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/random.h>
35#include <linux/export.h>
36
37#include "rds.h"
38
39/*
40 * All of connection management is simplified by serializing it through
41 * work queues that execute in a connection managing thread.
42 *
43 * TCP wants to send acks through sendpage() in response to data_ready(),
44 * but it needs a process context to do so.
45 *
46 * The receive paths need to allocate but can't drop packets (!) so we have
47 * a thread around to block allocating if the receive fast path sees an
48 * allocation failure.
49 */
50
51/* Grand Unified Theory of connection life cycle:
52 * At any point in time, the connection can be in one of these states:
53 * DOWN, CONNECTING, UP, DISCONNECTING, ERROR
54 *
55 * The following transitions are possible:
56 *  ANY		  -> ERROR
57 *  UP		  -> DISCONNECTING
58 *  ERROR	  -> DISCONNECTING
59 *  DISCONNECTING -> DOWN
60 *  DOWN	  -> CONNECTING
61 *  CONNECTING	  -> UP
62 *
63 * Transition to state DISCONNECTING/DOWN:
64 *  -	Inside the shutdown worker; synchronizes with xmit path
65 *	through RDS_IN_XMIT, and with connection management callbacks
66 *	via c_cm_lock.
67 *
68 *	For receive callbacks, we rely on the underlying transport
69 *	(TCP, IB/RDMA) to provide the necessary synchronisation.
70 */
71struct workqueue_struct *rds_wq;
72EXPORT_SYMBOL_GPL(rds_wq);
73
74void rds_connect_complete(struct rds_connection *conn)
75{
76	if (!rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_UP)) {
77		printk(KERN_WARNING "%s: Cannot transition to state UP, "
78				"current state is %d\n",
79				__func__,
80				atomic_read(&conn->c_state));
81		rds_conn_drop(conn);
82		return;
83	}
84
85	rdsdebug("conn %p for %pI4 to %pI4 complete\n",
86	  conn, &conn->c_laddr, &conn->c_faddr);
87
88	conn->c_reconnect_jiffies = 0;
89	set_bit(0, &conn->c_map_queued);
90	queue_delayed_work(rds_wq, &conn->c_send_w, 0);
91	queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
92}
93EXPORT_SYMBOL_GPL(rds_connect_complete);
94
95/*
96 * This random exponential backoff is relied on to eventually resolve racing
97 * connects.
98 *
99 * If connect attempts race then both parties drop both connections and come
100 * here to wait for a random amount of time before trying again.  Eventually
101 * the backoff range will be so much greater than the time it takes to
102 * establish a connection that one of the pair will establish the connection
103 * before the other's random delay fires.
104 *
105 * Connection attempts that arrive while a connection is already established
106 * are also considered to be racing connects.  This lets a connection from
107 * a rebooted machine replace an existing stale connection before the transport
108 * notices that the connection has failed.
109 *
110 * We should *always* start with a random backoff; otherwise a broken connection
111 * will always take several iterations to be re-established.
112 */
113void rds_queue_reconnect(struct rds_connection *conn)
114{
115	unsigned long rand;
116
117	rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n",
118	  conn, &conn->c_laddr, &conn->c_faddr,
119	  conn->c_reconnect_jiffies);
120
121	set_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
122	if (conn->c_reconnect_jiffies == 0) {
123		conn->c_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies;
124		queue_delayed_work(rds_wq, &conn->c_conn_w, 0);
125		return;
126	}
127
128	get_random_bytes(&rand, sizeof(rand));
129	rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n",
130		 rand % conn->c_reconnect_jiffies, conn->c_reconnect_jiffies,
131		 conn, &conn->c_laddr, &conn->c_faddr);
132	queue_delayed_work(rds_wq, &conn->c_conn_w,
133			   rand % conn->c_reconnect_jiffies);
134
135	conn->c_reconnect_jiffies = min(conn->c_reconnect_jiffies * 2,
136					rds_sysctl_reconnect_max_jiffies);
137}
138
139void rds_connect_worker(struct work_struct *work)
140{
141	struct rds_connection *conn = container_of(work, struct rds_connection, c_conn_w.work);
142	int ret;
143
144	clear_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
145	if (rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) {
146		ret = conn->c_trans->conn_connect(conn);
147		rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n",
148			conn, &conn->c_laddr, &conn->c_faddr, ret);
149
150		if (ret) {
151			if (rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_DOWN))
152				rds_queue_reconnect(conn);
153			else
154				rds_conn_error(conn, "RDS: connect failed\n");
155		}
156	}
157}
158
159void rds_send_worker(struct work_struct *work)
160{
161	struct rds_connection *conn = container_of(work, struct rds_connection, c_send_w.work);
162	int ret;
163
164	if (rds_conn_state(conn) == RDS_CONN_UP) {
165		clear_bit(RDS_LL_SEND_FULL, &conn->c_flags);
166		ret = rds_send_xmit(conn);
167		cond_resched();
168		rdsdebug("conn %p ret %d\n", conn, ret);
169		switch (ret) {
170		case -EAGAIN:
171			rds_stats_inc(s_send_immediate_retry);
172			queue_delayed_work(rds_wq, &conn->c_send_w, 0);
173			break;
174		case -ENOMEM:
175			rds_stats_inc(s_send_delayed_retry);
176			queue_delayed_work(rds_wq, &conn->c_send_w, 2);
177		default:
178			break;
179		}
180	}
181}
182
183void rds_recv_worker(struct work_struct *work)
184{
185	struct rds_connection *conn = container_of(work, struct rds_connection, c_recv_w.work);
186	int ret;
187
188	if (rds_conn_state(conn) == RDS_CONN_UP) {
189		ret = conn->c_trans->recv(conn);
190		rdsdebug("conn %p ret %d\n", conn, ret);
191		switch (ret) {
192		case -EAGAIN:
193			rds_stats_inc(s_recv_immediate_retry);
194			queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
195			break;
196		case -ENOMEM:
197			rds_stats_inc(s_recv_delayed_retry);
198			queue_delayed_work(rds_wq, &conn->c_recv_w, 2);
199		default:
200			break;
201		}
202	}
203}
204
205void rds_shutdown_worker(struct work_struct *work)
206{
207	struct rds_connection *conn = container_of(work, struct rds_connection, c_down_w);
208
209	rds_conn_shutdown(conn);
210}
211
212void rds_threads_exit(void)
213{
214	destroy_workqueue(rds_wq);
215}
216
217int rds_threads_init(void)
218{
219	rds_wq = create_singlethread_workqueue("krdsd");
220	if (!rds_wq)
221		return -ENOMEM;
222
223	return 0;
224}
225