LXR linux/net/rds/tcp

   1/*
   2 * Copyright (c) 2006, 2017 Oracle and/or its affiliates. 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_single_path.h"
  38#include "rds.h"
  39#include "tcp.h"
  40
  41void rds_tcp_xmit_path_prepare(struct rds_conn_path *cp)
  42{
  43        struct rds_tcp_connection *tc = cp->cp_transport_data;
  44
  45        tcp_sock_set_cork(tc->t_sock->sk, true);
  46}
  47
  48void rds_tcp_xmit_path_complete(struct rds_conn_path *cp)
  49{
  50        struct rds_tcp_connection *tc = cp->cp_transport_data;
  51
  52        tcp_sock_set_cork(tc->t_sock->sk, false);
  53}
  54
  55/* the core send_sem serializes this with other xmit and shutdown */
  56static int rds_tcp_sendmsg(struct socket *sock, void *data, unsigned int len)
  57{
  58        struct kvec vec = {
  59                .iov_base = data,
  60                .iov_len = len,
  61        };
  62        struct msghdr msg = {
  63                .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL,
  64        };
  65
  66        return kernel_sendmsg(sock, &msg, &vec, 1, vec.iov_len);
  67}
  68
  69/* the core send_sem serializes this with other xmit and shutdown */
  70int rds_tcp_xmit(struct rds_connection *conn, struct rds_message *rm,
  71                 unsigned int hdr_off, unsigned int sg, unsigned int off)
  72{
  73        struct rds_conn_path *cp = rm->m_inc.i_conn_path;
  74        struct rds_tcp_connection *tc = cp->cp_transport_data;
  75        int done = 0;
  76        int ret = 0;
  77        int more;
  78
  79        if (hdr_off == 0) {
  80                /*
  81                 * m_ack_seq is set to the sequence number of the last byte of
  82                 * header and data.  see rds_tcp_is_acked().
  83                 */
  84                tc->t_last_sent_nxt = rds_tcp_write_seq(tc);
  85                rm->m_ack_seq = tc->t_last_sent_nxt +
  86                                sizeof(struct rds_header) +
  87                                be32_to_cpu(rm->m_inc.i_hdr.h_len) - 1;
  88                smp_mb__before_atomic();
  89                set_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags);
  90                tc->t_last_expected_una = rm->m_ack_seq + 1;
  91
  92                if (test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))
  93                        rm->m_inc.i_hdr.h_flags |= RDS_FLAG_RETRANSMITTED;
  94
  95                rdsdebug("rm %p tcp nxt %u ack_seq %llu\n",
  96                         rm, rds_tcp_write_seq(tc),
  97                         (unsigned long long)rm->m_ack_seq);
  98        }
  99
 100        if (hdr_off < sizeof(struct rds_header)) {
 101                /* see rds_tcp_write_space() */
 102                set_bit(SOCK_NOSPACE, &tc->t_sock->sk->sk_socket->flags);
 103
 104                ret = rds_tcp_sendmsg(tc->t_sock,
 105                                      (void *)&rm->m_inc.i_hdr + hdr_off,
 106                                      sizeof(rm->m_inc.i_hdr) - hdr_off);
 107                if (ret < 0)
 108                        goto out;
 109                done += ret;
 110                if (hdr_off + done != sizeof(struct rds_header))
 111                        goto out;
 112        }
 113
 114        more = rm->data.op_nents > 1 ? (MSG_MORE | MSG_SENDPAGE_NOTLAST) : 0;
 115        while (sg < rm->data.op_nents) {
 116                int flags = MSG_DONTWAIT | MSG_NOSIGNAL | more;
 117
 118                ret = tc->t_sock->ops->sendpage(tc->t_sock,
 119                                                sg_page(&rm->data.op_sg[sg]),
 120                                                rm->data.op_sg[sg].offset + off,
 121                                                rm->data.op_sg[sg].length - off,
 122                                                flags);
 123                rdsdebug("tcp sendpage %p:%u:%u ret %d\n", (void *)sg_page(&rm->data.op_sg[sg]),
 124                         rm->data.op_sg[sg].offset + off, rm->data.op_sg[sg].length - off,
 125                         ret);
 126                if (ret <= 0)
 127                        break;
 128
 129                off += ret;
 130                done += ret;
 131                if (off == rm->data.op_sg[sg].length) {
 132                        off = 0;
 133                        sg++;
 134                }
 135                if (sg == rm->data.op_nents - 1)
 136                        more = 0;
 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                        /* No need to disconnect/reconnect if path_drop
 147                         * has already been triggered, because, e.g., of
 148                         * an incoming RST.
 149                         */
 150                        if (rds_conn_path_up(cp)) {
 151                                pr_warn("RDS/tcp: send to %pI6c on cp [%d]"
 152                                        "returned %d, "
 153                                        "disconnecting and reconnecting\n",
 154                                        &conn->c_faddr, cp->cp_index, ret);
 155                                rds_conn_path_drop(cp, false);
 156                        }
 157                }
 158        }
 159        if (done == 0)
 160                done = ret;
 161        return done;
 162}
 163
 164/*
 165 * rm->m_ack_seq is set to the tcp sequence number that corresponds to the
 166 * last byte of the message, including the header.  This means that the
 167 * entire message has been received if rm->m_ack_seq is "before" the next
 168 * unacked byte of the TCP sequence space.  We have to do very careful
 169 * wrapping 32bit comparisons here.
 170 */
 171static int rds_tcp_is_acked(struct rds_message *rm, uint64_t ack)
 172{
 173        if (!test_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags))
 174                return 0;
 175        return (__s32)((u32)rm->m_ack_seq - (u32)ack) < 0;
 176}
 177
 178void rds_tcp_write_space(struct sock *sk)
 179{
 180        void (*write_space)(struct sock *sk);
 181        struct rds_conn_path *cp;
 182        struct rds_tcp_connection *tc;
 183
 184        read_lock_bh(&sk->sk_callback_lock);
 185        cp = sk->sk_user_data;
 186        if (!cp) {
 187                write_space = sk->sk_write_space;
 188                goto out;
 189        }
 190
 191        tc = cp->cp_transport_data;
 192        rdsdebug("write_space for tc %p\n", tc);
 193        write_space = tc->t_orig_write_space;
 194        rds_tcp_stats_inc(s_tcp_write_space_calls);
 195
 196        rdsdebug("tcp una %u\n", rds_tcp_snd_una(tc));
 197        tc->t_last_seen_una = rds_tcp_snd_una(tc);
 198        rds_send_path_drop_acked(cp, rds_tcp_snd_una(tc), rds_tcp_is_acked);
 199
 200        rcu_read_lock();
 201        if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf &&
 202            !rds_destroy_pending(cp->cp_conn))
 203                queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
 204        rcu_read_unlock();
 205
 206out:
 207        read_unlock_bh(&sk->sk_callback_lock);
 208
 209        /*
 210         * write_space is only called when data leaves tcp's send queue if
 211         * SOCK_NOSPACE is set.  We set SOCK_NOSPACE every time we put
 212         * data in tcp's send queue because we use write_space to parse the
 213         * sequence numbers and notice that rds messages have been fully
 214         * received.
 215         *
 216         * tcp's write_space clears SOCK_NOSPACE if the send queue has more
 217         * than a certain amount of space. So we need to set it again *after*
 218         * we call tcp's write_space or else we might only get called on the
 219         * first of a series of incoming tcp acks.
 220         */
 221        write_space(sk);
 222
 223        if (sk->sk_socket)
 224                set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 225}
 226