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 */ 71 struct workqueue_struct *rds_wq; 72 EXPORT_SYMBOL_GPL(rds_wq); 73 74 void rds_connect_path_complete(struct rds_conn_path *cp, int curr) 75 { 76 if (!rds_conn_path_transition(cp, curr, RDS_CONN_UP)) { 77 printk(KERN_WARNING "%s: Cannot transition to state UP, " 78 "current state is %d\n", 79 __func__, 80 atomic_read(&cp->cp_state)); 81 rds_conn_path_drop(cp, false); 82 return; 83 } 84 85 rdsdebug("conn %p for %pI4 to %pI4 complete\n", 86 cp->cp_conn, &cp->cp_conn->c_laddr, &cp->cp_conn->c_faddr); 87 88 cp->cp_reconnect_jiffies = 0; 89 set_bit(0, &cp->cp_conn->c_map_queued); 90 rcu_read_lock(); 91 if (!rds_destroy_pending(cp->cp_conn)) { 92 queue_delayed_work(rds_wq, &cp->cp_send_w, 0); 93 queue_delayed_work(rds_wq, &cp->cp_recv_w, 0); 94 } 95 rcu_read_unlock(); 96 } 97 EXPORT_SYMBOL_GPL(rds_connect_path_complete); 98 99 void rds_connect_complete(struct rds_connection *conn) 100 { 101 rds_connect_path_complete(&conn->c_path[0], RDS_CONN_CONNECTING); 102 } 103 EXPORT_SYMBOL_GPL(rds_connect_complete); 104 105 /* 106 * This random exponential backoff is relied on to eventually resolve racing 107 * connects. 108 * 109 * If connect attempts race then both parties drop both connections and come 110 * here to wait for a random amount of time before trying again. Eventually 111 * the backoff range will be so much greater than the time it takes to 112 * establish a connection that one of the pair will establish the connection 113 * before the other's random delay fires. 114 * 115 * Connection attempts that arrive while a connection is already established 116 * are also considered to be racing connects. This lets a connection from 117 * a rebooted machine replace an existing stale connection before the transport 118 * notices that the connection has failed. 119 * 120 * We should *always* start with a random backoff; otherwise a broken connection 121 * will always take several iterations to be re-established. 122 */ 123 void rds_queue_reconnect(struct rds_conn_path *cp) 124 { 125 unsigned long rand; 126 struct rds_connection *conn = cp->cp_conn; 127 128 rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n", 129 conn, &conn->c_laddr, &conn->c_faddr, 130 cp->cp_reconnect_jiffies); 131 132 /* let peer with smaller addr initiate reconnect, to avoid duels */ 133 if (conn->c_trans->t_type == RDS_TRANS_TCP && 134 !IS_CANONICAL(conn->c_laddr, conn->c_faddr)) 135 return; 136 137 set_bit(RDS_RECONNECT_PENDING, &cp->cp_flags); 138 if (cp->cp_reconnect_jiffies == 0) { 139 cp->cp_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies; 140 rcu_read_lock(); 141 if (!rds_destroy_pending(cp->cp_conn)) 142 queue_delayed_work(rds_wq, &cp->cp_conn_w, 0); 143 rcu_read_unlock(); 144 return; 145 } 146 147 get_random_bytes(&rand, sizeof(rand)); 148 rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n", 149 rand % cp->cp_reconnect_jiffies, cp->cp_reconnect_jiffies, 150 conn, &conn->c_laddr, &conn->c_faddr); 151 rcu_read_lock(); 152 if (!rds_destroy_pending(cp->cp_conn)) 153 queue_delayed_work(rds_wq, &cp->cp_conn_w, 154 rand % cp->cp_reconnect_jiffies); 155 rcu_read_unlock(); 156 157 cp->cp_reconnect_jiffies = min(cp->cp_reconnect_jiffies * 2, 158 rds_sysctl_reconnect_max_jiffies); 159 } 160 161 void rds_connect_worker(struct work_struct *work) 162 { 163 struct rds_conn_path *cp = container_of(work, 164 struct rds_conn_path, 165 cp_conn_w.work); 166 struct rds_connection *conn = cp->cp_conn; 167 int ret; 168 169 if (cp->cp_index > 0 && 170 !IS_CANONICAL(cp->cp_conn->c_laddr, cp->cp_conn->c_faddr)) 171 return; 172 clear_bit(RDS_RECONNECT_PENDING, &cp->cp_flags); 173 ret = rds_conn_path_transition(cp, RDS_CONN_DOWN, RDS_CONN_CONNECTING); 174 if (ret) { 175 ret = conn->c_trans->conn_path_connect(cp); 176 rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n", 177 conn, &conn->c_laddr, &conn->c_faddr, ret); 178 179 if (ret) { 180 if (rds_conn_path_transition(cp, 181 RDS_CONN_CONNECTING, 182 RDS_CONN_DOWN)) 183 rds_queue_reconnect(cp); 184 else 185 rds_conn_path_error(cp, "connect failed\n"); 186 } 187 } 188 } 189 190 void rds_send_worker(struct work_struct *work) 191 { 192 struct rds_conn_path *cp = container_of(work, 193 struct rds_conn_path, 194 cp_send_w.work); 195 int ret; 196 197 if (rds_conn_path_state(cp) == RDS_CONN_UP) { 198 clear_bit(RDS_LL_SEND_FULL, &cp->cp_flags); 199 ret = rds_send_xmit(cp); 200 cond_resched(); 201 rdsdebug("conn %p ret %d\n", cp->cp_conn, ret); 202 switch (ret) { 203 case -EAGAIN: 204 rds_stats_inc(s_send_immediate_retry); 205 queue_delayed_work(rds_wq, &cp->cp_send_w, 0); 206 break; 207 case -ENOMEM: 208 rds_stats_inc(s_send_delayed_retry); 209 queue_delayed_work(rds_wq, &cp->cp_send_w, 2); 210 default: 211 break; 212 } 213 } 214 } 215 216 void rds_recv_worker(struct work_struct *work) 217 { 218 struct rds_conn_path *cp = container_of(work, 219 struct rds_conn_path, 220 cp_recv_w.work); 221 int ret; 222 223 if (rds_conn_path_state(cp) == RDS_CONN_UP) { 224 ret = cp->cp_conn->c_trans->recv_path(cp); 225 rdsdebug("conn %p ret %d\n", cp->cp_conn, ret); 226 switch (ret) { 227 case -EAGAIN: 228 rds_stats_inc(s_recv_immediate_retry); 229 queue_delayed_work(rds_wq, &cp->cp_recv_w, 0); 230 break; 231 case -ENOMEM: 232 rds_stats_inc(s_recv_delayed_retry); 233 queue_delayed_work(rds_wq, &cp->cp_recv_w, 2); 234 default: 235 break; 236 } 237 } 238 } 239 240 void rds_shutdown_worker(struct work_struct *work) 241 { 242 struct rds_conn_path *cp = container_of(work, 243 struct rds_conn_path, 244 cp_down_w); 245 246 rds_conn_shutdown(cp); 247 } 248 249 void rds_threads_exit(void) 250 { 251 destroy_workqueue(rds_wq); 252 } 253 254 int rds_threads_init(void) 255 { 256 rds_wq = create_singlethread_workqueue("krdsd"); 257 if (!rds_wq) 258 return -ENOMEM; 259 260 return 0; 261 } 262