net/rds/tcp_send.c

   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
  40 static 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
  51 void 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
  58 void 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 */
  66 static 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 */
  80 int 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
 139 out:
 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  */
 164 static 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
 171 void 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(&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
 196 out:
 197         read_unlock(&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 }