net/rxrpc/conn_client.c

   1 /* Client connection-specific management code.
   2  *
   3  * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  *
  11  *
  12  * Client connections need to be cached for a little while after they've made a
  13  * call so as to handle retransmitted DATA packets in case the server didn't
  14  * receive the final ACK or terminating ABORT we sent it.
  15  *
  16  * Client connections can be in one of a number of cache states:
  17  *
  18  *  (1) INACTIVE - The connection is not held in any list and may not have been
  19  *      exposed to the world.  If it has been previously exposed, it was
  20  *      discarded from the idle list after expiring.
  21  *
  22  *  (2) WAITING - The connection is waiting for the number of client conns to
  23  *      drop below the maximum capacity.  Calls may be in progress upon it from
  24  *      when it was active and got culled.
  25  *
  26  *      The connection is on the rxrpc_waiting_client_conns list which is kept
  27  *      in to-be-granted order.  Culled conns with waiters go to the back of
  28  *      the queue just like new conns.
  29  *
  30  *  (3) ACTIVE - The connection has at least one call in progress upon it, it
  31  *      may freely grant available channels to new calls and calls may be
  32  *      waiting on it for channels to become available.
  33  *
  34  *      The connection is on the rxnet->active_client_conns list which is kept
  35  *      in activation order for culling purposes.
  36  *
  37  *      rxrpc_nr_active_client_conns is held incremented also.
  38  *
  39  *  (4) UPGRADE - As for ACTIVE, but only one call may be in progress and is
  40  *      being used to probe for service upgrade.
  41  *
  42  *  (5) CULLED - The connection got summarily culled to try and free up
  43  *      capacity.  Calls currently in progress on the connection are allowed to
  44  *      continue, but new calls will have to wait.  There can be no waiters in
  45  *      this state - the conn would have to go to the WAITING state instead.
  46  *
  47  *  (6) IDLE - The connection has no calls in progress upon it and must have
  48  *      been exposed to the world (ie. the EXPOSED flag must be set).  When it
  49  *      expires, the EXPOSED flag is cleared and the connection transitions to
  50  *      the INACTIVE state.
  51  *
  52  *      The connection is on the rxnet->idle_client_conns list which is kept in
  53  *      order of how soon they'll expire.
  54  *
  55  * There are flags of relevance to the cache:
  56  *
  57  *  (1) EXPOSED - The connection ID got exposed to the world.  If this flag is
  58  *      set, an extra ref is added to the connection preventing it from being
  59  *      reaped when it has no calls outstanding.  This flag is cleared and the
  60  *      ref dropped when a conn is discarded from the idle list.
  61  *
  62  *      This allows us to move terminal call state retransmission to the
  63  *      connection and to discard the call immediately we think it is done
  64  *      with.  It also give us a chance to reuse the connection.
  65  *
  66  *  (2) DONT_REUSE - The connection should be discarded as soon as possible and
  67  *      should not be reused.  This is set when an exclusive connection is used
  68  *      or a call ID counter overflows.
  69  *
  70  * The caching state may only be changed if the cache lock is held.
  71  *
  72  * There are two idle client connection expiry durations.  If the total number
  73  * of connections is below the reap threshold, we use the normal duration; if
  74  * it's above, we use the fast duration.
  75  */
  76
  77 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  78
  79 #include <linux/slab.h>
  80 #include <linux/idr.h>
  81 #include <linux/timer.h>
  82 #include <linux/sched/signal.h>
  83
  84 #include "ar-internal.h"
  85
  86 __read_mostly unsigned int rxrpc_max_client_connections = 1000;
  87 __read_mostly unsigned int rxrpc_reap_client_connections = 900;
  88 __read_mostly unsigned int rxrpc_conn_idle_client_expiry = 2 * 60 * HZ;
  89 __read_mostly unsigned int rxrpc_conn_idle_client_fast_expiry = 2 * HZ;
  90
  91 /*
  92  * We use machine-unique IDs for our client connections.
  93  */
  94 DEFINE_IDR(rxrpc_client_conn_ids);
  95 static DEFINE_SPINLOCK(rxrpc_conn_id_lock);
  96
  97 static void rxrpc_cull_active_client_conns(struct rxrpc_net *);
  98
  99 /*
 100  * Get a connection ID and epoch for a client connection from the global pool.
 101  * The connection struct pointer is then recorded in the idr radix tree.  The
 102  * epoch doesn't change until the client is rebooted (or, at least, unless the
 103  * module is unloaded).
 104  */
 105 static int rxrpc_get_client_connection_id(struct rxrpc_connection *conn,
 106                                           gfp_t gfp)
 107 {
 108         struct rxrpc_net *rxnet = conn->params.local->rxnet;
 109         int id;
 110
 111         _enter("");
 112
 113         idr_preload(gfp);
 114         spin_lock(&rxrpc_conn_id_lock);
 115
 116         id = idr_alloc_cyclic(&rxrpc_client_conn_ids, conn,
 117                               1, 0x40000000, GFP_NOWAIT);
 118         if (id < 0)
 119                 goto error;
 120
 121         spin_unlock(&rxrpc_conn_id_lock);
 122         idr_preload_end();
 123
 124         conn->proto.epoch = rxnet->epoch;
 125         conn->proto.cid = id << RXRPC_CIDSHIFT;
 126         set_bit(RXRPC_CONN_HAS_IDR, &conn->flags);
 127         _leave(" [CID %x]", conn->proto.cid);
 128         return 0;
 129
 130 error:
 131         spin_unlock(&rxrpc_conn_id_lock);
 132         idr_preload_end();
 133         _leave(" = %d", id);
 134         return id;
 135 }
 136
 137 /*
 138  * Release a connection ID for a client connection from the global pool.
 139  */
 140 static void rxrpc_put_client_connection_id(struct rxrpc_connection *conn)
 141 {
 142         if (test_bit(RXRPC_CONN_HAS_IDR, &conn->flags)) {
 143                 spin_lock(&rxrpc_conn_id_lock);
 144                 idr_remove(&rxrpc_client_conn_ids,
 145                            conn->proto.cid >> RXRPC_CIDSHIFT);
 146                 spin_unlock(&rxrpc_conn_id_lock);
 147         }
 148 }
 149
 150 /*
 151  * Destroy the client connection ID tree.
 152  */
 153 void rxrpc_destroy_client_conn_ids(void)
 154 {
 155         struct rxrpc_connection *conn;
 156         int id;
 157
 158         if (!idr_is_empty(&rxrpc_client_conn_ids)) {
 159                 idr_for_each_entry(&rxrpc_client_conn_ids, conn, id) {
 160                         pr_err("AF_RXRPC: Leaked client conn %p {%d}\n",
 161                                conn, atomic_read(&conn->usage));
 162                 }
 163                 BUG();
 164         }
 165
 166         idr_destroy(&rxrpc_client_conn_ids);
 167 }
 168
 169 /*
 170  * Allocate a client connection.
 171  */
 172 static struct rxrpc_connection *
 173 rxrpc_alloc_client_connection(struct rxrpc_conn_parameters *cp, gfp_t gfp)
 174 {
 175         struct rxrpc_connection *conn;
 176         struct rxrpc_net *rxnet = cp->local->rxnet;
 177         int ret;
 178
 179         _enter("");
 180
 181         conn = rxrpc_alloc_connection(gfp);
 182         if (!conn) {
 183                 _leave(" = -ENOMEM");
 184                 return ERR_PTR(-ENOMEM);
 185         }
 186
 187         atomic_set(&conn->usage, 1);
 188         if (cp->exclusive)
 189                 __set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags);
 190         if (cp->upgrade)
 191                 __set_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags);
 192
 193         conn->params            = *cp;
 194         conn->out_clientflag    = RXRPC_CLIENT_INITIATED;
 195         conn->state             = RXRPC_CONN_CLIENT;
 196         conn->service_id        = cp->service_id;
 197
 198         ret = rxrpc_get_client_connection_id(conn, gfp);
 199         if (ret < 0)
 200                 goto error_0;
 201
 202         ret = rxrpc_init_client_conn_security(conn);
 203         if (ret < 0)
 204                 goto error_1;
 205
 206         ret = conn->security->prime_packet_security(conn);
 207         if (ret < 0)
 208                 goto error_2;
 209
 210         write_lock(&rxnet->conn_lock);
 211         list_add_tail(&conn->proc_link, &rxnet->conn_proc_list);
 212         write_unlock(&rxnet->conn_lock);
 213
 214         /* We steal the caller's peer ref. */
 215         cp->peer = NULL;
 216         rxrpc_get_local(conn->params.local);
 217         key_get(conn->params.key);
 218
 219         trace_rxrpc_conn(conn, rxrpc_conn_new_client, atomic_read(&conn->usage),
 220                          __builtin_return_address(0));
 221         trace_rxrpc_client(conn, -1, rxrpc_client_alloc);
 222         _leave(" = %p", conn);
 223         return conn;
 224
 225 error_2:
 226         conn->security->clear(conn);
 227 error_1:
 228         rxrpc_put_client_connection_id(conn);
 229 error_0:
 230         kfree(conn);
 231         _leave(" = %d", ret);
 232         return ERR_PTR(ret);
 233 }
 234
 235 /*
 236  * Determine if a connection may be reused.
 237  */
 238 static bool rxrpc_may_reuse_conn(struct rxrpc_connection *conn)
 239 {
 240         struct rxrpc_net *rxnet = conn->params.local->rxnet;
 241         int id_cursor, id, distance, limit;
 242
 243         if (test_bit(RXRPC_CONN_DONT_REUSE, &conn->flags))
 244                 goto dont_reuse;
 245
 246         if (conn->proto.epoch != rxnet->epoch)
 247                 goto mark_dont_reuse;
 248
 249         /* The IDR tree gets very expensive on memory if the connection IDs are
 250          * widely scattered throughout the number space, so we shall want to
 251          * kill off connections that, say, have an ID more than about four
 252          * times the maximum number of client conns away from the current
 253          * allocation point to try and keep the IDs concentrated.
 254          */
 255         id_cursor = idr_get_cursor(&rxrpc_client_conn_ids);
 256         id = conn->proto.cid >> RXRPC_CIDSHIFT;
 257         distance = id - id_cursor;
 258         if (distance < 0)
 259                 distance = -distance;
 260         limit = max(rxrpc_max_client_connections * 4, 1024U);
 261         if (distance > limit)
 262                 goto mark_dont_reuse;
 263
 264         return true;
 265
 266 mark_dont_reuse:
 267         set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags);
 268 dont_reuse:
 269         return false;
 270 }
 271
 272 /*
 273  * Create or find a client connection to use for a call.
 274  *
 275  * If we return with a connection, the call will be on its waiting list.  It's
 276  * left to the caller to assign a channel and wake up the call.
 277  */
 278 static int rxrpc_get_client_conn(struct rxrpc_call *call,
 279                                  struct rxrpc_conn_parameters *cp,
 280                                  struct sockaddr_rxrpc *srx,
 281                                  gfp_t gfp)
 282 {
 283         struct rxrpc_connection *conn, *candidate = NULL;
 284         struct rxrpc_local *local = cp->local;
 285         struct rb_node *p, **pp, *parent;
 286         long diff;
 287         int ret = -ENOMEM;
 288
 289         _enter("{%d,%lx},", call->debug_id, call->user_call_ID);
 290
 291         cp->peer = rxrpc_lookup_peer(cp->local, srx, gfp);
 292         if (!cp->peer)
 293                 goto error;
 294
 295         call->cong_cwnd = cp->peer->cong_cwnd;
 296         if (call->cong_cwnd >= call->cong_ssthresh)
 297                 call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
 298         else
 299                 call->cong_mode = RXRPC_CALL_SLOW_START;
 300
 301         /* If the connection is not meant to be exclusive, search the available
 302          * connections to see if the connection we want to use already exists.
 303          */
 304         if (!cp->exclusive) {
 305                 _debug("search 1");
 306                 spin_lock(&local->client_conns_lock);
 307                 p = local->client_conns.rb_node;
 308                 while (p) {
 309                         conn = rb_entry(p, struct rxrpc_connection, client_node);
 310
 311 #define cmp(X) ((long)conn->params.X - (long)cp->X)
 312                         diff = (cmp(peer) ?:
 313                                 cmp(key) ?:
 314                                 cmp(security_level) ?:
 315                                 cmp(upgrade));
 316 #undef cmp
 317                         if (diff < 0) {
 318                                 p = p->rb_left;
 319                         } else if (diff > 0) {
 320                                 p = p->rb_right;
 321                         } else {
 322                                 if (rxrpc_may_reuse_conn(conn) &&
 323                                     rxrpc_get_connection_maybe(conn))
 324                                         goto found_extant_conn;
 325                                 /* The connection needs replacing.  It's better
 326                                  * to effect that when we have something to
 327                                  * replace it with so that we don't have to
 328                                  * rebalance the tree twice.
 329                                  */
 330                                 break;
 331                         }
 332                 }
 333                 spin_unlock(&local->client_conns_lock);
 334         }
 335
 336         /* There wasn't a connection yet or we need an exclusive connection.
 337          * We need to create a candidate and then potentially redo the search
 338          * in case we're racing with another thread also trying to connect on a
 339          * shareable connection.
 340          */
 341         _debug("new conn");
 342         candidate = rxrpc_alloc_client_connection(cp, gfp);
 343         if (IS_ERR(candidate)) {
 344                 ret = PTR_ERR(candidate);
 345                 goto error_peer;
 346         }
 347
 348         /* Add the call to the new connection's waiting list in case we're
 349          * going to have to wait for the connection to come live.  It's our
 350          * connection, so we want first dibs on the channel slots.  We would
 351          * normally have to take channel_lock but we do this before anyone else
 352          * can see the connection.
 353          */
 354         list_add_tail(&call->chan_wait_link, &candidate->waiting_calls);
 355
 356         if (cp->exclusive) {
 357                 call->conn = candidate;
 358                 call->security_ix = candidate->security_ix;
 359                 call->service_id = candidate->service_id;
 360                 _leave(" = 0 [exclusive %d]", candidate->debug_id);
 361                 return 0;
 362         }
 363
 364         /* Publish the new connection for userspace to find.  We need to redo
 365          * the search before doing this lest we race with someone else adding a
 366          * conflicting instance.
 367          */
 368         _debug("search 2");
 369         spin_lock(&local->client_conns_lock);
 370
 371         pp = &local->client_conns.rb_node;
 372         parent = NULL;
 373         while (*pp) {
 374                 parent = *pp;
 375                 conn = rb_entry(parent, struct rxrpc_connection, client_node);
 376
 377 #define cmp(X) ((long)conn->params.X - (long)candidate->params.X)
 378                 diff = (cmp(peer) ?:
 379                         cmp(key) ?:
 380                         cmp(security_level) ?:
 381                         cmp(upgrade));
 382 #undef cmp
 383                 if (diff < 0) {
 384                         pp = &(*pp)->rb_left;
 385                 } else if (diff > 0) {
 386                         pp = &(*pp)->rb_right;
 387                 } else {
 388                         if (rxrpc_may_reuse_conn(conn) &&
 389                             rxrpc_get_connection_maybe(conn))
 390                                 goto found_extant_conn;
 391                         /* The old connection is from an outdated epoch. */
 392                         _debug("replace conn");
 393                         clear_bit(RXRPC_CONN_IN_CLIENT_CONNS, &conn->flags);
 394                         rb_replace_node(&conn->client_node,
 395                                         &candidate->client_node,
 396                                         &local->client_conns);
 397                         trace_rxrpc_client(conn, -1, rxrpc_client_replace);
 398                         goto candidate_published;
 399                 }
 400         }
 401
 402         _debug("new conn");
 403         rb_link_node(&candidate->client_node, parent, pp);
 404         rb_insert_color(&candidate->client_node, &local->client_conns);
 405
 406 candidate_published:
 407         set_bit(RXRPC_CONN_IN_CLIENT_CONNS, &candidate->flags);
 408         call->conn = candidate;
 409         call->security_ix = candidate->security_ix;
 410         call->service_id = candidate->service_id;
 411         spin_unlock(&local->client_conns_lock);
 412         _leave(" = 0 [new %d]", candidate->debug_id);
 413         return 0;
 414
 415         /* We come here if we found a suitable connection already in existence.
 416          * Discard any candidate we may have allocated, and try to get a
 417          * channel on this one.
 418          */
 419 found_extant_conn:
 420         _debug("found conn");
 421         spin_unlock(&local->client_conns_lock);
 422
 423         if (candidate) {
 424                 trace_rxrpc_client(candidate, -1, rxrpc_client_duplicate);
 425                 rxrpc_put_connection(candidate);
 426                 candidate = NULL;
 427         }
 428
 429         spin_lock(&conn->channel_lock);
 430         call->conn = conn;
 431         call->security_ix = conn->security_ix;
 432         call->service_id = conn->service_id;
 433         list_add(&call->chan_wait_link, &conn->waiting_calls);
 434         spin_unlock(&conn->channel_lock);
 435         _leave(" = 0 [extant %d]", conn->debug_id);
 436         return 0;
 437
 438 error_peer:
 439         rxrpc_put_peer(cp->peer);
 440         cp->peer = NULL;
 441 error:
 442         _leave(" = %d", ret);
 443         return ret;
 444 }
 445
 446 /*
 447  * Activate a connection.
 448  */
 449 static void rxrpc_activate_conn(struct rxrpc_net *rxnet,
 450                                 struct rxrpc_connection *conn)
 451 {
 452         if (test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags)) {
 453                 trace_rxrpc_client(conn, -1, rxrpc_client_to_upgrade);
 454                 conn->cache_state = RXRPC_CONN_CLIENT_UPGRADE;
 455         } else {
 456                 trace_rxrpc_client(conn, -1, rxrpc_client_to_active);
 457                 conn->cache_state = RXRPC_CONN_CLIENT_ACTIVE;
 458         }
 459         rxnet->nr_active_client_conns++;
 460         list_move_tail(&conn->cache_link, &rxnet->active_client_conns);
 461 }
 462
 463 /*
 464  * Attempt to animate a connection for a new call.
 465  *
 466  * If it's not exclusive, the connection is in the endpoint tree, and we're in
 467  * the conn's list of those waiting to grab a channel.  There is, however, a
 468  * limit on the number of live connections allowed at any one time, so we may
 469  * have to wait for capacity to become available.
 470  *
 471  * Note that a connection on the waiting queue might *also* have active
 472  * channels if it has been culled to make space and then re-requested by a new
 473  * call.
 474  */
 475 static void rxrpc_animate_client_conn(struct rxrpc_net *rxnet,
 476                                       struct rxrpc_connection *conn)
 477 {
 478         unsigned int nr_conns;
 479
 480         _enter("%d,%d", conn->debug_id, conn->cache_state);
 481
 482         if (conn->cache_state == RXRPC_CONN_CLIENT_ACTIVE ||
 483             conn->cache_state == RXRPC_CONN_CLIENT_UPGRADE)
 484                 goto out;
 485
 486         spin_lock(&rxnet->client_conn_cache_lock);
 487
 488         nr_conns = rxnet->nr_client_conns;
 489         if (!test_and_set_bit(RXRPC_CONN_COUNTED, &conn->flags)) {
 490                 trace_rxrpc_client(conn, -1, rxrpc_client_count);
 491                 rxnet->nr_client_conns = nr_conns + 1;
 492         }
 493
 494         switch (conn->cache_state) {
 495         case RXRPC_CONN_CLIENT_ACTIVE:
 496         case RXRPC_CONN_CLIENT_UPGRADE:
 497         case RXRPC_CONN_CLIENT_WAITING:
 498                 break;
 499
 500         case RXRPC_CONN_CLIENT_INACTIVE:
 501         case RXRPC_CONN_CLIENT_CULLED:
 502         case RXRPC_CONN_CLIENT_IDLE:
 503                 if (nr_conns >= rxrpc_max_client_connections)
 504                         goto wait_for_capacity;
 505                 goto activate_conn;
 506
 507         default:
 508                 BUG();
 509         }
 510
 511 out_unlock:
 512         spin_unlock(&rxnet->client_conn_cache_lock);
 513 out:
 514         _leave(" [%d]", conn->cache_state);
 515         return;
 516
 517 activate_conn:
 518         _debug("activate");
 519         rxrpc_activate_conn(rxnet, conn);
 520         goto out_unlock;
 521
 522 wait_for_capacity:
 523         _debug("wait");
 524         trace_rxrpc_client(conn, -1, rxrpc_client_to_waiting);
 525         conn->cache_state = RXRPC_CONN_CLIENT_WAITING;
 526         list_move_tail(&conn->cache_link, &rxnet->waiting_client_conns);
 527         goto out_unlock;
 528 }
 529
 530 /*
 531  * Deactivate a channel.
 532  */
 533 static void rxrpc_deactivate_one_channel(struct rxrpc_connection *conn,
 534                                          unsigned int channel)
 535 {
 536         struct rxrpc_channel *chan = &conn->channels[channel];
 537
 538         rcu_assign_pointer(chan->call, NULL);
 539         conn->active_chans &= ~(1 << channel);
 540 }
 541
 542 /*
 543  * Assign a channel to the call at the front of the queue and wake the call up.
 544  * We don't increment the callNumber counter until this number has been exposed
 545  * to the world.
 546  */
 547 static void rxrpc_activate_one_channel(struct rxrpc_connection *conn,
 548                                        unsigned int channel)
 549 {
 550         struct rxrpc_channel *chan = &conn->channels[channel];
 551         struct rxrpc_call *call = list_entry(conn->waiting_calls.next,
 552                                              struct rxrpc_call, chan_wait_link);
 553         u32 call_id = chan->call_counter + 1;
 554
 555         trace_rxrpc_client(conn, channel, rxrpc_client_chan_activate);
 556
 557         write_lock_bh(&call->state_lock);
 558         if (!test_bit(RXRPC_CALL_TX_LASTQ, &call->flags))
 559                 call->state = RXRPC_CALL_CLIENT_SEND_REQUEST;
 560         else
 561                 call->state = RXRPC_CALL_CLIENT_AWAIT_REPLY;
 562         write_unlock_bh(&call->state_lock);
 563
 564         rxrpc_see_call(call);
 565         list_del_init(&call->chan_wait_link);
 566         conn->active_chans |= 1 << channel;
 567         call->peer      = rxrpc_get_peer(conn->params.peer);
 568         call->cid       = conn->proto.cid | channel;
 569         call->call_id   = call_id;
 570
 571         trace_rxrpc_connect_call(call);
 572         _net("CONNECT call %08x:%08x as call %d on conn %d",
 573              call->cid, call->call_id, call->debug_id, conn->debug_id);
 574
 575         /* Paired with the read barrier in rxrpc_wait_for_channel().  This
 576          * orders cid and epoch in the connection wrt to call_id without the
 577          * need to take the channel_lock.
 578          *
 579          * We provisionally assign a callNumber at this point, but we don't
 580          * confirm it until the call is about to be exposed.
 581          *
 582          * TODO: Pair with a barrier in the data_ready handler when that looks
 583          * at the call ID through a connection channel.
 584          */
 585         smp_wmb();
 586         chan->call_id   = call_id;
 587         rcu_assign_pointer(chan->call, call);
 588         wake_up(&call->waitq);
 589 }
 590
 591 /*
 592  * Assign channels and callNumbers to waiting calls with channel_lock
 593  * held by caller.
 594  */
 595 static void rxrpc_activate_channels_locked(struct rxrpc_connection *conn)
 596 {
 597         u8 avail, mask;
 598
 599         switch (conn->cache_state) {
 600         case RXRPC_CONN_CLIENT_ACTIVE:
 601                 mask = RXRPC_ACTIVE_CHANS_MASK;
 602                 break;
 603         case RXRPC_CONN_CLIENT_UPGRADE:
 604                 mask = 0x01;
 605                 break;
 606         default:
 607                 return;
 608         }
 609
 610         while (!list_empty(&conn->waiting_calls) &&
 611                (avail = ~conn->active_chans,
 612                 avail &= mask,
 613                 avail != 0))
 614                 rxrpc_activate_one_channel(conn, __ffs(avail));
 615 }
 616
 617 /*
 618  * Assign channels and callNumbers to waiting calls.
 619  */
 620 static void rxrpc_activate_channels(struct rxrpc_connection *conn)
 621 {
 622         _enter("%d", conn->debug_id);
 623
 624         trace_rxrpc_client(conn, -1, rxrpc_client_activate_chans);
 625
 626         if (conn->active_chans == RXRPC_ACTIVE_CHANS_MASK)
 627                 return;
 628
 629         spin_lock(&conn->channel_lock);
 630         rxrpc_activate_channels_locked(conn);
 631         spin_unlock(&conn->channel_lock);
 632         _leave("");
 633 }
 634
 635 /*
 636  * Wait for a callNumber and a channel to be granted to a call.
 637  */
 638 static int rxrpc_wait_for_channel(struct rxrpc_call *call, gfp_t gfp)
 639 {
 640         int ret = 0;
 641
 642         _enter("%d", call->debug_id);
 643
 644         if (!call->call_id) {
 645                 DECLARE_WAITQUEUE(myself, current);
 646
 647                 if (!gfpflags_allow_blocking(gfp)) {
 648                         ret = -EAGAIN;
 649                         goto out;
 650                 }
 651
 652                 add_wait_queue_exclusive(&call->waitq, &myself);
 653                 for (;;) {
 654                         set_current_state(TASK_INTERRUPTIBLE);
 655                         if (call->call_id)
 656                                 break;
 657                         if (signal_pending(current)) {
 658                                 ret = -ERESTARTSYS;
 659                                 break;
 660                         }
 661                         schedule();
 662                 }
 663                 remove_wait_queue(&call->waitq, &myself);
 664                 __set_current_state(TASK_RUNNING);
 665         }
 666
 667         /* Paired with the write barrier in rxrpc_activate_one_channel(). */
 668         smp_rmb();
 669
 670 out:
 671         _leave(" = %d", ret);
 672         return ret;
 673 }
 674
 675 /*
 676  * find a connection for a call
 677  * - called in process context with IRQs enabled
 678  */
 679 int rxrpc_connect_call(struct rxrpc_call *call,
 680                        struct rxrpc_conn_parameters *cp,
 681                        struct sockaddr_rxrpc *srx,
 682                        gfp_t gfp)
 683 {
 684         struct rxrpc_net *rxnet = cp->local->rxnet;
 685         int ret;
 686
 687         _enter("{%d,%lx},", call->debug_id, call->user_call_ID);
 688
 689         rxrpc_discard_expired_client_conns(&rxnet->client_conn_reaper.work);
 690         rxrpc_cull_active_client_conns(rxnet);
 691
 692         ret = rxrpc_get_client_conn(call, cp, srx, gfp);
 693         if (ret < 0)
 694                 goto out;
 695
 696         rxrpc_animate_client_conn(rxnet, call->conn);
 697         rxrpc_activate_channels(call->conn);
 698
 699         ret = rxrpc_wait_for_channel(call, gfp);
 700         if (ret < 0) {
 701                 rxrpc_disconnect_client_call(call);
 702                 goto out;
 703         }
 704
 705         spin_lock_bh(&call->conn->params.peer->lock);
 706         hlist_add_head(&call->error_link,
 707                        &call->conn->params.peer->error_targets);
 708         spin_unlock_bh(&call->conn->params.peer->lock);
 709
 710 out:
 711         _leave(" = %d", ret);
 712         return ret;
 713 }
 714
 715 /*
 716  * Note that a connection is about to be exposed to the world.  Once it is
 717  * exposed, we maintain an extra ref on it that stops it from being summarily
 718  * discarded before it's (a) had a chance to deal with retransmission and (b)
 719  * had a chance at re-use (the per-connection security negotiation is
 720  * expensive).
 721  */
 722 static void rxrpc_expose_client_conn(struct rxrpc_connection *conn,
 723                                      unsigned int channel)
 724 {
 725         if (!test_and_set_bit(RXRPC_CONN_EXPOSED, &conn->flags)) {
 726                 trace_rxrpc_client(conn, channel, rxrpc_client_exposed);
 727                 rxrpc_get_connection(conn);
 728         }
 729 }
 730
 731 /*
 732  * Note that a call, and thus a connection, is about to be exposed to the
 733  * world.
 734  */
 735 void rxrpc_expose_client_call(struct rxrpc_call *call)
 736 {
 737         unsigned int channel = call->cid & RXRPC_CHANNELMASK;
 738         struct rxrpc_connection *conn = call->conn;
 739         struct rxrpc_channel *chan = &conn->channels[channel];
 740
 741         if (!test_and_set_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
 742                 /* Mark the call ID as being used.  If the callNumber counter
 743                  * exceeds ~2 billion, we kill the connection after its
 744                  * outstanding calls have finished so that the counter doesn't
 745                  * wrap.
 746                  */
 747                 chan->call_counter++;
 748                 if (chan->call_counter >= INT_MAX)
 749                         set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags);
 750                 rxrpc_expose_client_conn(conn, channel);
 751         }
 752 }
 753
 754 /*
 755  * Disconnect a client call.
 756  */
 757 void rxrpc_disconnect_client_call(struct rxrpc_call *call)
 758 {
 759         unsigned int channel = call->cid & RXRPC_CHANNELMASK;
 760         struct rxrpc_connection *conn = call->conn;
 761         struct rxrpc_channel *chan = &conn->channels[channel];
 762         struct rxrpc_net *rxnet = rxrpc_net(sock_net(&call->socket->sk));
 763
 764         trace_rxrpc_client(conn, channel, rxrpc_client_chan_disconnect);
 765         call->conn = NULL;
 766
 767         spin_lock(&conn->channel_lock);
 768
 769         /* Calls that have never actually been assigned a channel can simply be
 770          * discarded.  If the conn didn't get used either, it will follow
 771          * immediately unless someone else grabs it in the meantime.
 772          */
 773         if (!list_empty(&call->chan_wait_link)) {
 774                 _debug("call is waiting");
 775                 ASSERTCMP(call->call_id, ==, 0);
 776                 ASSERT(!test_bit(RXRPC_CALL_EXPOSED, &call->flags));
 777                 list_del_init(&call->chan_wait_link);
 778
 779                 trace_rxrpc_client(conn, channel, rxrpc_client_chan_unstarted);
 780
 781                 /* We must deactivate or idle the connection if it's now
 782                  * waiting for nothing.
 783                  */
 784                 spin_lock(&rxnet->client_conn_cache_lock);
 785                 if (conn->cache_state == RXRPC_CONN_CLIENT_WAITING &&
 786                     list_empty(&conn->waiting_calls) &&
 787                     !conn->active_chans)
 788                         goto idle_connection;
 789                 goto out;
 790         }
 791
 792         ASSERTCMP(rcu_access_pointer(chan->call), ==, call);
 793
 794         /* If a client call was exposed to the world, we save the result for
 795          * retransmission.
 796          *
 797          * We use a barrier here so that the call number and abort code can be
 798          * read without needing to take a lock.
 799          *
 800          * TODO: Make the incoming packet handler check this and handle
 801          * terminal retransmission without requiring access to the call.
 802          */
 803         if (test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
 804                 _debug("exposed %u,%u", call->call_id, call->abort_code);
 805                 __rxrpc_disconnect_call(conn, call);
 806         }
 807
 808         /* See if we can pass the channel directly to another call. */
 809         if (conn->cache_state == RXRPC_CONN_CLIENT_ACTIVE &&
 810             !list_empty(&conn->waiting_calls)) {
 811                 trace_rxrpc_client(conn, channel, rxrpc_client_chan_pass);
 812                 rxrpc_activate_one_channel(conn, channel);
 813                 goto out_2;
 814         }
 815
 816         /* Things are more complex and we need the cache lock.  We might be
 817          * able to simply idle the conn or it might now be lurking on the wait
 818          * list.  It might even get moved back to the active list whilst we're
 819          * waiting for the lock.
 820          */
 821         spin_lock(&rxnet->client_conn_cache_lock);
 822
 823         switch (conn->cache_state) {
 824         case RXRPC_CONN_CLIENT_UPGRADE:
 825                 /* Deal with termination of a service upgrade probe. */
 826                 if (test_bit(RXRPC_CONN_EXPOSED, &conn->flags)) {
 827                         clear_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags);
 828                         trace_rxrpc_client(conn, channel, rxrpc_client_to_active);
 829                         conn->cache_state = RXRPC_CONN_CLIENT_ACTIVE;
 830                         rxrpc_activate_channels_locked(conn);
 831                 }
 832                 /* fall through */
 833         case RXRPC_CONN_CLIENT_ACTIVE:
 834                 if (list_empty(&conn->waiting_calls)) {
 835                         rxrpc_deactivate_one_channel(conn, channel);
 836                         if (!conn->active_chans) {
 837                                 rxnet->nr_active_client_conns--;
 838                                 goto idle_connection;
 839                         }
 840                         goto out;
 841                 }
 842
 843                 trace_rxrpc_client(conn, channel, rxrpc_client_chan_pass);
 844                 rxrpc_activate_one_channel(conn, channel);
 845                 goto out;
 846
 847         case RXRPC_CONN_CLIENT_CULLED:
 848                 rxrpc_deactivate_one_channel(conn, channel);
 849                 ASSERT(list_empty(&conn->waiting_calls));
 850                 if (!conn->active_chans)
 851                         goto idle_connection;
 852                 goto out;
 853
 854         case RXRPC_CONN_CLIENT_WAITING:
 855                 rxrpc_deactivate_one_channel(conn, channel);
 856                 goto out;
 857
 858         default:
 859                 BUG();
 860         }
 861
 862 out:
 863         spin_unlock(&rxnet->client_conn_cache_lock);
 864 out_2:
 865         spin_unlock(&conn->channel_lock);
 866         rxrpc_put_connection(conn);
 867         _leave("");
 868         return;
 869
 870 idle_connection:
 871         /* As no channels remain active, the connection gets deactivated
 872          * immediately or moved to the idle list for a short while.
 873          */
 874         if (test_bit(RXRPC_CONN_EXPOSED, &conn->flags)) {
 875                 trace_rxrpc_client(conn, channel, rxrpc_client_to_idle);
 876                 conn->idle_timestamp = jiffies;
 877                 conn->cache_state = RXRPC_CONN_CLIENT_IDLE;
 878                 list_move_tail(&conn->cache_link, &rxnet->idle_client_conns);
 879                 if (rxnet->idle_client_conns.next == &conn->cache_link &&
 880                     !rxnet->kill_all_client_conns)
 881                         queue_delayed_work(rxrpc_workqueue,
 882                                            &rxnet->client_conn_reaper,
 883                                            rxrpc_conn_idle_client_expiry);
 884         } else {
 885                 trace_rxrpc_client(conn, channel, rxrpc_client_to_inactive);
 886                 conn->cache_state = RXRPC_CONN_CLIENT_INACTIVE;
 887                 list_del_init(&conn->cache_link);
 888         }
 889         goto out;
 890 }
 891
 892 /*
 893  * Clean up a dead client connection.
 894  */
 895 static struct rxrpc_connection *
 896 rxrpc_put_one_client_conn(struct rxrpc_connection *conn)
 897 {
 898         struct rxrpc_connection *next = NULL;
 899         struct rxrpc_local *local = conn->params.local;
 900         struct rxrpc_net *rxnet = local->rxnet;
 901         unsigned int nr_conns;
 902
 903         trace_rxrpc_client(conn, -1, rxrpc_client_cleanup);
 904
 905         if (test_bit(RXRPC_CONN_IN_CLIENT_CONNS, &conn->flags)) {
 906                 spin_lock(&local->client_conns_lock);
 907                 if (test_and_clear_bit(RXRPC_CONN_IN_CLIENT_CONNS,
 908                                        &conn->flags))
 909                         rb_erase(&conn->client_node, &local->client_conns);
 910                 spin_unlock(&local->client_conns_lock);
 911         }
 912
 913         rxrpc_put_client_connection_id(conn);
 914
 915         ASSERTCMP(conn->cache_state, ==, RXRPC_CONN_CLIENT_INACTIVE);
 916
 917         if (test_bit(RXRPC_CONN_COUNTED, &conn->flags)) {
 918                 trace_rxrpc_client(conn, -1, rxrpc_client_uncount);
 919                 spin_lock(&rxnet->client_conn_cache_lock);
 920                 nr_conns = --rxnet->nr_client_conns;
 921
 922                 if (nr_conns < rxrpc_max_client_connections &&
 923                     !list_empty(&rxnet->waiting_client_conns)) {
 924                         next = list_entry(rxnet->waiting_client_conns.next,
 925                                           struct rxrpc_connection, cache_link);
 926                         rxrpc_get_connection(next);
 927                         rxrpc_activate_conn(rxnet, next);
 928                 }
 929
 930                 spin_unlock(&rxnet->client_conn_cache_lock);
 931         }
 932
 933         rxrpc_kill_connection(conn);
 934         if (next)
 935                 rxrpc_activate_channels(next);
 936
 937         /* We need to get rid of the temporary ref we took upon next, but we
 938          * can't call rxrpc_put_connection() recursively.
 939          */
 940         return next;
 941 }
 942
 943 /*
 944  * Clean up a dead client connections.
 945  */
 946 void rxrpc_put_client_conn(struct rxrpc_connection *conn)
 947 {
 948         const void *here = __builtin_return_address(0);
 949         int n;
 950
 951         do {
 952                 n = atomic_dec_return(&conn->usage);
 953                 trace_rxrpc_conn(conn, rxrpc_conn_put_client, n, here);
 954                 if (n > 0)
 955                         return;
 956                 ASSERTCMP(n, >=, 0);
 957
 958                 conn = rxrpc_put_one_client_conn(conn);
 959         } while (conn);
 960 }
 961
 962 /*
 963  * Kill the longest-active client connections to make room for new ones.
 964  */
 965 static void rxrpc_cull_active_client_conns(struct rxrpc_net *rxnet)
 966 {
 967         struct rxrpc_connection *conn;
 968         unsigned int nr_conns = rxnet->nr_client_conns;
 969         unsigned int nr_active, limit;
 970
 971         _enter("");
 972
 973         ASSERTCMP(nr_conns, >=, 0);
 974         if (nr_conns < rxrpc_max_client_connections) {
 975                 _leave(" [ok]");
 976                 return;
 977         }
 978         limit = rxrpc_reap_client_connections;
 979
 980         spin_lock(&rxnet->client_conn_cache_lock);
 981         nr_active = rxnet->nr_active_client_conns;
 982
 983         while (nr_active > limit) {
 984                 ASSERT(!list_empty(&rxnet->active_client_conns));
 985                 conn = list_entry(rxnet->active_client_conns.next,
 986                                   struct rxrpc_connection, cache_link);
 987                 ASSERTIFCMP(conn->cache_state != RXRPC_CONN_CLIENT_ACTIVE,
 988                             conn->cache_state, ==, RXRPC_CONN_CLIENT_UPGRADE);
 989
 990                 if (list_empty(&conn->waiting_calls)) {
 991                         trace_rxrpc_client(conn, -1, rxrpc_client_to_culled);
 992                         conn->cache_state = RXRPC_CONN_CLIENT_CULLED;
 993                         list_del_init(&conn->cache_link);
 994                 } else {
 995                         trace_rxrpc_client(conn, -1, rxrpc_client_to_waiting);
 996                         conn->cache_state = RXRPC_CONN_CLIENT_WAITING;
 997                         list_move_tail(&conn->cache_link,
 998                                        &rxnet->waiting_client_conns);
 999                 }
1000
1001                 nr_active--;
1002         }
1003
1004         rxnet->nr_active_client_conns = nr_active;
1005         spin_unlock(&rxnet->client_conn_cache_lock);
1006         ASSERTCMP(nr_active, >=, 0);
1007         _leave(" [culled]");
1008 }
1009
1010 /*
1011  * Discard expired client connections from the idle list.  Each conn in the
1012  * idle list has been exposed and holds an extra ref because of that.
1013  *
1014  * This may be called from conn setup or from a work item so cannot be
1015  * considered non-reentrant.
1016  */
1017 void rxrpc_discard_expired_client_conns(struct work_struct *work)
1018 {
1019         struct rxrpc_connection *conn;
1020         struct rxrpc_net *rxnet =
1021                 container_of(to_delayed_work(work),
1022                              struct rxrpc_net, client_conn_reaper);
1023         unsigned long expiry, conn_expires_at, now;
1024         unsigned int nr_conns;
1025         bool did_discard = false;
1026
1027         _enter("");
1028
1029         if (list_empty(&rxnet->idle_client_conns)) {
1030                 _leave(" [empty]");
1031                 return;
1032         }
1033
1034         /* Don't double up on the discarding */
1035         if (!spin_trylock(&rxnet->client_conn_discard_lock)) {
1036                 _leave(" [already]");
1037                 return;
1038         }
1039
1040         /* We keep an estimate of what the number of conns ought to be after
1041          * we've discarded some so that we don't overdo the discarding.
1042          */
1043         nr_conns = rxnet->nr_client_conns;
1044
1045 next:
1046         spin_lock(&rxnet->client_conn_cache_lock);
1047
1048         if (list_empty(&rxnet->idle_client_conns))
1049                 goto out;
1050
1051         conn = list_entry(rxnet->idle_client_conns.next,
1052                           struct rxrpc_connection, cache_link);
1053         ASSERT(test_bit(RXRPC_CONN_EXPOSED, &conn->flags));
1054
1055         if (!rxnet->kill_all_client_conns) {
1056                 /* If the number of connections is over the reap limit, we
1057                  * expedite discard by reducing the expiry timeout.  We must,
1058                  * however, have at least a short grace period to be able to do
1059                  * final-ACK or ABORT retransmission.
1060                  */
1061                 expiry = rxrpc_conn_idle_client_expiry;
1062                 if (nr_conns > rxrpc_reap_client_connections)
1063                         expiry = rxrpc_conn_idle_client_fast_expiry;
1064
1065                 conn_expires_at = conn->idle_timestamp + expiry;
1066
1067                 now = READ_ONCE(jiffies);
1068                 if (time_after(conn_expires_at, now))
1069                         goto not_yet_expired;
1070         }
1071
1072         trace_rxrpc_client(conn, -1, rxrpc_client_discard);
1073         if (!test_and_clear_bit(RXRPC_CONN_EXPOSED, &conn->flags))
1074                 BUG();
1075         conn->cache_state = RXRPC_CONN_CLIENT_INACTIVE;
1076         list_del_init(&conn->cache_link);
1077
1078         spin_unlock(&rxnet->client_conn_cache_lock);
1079
1080         /* When we cleared the EXPOSED flag, we took on responsibility for the
1081          * reference that that had on the usage count.  We deal with that here.
1082          * If someone re-sets the flag and re-gets the ref, that's fine.
1083          */
1084         rxrpc_put_connection(conn);
1085         did_discard = true;
1086         nr_conns--;
1087         goto next;
1088
1089 not_yet_expired:
1090         /* The connection at the front of the queue hasn't yet expired, so
1091          * schedule the work item for that point if we discarded something.
1092          *
1093          * We don't worry if the work item is already scheduled - it can look
1094          * after rescheduling itself at a later time.  We could cancel it, but
1095          * then things get messier.
1096          */
1097         _debug("not yet");
1098         if (!rxnet->kill_all_client_conns)
1099                 queue_delayed_work(rxrpc_workqueue,
1100                                    &rxnet->client_conn_reaper,
1101                                    conn_expires_at - now);
1102
1103 out:
1104         spin_unlock(&rxnet->client_conn_cache_lock);
1105         spin_unlock(&rxnet->client_conn_discard_lock);
1106         _leave("");
1107 }
1108
1109 /*
1110  * Preemptively destroy all the client connection records rather than waiting
1111  * for them to time out
1112  */
1113 void rxrpc_destroy_all_client_connections(struct rxrpc_net *rxnet)
1114 {
1115         _enter("");
1116
1117         spin_lock(&rxnet->client_conn_cache_lock);
1118         rxnet->kill_all_client_conns = true;
1119         spin_unlock(&rxnet->client_conn_cache_lock);
1120
1121         cancel_delayed_work(&rxnet->client_conn_reaper);
1122
1123         if (!queue_delayed_work(rxrpc_workqueue, &rxnet->client_conn_reaper, 0))
1124                 _debug("destroy: queue failed");
1125
1126         _leave("");
1127 }