1. 根目录:
2. net
3. rds
4. tcp_send.c

/*
 * Copyright (c) 2006 Oracle.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <linux/kernel.h>
#include <linux/in.h>
#include <net/tcp.h>

#include "rds.h"
#include "tcp.h"

static void rds_tcp_cork(struct socket *sock, int val)
{
	mm_segment_t oldfs;

	oldfs = get_fs();
	set_fs(KERNEL_DS);
	sock->ops->setsockopt(sock, SOL_TCP, TCP_CORK, (char __user *)&val,
			      sizeof(val));
	set_fs(oldfs);
}

void rds_tcp_xmit_prepare(struct rds_connection *conn)
{
	struct rds_tcp_connection *tc = conn->c_transport_data;

	rds_tcp_cork(tc->t_sock, 1);
}

void rds_tcp_xmit_complete(struct rds_connection *conn)
{
	struct rds_tcp_connection *tc = conn->c_transport_data;

	rds_tcp_cork(tc->t_sock, 0);
}

/* the core send_sem serializes this with other xmit and shutdown */
static int rds_tcp_sendmsg(struct socket *sock, void *data, unsigned int len)
{
	struct kvec vec = {
                .iov_base = data,
                .iov_len = len,
	};
        struct msghdr msg = {
                .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL,
        };

	return kernel_sendmsg(sock, &msg, &vec, 1, vec.iov_len);
}

/* the core send_sem serializes this with other xmit and shutdown */
int rds_tcp_xmit(struct rds_connection *conn, struct rds_message *rm,
	         unsigned int hdr_off, unsigned int sg, unsigned int off)
{
	struct rds_tcp_connection *tc = conn->c_transport_data;
	int done = 0;
	int ret = 0;
	int more;

	if (hdr_off == 0) {
		/*
		 * m_ack_seq is set to the sequence number of the last byte of
		 * header and data.  see rds_tcp_is_acked().
		 */
		tc->t_last_sent_nxt = rds_tcp_snd_nxt(tc);
		rm->m_ack_seq = tc->t_last_sent_nxt +
				sizeof(struct rds_header) +
				be32_to_cpu(rm->m_inc.i_hdr.h_len) - 1;
		smp_mb__before_atomic();
		set_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags);
		tc->t_last_expected_una = rm->m_ack_seq + 1;

		rdsdebug("rm %p tcp nxt %u ack_seq %llu\n",
			 rm, rds_tcp_snd_nxt(tc),
			 (unsigned long long)rm->m_ack_seq);
	}

	if (hdr_off < sizeof(struct rds_header)) {
		/* see rds_tcp_write_space() */
		set_bit(SOCK_NOSPACE, &tc->t_sock->sk->sk_socket->flags);

		ret = rds_tcp_sendmsg(tc->t_sock,
				      (void *)&rm->m_inc.i_hdr + hdr_off,
				      sizeof(rm->m_inc.i_hdr) - hdr_off);
		if (ret < 0)
			goto out;
		done += ret;
		if (hdr_off + done != sizeof(struct rds_header))
			goto out;
	}

	more = rm->data.op_nents > 1 ? (MSG_MORE | MSG_SENDPAGE_NOTLAST) : 0;
	while (sg < rm->data.op_nents) {
		int flags = MSG_DONTWAIT | MSG_NOSIGNAL | more;

		ret = tc->t_sock->ops->sendpage(tc->t_sock,
						sg_page(&rm->data.op_sg[sg]),
						rm->data.op_sg[sg].offset + off,
						rm->data.op_sg[sg].length - off,
						flags);
		rdsdebug("tcp sendpage %p:%u:%u ret %d\n", (void *)sg_page(&rm->data.op_sg[sg]),
			 rm->data.op_sg[sg].offset + off, rm->data.op_sg[sg].length - off,
			 ret);
		if (ret <= 0)
			break;

		off += ret;
		done += ret;
		if (off == rm->data.op_sg[sg].length) {
			off = 0;
			sg++;
		}
		if (sg == rm->data.op_nents - 1)
			more = 0;
	}

out:
	if (ret <= 0) {
		/* write_space will hit after EAGAIN, all else fatal */
		if (ret == -EAGAIN) {
			rds_tcp_stats_inc(s_tcp_sndbuf_full);
			ret = 0;
		} else {
			printk(KERN_WARNING "RDS/tcp: send to %pI4 "
			       "returned %d, disconnecting and reconnecting\n",
			       &conn->c_faddr, ret);
			rds_conn_drop(conn);
		}
	}
	if (done == 0)
		done = ret;
	return done;
}

/*
 * rm->m_ack_seq is set to the tcp sequence number that corresponds to the
 * last byte of the message, including the header.  This means that the
 * entire message has been received if rm->m_ack_seq is "before" the next
 * unacked byte of the TCP sequence space.  We have to do very careful
 * wrapping 32bit comparisons here.
 */
static int rds_tcp_is_acked(struct rds_message *rm, uint64_t ack)
{
	if (!test_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags))
		return 0;
	return (__s32)((u32)rm->m_ack_seq - (u32)ack) < 0;
}

void rds_tcp_write_space(struct sock *sk)
{
	void (*write_space)(struct sock *sk);
	struct rds_connection *conn;
	struct rds_tcp_connection *tc;

	read_lock(&sk->sk_callback_lock);
	conn = sk->sk_user_data;
	if (!conn) {
		write_space = sk->sk_write_space;
		goto out;
	}

	tc = conn->c_transport_data;
	rdsdebug("write_space for tc %p\n", tc);
	write_space = tc->t_orig_write_space;
	rds_tcp_stats_inc(s_tcp_write_space_calls);

	rdsdebug("tcp una %u\n", rds_tcp_snd_una(tc));
	tc->t_last_seen_una = rds_tcp_snd_una(tc);
	rds_send_drop_acked(conn, rds_tcp_snd_una(tc), rds_tcp_is_acked);

        if ((atomic_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf)
		queue_delayed_work(rds_wq, &conn->c_send_w, 0);

out:
	read_unlock(&sk->sk_callback_lock);

	/*
	 * write_space is only called when data leaves tcp's send queue if
	 * SOCK_NOSPACE is set.  We set SOCK_NOSPACE every time we put
	 * data in tcp's send queue because we use write_space to parse the
	 * sequence numbers and notice that rds messages have been fully
	 * received.
	 *
	 * tcp's write_space clears SOCK_NOSPACE if the send queue has more
	 * than a certain amount of space. So we need to set it again *after*
	 * we call tcp's write_space or else we might only get called on the
	 * first of a series of incoming tcp acks.
	 */
	write_space(sk);

	if (sk->sk_socket)
		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
}