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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 
40 static void rds_tcp_cork(struct socket *sock, int val)
41 {
42  mm_segment_t oldfs;
43 
44  oldfs = get_fs();
46  sock->ops->setsockopt(sock, SOL_TCP, TCP_CORK, (char __user *)&val,
47  sizeof(val));
48  set_fs(oldfs);
49 }
50 
52 {
53  struct rds_tcp_connection *tc = conn->c_transport_data;
54 
55  rds_tcp_cork(tc->t_sock, 1);
56 }
57 
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  */
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;
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,
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 {
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 
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));
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:
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 }