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

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /* Client connection-specific management code.
  3  *
  4  * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
  5  * Written by David Howells (dhowells@redhat.com)
  6  *
  7  * Client connections need to be cached for a little while after they've made a
  8  * call so as to handle retransmitted DATA packets in case the server didn't
  9  * receive the final ACK or terminating ABORT we sent it.
 10  *
 11  * Client connections can be in one of a number of cache states:
 12  *
 13  *  (1) INACTIVE - The connection is not held in any list and may not have been
 14  *      exposed to the world.  If it has been previously exposed, it was
 15  *      discarded from the idle list after expiring.
 16  *
 17  *  (2) WAITING - The connection is waiting for the number of client conns to
 18  *      drop below the maximum capacity.  Calls may be in progress upon it from
 19  *      when it was active and got culled.
 20  *
 21  *      The connection is on the rxrpc_waiting_client_conns list which is kept
 22  *      in to-be-granted order.  Culled conns with waiters go to the back of
 23  *      the queue just like new conns.
 24  *
 25  *  (3) ACTIVE - The connection has at least one call in progress upon it, it
 26  *      may freely grant available channels to new calls and calls may be
 27  *      waiting on it for channels to become available.
 28  *
 29  *      The connection is on the rxnet->active_client_conns list which is kept
 30  *      in activation order for culling purposes.
 31  *
 32  *      rxrpc_nr_active_client_conns is held incremented also.
 33  *
 34  *  (4) UPGRADE - As for ACTIVE, but only one call may be in progress and is
 35  *      being used to probe for service upgrade.
 36  *
 37  *  (5) CULLED - The connection got summarily culled to try and free up
 38  *      capacity.  Calls currently in progress on the connection are allowed to
 39  *      continue, but new calls will have to wait.  There can be no waiters in
 40  *      this state - the conn would have to go to the WAITING state instead.
 41  *
 42  *  (6) IDLE - The connection has no calls in progress upon it and must have
 43  *      been exposed to the world (ie. the EXPOSED flag must be set).  When it
 44  *      expires, the EXPOSED flag is cleared and the connection transitions to
 45  *      the INACTIVE state.
 46  *
 47  *      The connection is on the rxnet->idle_client_conns list which is kept in
 48  *      order of how soon they'll expire.
 49  *
 50  * There are flags of relevance to the cache:
 51  *
 52  *  (1) EXPOSED - The connection ID got exposed to the world.  If this flag is
 53  *      set, an extra ref is added to the connection preventing it from being
 54  *      reaped when it has no calls outstanding.  This flag is cleared and the
 55  *      ref dropped when a conn is discarded from the idle list.
 56  *
 57  *      This allows us to move terminal call state retransmission to the
 58  *      connection and to discard the call immediately we think it is done
 59  *      with.  It also give us a chance to reuse the connection.
 60  *
 61  *  (2) DONT_REUSE - The connection should be discarded as soon as possible and
 62  *      should not be reused.  This is set when an exclusive connection is used
 63  *      or a call ID counter overflows.
 64  *
 65  * The caching state may only be changed if the cache lock is held.
 66  *
 67  * There are two idle client connection expiry durations.  If the total number
 68  * of connections is below the reap threshold, we use the normal duration; if
 69  * it's above, we use the fast duration.
 70  */
 71 
 72 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 73 
 74 #include <linux/slab.h>
 75 #include <linux/idr.h>
 76 #include <linux/timer.h>
 77 #include <linux/sched/signal.h>
 78 
 79 #include "ar-internal.h"
 80 
 81 __read_mostly unsigned int rxrpc_max_client_connections = 1000;
 82 __read_mostly unsigned int rxrpc_reap_client_connections = 900;
 83 __read_mostly unsigned long rxrpc_conn_idle_client_expiry = 2 * 60 * HZ;
 84 __read_mostly unsigned long rxrpc_conn_idle_client_fast_expiry = 2 * HZ;
 85 
 86 /*
 87  * We use machine-unique IDs for our client connections.
 88  */
 89 DEFINE_IDR(rxrpc_client_conn_ids);
 90 static DEFINE_SPINLOCK(rxrpc_conn_id_lock);
 91 
 92 static void rxrpc_cull_active_client_conns(struct rxrpc_net *);
 93 
 94 /*
 95  * Get a connection ID and epoch for a client connection from the global pool.
 96  * The connection struct pointer is then recorded in the idr radix tree.  The
 97  * epoch doesn't change until the client is rebooted (or, at least, unless the
 98  * module is unloaded).
 99  */
100 static int rxrpc_get_client_connection_id(struct rxrpc_connection *conn,
101                                           gfp_t gfp)
102 {
103         struct rxrpc_net *rxnet = conn->params.local->rxnet;
104         int id;
105 
106         _enter("");
107 
108         idr_preload(gfp);
109         spin_lock(&rxrpc_conn_id_lock);
110 
111         id = idr_alloc_cyclic(&rxrpc_client_conn_ids, conn,
112                               1, 0x40000000, GFP_NOWAIT);
113         if (id < 0)
114                 goto error;
115 
116         spin_unlock(&rxrpc_conn_id_lock);
117         idr_preload_end();
118 
119         conn->proto.epoch = rxnet->epoch;
120         conn->proto.cid = id << RXRPC_CIDSHIFT;
121         set_bit(RXRPC_CONN_HAS_IDR, &conn->flags);
122         _leave(" [CID %x]", conn->proto.cid);
123         return 0;
124 
125 error:
126         spin_unlock(&rxrpc_conn_id_lock);
127         idr_preload_end();
128         _leave(" = %d", id);
129         return id;
130 }
131 
132 /*
133  * Release a connection ID for a client connection from the global pool.
134  */
135 static void rxrpc_put_client_connection_id(struct rxrpc_connection *conn)
136 {
137         if (test_bit(RXRPC_CONN_HAS_IDR, &conn->flags)) {
138                 spin_lock(&rxrpc_conn_id_lock);
139                 idr_remove(&rxrpc_client_conn_ids,
140                            conn->proto.cid >> RXRPC_CIDSHIFT);
141                 spin_unlock(&rxrpc_conn_id_lock);
142         }
143 }
144 
145 /*
146  * Destroy the client connection ID tree.
147  */
148 void rxrpc_destroy_client_conn_ids(void)
149 {
150         struct rxrpc_connection *conn;
151         int id;
152 
153         if (!idr_is_empty(&rxrpc_client_conn_ids)) {
154                 idr_for_each_entry(&rxrpc_client_conn_ids, conn, id) {
155                         pr_err("AF_RXRPC: Leaked client conn %p {%d}\n",
156                                conn, atomic_read(&conn->usage));
157                 }
158                 BUG();
159         }
160 
161         idr_destroy(&rxrpc_client_conn_ids);
162 }
163 
164 /*
165  * Allocate a client connection.
166  */
167 static struct rxrpc_connection *
168 rxrpc_alloc_client_connection(struct rxrpc_conn_parameters *cp, gfp_t gfp)
169 {
170         struct rxrpc_connection *conn;
171         struct rxrpc_net *rxnet = cp->local->rxnet;
172         int ret;
173 
174         _enter("");
175 
176         conn = rxrpc_alloc_connection(gfp);
177         if (!conn) {
178                 _leave(" = -ENOMEM");
179                 return ERR_PTR(-ENOMEM);
180         }
181 
182         atomic_set(&conn->usage, 1);
183         if (cp->exclusive)
184                 __set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags);
185         if (cp->upgrade)
186                 __set_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags);
187 
188         conn->params            = *cp;
189         conn->out_clientflag    = RXRPC_CLIENT_INITIATED;
190         conn->state             = RXRPC_CONN_CLIENT;
191         conn->service_id        = cp->service_id;
192 
193         ret = rxrpc_get_client_connection_id(conn, gfp);
194         if (ret < 0)
195                 goto error_0;
196 
197         ret = rxrpc_init_client_conn_security(conn);
198         if (ret < 0)
199                 goto error_1;
200 
201         ret = conn->security->prime_packet_security(conn);
202         if (ret < 0)
203                 goto error_2;
204 
205         atomic_inc(&rxnet->nr_conns);
206         write_lock(&rxnet->conn_lock);
207         list_add_tail(&conn->proc_link, &rxnet->conn_proc_list);
208         write_unlock(&rxnet->conn_lock);
209 
210         /* We steal the caller's peer ref. */
211         cp->peer = NULL;
212         rxrpc_get_local(conn->params.local);
213         key_get(conn->params.key);
214 
215         trace_rxrpc_conn(conn, rxrpc_conn_new_client, atomic_read(&conn->usage),
216                          __builtin_return_address(0));
217         trace_rxrpc_client(conn, -1, rxrpc_client_alloc);
218         _leave(" = %p", conn);
219         return conn;
220 
221 error_2:
222         conn->security->clear(conn);
223 error_1:
224         rxrpc_put_client_connection_id(conn);
225 error_0:
226         kfree(conn);
227         _leave(" = %d", ret);
228         return ERR_PTR(ret);
229 }
230 
231 /*
232  * Determine if a connection may be reused.
233  */
234 static bool rxrpc_may_reuse_conn(struct rxrpc_connection *conn)
235 {
236         struct rxrpc_net *rxnet = conn->params.local->rxnet;
237         int id_cursor, id, distance, limit;
238 
239         if (test_bit(RXRPC_CONN_DONT_REUSE, &conn->flags))
240                 goto dont_reuse;
241 
242         if (conn->proto.epoch != rxnet->epoch)
243                 goto mark_dont_reuse;
244 
245         /* The IDR tree gets very expensive on memory if the connection IDs are
246          * widely scattered throughout the number space, so we shall want to
247          * kill off connections that, say, have an ID more than about four
248          * times the maximum number of client conns away from the current
249          * allocation point to try and keep the IDs concentrated.
250          */
251         id_cursor = idr_get_cursor(&rxrpc_client_conn_ids);
252         id = conn->proto.cid >> RXRPC_CIDSHIFT;
253         distance = id - id_cursor;
254         if (distance < 0)
255                 distance = -distance;
256         limit = max(rxrpc_max_client_connections * 4, 1024U);
257         if (distance > limit)
258                 goto mark_dont_reuse;
259 
260         return true;
261 
262 mark_dont_reuse:
263         set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags);
264 dont_reuse:
265         return false;
266 }
267 
268 /*
269  * Create or find a client connection to use for a call.
270  *
271  * If we return with a connection, the call will be on its waiting list.  It's
272  * left to the caller to assign a channel and wake up the call.
273  */
274 static int rxrpc_get_client_conn(struct rxrpc_sock *rx,
275                                  struct rxrpc_call *call,
276                                  struct rxrpc_conn_parameters *cp,
277                                  struct sockaddr_rxrpc *srx,
278                                  gfp_t gfp)
279 {
280         struct rxrpc_connection *conn, *candidate = NULL;
281         struct rxrpc_local *local = cp->local;
282         struct rb_node *p, **pp, *parent;
283         long diff;
284         int ret = -ENOMEM;
285 
286         _enter("{%d,%lx},", call->debug_id, call->user_call_ID);
287 
288         cp->peer = rxrpc_lookup_peer(rx, cp->local, srx, gfp);
289         if (!cp->peer)
290                 goto error;
291 
292         call->cong_cwnd = cp->peer->cong_cwnd;
293         if (call->cong_cwnd >= call->cong_ssthresh)
294                 call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
295         else
296                 call->cong_mode = RXRPC_CALL_SLOW_START;
297 
298         /* If the connection is not meant to be exclusive, search the available
299          * connections to see if the connection we want to use already exists.
300          */
301         if (!cp->exclusive) {
302                 _debug("search 1");
303                 spin_lock(&local->client_conns_lock);
304                 p = local->client_conns.rb_node;
305                 while (p) {
306                         conn = rb_entry(p, struct rxrpc_connection, client_node);
307 
308 #define cmp(X) ((long)conn->params.X - (long)cp->X)
309                         diff = (cmp(peer) ?:
310                                 cmp(key) ?:
311                                 cmp(security_level) ?:
312                                 cmp(upgrade));
313 #undef cmp
314                         if (diff < 0) {
315                                 p = p->rb_left;
316                         } else if (diff > 0) {
317                                 p = p->rb_right;
318                         } else {
319                                 if (rxrpc_may_reuse_conn(conn) &&
320                                     rxrpc_get_connection_maybe(conn))
321                                         goto found_extant_conn;
322                                 /* The connection needs replacing.  It's better
323                                  * to effect that when we have something to
324                                  * replace it with so that we don't have to
325                                  * rebalance the tree twice.
326                                  */
327                                 break;
328                         }
329                 }
330                 spin_unlock(&local->client_conns_lock);
331         }
332 
333         /* There wasn't a connection yet or we need an exclusive connection.
334          * We need to create a candidate and then potentially redo the search
335          * in case we're racing with another thread also trying to connect on a
336          * shareable connection.
337          */
338         _debug("new conn");
339         candidate = rxrpc_alloc_client_connection(cp, gfp);
340         if (IS_ERR(candidate)) {
341                 ret = PTR_ERR(candidate);
342                 goto error_peer;
343         }
344 
345         /* Add the call to the new connection's waiting list in case we're
346          * going to have to wait for the connection to come live.  It's our
347          * connection, so we want first dibs on the channel slots.  We would
348          * normally have to take channel_lock but we do this before anyone else
349          * can see the connection.
350          */
351         list_add(&call->chan_wait_link, &candidate->waiting_calls);
352 
353         if (cp->exclusive) {
354                 call->conn = candidate;
355                 call->security_ix = candidate->security_ix;
356                 call->service_id = candidate->service_id;
357                 _leave(" = 0 [exclusive %d]", candidate->debug_id);
358                 return 0;
359         }
360 
361         /* Publish the new connection for userspace to find.  We need to redo
362          * the search before doing this lest we race with someone else adding a
363          * conflicting instance.
364          */
365         _debug("search 2");
366         spin_lock(&local->client_conns_lock);
367 
368         pp = &local->client_conns.rb_node;
369         parent = NULL;
370         while (*pp) {
371                 parent = *pp;
372                 conn = rb_entry(parent, struct rxrpc_connection, client_node);
373 
374 #define cmp(X) ((long)conn->params.X - (long)candidate->params.X)
375                 diff = (cmp(peer) ?:
376                         cmp(key) ?:
377                         cmp(security_level) ?:
378                         cmp(upgrade));
379 #undef cmp
380                 if (diff < 0) {
381                         pp = &(*pp)->rb_left;
382                 } else if (diff > 0) {
383                         pp = &(*pp)->rb_right;
384                 } else {
385                         if (rxrpc_may_reuse_conn(conn) &&
386                             rxrpc_get_connection_maybe(conn))
387                                 goto found_extant_conn;
388                         /* The old connection is from an outdated epoch. */
389                         _debug("replace conn");
390                         clear_bit(RXRPC_CONN_IN_CLIENT_CONNS, &conn->flags);
391                         rb_replace_node(&conn->client_node,
392                                         &candidate->client_node,
393                                         &local->client_conns);
394                         trace_rxrpc_client(conn, -1, rxrpc_client_replace);
395                         goto candidate_published;
396                 }
397         }
398 
399         _debug("new conn");
400         rb_link_node(&candidate->client_node, parent, pp);
401         rb_insert_color(&candidate->client_node, &local->client_conns);
402 
403 candidate_published:
404         set_bit(RXRPC_CONN_IN_CLIENT_CONNS, &candidate->flags);
405         call->conn = candidate;
406         call->security_ix = candidate->security_ix;
407         call->service_id = candidate->service_id;
408         spin_unlock(&local->client_conns_lock);
409         _leave(" = 0 [new %d]", candidate->debug_id);
410         return 0;
411 
412         /* We come here if we found a suitable connection already in existence.
413          * Discard any candidate we may have allocated, and try to get a
414          * channel on this one.
415          */
416 found_extant_conn:
417         _debug("found conn");
418         spin_unlock(&local->client_conns_lock);
419 
420         if (candidate) {
421                 trace_rxrpc_client(candidate, -1, rxrpc_client_duplicate);
422                 rxrpc_put_connection(candidate);
423                 candidate = NULL;
424         }
425 
426         spin_lock(&conn->channel_lock);
427         call->conn = conn;
428         call->security_ix = conn->security_ix;
429         call->service_id = conn->service_id;
430         list_add_tail(&call->chan_wait_link, &conn->waiting_calls);
431         spin_unlock(&conn->channel_lock);
432         _leave(" = 0 [extant %d]", conn->debug_id);
433         return 0;
434 
435 error_peer:
436         rxrpc_put_peer(cp->peer);
437         cp->peer = NULL;
438 error:
439         _leave(" = %d", ret);
440         return ret;
441 }
442 
443 /*
444  * Activate a connection.
445  */
446 static void rxrpc_activate_conn(struct rxrpc_net *rxnet,
447                                 struct rxrpc_connection *conn)
448 {
449         if (test_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags)) {
450                 trace_rxrpc_client(conn, -1, rxrpc_client_to_upgrade);
451                 conn->cache_state = RXRPC_CONN_CLIENT_UPGRADE;
452         } else {
453                 trace_rxrpc_client(conn, -1, rxrpc_client_to_active);
454                 conn->cache_state = RXRPC_CONN_CLIENT_ACTIVE;
455         }
456         rxnet->nr_active_client_conns++;
457         list_move_tail(&conn->cache_link, &rxnet->active_client_conns);
458 }
459 
460 /*
461  * Attempt to animate a connection for a new call.
462  *
463  * If it's not exclusive, the connection is in the endpoint tree, and we're in
464  * the conn's list of those waiting to grab a channel.  There is, however, a
465  * limit on the number of live connections allowed at any one time, so we may
466  * have to wait for capacity to become available.
467  *
468  * Note that a connection on the waiting queue might *also* have active
469  * channels if it has been culled to make space and then re-requested by a new
470  * call.
471  */
472 static void rxrpc_animate_client_conn(struct rxrpc_net *rxnet,
473                                       struct rxrpc_connection *conn)
474 {
475         unsigned int nr_conns;
476 
477         _enter("%d,%d", conn->debug_id, conn->cache_state);
478 
479         if (conn->cache_state == RXRPC_CONN_CLIENT_ACTIVE ||
480             conn->cache_state == RXRPC_CONN_CLIENT_UPGRADE)
481                 goto out;
482 
483         spin_lock(&rxnet->client_conn_cache_lock);
484 
485         nr_conns = rxnet->nr_client_conns;
486         if (!test_and_set_bit(RXRPC_CONN_COUNTED, &conn->flags)) {
487                 trace_rxrpc_client(conn, -1, rxrpc_client_count);
488                 rxnet->nr_client_conns = nr_conns + 1;
489         }
490 
491         switch (conn->cache_state) {
492         case RXRPC_CONN_CLIENT_ACTIVE:
493         case RXRPC_CONN_CLIENT_UPGRADE:
494         case RXRPC_CONN_CLIENT_WAITING:
495                 break;
496 
497         case RXRPC_CONN_CLIENT_INACTIVE:
498         case RXRPC_CONN_CLIENT_CULLED:
499         case RXRPC_CONN_CLIENT_IDLE:
500                 if (nr_conns >= rxrpc_max_client_connections)
501                         goto wait_for_capacity;
502                 goto activate_conn;
503 
504         default:
505                 BUG();
506         }
507 
508 out_unlock:
509         spin_unlock(&rxnet->client_conn_cache_lock);
510 out:
511         _leave(" [%d]", conn->cache_state);
512         return;
513 
514 activate_conn:
515         _debug("activate");
516         rxrpc_activate_conn(rxnet, conn);
517         goto out_unlock;
518 
519 wait_for_capacity:
520         _debug("wait");
521         trace_rxrpc_client(conn, -1, rxrpc_client_to_waiting);
522         conn->cache_state = RXRPC_CONN_CLIENT_WAITING;
523         list_move_tail(&conn->cache_link, &rxnet->waiting_client_conns);
524         goto out_unlock;
525 }
526 
527 /*
528  * Deactivate a channel.
529  */
530 static void rxrpc_deactivate_one_channel(struct rxrpc_connection *conn,
531                                          unsigned int channel)
532 {
533         struct rxrpc_channel *chan = &conn->channels[channel];
534 
535         rcu_assign_pointer(chan->call, NULL);
536         conn->active_chans &= ~(1 << channel);
537 }
538 
539 /*
540  * Assign a channel to the call at the front of the queue and wake the call up.
541  * We don't increment the callNumber counter until this number has been exposed
542  * to the world.
543  */
544 static void rxrpc_activate_one_channel(struct rxrpc_connection *conn,
545                                        unsigned int channel)
546 {
547         struct rxrpc_channel *chan = &conn->channels[channel];
548         struct rxrpc_call *call = list_entry(conn->waiting_calls.next,
549                                              struct rxrpc_call, chan_wait_link);
550         u32 call_id = chan->call_counter + 1;
551 
552         trace_rxrpc_client(conn, channel, rxrpc_client_chan_activate);
553 
554         /* Cancel the final ACK on the previous call if it hasn't been sent yet
555          * as the DATA packet will implicitly ACK it.
556          */
557         clear_bit(RXRPC_CONN_FINAL_ACK_0 + channel, &conn->flags);
558 
559         write_lock_bh(&call->state_lock);
560         call->state = RXRPC_CALL_CLIENT_SEND_REQUEST;
561         write_unlock_bh(&call->state_lock);
562 
563         rxrpc_see_call(call);
564         list_del_init(&call->chan_wait_link);
565         conn->active_chans |= 1 << channel;
566         call->peer      = rxrpc_get_peer(conn->params.peer);
567         call->cid       = conn->proto.cid | channel;
568         call->call_id   = call_id;
569 
570         trace_rxrpc_connect_call(call);
571         _net("CONNECT call %08x:%08x as call %d on conn %d",
572              call->cid, call->call_id, call->debug_id, conn->debug_id);
573 
574         /* Paired with the read barrier in rxrpc_wait_for_channel().  This
575          * orders cid and epoch in the connection wrt to call_id without the
576          * need to take the channel_lock.
577          *
578          * We provisionally assign a callNumber at this point, but we don't
579          * confirm it until the call is about to be exposed.
580          *
581          * TODO: Pair with a barrier in the data_ready handler when that looks
582          * at the call ID through a connection channel.
583          */
584         smp_wmb();
585         chan->call_id   = call_id;
586         chan->call_debug_id = call->debug_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                         if (test_bit(RXRPC_CALL_IS_INTR, &call->flags))
655                                 set_current_state(TASK_INTERRUPTIBLE);
656                         else
657                                 set_current_state(TASK_UNINTERRUPTIBLE);
658                         if (call->call_id)
659                                 break;
660                         if (test_bit(RXRPC_CALL_IS_INTR, &call->flags) &&
661                             signal_pending(current)) {
662                                 ret = -ERESTARTSYS;
663                                 break;
664                         }
665                         schedule();
666                 }
667                 remove_wait_queue(&call->waitq, &myself);
668                 __set_current_state(TASK_RUNNING);
669         }
670 
671         /* Paired with the write barrier in rxrpc_activate_one_channel(). */
672         smp_rmb();
673 
674 out:
675         _leave(" = %d", ret);
676         return ret;
677 }
678 
679 /*
680  * find a connection for a call
681  * - called in process context with IRQs enabled
682  */
683 int rxrpc_connect_call(struct rxrpc_sock *rx,
684                        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(rx, 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                 trace_rxrpc_client(call->conn, ret, rxrpc_client_chan_wait_failed);
707                 rxrpc_disconnect_client_call(call);
708                 goto out;
709         }
710 
711         spin_lock_bh(&call->conn->params.peer->lock);
712         hlist_add_head_rcu(&call->error_link,
713                            &call->conn->params.peer->error_targets);
714         spin_unlock_bh(&call->conn->params.peer->lock);
715 
716 out:
717         _leave(" = %d", ret);
718         return ret;
719 }
720 
721 /*
722  * Note that a connection is about to be exposed to the world.  Once it is
723  * exposed, we maintain an extra ref on it that stops it from being summarily
724  * discarded before it's (a) had a chance to deal with retransmission and (b)
725  * had a chance at re-use (the per-connection security negotiation is
726  * expensive).
727  */
728 static void rxrpc_expose_client_conn(struct rxrpc_connection *conn,
729                                      unsigned int channel)
730 {
731         if (!test_and_set_bit(RXRPC_CONN_EXPOSED, &conn->flags)) {
732                 trace_rxrpc_client(conn, channel, rxrpc_client_exposed);
733                 rxrpc_get_connection(conn);
734         }
735 }
736 
737 /*
738  * Note that a call, and thus a connection, is about to be exposed to the
739  * world.
740  */
741 void rxrpc_expose_client_call(struct rxrpc_call *call)
742 {
743         unsigned int channel = call->cid & RXRPC_CHANNELMASK;
744         struct rxrpc_connection *conn = call->conn;
745         struct rxrpc_channel *chan = &conn->channels[channel];
746 
747         if (!test_and_set_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
748                 /* Mark the call ID as being used.  If the callNumber counter
749                  * exceeds ~2 billion, we kill the connection after its
750                  * outstanding calls have finished so that the counter doesn't
751                  * wrap.
752                  */
753                 chan->call_counter++;
754                 if (chan->call_counter >= INT_MAX)
755                         set_bit(RXRPC_CONN_DONT_REUSE, &conn->flags);
756                 rxrpc_expose_client_conn(conn, channel);
757         }
758 }
759 
760 /*
761  * Set the reap timer.
762  */
763 static void rxrpc_set_client_reap_timer(struct rxrpc_net *rxnet)
764 {
765         unsigned long now = jiffies;
766         unsigned long reap_at = now + rxrpc_conn_idle_client_expiry;
767 
768         if (rxnet->live)
769                 timer_reduce(&rxnet->client_conn_reap_timer, reap_at);
770 }
771 
772 /*
773  * Disconnect a client call.
774  */
775 void rxrpc_disconnect_client_call(struct rxrpc_call *call)
776 {
777         struct rxrpc_connection *conn = call->conn;
778         struct rxrpc_channel *chan = NULL;
779         struct rxrpc_net *rxnet = conn->params.local->rxnet;
780         unsigned int channel = -1;
781         u32 cid;
782 
783         spin_lock(&conn->channel_lock);
784 
785         cid = call->cid;
786         if (cid) {
787                 channel = cid & RXRPC_CHANNELMASK;
788                 chan = &conn->channels[channel];
789         }
790         trace_rxrpc_client(conn, channel, rxrpc_client_chan_disconnect);
791         call->conn = NULL;
792 
793         /* Calls that have never actually been assigned a channel can simply be
794          * discarded.  If the conn didn't get used either, it will follow
795          * immediately unless someone else grabs it in the meantime.
796          */
797         if (!list_empty(&call->chan_wait_link)) {
798                 _debug("call is waiting");
799                 ASSERTCMP(call->call_id, ==, 0);
800                 ASSERT(!test_bit(RXRPC_CALL_EXPOSED, &call->flags));
801                 list_del_init(&call->chan_wait_link);
802 
803                 trace_rxrpc_client(conn, channel, rxrpc_client_chan_unstarted);
804 
805                 /* We must deactivate or idle the connection if it's now
806                  * waiting for nothing.
807                  */
808                 spin_lock(&rxnet->client_conn_cache_lock);
809                 if (conn->cache_state == RXRPC_CONN_CLIENT_WAITING &&
810                     list_empty(&conn->waiting_calls) &&
811                     !conn->active_chans)
812                         goto idle_connection;
813                 goto out;
814         }
815 
816         if (rcu_access_pointer(chan->call) != call) {
817                 spin_unlock(&conn->channel_lock);
818                 BUG();
819         }
820 
821         /* If a client call was exposed to the world, we save the result for
822          * retransmission.
823          *
824          * We use a barrier here so that the call number and abort code can be
825          * read without needing to take a lock.
826          *
827          * TODO: Make the incoming packet handler check this and handle
828          * terminal retransmission without requiring access to the call.
829          */
830         if (test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
831                 _debug("exposed %u,%u", call->call_id, call->abort_code);
832                 __rxrpc_disconnect_call(conn, call);
833         }
834 
835         /* See if we can pass the channel directly to another call. */
836         if (conn->cache_state == RXRPC_CONN_CLIENT_ACTIVE &&
837             !list_empty(&conn->waiting_calls)) {
838                 trace_rxrpc_client(conn, channel, rxrpc_client_chan_pass);
839                 rxrpc_activate_one_channel(conn, channel);
840                 goto out_2;
841         }
842 
843         /* Schedule the final ACK to be transmitted in a short while so that it
844          * can be skipped if we find a follow-on call.  The first DATA packet
845          * of the follow on call will implicitly ACK this call.
846          */
847         if (call->completion == RXRPC_CALL_SUCCEEDED &&
848             test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
849                 unsigned long final_ack_at = jiffies + 2;
850 
851                 WRITE_ONCE(chan->final_ack_at, final_ack_at);
852                 smp_wmb(); /* vs rxrpc_process_delayed_final_acks() */
853                 set_bit(RXRPC_CONN_FINAL_ACK_0 + channel, &conn->flags);
854                 rxrpc_reduce_conn_timer(conn, final_ack_at);
855         }
856 
857         /* Things are more complex and we need the cache lock.  We might be
858          * able to simply idle the conn or it might now be lurking on the wait
859          * list.  It might even get moved back to the active list whilst we're
860          * waiting for the lock.
861          */
862         spin_lock(&rxnet->client_conn_cache_lock);
863 
864         switch (conn->cache_state) {
865         case RXRPC_CONN_CLIENT_UPGRADE:
866                 /* Deal with termination of a service upgrade probe. */
867                 if (test_bit(RXRPC_CONN_EXPOSED, &conn->flags)) {
868                         clear_bit(RXRPC_CONN_PROBING_FOR_UPGRADE, &conn->flags);
869                         trace_rxrpc_client(conn, channel, rxrpc_client_to_active);
870                         conn->cache_state = RXRPC_CONN_CLIENT_ACTIVE;
871                         rxrpc_activate_channels_locked(conn);
872                 }
873                 /* fall through */
874         case RXRPC_CONN_CLIENT_ACTIVE:
875                 if (list_empty(&conn->waiting_calls)) {
876                         rxrpc_deactivate_one_channel(conn, channel);
877                         if (!conn->active_chans) {
878                                 rxnet->nr_active_client_conns--;
879                                 goto idle_connection;
880                         }
881                         goto out;
882                 }
883 
884                 trace_rxrpc_client(conn, channel, rxrpc_client_chan_pass);
885                 rxrpc_activate_one_channel(conn, channel);
886                 goto out;
887 
888         case RXRPC_CONN_CLIENT_CULLED:
889                 rxrpc_deactivate_one_channel(conn, channel);
890                 ASSERT(list_empty(&conn->waiting_calls));
891                 if (!conn->active_chans)
892                         goto idle_connection;
893                 goto out;
894 
895         case RXRPC_CONN_CLIENT_WAITING:
896                 rxrpc_deactivate_one_channel(conn, channel);
897                 goto out;
898 
899         default:
900                 BUG();
901         }
902 
903 out:
904         spin_unlock(&rxnet->client_conn_cache_lock);
905 out_2:
906         spin_unlock(&conn->channel_lock);
907         rxrpc_put_connection(conn);
908         _leave("");
909         return;
910 
911 idle_connection:
912         /* As no channels remain active, the connection gets deactivated
913          * immediately or moved to the idle list for a short while.
914          */
915         if (test_bit(RXRPC_CONN_EXPOSED, &conn->flags)) {
916                 trace_rxrpc_client(conn, channel, rxrpc_client_to_idle);
917                 conn->idle_timestamp = jiffies;
918                 conn->cache_state = RXRPC_CONN_CLIENT_IDLE;
919                 list_move_tail(&conn->cache_link, &rxnet->idle_client_conns);
920                 if (rxnet->idle_client_conns.next == &conn->cache_link &&
921                     !rxnet->kill_all_client_conns)
922                         rxrpc_set_client_reap_timer(rxnet);
923         } else {
924                 trace_rxrpc_client(conn, channel, rxrpc_client_to_inactive);
925                 conn->cache_state = RXRPC_CONN_CLIENT_INACTIVE;
926                 list_del_init(&conn->cache_link);
927         }
928         goto out;
929 }
930 
931 /*
932  * Clean up a dead client connection.
933  */
934 static struct rxrpc_connection *
935 rxrpc_put_one_client_conn(struct rxrpc_connection *conn)
936 {
937         struct rxrpc_connection *next = NULL;
938         struct rxrpc_local *local = conn->params.local;
939         struct rxrpc_net *rxnet = local->rxnet;
940         unsigned int nr_conns;
941 
942         trace_rxrpc_client(conn, -1, rxrpc_client_cleanup);
943 
944         if (test_bit(RXRPC_CONN_IN_CLIENT_CONNS, &conn->flags)) {
945                 spin_lock(&local->client_conns_lock);
946                 if (test_and_clear_bit(RXRPC_CONN_IN_CLIENT_CONNS,
947                                        &conn->flags))
948                         rb_erase(&conn->client_node, &local->client_conns);
949                 spin_unlock(&local->client_conns_lock);
950         }
951 
952         rxrpc_put_client_connection_id(conn);
953 
954         ASSERTCMP(conn->cache_state, ==, RXRPC_CONN_CLIENT_INACTIVE);
955 
956         if (test_bit(RXRPC_CONN_COUNTED, &conn->flags)) {
957                 trace_rxrpc_client(conn, -1, rxrpc_client_uncount);
958                 spin_lock(&rxnet->client_conn_cache_lock);
959                 nr_conns = --rxnet->nr_client_conns;
960 
961                 if (nr_conns < rxrpc_max_client_connections &&
962                     !list_empty(&rxnet->waiting_client_conns)) {
963                         next = list_entry(rxnet->waiting_client_conns.next,
964                                           struct rxrpc_connection, cache_link);
965                         rxrpc_get_connection(next);
966                         rxrpc_activate_conn(rxnet, next);
967                 }
968 
969                 spin_unlock(&rxnet->client_conn_cache_lock);
970         }
971 
972         rxrpc_kill_connection(conn);
973         if (next)
974                 rxrpc_activate_channels(next);
975 
976         /* We need to get rid of the temporary ref we took upon next, but we
977          * can't call rxrpc_put_connection() recursively.
978          */
979         return next;
980 }
981 
982 /*
983  * Clean up a dead client connections.
984  */
985 void rxrpc_put_client_conn(struct rxrpc_connection *conn)
986 {
987         const void *here = __builtin_return_address(0);
988         int n;
989 
990         do {
991                 n = atomic_dec_return(&conn->usage);
992                 trace_rxrpc_conn(conn, rxrpc_conn_put_client, n, here);
993                 if (n > 0)
994                         return;
995                 ASSERTCMP(n, >=, 0);
996 
997                 conn = rxrpc_put_one_client_conn(conn);
998         } while (conn);
999 }
1000 
1001 /*
1002  * Kill the longest-active client connections to make room for new ones.
1003  */
1004 static void rxrpc_cull_active_client_conns(struct rxrpc_net *rxnet)
1005 {
1006         struct rxrpc_connection *conn;
1007         unsigned int nr_conns = rxnet->nr_client_conns;
1008         unsigned int nr_active, limit;
1009 
1010         _enter("");
1011 
1012         ASSERTCMP(nr_conns, >=, 0);
1013         if (nr_conns < rxrpc_max_client_connections) {
1014                 _leave(" [ok]");
1015                 return;
1016         }
1017         limit = rxrpc_reap_client_connections;
1018 
1019         spin_lock(&rxnet->client_conn_cache_lock);
1020         nr_active = rxnet->nr_active_client_conns;
1021 
1022         while (nr_active > limit) {
1023                 ASSERT(!list_empty(&rxnet->active_client_conns));
1024                 conn = list_entry(rxnet->active_client_conns.next,
1025                                   struct rxrpc_connection, cache_link);
1026                 ASSERTIFCMP(conn->cache_state != RXRPC_CONN_CLIENT_ACTIVE,
1027                             conn->cache_state, ==, RXRPC_CONN_CLIENT_UPGRADE);
1028 
1029                 if (list_empty(&conn->waiting_calls)) {
1030                         trace_rxrpc_client(conn, -1, rxrpc_client_to_culled);
1031                         conn->cache_state = RXRPC_CONN_CLIENT_CULLED;
1032                         list_del_init(&conn->cache_link);
1033                 } else {
1034                         trace_rxrpc_client(conn, -1, rxrpc_client_to_waiting);
1035                         conn->cache_state = RXRPC_CONN_CLIENT_WAITING;
1036                         list_move_tail(&conn->cache_link,
1037                                        &rxnet->waiting_client_conns);
1038                 }
1039 
1040                 nr_active--;
1041         }
1042 
1043         rxnet->nr_active_client_conns = nr_active;
1044         spin_unlock(&rxnet->client_conn_cache_lock);
1045         ASSERTCMP(nr_active, >=, 0);
1046         _leave(" [culled]");
1047 }
1048 
1049 /*
1050  * Discard expired client connections from the idle list.  Each conn in the
1051  * idle list has been exposed and holds an extra ref because of that.
1052  *
1053  * This may be called from conn setup or from a work item so cannot be
1054  * considered non-reentrant.
1055  */
1056 void rxrpc_discard_expired_client_conns(struct work_struct *work)
1057 {
1058         struct rxrpc_connection *conn;
1059         struct rxrpc_net *rxnet =
1060                 container_of(work, struct rxrpc_net, client_conn_reaper);
1061         unsigned long expiry, conn_expires_at, now;
1062         unsigned int nr_conns;
1063 
1064         _enter("");
1065 
1066         if (list_empty(&rxnet->idle_client_conns)) {
1067                 _leave(" [empty]");
1068                 return;
1069         }
1070 
1071         /* Don't double up on the discarding */
1072         if (!spin_trylock(&rxnet->client_conn_discard_lock)) {
1073                 _leave(" [already]");
1074                 return;
1075         }
1076 
1077         /* We keep an estimate of what the number of conns ought to be after
1078          * we've discarded some so that we don't overdo the discarding.
1079          */
1080         nr_conns = rxnet->nr_client_conns;
1081 
1082 next:
1083         spin_lock(&rxnet->client_conn_cache_lock);
1084 
1085         if (list_empty(&rxnet->idle_client_conns))
1086                 goto out;
1087 
1088         conn = list_entry(rxnet->idle_client_conns.next,
1089                           struct rxrpc_connection, cache_link);
1090         ASSERT(test_bit(RXRPC_CONN_EXPOSED, &conn->flags));
1091 
1092         if (!rxnet->kill_all_client_conns) {
1093                 /* If the number of connections is over the reap limit, we
1094                  * expedite discard by reducing the expiry timeout.  We must,
1095                  * however, have at least a short grace period to be able to do
1096                  * final-ACK or ABORT retransmission.
1097                  */
1098                 expiry = rxrpc_conn_idle_client_expiry;
1099                 if (nr_conns > rxrpc_reap_client_connections)
1100                         expiry = rxrpc_conn_idle_client_fast_expiry;
1101                 if (conn->params.local->service_closed)
1102                         expiry = rxrpc_closed_conn_expiry * HZ;
1103 
1104                 conn_expires_at = conn->idle_timestamp + expiry;
1105 
1106                 now = READ_ONCE(jiffies);
1107                 if (time_after(conn_expires_at, now))
1108                         goto not_yet_expired;
1109         }
1110 
1111         trace_rxrpc_client(conn, -1, rxrpc_client_discard);
1112         if (!test_and_clear_bit(RXRPC_CONN_EXPOSED, &conn->flags))
1113                 BUG();
1114         conn->cache_state = RXRPC_CONN_CLIENT_INACTIVE;
1115         list_del_init(&conn->cache_link);
1116 
1117         spin_unlock(&rxnet->client_conn_cache_lock);
1118 
1119         /* When we cleared the EXPOSED flag, we took on responsibility for the
1120          * reference that that had on the usage count.  We deal with that here.
1121          * If someone re-sets the flag and re-gets the ref, that's fine.
1122          */
1123         rxrpc_put_connection(conn);
1124         nr_conns--;
1125         goto next;
1126 
1127 not_yet_expired:
1128         /* The connection at the front of the queue hasn't yet expired, so
1129          * schedule the work item for that point if we discarded something.
1130          *
1131          * We don't worry if the work item is already scheduled - it can look
1132          * after rescheduling itself at a later time.  We could cancel it, but
1133          * then things get messier.
1134          */
1135         _debug("not yet");
1136         if (!rxnet->kill_all_client_conns)
1137                 timer_reduce(&rxnet->client_conn_reap_timer,
1138                              conn_expires_at);
1139 
1140 out:
1141         spin_unlock(&rxnet->client_conn_cache_lock);
1142         spin_unlock(&rxnet->client_conn_discard_lock);
1143         _leave("");
1144 }
1145 
1146 /*
1147  * Preemptively destroy all the client connection records rather than waiting
1148  * for them to time out
1149  */
1150 void rxrpc_destroy_all_client_connections(struct rxrpc_net *rxnet)
1151 {
1152         _enter("");
1153 
1154         spin_lock(&rxnet->client_conn_cache_lock);
1155         rxnet->kill_all_client_conns = true;
1156         spin_unlock(&rxnet->client_conn_cache_lock);
1157 
1158         del_timer_sync(&rxnet->client_conn_reap_timer);
1159 
1160         if (!rxrpc_queue_work(&rxnet->client_conn_reaper))
1161                 _debug("destroy: queue failed");
1162 
1163         _leave("");
1164 }
1165 
1166 /*
1167  * Clean up the client connections on a local endpoint.
1168  */
1169 void rxrpc_clean_up_local_conns(struct rxrpc_local *local)
1170 {
1171         struct rxrpc_connection *conn, *tmp;
1172         struct rxrpc_net *rxnet = local->rxnet;
1173         unsigned int nr_active;
1174         LIST_HEAD(graveyard);
1175 
1176         _enter("");
1177 
1178         spin_lock(&rxnet->client_conn_cache_lock);
1179         nr_active = rxnet->nr_active_client_conns;
1180 
1181         list_for_each_entry_safe(conn, tmp, &rxnet->idle_client_conns,
1182                                  cache_link) {
1183                 if (conn->params.local == local) {
1184                         ASSERTCMP(conn->cache_state, ==, RXRPC_CONN_CLIENT_IDLE);
1185 
1186                         trace_rxrpc_client(conn, -1, rxrpc_client_discard);
1187                         if (!test_and_clear_bit(RXRPC_CONN_EXPOSED, &conn->flags))
1188                                 BUG();
1189                         conn->cache_state = RXRPC_CONN_CLIENT_INACTIVE;
1190                         list_move(&conn->cache_link, &graveyard);
1191                         nr_active--;
1192                 }
1193         }
1194 
1195         rxnet->nr_active_client_conns = nr_active;
1196         spin_unlock(&rxnet->client_conn_cache_lock);
1197         ASSERTCMP(nr_active, >=, 0);
1198 
1199         while (!list_empty(&graveyard)) {
1200                 conn = list_entry(graveyard.next,
1201                                   struct rxrpc_connection, cache_link);
1202                 list_del_init(&conn->cache_link);
1203 
1204                 rxrpc_put_connection(conn);
1205         }
1206 
1207         _leave(" [culled]");
1208 }
1209 

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