linux/net/rds/tcp_send.c
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   1/*
   2 * Copyright (c) 2006 Oracle.  All rights reserved.
   3 *
   4 * This software is available to you under a choice of one of two
   5 * licenses.  You may choose to be licensed under the terms of the GNU
   6 * General Public License (GPL) Version 2, available from the file
   7 * COPYING in the main directory of this source tree, or the
   8 * OpenIB.org BSD license below:
   9 *
  10 *     Redistribution and use in source and binary forms, with or
  11 *     without modification, are permitted provided that the following
  12 *     conditions are met:
  13 *
  14 *      - Redistributions of source code must retain the above
  15 *        copyright notice, this list of conditions and the following
  16 *        disclaimer.
  17 *
  18 *      - Redistributions in binary form must reproduce the above
  19 *        copyright notice, this list of conditions and the following
  20 *        disclaimer in the documentation and/or other materials
  21 *        provided with the distribution.
  22 *
  23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  27 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  28 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  29 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  30 * SOFTWARE.
  31 *
  32 */
  33#include <linux/kernel.h>
  34#include <linux/in.h>
  35#include <net/tcp.h>
  36
  37#include "rds.h"
  38#include "tcp.h"
  39
  40static void rds_tcp_cork(struct socket *sock, int val)
  41{
  42        mm_segment_t oldfs;
  43
  44        oldfs = get_fs();
  45        set_fs(KERNEL_DS);
  46        sock->ops->setsockopt(sock, SOL_TCP, TCP_CORK, (char __user *)&val,
  47                              sizeof(val));
  48        set_fs(oldfs);
  49}
  50
  51void rds_tcp_xmit_prepare(struct rds_connection *conn)
  52{
  53        struct rds_tcp_connection *tc = conn->c_transport_data;
  54
  55        rds_tcp_cork(tc->t_sock, 1);
  56}
  57
  58void rds_tcp_xmit_complete(struct rds_connection *conn)
  59{
  60        struct rds_tcp_connection *tc = conn->c_transport_data;
  61
  62        rds_tcp_cork(tc->t_sock, 0);
  63}
  64
  65/* the core send_sem serializes this with other xmit and shutdown */
  66static int rds_tcp_sendmsg(struct socket *sock, void *data, unsigned int len)
  67{
  68        struct kvec vec = {
  69                .iov_base = data,
  70                .iov_len = len,
  71        };
  72        struct msghdr msg = {
  73                .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL,
  74        };
  75
  76        return kernel_sendmsg(sock, &msg, &vec, 1, vec.iov_len);
  77}
  78
  79/* the core send_sem serializes this with other xmit and shutdown */
  80int rds_tcp_xmit(struct rds_connection *conn, struct rds_message *rm,
  81                 unsigned int hdr_off, unsigned int sg, unsigned int off)
  82{
  83        struct rds_tcp_connection *tc = conn->c_transport_data;
  84        int done = 0;
  85        int ret = 0;
  86
  87        if (hdr_off == 0) {
  88                /*
  89                 * m_ack_seq is set to the sequence number of the last byte of
  90                 * header and data.  see rds_tcp_is_acked().
  91                 */
  92                tc->t_last_sent_nxt = rds_tcp_snd_nxt(tc);
  93                rm->m_ack_seq = tc->t_last_sent_nxt +
  94                                sizeof(struct rds_header) +
  95                                be32_to_cpu(rm->m_inc.i_hdr.h_len) - 1;
  96                smp_mb__before_clear_bit();
  97                set_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags);
  98                tc->t_last_expected_una = rm->m_ack_seq + 1;
  99
 100                rdsdebug("rm %p tcp nxt %u ack_seq %llu\n",
 101                         rm, rds_tcp_snd_nxt(tc),
 102                         (unsigned long long)rm->m_ack_seq);
 103        }
 104
 105        if (hdr_off < sizeof(struct rds_header)) {
 106                /* see rds_tcp_write_space() */
 107                set_bit(SOCK_NOSPACE, &tc->t_sock->sk->sk_socket->flags);
 108
 109                ret = rds_tcp_sendmsg(tc->t_sock,
 110                                      (void *)&rm->m_inc.i_hdr + hdr_off,
 111                                      sizeof(rm->m_inc.i_hdr) - hdr_off);
 112                if (ret < 0)
 113                        goto out;
 114                done += ret;
 115                if (hdr_off + done != sizeof(struct rds_header))
 116                        goto out;
 117        }
 118
 119        while (sg < rm->data.op_nents) {
 120                ret = tc->t_sock->ops->sendpage(tc->t_sock,
 121                                                sg_page(&rm->data.op_sg[sg]),
 122                                                rm->data.op_sg[sg].offset + off,
 123                                                rm->data.op_sg[sg].length - off,
 124                                                MSG_DONTWAIT|MSG_NOSIGNAL);
 125                rdsdebug("tcp sendpage %p:%u:%u ret %d\n", (void *)sg_page(&rm->data.op_sg[sg]),
 126                         rm->data.op_sg[sg].offset + off, rm->data.op_sg[sg].length - off,
 127                         ret);
 128                if (ret <= 0)
 129                        break;
 130
 131                off += ret;
 132                done += ret;
 133                if (off == rm->data.op_sg[sg].length) {
 134                        off = 0;
 135                        sg++;
 136                }
 137        }
 138
 139out:
 140        if (ret <= 0) {
 141                /* write_space will hit after EAGAIN, all else fatal */
 142                if (ret == -EAGAIN) {
 143                        rds_tcp_stats_inc(s_tcp_sndbuf_full);
 144                        ret = 0;
 145                } else {
 146                        printk(KERN_WARNING "RDS/tcp: send to %pI4 "
 147                               "returned %d, disconnecting and reconnecting\n",
 148                               &conn->c_faddr, ret);
 149                        rds_conn_drop(conn);
 150                }
 151        }
 152        if (done == 0)
 153                done = ret;
 154        return done;
 155}
 156
 157/*
 158 * rm->m_ack_seq is set to the tcp sequence number that corresponds to the
 159 * last byte of the message, including the header.  This means that the
 160 * entire message has been received if rm->m_ack_seq is "before" the next
 161 * unacked byte of the TCP sequence space.  We have to do very careful
 162 * wrapping 32bit comparisons here.
 163 */
 164static int rds_tcp_is_acked(struct rds_message *rm, uint64_t ack)
 165{
 166        if (!test_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags))
 167                return 0;
 168        return (__s32)((u32)rm->m_ack_seq - (u32)ack) < 0;
 169}
 170
 171void rds_tcp_write_space(struct sock *sk)
 172{
 173        void (*write_space)(struct sock *sk);
 174        struct rds_connection *conn;
 175        struct rds_tcp_connection *tc;
 176
 177        read_lock_bh(&sk->sk_callback_lock);
 178        conn = sk->sk_user_data;
 179        if (!conn) {
 180                write_space = sk->sk_write_space;
 181                goto out;
 182        }
 183
 184        tc = conn->c_transport_data;
 185        rdsdebug("write_space for tc %p\n", tc);
 186        write_space = tc->t_orig_write_space;
 187        rds_tcp_stats_inc(s_tcp_write_space_calls);
 188
 189        rdsdebug("tcp una %u\n", rds_tcp_snd_una(tc));
 190        tc->t_last_seen_una = rds_tcp_snd_una(tc);
 191        rds_send_drop_acked(conn, rds_tcp_snd_una(tc), rds_tcp_is_acked);
 192
 193        if ((atomic_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf)
 194                queue_delayed_work(rds_wq, &conn->c_send_w, 0);
 195
 196out:
 197        read_unlock_bh(&sk->sk_callback_lock);
 198
 199        /*
 200         * write_space is only called when data leaves tcp's send queue if
 201         * SOCK_NOSPACE is set.  We set SOCK_NOSPACE every time we put
 202         * data in tcp's send queue because we use write_space to parse the
 203         * sequence numbers and notice that rds messages have been fully
 204         * received.
 205         *
 206         * tcp's write_space clears SOCK_NOSPACE if the send queue has more
 207         * than a certain amount of space. So we need to set it again *after*
 208         * we call tcp's write_space or else we might only get called on the
 209         * first of a series of incoming tcp acks.
 210         */
 211        write_space(sk);
 212
 213        if (sk->sk_socket)
 214                set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 215}
 216
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