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TOMOYO Linux Cross Reference
Linux/net/rxrpc/conn_client.c

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  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 long rxrpc_conn_idle_client_expiry = 2 * 60 * HZ;
 89 __read_mostly unsigned long 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         /* Cancel the final ACK on the previous call if it hasn't been sent yet
558          * as the DATA packet will implicitly ACK it.
559          */
560         clear_bit(RXRPC_CONN_FINAL_ACK_0 + channel, &conn->flags);
561 
562         write_lock_bh(&call->state_lock);
563         if (!test_bit(RXRPC_CALL_TX_LASTQ, &call->flags))
564                 call->state = RXRPC_CALL_CLIENT_SEND_REQUEST;
565         else
566                 call->state = RXRPC_CALL_CLIENT_AWAIT_REPLY;
567         write_unlock_bh(&call->state_lock);
568 
569         rxrpc_see_call(call);
570         list_del_init(&call->chan_wait_link);
571         conn->active_chans |= 1 << channel;
572         call->peer      = rxrpc_get_peer(conn->params.peer);
573         call->cid       = conn->proto.cid | channel;
574         call->call_id   = call_id;
575 
576         trace_rxrpc_connect_call(call);
577         _net("CONNECT call %08x:%08x as call %d on conn %d",
578              call->cid, call->call_id, call->debug_id, conn->debug_id);
579 
580         /* Paired with the read barrier in rxrpc_wait_for_channel().  This
581          * orders cid and epoch in the connection wrt to call_id without the
582          * need to take the channel_lock.
583          *
584          * We provisionally assign a callNumber at this point, but we don't
585          * confirm it until the call is about to be exposed.
586          *
587          * TODO: Pair with a barrier in the data_ready handler when that looks
588          * at the call ID through a connection channel.
589          */
590         smp_wmb();
591         chan->call_id   = call_id;
592         rcu_assign_pointer(chan->call, call);
593         wake_up(&call->waitq);
594 }
595 
596 /*
597  * Assign channels and callNumbers to waiting calls with channel_lock
598  * held by caller.
599  */
600 static void rxrpc_activate_channels_locked(struct rxrpc_connection *conn)
601 {
602         u8 avail, mask;
603 
604         switch (conn->cache_state) {
605         case RXRPC_CONN_CLIENT_ACTIVE:
606                 mask = RXRPC_ACTIVE_CHANS_MASK;
607                 break;
608         case RXRPC_CONN_CLIENT_UPGRADE:
609                 mask = 0x01;
610                 break;
611         default:
612                 return;
613         }
614 
615         while (!list_empty(&conn->waiting_calls) &&
616                (avail = ~conn->active_chans,
617                 avail &= mask,
618                 avail != 0))
619                 rxrpc_activate_one_channel(conn, __ffs(avail));
620 }
621 
622 /*
623  * Assign channels and callNumbers to waiting calls.
624  */
625 static void rxrpc_activate_channels(struct rxrpc_connection *conn)
626 {
627         _enter("%d", conn->debug_id);
628 
629         trace_rxrpc_client(conn, -1, rxrpc_client_activate_chans);
630 
631         if (conn->active_chans == RXRPC_ACTIVE_CHANS_MASK)
632                 return;
633 
634         spin_lock(&conn->channel_lock);
635         rxrpc_activate_channels_locked(conn);
636         spin_unlock(&conn->channel_lock);
637         _leave("");
638 }
639 
640 /*
641  * Wait for a callNumber and a channel to be granted to a call.
642  */
643 static int rxrpc_wait_for_channel(struct rxrpc_call *call, gfp_t gfp)
644 {
645         int ret = 0;
646 
647         _enter("%d", call->debug_id);
648 
649         if (!call->call_id) {
650                 DECLARE_WAITQUEUE(myself, current);
651 
652                 if (!gfpflags_allow_blocking(gfp)) {
653                         ret = -EAGAIN;
654                         goto out;
655                 }
656 
657                 add_wait_queue_exclusive(&call->waitq, &myself);
658                 for (;;) {
659                         set_current_state(TASK_INTERRUPTIBLE);
660                         if (call->call_id)
661                                 break;
662                         if (signal_pending(current)) {
663                                 ret = -ERESTARTSYS;
664                                 break;
665                         }
666                         schedule();
667                 }
668                 remove_wait_queue(&call->waitq, &myself);
669                 __set_current_state(TASK_RUNNING);
670         }
671 
672         /* Paired with the write barrier in rxrpc_activate_one_channel(). */
673         smp_rmb();
674 
675 out:
676         _leave(" = %d", ret);
677         return ret;
678 }
679 
680 /*
681  * find a connection for a call
682  * - called in process context with IRQs enabled
683  */
684 int rxrpc_connect_call(struct rxrpc_call *call,
685                        struct rxrpc_conn_parameters *cp,
686                        struct sockaddr_rxrpc *srx,
687                        gfp_t gfp)
688 {
689         struct rxrpc_net *rxnet = cp->local->rxnet;
690         int ret;
691 
692         _enter("{%d,%lx},", call->debug_id, call->user_call_ID);
693 
694         rxrpc_discard_expired_client_conns(&rxnet->client_conn_reaper);
695         rxrpc_cull_active_client_conns(rxnet);
696 
697         ret = rxrpc_get_client_conn(call, cp, srx, gfp);
698         if (ret < 0)
699                 goto out;
700 
701         rxrpc_animate_client_conn(rxnet, call->conn);
702         rxrpc_activate_channels(call->conn);
703 
704         ret = rxrpc_wait_for_channel(call, gfp);
705         if (ret < 0) {
706                 rxrpc_disconnect_client_call(call);
707                 goto out;
708         }
709 
710         spin_lock_bh(&call->conn->params.peer->lock);
711         hlist_add_head(&call->error_link,
712                        &call->conn->params.peer->error_targets);
713         spin_unlock_bh(&call->conn->params.peer->lock);
714 
715 out:
716         _leave(" = %d", ret);
717         return ret;
718 }
719 
720 /*
721  * Note that a connection is about to be exposed to the world.  Once it is
722  * exposed, we maintain an extra ref on it that stops it from being summarily
723  * discarded before it's (a) had a chance to deal with retransmission and (b)
724  * had a chance at re-use (the per-connection security negotiation is
725  * expensive).
726  */
727 static void rxrpc_expose_client_conn(struct rxrpc_connection *conn,
728                                      unsigned int channel)
729 {
730         if (!test_and_set_bit(RXRPC_CONN_EXPOSED, &conn->flags)) {
731                 trace_rxrpc_client(conn, channel, rxrpc_client_exposed);
732                 rxrpc_get_connection(conn);
733         }
734 }
735 
736 /*
737  * Note that a call, and thus a connection, is about to be exposed to the
738  * world.
739  */
740 void rxrpc_expose_client_call(struct rxrpc_call *call)
741 {
742         unsigned int channel = call->cid & RXRPC_CHANNELMASK;
743         struct rxrpc_connection *conn = call->conn;
744         struct rxrpc_channel *chan = &conn->channels[channel];
745 
746         if (!test_and_set_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
747                 /* Mark the call ID as being used.  If the callNumber counter
748                  * exceeds ~2 billion, we kill the connection after its
749                  * outstanding calls have finished so that the counter doesn't
750                  * wrap.
751                  */
752                 chan->call_counter++;
753                 if (chan->call_counter >= INT_MAX)
754                         set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags);
755                 rxrpc_expose_client_conn(conn, channel);
756         }
757 }
758 
759 /*
760  * Set the reap timer.
761  */
762 static void rxrpc_set_client_reap_timer(struct rxrpc_net *rxnet)
763 {
764         unsigned long now = jiffies;
765         unsigned long reap_at = now + rxrpc_conn_idle_client_expiry;
766 
767         if (rxnet->live)
768                 timer_reduce(&rxnet->client_conn_reap_timer, reap_at);
769 }
770 
771 /*
772  * Disconnect a client call.
773  */
774 void rxrpc_disconnect_client_call(struct rxrpc_call *call)
775 {
776         unsigned int channel = call->cid & RXRPC_CHANNELMASK;
777         struct rxrpc_connection *conn = call->conn;
778         struct rxrpc_channel *chan = &conn->channels[channel];
779         struct rxrpc_net *rxnet = rxrpc_net(sock_net(&call->socket->sk));
780 
781         trace_rxrpc_client(conn, channel, rxrpc_client_chan_disconnect);
782         call->conn = NULL;
783 
784         spin_lock(&conn->channel_lock);
785 
786         /* Calls that have never actually been assigned a channel can simply be
787          * discarded.  If the conn didn't get used either, it will follow
788          * immediately unless someone else grabs it in the meantime.
789          */
790         if (!list_empty(&call->chan_wait_link)) {
791                 _debug("call is waiting");
792                 ASSERTCMP(call->call_id, ==, 0);
793                 ASSERT(!test_bit(RXRPC_CALL_EXPOSED, &call->flags));
794                 list_del_init(&call->chan_wait_link);
795 
796                 trace_rxrpc_client(conn, channel, rxrpc_client_chan_unstarted);
797 
798                 /* We must deactivate or idle the connection if it's now
799                  * waiting for nothing.
800                  */
801                 spin_lock(&rxnet->client_conn_cache_lock);
802                 if (conn->cache_state == RXRPC_CONN_CLIENT_WAITING &&
803                     list_empty(&conn->waiting_calls) &&
804                     !conn->active_chans)
805                         goto idle_connection;
806                 goto out;
807         }
808 
809         ASSERTCMP(rcu_access_pointer(chan->call), ==, call);
810 
811         /* If a client call was exposed to the world, we save the result for
812          * retransmission.
813          *
814          * We use a barrier here so that the call number and abort code can be
815          * read without needing to take a lock.
816          *
817          * TODO: Make the incoming packet handler check this and handle
818          * terminal retransmission without requiring access to the call.
819          */
820         if (test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
821                 _debug("exposed %u,%u", call->call_id, call->abort_code);
822                 __rxrpc_disconnect_call(conn, call);
823         }
824 
825         /* See if we can pass the channel directly to another call. */
826         if (conn->cache_state == RXRPC_CONN_CLIENT_ACTIVE &&
827             !list_empty(&conn->waiting_calls)) {
828                 trace_rxrpc_client(conn, channel, rxrpc_client_chan_pass);
829                 rxrpc_activate_one_channel(conn, channel);
830                 goto out_2;
831         }
832 
833         /* Schedule the final ACK to be transmitted in a short while so that it
834          * can be skipped if we find a follow-on call.  The first DATA packet
835          * of the follow on call will implicitly ACK this call.
836          */
837         if (test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
838                 unsigned long final_ack_at = jiffies + 2;
839 
840                 WRITE_ONCE(chan->final_ack_at, final_ack_at);
841                 smp_wmb(); /* vs rxrpc_process_delayed_final_acks() */
842                 set_bit(RXRPC_CONN_FINAL_ACK_0 + channel, &conn->flags);
843                 rxrpc_reduce_conn_timer(conn, final_ack_at);
844         }
845 
846         /* Things are more complex and we need the cache lock.  We might be
847          * able to simply idle the conn or it might now be lurking on the wait
848          * list.  It might even get moved back to the active list whilst we're
849          * waiting for the lock.
850          */
851         spin_lock(&rxnet->client_conn_cache_lock);
852 
853         switch (conn->cache_state) {
854         case RXRPC_CONN_CLIENT_UPGRADE:
855                 /* Deal with termination of a service upgrade probe. */
856                 if (test_bit(RXRPC_CONN_EXPOSED, &conn->flags)) {
857                         clear_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags);
858                         trace_rxrpc_client(conn, channel, rxrpc_client_to_active);
859                         conn->cache_state = RXRPC_CONN_CLIENT_ACTIVE;
860                         rxrpc_activate_channels_locked(conn);
861                 }
862                 /* fall through */
863         case RXRPC_CONN_CLIENT_ACTIVE:
864                 if (list_empty(&conn->waiting_calls)) {
865                         rxrpc_deactivate_one_channel(conn, channel);
866                         if (!conn->active_chans) {
867                                 rxnet->nr_active_client_conns--;
868                                 goto idle_connection;
869                         }
870                         goto out;
871                 }
872 
873                 trace_rxrpc_client(conn, channel, rxrpc_client_chan_pass);
874                 rxrpc_activate_one_channel(conn, channel);
875                 goto out;
876 
877         case RXRPC_CONN_CLIENT_CULLED:
878                 rxrpc_deactivate_one_channel(conn, channel);
879                 ASSERT(list_empty(&conn->waiting_calls));
880                 if (!conn->active_chans)
881                         goto idle_connection;
882                 goto out;
883 
884         case RXRPC_CONN_CLIENT_WAITING:
885                 rxrpc_deactivate_one_channel(conn, channel);
886                 goto out;
887 
888         default:
889                 BUG();
890         }
891 
892 out:
893         spin_unlock(&rxnet->client_conn_cache_lock);
894 out_2:
895         spin_unlock(&conn->channel_lock);
896         rxrpc_put_connection(conn);
897         _leave("");
898         return;
899 
900 idle_connection:
901         /* As no channels remain active, the connection gets deactivated
902          * immediately or moved to the idle list for a short while.
903          */
904         if (test_bit(RXRPC_CONN_EXPOSED, &conn->flags)) {
905                 trace_rxrpc_client(conn, channel, rxrpc_client_to_idle);
906                 conn->idle_timestamp = jiffies;
907                 conn->cache_state = RXRPC_CONN_CLIENT_IDLE;
908                 list_move_tail(&conn->cache_link, &rxnet->idle_client_conns);
909                 if (rxnet->idle_client_conns.next == &conn->cache_link &&
910                     !rxnet->kill_all_client_conns)
911                         rxrpc_set_client_reap_timer(rxnet);
912         } else {
913                 trace_rxrpc_client(conn, channel, rxrpc_client_to_inactive);
914                 conn->cache_state = RXRPC_CONN_CLIENT_INACTIVE;
915                 list_del_init(&conn->cache_link);
916         }
917         goto out;
918 }
919 
920 /*
921  * Clean up a dead client connection.
922  */
923 static struct rxrpc_connection *
924 rxrpc_put_one_client_conn(struct rxrpc_connection *conn)
925 {
926         struct rxrpc_connection *next = NULL;
927         struct rxrpc_local *local = conn->params.local;
928         struct rxrpc_net *rxnet = local->rxnet;
929         unsigned int nr_conns;
930 
931         trace_rxrpc_client(conn, -1, rxrpc_client_cleanup);
932 
933         if (test_bit(RXRPC_CONN_IN_CLIENT_CONNS, &conn->flags)) {
934                 spin_lock(&local->client_conns_lock);
935                 if (test_and_clear_bit(RXRPC_CONN_IN_CLIENT_CONNS,
936                                        &conn->flags))
937                         rb_erase(&conn->client_node, &local->client_conns);
938                 spin_unlock(&local->client_conns_lock);
939         }
940 
941         rxrpc_put_client_connection_id(conn);
942 
943         ASSERTCMP(conn->cache_state, ==, RXRPC_CONN_CLIENT_INACTIVE);
944 
945         if (test_bit(RXRPC_CONN_COUNTED, &conn->flags)) {
946                 trace_rxrpc_client(conn, -1, rxrpc_client_uncount);
947                 spin_lock(&rxnet->client_conn_cache_lock);
948                 nr_conns = --rxnet->nr_client_conns;
949 
950                 if (nr_conns < rxrpc_max_client_connections &&
951                     !list_empty(&rxnet->waiting_client_conns)) {
952                         next = list_entry(rxnet->waiting_client_conns.next,
953                                           struct rxrpc_connection, cache_link);
954                         rxrpc_get_connection(next);
955                         rxrpc_activate_conn(rxnet, next);
956                 }
957 
958                 spin_unlock(&rxnet->client_conn_cache_lock);
959         }
960 
961         rxrpc_kill_connection(conn);
962         if (next)
963                 rxrpc_activate_channels(next);
964 
965         /* We need to get rid of the temporary ref we took upon next, but we
966          * can't call rxrpc_put_connection() recursively.
967          */
968         return next;
969 }
970 
971 /*
972  * Clean up a dead client connections.
973  */
974 void rxrpc_put_client_conn(struct rxrpc_connection *conn)
975 {
976         const void *here = __builtin_return_address(0);
977         int n;
978 
979         do {
980                 n = atomic_dec_return(&conn->usage);
981                 trace_rxrpc_conn(conn, rxrpc_conn_put_client, n, here);
982                 if (n > 0)
983                         return;
984                 ASSERTCMP(n, >=, 0);
985 
986                 conn = rxrpc_put_one_client_conn(conn);
987         } while (conn);
988 }
989 
990 /*
991  * Kill the longest-active client connections to make room for new ones.
992  */
993 static void rxrpc_cull_active_client_conns(struct rxrpc_net *rxnet)
994 {
995         struct rxrpc_connection *conn;
996         unsigned int nr_conns = rxnet->nr_client_conns;
997         unsigned int nr_active, limit;
998 
999         _enter("");
1000 
1001         ASSERTCMP(nr_conns, >=, 0);
1002         if (nr_conns < rxrpc_max_client_connections) {
1003                 _leave(" [ok]");
1004                 return;
1005         }
1006         limit = rxrpc_reap_client_connections;
1007 
1008         spin_lock(&rxnet->client_conn_cache_lock);
1009         nr_active = rxnet->nr_active_client_conns;
1010 
1011         while (nr_active > limit) {
1012                 ASSERT(!list_empty(&rxnet->active_client_conns));
1013                 conn = list_entry(rxnet->active_client_conns.next,
1014                                   struct rxrpc_connection, cache_link);
1015                 ASSERTIFCMP(conn->cache_state != RXRPC_CONN_CLIENT_ACTIVE,
1016                             conn->cache_state, ==, RXRPC_CONN_CLIENT_UPGRADE);
1017 
1018                 if (list_empty(&conn->waiting_calls)) {
1019                         trace_rxrpc_client(conn, -1, rxrpc_client_to_culled);
1020                         conn->cache_state = RXRPC_CONN_CLIENT_CULLED;
1021                         list_del_init(&conn->cache_link);
1022                 } else {
1023                         trace_rxrpc_client(conn, -1, rxrpc_client_to_waiting);
1024                         conn->cache_state = RXRPC_CONN_CLIENT_WAITING;
1025                         list_move_tail(&conn->cache_link,
1026                                        &rxnet->waiting_client_conns);
1027                 }
1028 
1029                 nr_active--;
1030         }
1031 
1032         rxnet->nr_active_client_conns = nr_active;
1033         spin_unlock(&rxnet->client_conn_cache_lock);
1034         ASSERTCMP(nr_active, >=, 0);
1035         _leave(" [culled]");
1036 }
1037 
1038 /*
1039  * Discard expired client connections from the idle list.  Each conn in the
1040  * idle list has been exposed and holds an extra ref because of that.
1041  *
1042  * This may be called from conn setup or from a work item so cannot be
1043  * considered non-reentrant.
1044  */
1045 void rxrpc_discard_expired_client_conns(struct work_struct *work)
1046 {
1047         struct rxrpc_connection *conn;
1048         struct rxrpc_net *rxnet =
1049                 container_of(work, struct rxrpc_net, client_conn_reaper);
1050         unsigned long expiry, conn_expires_at, now;
1051         unsigned int nr_conns;
1052         bool did_discard = false;
1053 
1054         _enter("");
1055 
1056         if (list_empty(&rxnet->idle_client_conns)) {
1057                 _leave(" [empty]");
1058                 return;
1059         }
1060 
1061         /* Don't double up on the discarding */
1062         if (!spin_trylock(&rxnet->client_conn_discard_lock)) {
1063                 _leave(" [already]");
1064                 return;
1065         }
1066 
1067         /* We keep an estimate of what the number of conns ought to be after
1068          * we've discarded some so that we don't overdo the discarding.
1069          */
1070         nr_conns = rxnet->nr_client_conns;
1071 
1072 next:
1073         spin_lock(&rxnet->client_conn_cache_lock);
1074 
1075         if (list_empty(&rxnet->idle_client_conns))
1076                 goto out;
1077 
1078         conn = list_entry(rxnet->idle_client_conns.next,
1079                           struct rxrpc_connection, cache_link);
1080         ASSERT(test_bit(RXRPC_CONN_EXPOSED, &conn->flags));
1081 
1082         if (!rxnet->kill_all_client_conns) {
1083                 /* If the number of connections is over the reap limit, we
1084                  * expedite discard by reducing the expiry timeout.  We must,
1085                  * however, have at least a short grace period to be able to do
1086                  * final-ACK or ABORT retransmission.
1087                  */
1088                 expiry = rxrpc_conn_idle_client_expiry;
1089                 if (nr_conns > rxrpc_reap_client_connections)
1090                         expiry = rxrpc_conn_idle_client_fast_expiry;
1091                 if (conn->params.local->service_closed)
1092                         expiry = rxrpc_closed_conn_expiry * HZ;
1093 
1094                 conn_expires_at = conn->idle_timestamp + expiry;
1095 
1096                 now = READ_ONCE(jiffies);
1097                 if (time_after(conn_expires_at, now))
1098                         goto not_yet_expired;
1099         }
1100 
1101         trace_rxrpc_client(conn, -1, rxrpc_client_discard);
1102         if (!test_and_clear_bit(RXRPC_CONN_EXPOSED, &conn->flags))
1103                 BUG();
1104         conn->cache_state = RXRPC_CONN_CLIENT_INACTIVE;
1105         list_del_init(&conn->cache_link);
1106 
1107         spin_unlock(&rxnet->client_conn_cache_lock);
1108 
1109         /* When we cleared the EXPOSED flag, we took on responsibility for the
1110          * reference that that had on the usage count.  We deal with that here.
1111          * If someone re-sets the flag and re-gets the ref, that's fine.
1112          */
1113         rxrpc_put_connection(conn);
1114         did_discard = true;
1115         nr_conns--;
1116         goto next;
1117 
1118 not_yet_expired:
1119         /* The connection at the front of the queue hasn't yet expired, so
1120          * schedule the work item for that point if we discarded something.
1121          *
1122          * We don't worry if the work item is already scheduled - it can look
1123          * after rescheduling itself at a later time.  We could cancel it, but
1124          * then things get messier.
1125          */
1126         _debug("not yet");
1127         if (!rxnet->kill_all_client_conns)
1128                 timer_reduce(&rxnet->client_conn_reap_timer,
1129                              conn_expires_at);
1130 
1131 out:
1132         spin_unlock(&rxnet->client_conn_cache_lock);
1133         spin_unlock(&rxnet->client_conn_discard_lock);
1134         _leave("");
1135 }
1136 
1137 /*
1138  * Preemptively destroy all the client connection records rather than waiting
1139  * for them to time out
1140  */
1141 void rxrpc_destroy_all_client_connections(struct rxrpc_net *rxnet)
1142 {
1143         _enter("");
1144 
1145         spin_lock(&rxnet->client_conn_cache_lock);
1146         rxnet->kill_all_client_conns = true;
1147         spin_unlock(&rxnet->client_conn_cache_lock);
1148 
1149         del_timer_sync(&rxnet->client_conn_reap_timer);
1150 
1151         if (!rxrpc_queue_work(&rxnet->client_conn_reaper))
1152                 _debug("destroy: queue failed");
1153 
1154         _leave("");
1155 }
1156 

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