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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_single_path.h"
 38 #include "rds.h"
 39 #include "tcp.h"
 40 
 41 static void rds_tcp_cork(struct socket *sock, int val)
 42 {
 43         kernel_setsockopt(sock, SOL_TCP, TCP_CORK, (void *)&val, sizeof(val));
 44 }
 45 
 46 void rds_tcp_xmit_path_prepare(struct rds_conn_path *cp)
 47 {
 48         struct rds_tcp_connection *tc = cp->cp_transport_data;
 49 
 50         rds_tcp_cork(tc->t_sock, 1);
 51 }
 52 
 53 void rds_tcp_xmit_path_complete(struct rds_conn_path *cp)
 54 {
 55         struct rds_tcp_connection *tc = cp->cp_transport_data;
 56 
 57         rds_tcp_cork(tc->t_sock, 0);
 58 }
 59 
 60 /* the core send_sem serializes this with other xmit and shutdown */
 61 static int rds_tcp_sendmsg(struct socket *sock, void *data, unsigned int len)
 62 {
 63         struct kvec vec = {
 64                 .iov_base = data,
 65                 .iov_len = len,
 66         };
 67         struct msghdr msg = {
 68                 .msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL,
 69         };
 70 
 71         return kernel_sendmsg(sock, &msg, &vec, 1, vec.iov_len);
 72 }
 73 
 74 /* the core send_sem serializes this with other xmit and shutdown */
 75 int rds_tcp_xmit(struct rds_connection *conn, struct rds_message *rm,
 76                  unsigned int hdr_off, unsigned int sg, unsigned int off)
 77 {
 78         struct rds_conn_path *cp = rm->m_inc.i_conn_path;
 79         struct rds_tcp_connection *tc = cp->cp_transport_data;
 80         int done = 0;
 81         int ret = 0;
 82         int more;
 83 
 84         if (hdr_off == 0) {
 85                 /*
 86                  * m_ack_seq is set to the sequence number of the last byte of
 87                  * header and data.  see rds_tcp_is_acked().
 88                  */
 89                 tc->t_last_sent_nxt = rds_tcp_write_seq(tc);
 90                 rm->m_ack_seq = tc->t_last_sent_nxt +
 91                                 sizeof(struct rds_header) +
 92                                 be32_to_cpu(rm->m_inc.i_hdr.h_len) - 1;
 93                 smp_mb__before_atomic();
 94                 set_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags);
 95                 tc->t_last_expected_una = rm->m_ack_seq + 1;
 96 
 97                 if (test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))
 98                         rm->m_inc.i_hdr.h_flags |= RDS_FLAG_RETRANSMITTED;
 99 
100                 rdsdebug("rm %p tcp nxt %u ack_seq %llu\n",
101                          rm, rds_tcp_write_seq(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         more = rm->data.op_nents > 1 ? (MSG_MORE | MSG_SENDPAGE_NOTLAST) : 0;
120         while (sg < rm->data.op_nents) {
121                 int flags = MSG_DONTWAIT | MSG_NOSIGNAL | more;
122 
123                 ret = tc->t_sock->ops->sendpage(tc->t_sock,
124                                                 sg_page(&rm->data.op_sg[sg]),
125                                                 rm->data.op_sg[sg].offset + off,
126                                                 rm->data.op_sg[sg].length - off,
127                                                 flags);
128                 rdsdebug("tcp sendpage %p:%u:%u ret %d\n", (void *)sg_page(&rm->data.op_sg[sg]),
129                          rm->data.op_sg[sg].offset + off, rm->data.op_sg[sg].length - off,
130                          ret);
131                 if (ret <= 0)
132                         break;
133 
134                 off += ret;
135                 done += ret;
136                 if (off == rm->data.op_sg[sg].length) {
137                         off = 0;
138                         sg++;
139                 }
140                 if (sg == rm->data.op_nents - 1)
141                         more = 0;
142         }
143 
144 out:
145         if (ret <= 0) {
146                 /* write_space will hit after EAGAIN, all else fatal */
147                 if (ret == -EAGAIN) {
148                         rds_tcp_stats_inc(s_tcp_sndbuf_full);
149                         ret = 0;
150                 } else {
151                         /* No need to disconnect/reconnect if path_drop
152                          * has already been triggered, because, e.g., of
153                          * an incoming RST.
154                          */
155                         if (rds_conn_path_up(cp)) {
156                                 pr_warn("RDS/tcp: send to %pI4 on cp [%d]"
157                                         "returned %d, "
158                                         "disconnecting and reconnecting\n",
159                                         &conn->c_faddr, cp->cp_index, ret);
160                                 rds_conn_path_drop(cp, false);
161                         }
162                 }
163         }
164         if (done == 0)
165                 done = ret;
166         return done;
167 }
168 
169 /*
170  * rm->m_ack_seq is set to the tcp sequence number that corresponds to the
171  * last byte of the message, including the header.  This means that the
172  * entire message has been received if rm->m_ack_seq is "before" the next
173  * unacked byte of the TCP sequence space.  We have to do very careful
174  * wrapping 32bit comparisons here.
175  */
176 static int rds_tcp_is_acked(struct rds_message *rm, uint64_t ack)
177 {
178         if (!test_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags))
179                 return 0;
180         return (__s32)((u32)rm->m_ack_seq - (u32)ack) < 0;
181 }
182 
183 void rds_tcp_write_space(struct sock *sk)
184 {
185         void (*write_space)(struct sock *sk);
186         struct rds_conn_path *cp;
187         struct rds_tcp_connection *tc;
188 
189         read_lock_bh(&sk->sk_callback_lock);
190         cp = sk->sk_user_data;
191         if (!cp) {
192                 write_space = sk->sk_write_space;
193                 goto out;
194         }
195 
196         tc = cp->cp_transport_data;
197         rdsdebug("write_space for tc %p\n", tc);
198         write_space = tc->t_orig_write_space;
199         rds_tcp_stats_inc(s_tcp_write_space_calls);
200 
201         rdsdebug("tcp una %u\n", rds_tcp_snd_una(tc));
202         tc->t_last_seen_una = rds_tcp_snd_una(tc);
203         rds_send_path_drop_acked(cp, rds_tcp_snd_una(tc), rds_tcp_is_acked);
204 
205         rcu_read_lock();
206         if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf &&
207             !rds_destroy_pending(cp->cp_conn))
208                 queue_delayed_work(rds_wq, &cp->cp_send_w, 0);
209         rcu_read_unlock();
210 
211 out:
212         read_unlock_bh(&sk->sk_callback_lock);
213 
214         /*
215          * write_space is only called when data leaves tcp's send queue if
216          * SOCK_NOSPACE is set.  We set SOCK_NOSPACE every time we put
217          * data in tcp's send queue because we use write_space to parse the
218          * sequence numbers and notice that rds messages have been fully
219          * received.
220          *
221          * tcp's write_space clears SOCK_NOSPACE if the send queue has more
222          * than a certain amount of space. So we need to set it again *after*
223          * we call tcp's write_space or else we might only get called on the
224          * first of a series of incoming tcp acks.
225          */
226         write_space(sk);
227 
228         if (sk->sk_socket)
229                 set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
230 }
231 

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