->op_active && ro->op_notify && ro->op_notifier) {
  		notifier = ro->op_notifier;
  		rs = rm->m_rs;
  		sock_hold(rds_rs_to_sk(rs));
  
  		notifier->n_status = status;
  		spin_lock(&rs->rs_lock);
  		list_add_tail(&notifier->n_list, &rs->rs_notify_queue);
  		spin_unlock(&rs->rs_lock);
  
  		ro->op_notifier = NULL;
  	}
  
  	spin_unlock_irqrestore(&rm->m_rs_lock, flags);
  
  	if (rs) {
  		rds_wake_sk_sleep(rs);
  		sock_put(rds_rs_to_sk(rs));
  	}
  }
  EXPORT_SYMBOL_GPL(rds_rdma_send_complete);
  
  /*
   * Just like above, except looks at atomic op
   */
  void rds_atomic_send_complete(struct rds_message *rm, int status)
  {
  	struct rds_sock *rs = NULL;
  	struct rm_atomic_op *ao;
  	struct rds_notifier *notifier;
  	unsigned long flags;
  
  	spin_lock_irqsave(&rm->m_rs_lock, flags);
  
  	ao = &rm->atomic;
  	if (test_bit(RDS_MSG_ON_SOCK, &rm->m_flags)
  	    && ao->op_active && ao->op_notify && ao->op_notifier) {
  		notifier = ao->op_notifier;
  		rs = rm->m_rs;
  		sock_hold(rds_rs_to_sk(rs));
  
  		notifier->n_status = status;
  		spin_lock(&rs->rs_lock);
  		list_add_tail(&notifier->n_list, &rs->rs_notify_queue);
  		spin_unlock(&rs->rs_lock);
  
  		ao->op_notifier = NULL;
  	}
  
  	spin_unlock_irqrestore(&rm->m_rs_lock, flags);
  
  	if (rs) {
  		rds_wake_sk_sleep(rs);
  		sock_put(rds_rs_to_sk(rs));
  	}
  }
  EXPORT_SYMBOL_GPL(rds_atomic_send_complete);
  
  /*
   * This is the same as rds_rdma_send_complete except we
   * don't do any locking - we have all the ingredients (message,
   * socket, socket lock) and can just move the notifier.
   */
  static inline void
  __rds_send_complete(struct rds_sock *rs, struct rds_message *rm, int status)
  {
  	struct rm_rdma_op *ro;
  	struct rm_atomic_op *ao;
  
  	ro = &rm->rdma;
  	if (ro->op_active && ro->op_notify && ro->op_notifier) {
  		ro->op_notifier->n_status = status;
  		list_add_tail(&ro->op_notifier->n_list, &rs->rs_notify_queue);
  		ro->op_notifier = NULL;
  	}
  
  	ao = &rm->atomic;
  	if (ao->op_active && ao->op_notify && ao->op_notifier) {
  		ao->op_notifier->n_status = status;
  		list_add_tail(&ao->op_notifier->n_list, &rs->rs_notify_queue);
  		ao->op_notifier = NULL;
  	}
  
  	/* No need to wake the app - caller does this */
  }
  
  /*
   * This is called from the IB send completion when we detect
   * a RDMA operation that failed with remote access error.
   * So speed is not an issue here.
   */
  struct rds_message *rds_send_get_message(struct rds_connection *conn,
  					 struct rm_rdma_op *op)
  {
  	struct rds_message *rm, *tmp, *found = NULL;
  	unsigned long flags;
  
  	spin_lock_irqsave(&conn->c_lock, flags);
  
  	list_for_each_entry_safe(rm, tmp, &conn->c_retrans, m_conn_item) {
  		if (&rm->rdma == op) {
  			atomic_inc(&rm->m_refcount);
  			found = rm;
  			goto out;
  		}
  	}
  
  	list_for_each_entry_safe(rm, tmp, &conn->c_send_queue, m_conn_item) {
  		if (&rm->rdma == op) {
  			atomic_inc(&rm->m_refcount);
  			found = rm;
  			break;
  		}
  	}
  
  out:
  	spin_unlock_irqrestore(&conn->c_lock, flags);
  
  	return found;
  }
  EXPORT_SYMBOL_GPL(rds_send_get_message);
  
  /*
   * This removes messages from the socket's list if they're on it.  The list
   * argument must be private to the caller, we must be able to modify it
   * without locks.  The messages must have a reference held for their
   * position on the list.  This function will drop that reference after
   * removing the messages from the 'messages' list regardless of if it found
   * the messages on the socket list or not.
   */
  static void rds_send_remove_from_sock(struct list_head *messages, int status)
  {
  	unsigned long flags;
  	struct rds_sock *rs = NULL;
  	struct rds_message *rm;
  
  	while (!list_empty(messages)) {
  		int was_on_sock = 0;
  
  		rm = list_entry(messages->next, struct rds_message,
  				m_conn_item);
  		list_del_init(&rm->m_conn_item);
  
  		/*
  		 * If we see this flag cleared then we're *sure* that someone
  		 * else beat us to removing it from the sock.  If we race
  		 * with their flag update we'll get the lock and then really
  		 * see that the flag has been cleared.
  		 *
  		 * The message spinlock makes sure nobody clears rm->m_rs
  		 * while we're messing with it. It does not prevent the
  		 * message from being removed from the socket, though.
  		 */
  		spin_lock_irqsave(&rm->m_rs_lock, flags);
  		if (!test_bit(RDS_MSG_ON_SOCK, &rm->m_flags))
  			goto unlock_and_drop;
  
  		if (rs != rm->m_rs) {
  			if (rs) {
  				rds_wake_sk_sleep(rs);
  				sock_put(rds_rs_to_sk(rs));
  			}
  			rs = rm->m_rs;
  			sock_hold(rds_rs_to_sk(rs));
  		}
  		spin_lock(&rs->rs_lock);
  
  		if (test_and_clear_bit(RDS_MSG_ON_SOCK, &rm->m_flags)) {
  			struct rm_rdma_op *ro = &rm->rdma;
  			struct rds_notifier *notifier;
  
  			list_del_init(&rm->m_sock_item);
  			rds_send_sndbuf_remove(rs, rm);
  
  			if (ro->op_active && ro->op_notifier &&
  			       (ro->op_notify || (ro->op_recverr && status))) {
  				notifier = ro->op_notifier;
  				list_add_tail(&notifier->n_list,
  						&rs->rs_notify_queue);
  				if (!notifier->n_status)
  					notifier->n_status = status;
  				rm->rdma.op_notifier = NULL;
  			}
  			was_on_sock = 1;
  			rm->m_rs = NULL;
  		}
  		spin_unlock(&rs->rs_lock);
  
  unlock_and_drop:
  		spin_unlock_irqrestore(&rm->m_rs_lock, flags);
  		rds_message_put(rm);
  		if (was_on_sock)
  			rds_message_put(rm);
  	}
  
  	if (rs) {
  		rds_wake_sk_sleep(rs);
  		sock_put(rds_rs_to_sk(rs));
  	}
  }
  
  /*
   * Transports call here when they've determined that the receiver queued
   * messages up to, and including, the given sequence number.  Messages are
   * moved to the retrans queue when rds_send_xmit picks them off the send
   * queue. This means that in the TCP case, the message may not have been
   * assigned the m_ack_seq yet - but that's fine as long as tcp_is_acked
   * checks the RDS_MSG_HAS_ACK_SEQ bit.
   *
   * XXX It's not clear to me how this is safely serialized with socket
   * destruction.  Maybe it should bail if it sees SOCK_DEAD.
   */
  void rds_send_drop_acked(struct rds_connection *conn, u64 ack,
  			 is_acked_func is_acked)
  {
  	struct rds_message *rm, *tmp;
  	unsigned long flags;
  	LIST_HEAD(list);
  
  	spin_lock_irqsave(&conn->c_lock, flags);
  
  	list_for_each_entry_safe(rm, tmp, &conn->c_retrans, m_conn_item) {
  		if (!rds_send_is_acked(rm, ack, is_acked))
  			break;
  
  		list_move(&rm->m_conn_item, &list);
  		clear_bit(RDS_MSG_ON_CONN, &rm->m_flags);
  	}
  
  	/* order flag updates with spin locks */
  	if (!list_empty(&list))
  		smp_mb__after_clear_bit();
  
  	spin_unlock_irqrestore(&conn->c_lock, flags);
  
  	/* now remove the messages from the sock list as needed */
  	rds_send_remove_from_sock(&list, RDS_RDMA_SUCCESS);
  }
  EXPORT_SYMBOL_GPL(rds_send_drop_acked);
  
  void rds_send_drop_to(struct rds_sock *rs, struct sockaddr_in *dest)
  {
  	struct rds_message *rm, *tmp;
  	struct rds_connection *conn;
  	unsigned long flags;
  	LIST_HEAD(list);
  
  	/* get all the messages we're dropping under the rs lock */
  	spin_lock_irqsave(&rs->rs_lock, flags);
  
  	list_for_each_entry_safe(rm, tmp, &rs->rs_send_queue, m_sock_item) {
  		if (dest && (dest->sin_addr.s_addr != rm->m_daddr ||
  			     dest->sin_port != rm->m_inc.i_hdr.h_dport))
  			continue;
  
  		list_move(&rm->m_sock_item, &list);
  		rds_send_sndbuf_remove(rs, rm);
  		clear_bit(RDS_MSG_ON_SOCK, &rm->m_flags);
  	}
  
  	/* order flag updates with the rs lock */
  	smp_mb__after_clear_bit();
  
  	spin_unlock_irqrestore(&rs->rs_lock, flags);
  
  	if (list_empty(&list))
  		return;
  
  	/* Remove the messages from the conn */
  	list_for_each_entry(rm, &list, m_sock_item) {
  
  		conn = rm->m_inc.i_conn;
  
  		spin_lock_irqsave(&conn->c_lock, flags);
  		/*
  		 * Maybe someone else beat us to removing rm from the conn.
  		 * If we race with their flag update we'll get the lock and
  		 * then really see that the flag has been cleared.
  		 */
  		if (!test_and_clear_bit(RDS_MSG_ON_CONN, &rm->m_flags)) {
  			spin_unlock_irqrestore(&conn->c_lock, flags);
  			continue;
  		}
  		list_del_init(&rm->m_conn_item);
  		spin_unlock_irqrestore(&conn->c_lock, flags);
  
  		/*
  		 * Couldn't grab m_rs_lock in top loop (lock ordering),
  		 * but we can now.
  		 */
  		spin_lock_irqsave(&rm->m_rs_lock, flags);
  
  		spin_lock(&rs->rs_lock);
  		__rds_send_complete(rs, rm, RDS_RDMA_CANCELED);
  		spin_unlock(&rs->rs_lock);
  
  		rm->m_rs = NULL;
  		spin_unlock_irqrestore(&rm->m_rs_lock, flags);
  
  		rds_message_put(rm);
  	}
  
  	rds_wake_sk_sleep(rs);
  
  	while (!list_empty(&list)) {
  		rm = list_entry(list.next, struct rds_message, m_sock_item);
  		list_del_init(&rm->m_sock_item);
  
  		rds_message_wait(rm);
  		rds_message_put(rm);
  	}
  }
  
  /*
   * we only want this to fire once so we use the callers 'queued'.  It's
   * possible that another thread can race with us and remove the
   * message from the flow with RDS_CANCEL_SENT_TO.
   */
  static int rds_send_queue_rm(struct rds_sock *rs, struct rds_connection *conn,
  			     struct rds_message *rm, __be16 sport,
  			     __be16 dport, int *queued)
  {
  	unsigned long flags;
  	u32 len;
  
  	if (*queued)
  		goto out;
  
  	len = be32_to_cpu(rm->m_inc.i_hdr.h_len);
  
  	/* this is the only place which holds both the socket's rs_lock
  	 * and the connection's c_lock */
  	spin_lock_irqsave(&rs->rs_lock, flags);
  
  	/*
  	 * If there is a little space in sndbuf, we don't queue anything,
  	 * and userspace gets -EAGAIN. But poll() indicates there's send
  	 * room. This can lead to bad behavior (spinning) if snd_bytes isn't
  	 * freed up by incoming acks. So we check the *old* value of
  	 * rs_snd_bytes here to allow the last msg to exceed the buffer,
  	 * and poll() now knows no more data can be sent.
  	 */
  	if (rs->rs_snd_bytes < rds_sk_sndbuf(rs)) {
  		rs->rs_snd_bytes += len;
  
  		/* let recv side know we are close to send space exhaustion.
  		 * This is probably not the optimal way to do it, as this
  		 * means we set the flag on *all* messages as soon as our
  		 * throughput hits a certain threshold.
  		 */
  		if (rs->rs_snd_bytes >= rds_sk_sndbuf(rs) / 2)
  			__set_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags);
  
  		list_add_tail(&rm->m_sock_item, &rs->rs_send_queue);
  		set_bit(RDS_MSG_ON_SOCK, &rm->m_flags);
  		rds_message_addref(rm);
  		rm->m_rs = rs;
  
  		/* The code ordering is a little weird, but we're
  		   trying to minimize the time we hold c_lock */
  		rds_message_populate_header(&rm->m_inc.i_hdr, sport, dport, 0);
  		rm->m_inc.i_conn = conn;
  		rds_message_addref(rm);
  
  		spin_lock(&conn->c_lock);
  		rm->m_inc.i_hdr.h_sequence = cpu_to_be64(conn->c_next_tx_seq++);
  		list_add_tail(&rm->m_conn_item, &conn->c_send_queue);
  		set_bit(RDS_MSG_ON_CONN, &rm->m_flags);
  		spin_unlock(&conn->c_lock);
  
  		rdsdebug("queued msg %p len %d, rs %p bytes %d seq %llu\n",
  			 rm, len, rs, rs->rs_snd_bytes,
  			 (unsigned long long)be64_to_cpu(rm->m_inc.i_hdr.h_sequence));
  
  		*queued = 1;
  	}
  
  	spin_unlock_irqrestore(&rs->rs_lock, flags);
  out:
  	return *queued;
  }
  
  /*
   * rds_message is getting to be quite complicated, and we'd like to allocate
   * it all in one go. This figures out how big it needs to be up front.
   */
  static int rds_rm_size(struct msghdr *msg, int data_len)
  {
  	struct cmsghdr *cmsg;
  	int size = 0;
  	int cmsg_groups = 0;
  	int retval;
  
  	for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) {
  		if (!CMSG_OK(msg, cmsg))
  			return -EINVAL;
  
  		if (cmsg->cmsg_level != SOL_RDS)
  			continue;
  
  		switch (cmsg->cmsg_type) {
  		case RDS_CMSG_RDMA_ARGS:
  			cmsg_groups |= 1;
  			retval = rds_rdma_extra_size(CMSG_DATA(cmsg));
  			if (retval < 0)
  				return retval;
  			size += retval;
  
  			break;
  
  		case RDS_CMSG_RDMA_DEST:
  		case RDS_CMSG_RDMA_MAP:
  			cmsg_groups |= 2;
  			/* these are valid but do no add any size */
  			break;
  
  		case RDS_CMSG_ATOMIC_CSWP:
  		case RDS_CMSG_ATOMIC_FADD:
  		case RDS_CMSG_MASKED_ATOMIC_CSWP:
  		case RDS_CMSG_MASKED_ATOMIC_FADD:
  			cmsg_groups |= 1;
  			size += sizeof(struct scatterlist);
  			break;
  
  		default:
  			return -EINVAL;
  		}
  
  	}
  
  	size += ceil(data_len, PAGE_SIZE) * sizeof(struct scatterlist);
  
  	/* Ensure (DEST, MAP) are never used with (ARGS, ATOMIC) */
  	if (cmsg_groups == 3)
  		return -EINVAL;
  
  	return size;
  }
  
  static int rds_cmsg_send(struct rds_sock *rs, struct rds_message *rm,
  			 struct msghdr *msg, int *allocated_mr)
  {
  	struct cmsghdr *cmsg;
  	int ret = 0;
  
  	for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) {
  		if (!CMSG_OK(msg, cmsg))
  			return -EINVAL;
  
  		if (cmsg->cmsg_level != SOL_RDS)
  			continue;
  
  		/* As a side effect, RDMA_DEST and RDMA_MAP will set
  		 * rm->rdma.m_rdma_cookie and rm->rdma.m_rdma_mr.
  		 */
  		switch (cmsg->cmsg_type) {
  		case RDS_CMSG_RDMA_ARGS:
  			ret = rds_cmsg_rdma_args(rs, rm, cmsg);
  			break;
  
  		case RDS_CMSG_RDMA_DEST:
  			ret = rds_cmsg_rdma_dest(rs, rm, cmsg);
  			break;
  
  		case RDS_CMSG_RDMA_MAP:
  			ret = rds_cmsg_rdma_map(rs, rm, cmsg);
  			if (!ret)
  				*allocated_mr = 1;
  			break;
  		case RDS_CMSG_ATOMIC_CSWP:
  		case RDS_CMSG_ATOMIC_FADD:
  		case RDS_CMSG_MASKED_ATOMIC_CSWP:
  		case RDS_CMSG_MASKED_ATOMIC_FADD:
  			ret = rds_cmsg_atomic(rs, rm, cmsg);
  			break;
  
  		default:
  			return -EINVAL;
  		}
  
  		if (ret)
  			break;
  	}
  
  	return ret;
  }
  
  int rds_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
  		size_t payload_len)
  {
  	struct sock *sk = sock->sk;
  	struct rds_sock *rs = rds_sk_to_rs(sk);
  	DECLARE_SOCKADDR(struct sockaddr_in *, usin, msg->msg_name);
  	__be32 daddr;
  	__be16 dport;
  	struct rds_message *rm = NULL;
  	struct rds_connection *conn;
  	int ret = 0;
  	int queued = 0, allocated_mr = 0;
  	int nonblock = msg->msg_flags & MSG_DONTWAIT;
  	long timeo = sock_sndtimeo(sk, nonblock);
  
  	/* Mirror Linux UDP mirror of BSD error message compatibility */
  	/* XXX: Perhaps MSG_MORE someday */
  	if (msg->msg_flags & ~(MSG_DONTWAIT | MSG_CMSG_COMPAT)) {
  		ret = -EOPNOTSUPP;
  		goto out;
  	}
  
  	if (msg->msg_namelen) {
  		/* XXX fail non-unicast destination IPs? */
  		if (msg->msg_namelen < sizeof(*usin) || usin->sin_family != AF_INET) {
  			ret = -EINVAL;
  			goto out;
  		}
  		daddr = usin->sin_addr.s_addr;
  		dport = usin->sin_port;
  	} else {
  		/* We only care about consistency with ->connect() */
  		lock_sock(sk);
  		daddr = rs->rs_conn_addr;
  		dport = rs->rs_conn_port;
  		release_sock(sk);
  	}
  
  	/* racing with another thread binding seems ok here */
  	if (daddr == 0 || rs->rs_bound_addr == 0) {
  		ret = -ENOTCONN; /* XXX not a great errno */
  		goto out;
  	}
  
  	/* size of rm including all sgs */
  	ret = rds_rm_size(msg, payload_len);
  	if (ret < 0)
  		goto out;
  
  	rm = rds_message_alloc(ret, GFP_KERNEL);
  	if (!rm) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	/* Attach data to the rm */
  	if (payload_len) {
  		rm->data.op_sg = rds_message_alloc_sgs(rm, ceil(payload_len, PAGE_SIZE));
  		if (!rm->data.op_sg) {
  			ret = -ENOMEM;
  			goto out;
  		}
  		ret = rds_message_copy_from_user(rm, msg->msg_iov, payload_len);
  		if (ret)
  			goto out;
  	}
  	rm->data.op_active = 1;
  
  	rm->m_daddr = daddr;
  
  	/* rds_conn_create has a spinlock that runs with IRQ off.
  	 * Caching the conn in the socket helps a lot. */
  	if (rs->rs_conn && rs->rs_conn->c_faddr == daddr)
  		conn = rs->rs_conn;
  	else {
  		conn = rds_conn_create_outgoing(rs->rs_bound_addr, daddr,
  					rs->rs_transport,
  					sock->sk->sk_allocation);
  		if (IS_ERR(conn)) {
  			ret = PTR_ERR(conn);
  			goto out;
  		}
  		rs->rs_conn = conn;
  	}
  
  	/* Parse any control messages the user may have included. */
  	ret = rds_cmsg_send(rs, rm, msg, &allocated_mr);
  	if (ret)
  		goto out;
  
  	if (rm->rdma.op_active && !conn->c_trans->xmit_rdma) {
  		printk_ratelimited(KERN_NOTICE "rdma_op %p conn xmit_rdma %p\n",
  			       &rm->rdma, conn->c_trans->xmit_rdma);
  		ret = -EOPNOTSUPP;
  		goto out;
  	}
  
  	if (rm->atomic.op_active && !conn->c_trans->xmit_atomic) {
  		printk_ratelimited(KERN_NOTICE "atomic_op %p conn xmit_atomic %p\n",
  			       &rm->atomic, conn->c_trans->xmit_atomic);
  		ret = -EOPNOTSUPP;
  		goto out;
  	}
  
  	rds_conn_connect_if_down(conn);
  
  	ret = rds_cong_wait(conn->c_fcong, dport, nonblock, rs);
  	if (ret) {
  		rs->rs_seen_congestion = 1;
  		goto out;
  	}
  
  	while (!rds_send_queue_rm(rs, conn, rm, rs->rs_bound_port,
  				  dport, &queued)) {
  		rds_stats_inc(s_send_queue_full);
  		/* XXX make sure this is reasonable */
  		if (payload_len > rds_sk_sndbuf(rs)) {
  			ret = -EMSGSIZE;
  			goto out;
  		}
  		if (nonblock) {
  			ret = -EAGAIN;
  			goto out;
  		}
  
  		timeo = wait_event_interruptible_timeout(*sk_sleep(sk),
  					rds_send_queue_rm(rs, conn, rm,
  							  rs->rs_bound_port,
  							  dport,
  							  &queued),
  					timeo);
  		rdsdebug("sendmsg woke queued %d timeo %ld\n", queued, timeo);
  		if (timeo > 0 || timeo == MAX_SCHEDULE_TIMEOUT)
  			continue;
  
  		ret = timeo;
  		if (ret == 0)
  			ret = -ETIMEDOUT;
  		goto out;
  	}
  
  	/*
  	 * By now we've committed to the send.  We reuse rds_send_worker()
  	 * to retry sends in the rds thread if the transport asks us to.
  	 */
  	rds_stats_inc(s_send_queued);
  
  	if (!test_bit(RDS_LL_SEND_FULL, &conn->c_flags))
  		rds_send_xmit(conn);
  
  	rds_message_put(rm);
  	return payload_len;
  
  out:
  	/* If the user included a RDMA_MAP cmsg, we allocated a MR on the fly.
  	 * If the sendmsg goes through, we keep the MR. If it fails with EAGAIN
  	 * or in any other way, we need to destroy the MR again */
  	if (allocated_mr)
  		rds_rdma_unuse(rs, rds_rdma_cookie_key(rm->m_rdma_cookie), 1);
  
  	if (rm)
  		rds_message_put(rm);
  	return ret;
  }
  
  /*
   * Reply to a ping packet.
   */
  int
  rds_send_pong(struct rds_connection *conn, __be16 dport)
  {
  	struct rds_message *rm;
  	unsigned long flags;
  	int ret = 0;
  
  	rm = rds_message_alloc(0, GFP_ATOMIC);
  	if (!rm) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	rm->m_daddr = conn->c_faddr;
  	rm->data.op_active = 1;
  
  	rds_conn_connect_if_down(conn);
  
  	ret = rds_cong_wait(conn->c_fcong, dport, 1, NULL);
  	if (ret)
  		goto out;
  
  	spin_lock_irqsave(&conn->c_lock, flags);
  	list_add_tail(&rm->m_conn_item, &conn->c_send_queue);
  	set_bit(RDS_MSG_ON_CONN, &rm->m_flags);
  	rds_message_addref(rm);
  	rm->m_inc.i_conn = conn;
  
  	rds_message_populate_header(&rm->m_inc.i_hdr, 0, dport,
  				    conn->c_next_tx_seq);
  	conn->c_next_tx_seq++;
  	spin_unlock_irqrestore(&conn->c_lock, flags);
  
  	rds_stats_inc(s_send_queued);
  	rds_stats_inc(s_send_pong);
  
  	if (!test_bit(RDS_LL_SEND_FULL, &conn->c_flags))
  		queue_delayed_work(rds_wq, &conn->c_send_w, 0);
  
  	rds_message_put(rm);
  	return 0;
  
  out:
  	if (rm)
  		rds_message_put(rm);
  	return ret;
  }
  