fs/afs/server.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* AFS server record management
   3  *
   4  * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/sched.h>
   9 #include <linux/slab.h>
  10 #include "afs_fs.h"
  11 #include "internal.h"
  12 #include "protocol_yfs.h"
  13
  14 static unsigned afs_server_gc_delay = 10;       /* Server record timeout in seconds */
  15 static atomic_t afs_server_debug_id;
  16
  17 static struct afs_server *afs_maybe_use_server(struct afs_server *,
  18                                                enum afs_server_trace);
  19 static void __afs_put_server(struct afs_net *, struct afs_server *);
  20
  21 /*
  22  * Find a server by one of its addresses.
  23  */
  24 struct afs_server *afs_find_server(struct afs_net *net,
  25                                    const struct sockaddr_rxrpc *srx)
  26 {
  27         const struct afs_addr_list *alist;
  28         struct afs_server *server = NULL;
  29         unsigned int i;
  30         int seq = 1, diff;
  31
  32         rcu_read_lock();
  33
  34         do {
  35                 if (server)
  36                         afs_unuse_server_notime(net, server, afs_server_trace_put_find_rsq);
  37                 server = NULL;
  38                 seq++; /* 2 on the 1st/lockless path, otherwise odd */
  39                 read_seqbegin_or_lock(&net->fs_addr_lock, &seq);
  40
  41                 if (srx->transport.family == AF_INET6) {
  42                         const struct sockaddr_in6 *a = &srx->transport.sin6, *b;
  43                         hlist_for_each_entry_rcu(server, &net->fs_addresses6, addr6_link) {
  44                                 alist = rcu_dereference(server->addresses);
  45                                 for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
  46                                         b = &alist->addrs[i].transport.sin6;
  47                                         diff = ((u16 __force)a->sin6_port -
  48                                                 (u16 __force)b->sin6_port);
  49                                         if (diff == 0)
  50                                                 diff = memcmp(&a->sin6_addr,
  51                                                               &b->sin6_addr,
  52                                                               sizeof(struct in6_addr));
  53                                         if (diff == 0)
  54                                                 goto found;
  55                                 }
  56                         }
  57                 } else {
  58                         const struct sockaddr_in *a = &srx->transport.sin, *b;
  59                         hlist_for_each_entry_rcu(server, &net->fs_addresses4, addr4_link) {
  60                                 alist = rcu_dereference(server->addresses);
  61                                 for (i = 0; i < alist->nr_ipv4; i++) {
  62                                         b = &alist->addrs[i].transport.sin;
  63                                         diff = ((u16 __force)a->sin_port -
  64                                                 (u16 __force)b->sin_port);
  65                                         if (diff == 0)
  66                                                 diff = ((u32 __force)a->sin_addr.s_addr -
  67                                                         (u32 __force)b->sin_addr.s_addr);
  68                                         if (diff == 0)
  69                                                 goto found;
  70                                 }
  71                         }
  72                 }
  73
  74                 server = NULL;
  75                 continue;
  76         found:
  77                 server = afs_maybe_use_server(server, afs_server_trace_get_by_addr);
  78
  79         } while (need_seqretry(&net->fs_addr_lock, seq));
  80
  81         done_seqretry(&net->fs_addr_lock, seq);
  82
  83         rcu_read_unlock();
  84         return server;
  85 }
  86
  87 /*
  88  * Look up a server by its UUID and mark it active.
  89  */
  90 struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uuid)
  91 {
  92         struct afs_server *server = NULL;
  93         struct rb_node *p;
  94         int diff, seq = 1;
  95
  96         _enter("%pU", uuid);
  97
  98         do {
  99                 /* Unfortunately, rbtree walking doesn't give reliable results
 100                  * under just the RCU read lock, so we have to check for
 101                  * changes.
 102                  */
 103                 if (server)
 104                         afs_unuse_server(net, server, afs_server_trace_put_uuid_rsq);
 105                 server = NULL;
 106                 seq++; /* 2 on the 1st/lockless path, otherwise odd */
 107                 read_seqbegin_or_lock(&net->fs_lock, &seq);
 108
 109                 p = net->fs_servers.rb_node;
 110                 while (p) {
 111                         server = rb_entry(p, struct afs_server, uuid_rb);
 112
 113                         diff = memcmp(uuid, &server->uuid, sizeof(*uuid));
 114                         if (diff < 0) {
 115                                 p = p->rb_left;
 116                         } else if (diff > 0) {
 117                                 p = p->rb_right;
 118                         } else {
 119                                 afs_use_server(server, afs_server_trace_get_by_uuid);
 120                                 break;
 121                         }
 122
 123                         server = NULL;
 124                 }
 125         } while (need_seqretry(&net->fs_lock, seq));
 126
 127         done_seqretry(&net->fs_lock, seq);
 128
 129         _leave(" = %p", server);
 130         return server;
 131 }
 132
 133 /*
 134  * Install a server record in the namespace tree.  If there's a clash, we stick
 135  * it into a list anchored on whichever afs_server struct is actually in the
 136  * tree.
 137  */
 138 static struct afs_server *afs_install_server(struct afs_cell *cell,
 139                                              struct afs_server *candidate)
 140 {
 141         const struct afs_addr_list *alist;
 142         struct afs_server *server, *next;
 143         struct afs_net *net = cell->net;
 144         struct rb_node **pp, *p;
 145         int diff;
 146
 147         _enter("%p", candidate);
 148
 149         write_seqlock(&net->fs_lock);
 150
 151         /* Firstly install the server in the UUID lookup tree */
 152         pp = &net->fs_servers.rb_node;
 153         p = NULL;
 154         while (*pp) {
 155                 p = *pp;
 156                 _debug("- consider %p", p);
 157                 server = rb_entry(p, struct afs_server, uuid_rb);
 158                 diff = memcmp(&candidate->uuid, &server->uuid, sizeof(uuid_t));
 159                 if (diff < 0) {
 160                         pp = &(*pp)->rb_left;
 161                 } else if (diff > 0) {
 162                         pp = &(*pp)->rb_right;
 163                 } else {
 164                         if (server->cell == cell)
 165                                 goto exists;
 166
 167                         /* We have the same UUID representing servers in
 168                          * different cells.  Append the new server to the list.
 169                          */
 170                         for (;;) {
 171                                 next = rcu_dereference_protected(
 172                                         server->uuid_next,
 173                                         lockdep_is_held(&net->fs_lock.lock));
 174                                 if (!next)
 175                                         break;
 176                                 server = next;
 177                         }
 178                         rcu_assign_pointer(server->uuid_next, candidate);
 179                         candidate->uuid_prev = server;
 180                         server = candidate;
 181                         goto added_dup;
 182                 }
 183         }
 184
 185         server = candidate;
 186         rb_link_node(&server->uuid_rb, p, pp);
 187         rb_insert_color(&server->uuid_rb, &net->fs_servers);
 188         hlist_add_head_rcu(&server->proc_link, &net->fs_proc);
 189
 190 added_dup:
 191         write_seqlock(&net->fs_addr_lock);
 192         alist = rcu_dereference_protected(server->addresses,
 193                                           lockdep_is_held(&net->fs_addr_lock.lock));
 194
 195         /* Secondly, if the server has any IPv4 and/or IPv6 addresses, install
 196          * it in the IPv4 and/or IPv6 reverse-map lists.
 197          *
 198          * TODO: For speed we want to use something other than a flat list
 199          * here; even sorting the list in terms of lowest address would help a
 200          * bit, but anything we might want to do gets messy and memory
 201          * intensive.
 202          */
 203         if (alist->nr_ipv4 > 0)
 204                 hlist_add_head_rcu(&server->addr4_link, &net->fs_addresses4);
 205         if (alist->nr_addrs > alist->nr_ipv4)
 206                 hlist_add_head_rcu(&server->addr6_link, &net->fs_addresses6);
 207
 208         write_sequnlock(&net->fs_addr_lock);
 209
 210 exists:
 211         afs_get_server(server, afs_server_trace_get_install);
 212         write_sequnlock(&net->fs_lock);
 213         return server;
 214 }
 215
 216 /*
 217  * Allocate a new server record and mark it active.
 218  */
 219 static struct afs_server *afs_alloc_server(struct afs_cell *cell,
 220                                            const uuid_t *uuid,
 221                                            struct afs_addr_list *alist)
 222 {
 223         struct afs_server *server;
 224         struct afs_net *net = cell->net;
 225
 226         _enter("");
 227
 228         server = kzalloc(sizeof(struct afs_server), GFP_KERNEL);
 229         if (!server)
 230                 goto enomem;
 231
 232         atomic_set(&server->ref, 1);
 233         atomic_set(&server->active, 1);
 234         server->debug_id = atomic_inc_return(&afs_server_debug_id);
 235         RCU_INIT_POINTER(server->addresses, alist);
 236         server->addr_version = alist->version;
 237         server->uuid = *uuid;
 238         rwlock_init(&server->fs_lock);
 239         init_waitqueue_head(&server->probe_wq);
 240         INIT_LIST_HEAD(&server->probe_link);
 241         spin_lock_init(&server->probe_lock);
 242         server->cell = cell;
 243         server->rtt = UINT_MAX;
 244
 245         afs_inc_servers_outstanding(net);
 246         trace_afs_server(server, 1, 1, afs_server_trace_alloc);
 247         _leave(" = %p", server);
 248         return server;
 249
 250 enomem:
 251         _leave(" = NULL [nomem]");
 252         return NULL;
 253 }
 254
 255 /*
 256  * Look up an address record for a server
 257  */
 258 static struct afs_addr_list *afs_vl_lookup_addrs(struct afs_cell *cell,
 259                                                  struct key *key, const uuid_t *uuid)
 260 {
 261         struct afs_vl_cursor vc;
 262         struct afs_addr_list *alist = NULL;
 263         int ret;
 264
 265         ret = -ERESTARTSYS;
 266         if (afs_begin_vlserver_operation(&vc, cell, key)) {
 267                 while (afs_select_vlserver(&vc)) {
 268                         if (test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags))
 269                                 alist = afs_yfsvl_get_endpoints(&vc, uuid);
 270                         else
 271                                 alist = afs_vl_get_addrs_u(&vc, uuid);
 272                 }
 273
 274                 ret = afs_end_vlserver_operation(&vc);
 275         }
 276
 277         return ret < 0 ? ERR_PTR(ret) : alist;
 278 }
 279
 280 /*
 281  * Get or create a fileserver record.
 282  */
 283 struct afs_server *afs_lookup_server(struct afs_cell *cell, struct key *key,
 284                                      const uuid_t *uuid, u32 addr_version)
 285 {
 286         struct afs_addr_list *alist;
 287         struct afs_server *server, *candidate;
 288
 289         _enter("%p,%pU", cell->net, uuid);
 290
 291         server = afs_find_server_by_uuid(cell->net, uuid);
 292         if (server) {
 293                 if (server->addr_version != addr_version)
 294                         set_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags);
 295                 return server;
 296         }
 297
 298         alist = afs_vl_lookup_addrs(cell, key, uuid);
 299         if (IS_ERR(alist))
 300                 return ERR_CAST(alist);
 301
 302         candidate = afs_alloc_server(cell, uuid, alist);
 303         if (!candidate) {
 304                 afs_put_addrlist(alist);
 305                 return ERR_PTR(-ENOMEM);
 306         }
 307
 308         server = afs_install_server(cell, candidate);
 309         if (server != candidate) {
 310                 afs_put_addrlist(alist);
 311                 kfree(candidate);
 312         } else {
 313                 /* Immediately dispatch an asynchronous probe to each interface
 314                  * on the fileserver.  This will make sure the repeat-probing
 315                  * service is started.
 316                  */
 317                 afs_fs_probe_fileserver(cell->net, server, key, true);
 318         }
 319
 320         return server;
 321 }
 322
 323 /*
 324  * Set the server timer to fire after a given delay, assuming it's not already
 325  * set for an earlier time.
 326  */
 327 static void afs_set_server_timer(struct afs_net *net, time64_t delay)
 328 {
 329         if (net->live) {
 330                 afs_inc_servers_outstanding(net);
 331                 if (timer_reduce(&net->fs_timer, jiffies + delay * HZ))
 332                         afs_dec_servers_outstanding(net);
 333         }
 334 }
 335
 336 /*
 337  * Server management timer.  We have an increment on fs_outstanding that we
 338  * need to pass along to the work item.
 339  */
 340 void afs_servers_timer(struct timer_list *timer)
 341 {
 342         struct afs_net *net = container_of(timer, struct afs_net, fs_timer);
 343
 344         _enter("");
 345         if (!queue_work(afs_wq, &net->fs_manager))
 346                 afs_dec_servers_outstanding(net);
 347 }
 348
 349 /*
 350  * Get a reference on a server object.
 351  */
 352 struct afs_server *afs_get_server(struct afs_server *server,
 353                                   enum afs_server_trace reason)
 354 {
 355         unsigned int u = atomic_inc_return(&server->ref);
 356
 357         trace_afs_server(server, u, atomic_read(&server->active), reason);
 358         return server;
 359 }
 360
 361 /*
 362  * Try to get a reference on a server object.
 363  */
 364 static struct afs_server *afs_maybe_use_server(struct afs_server *server,
 365                                                enum afs_server_trace reason)
 366 {
 367         unsigned int r = atomic_fetch_add_unless(&server->ref, 1, 0);
 368         unsigned int a;
 369
 370         if (r == 0)
 371                 return NULL;
 372
 373         a = atomic_inc_return(&server->active);
 374         trace_afs_server(server, r, a, reason);
 375         return server;
 376 }
 377
 378 /*
 379  * Get an active count on a server object.
 380  */
 381 struct afs_server *afs_use_server(struct afs_server *server, enum afs_server_trace reason)
 382 {
 383         unsigned int r = atomic_inc_return(&server->ref);
 384         unsigned int a = atomic_inc_return(&server->active);
 385
 386         trace_afs_server(server, r, a, reason);
 387         return server;
 388 }
 389
 390 /*
 391  * Release a reference on a server record.
 392  */
 393 void afs_put_server(struct afs_net *net, struct afs_server *server,
 394                     enum afs_server_trace reason)
 395 {
 396         unsigned int usage;
 397
 398         if (!server)
 399                 return;
 400
 401         usage = atomic_dec_return(&server->ref);
 402         trace_afs_server(server, usage, atomic_read(&server->active), reason);
 403         if (unlikely(usage == 0))
 404                 __afs_put_server(net, server);
 405 }
 406
 407 /*
 408  * Drop an active count on a server object without updating the last-unused
 409  * time.
 410  */
 411 void afs_unuse_server_notime(struct afs_net *net, struct afs_server *server,
 412                              enum afs_server_trace reason)
 413 {
 414         if (server) {
 415                 unsigned int active = atomic_dec_return(&server->active);
 416
 417                 if (active == 0)
 418                         afs_set_server_timer(net, afs_server_gc_delay);
 419                 afs_put_server(net, server, reason);
 420         }
 421 }
 422
 423 /*
 424  * Drop an active count on a server object.
 425  */
 426 void afs_unuse_server(struct afs_net *net, struct afs_server *server,
 427                       enum afs_server_trace reason)
 428 {
 429         if (server) {
 430                 server->unuse_time = ktime_get_real_seconds();
 431                 afs_unuse_server_notime(net, server, reason);
 432         }
 433 }
 434
 435 static void afs_server_rcu(struct rcu_head *rcu)
 436 {
 437         struct afs_server *server = container_of(rcu, struct afs_server, rcu);
 438
 439         trace_afs_server(server, atomic_read(&server->ref),
 440                          atomic_read(&server->active), afs_server_trace_free);
 441         afs_put_addrlist(rcu_access_pointer(server->addresses));
 442         kfree(server);
 443 }
 444
 445 static void __afs_put_server(struct afs_net *net, struct afs_server *server)
 446 {
 447         call_rcu(&server->rcu, afs_server_rcu);
 448         afs_dec_servers_outstanding(net);
 449 }
 450
 451 static void afs_give_up_callbacks(struct afs_net *net, struct afs_server *server)
 452 {
 453         struct afs_addr_list *alist = rcu_access_pointer(server->addresses);
 454         struct afs_addr_cursor ac = {
 455                 .alist  = alist,
 456                 .index  = alist->preferred,
 457                 .error  = 0,
 458         };
 459
 460         afs_fs_give_up_all_callbacks(net, server, &ac, NULL);
 461 }
 462
 463 /*
 464  * destroy a dead server
 465  */
 466 static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
 467 {
 468         if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
 469                 afs_give_up_callbacks(net, server);
 470
 471         afs_put_server(net, server, afs_server_trace_destroy);
 472 }
 473
 474 /*
 475  * Garbage collect any expired servers.
 476  */
 477 static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
 478 {
 479         struct afs_server *server, *next, *prev;
 480         int active;
 481
 482         while ((server = gc_list)) {
 483                 gc_list = server->gc_next;
 484
 485                 write_seqlock(&net->fs_lock);
 486
 487                 active = atomic_read(&server->active);
 488                 if (active == 0) {
 489                         trace_afs_server(server, atomic_read(&server->ref),
 490                                          active, afs_server_trace_gc);
 491                         next = rcu_dereference_protected(
 492                                 server->uuid_next, lockdep_is_held(&net->fs_lock.lock));
 493                         prev = server->uuid_prev;
 494                         if (!prev) {
 495                                 /* The one at the front is in the tree */
 496                                 if (!next) {
 497                                         rb_erase(&server->uuid_rb, &net->fs_servers);
 498                                 } else {
 499                                         rb_replace_node_rcu(&server->uuid_rb,
 500                                                             &next->uuid_rb,
 501                                                             &net->fs_servers);
 502                                         next->uuid_prev = NULL;
 503                                 }
 504                         } else {
 505                                 /* This server is not at the front */
 506                                 rcu_assign_pointer(prev->uuid_next, next);
 507                                 if (next)
 508                                         next->uuid_prev = prev;
 509                         }
 510
 511                         list_del(&server->probe_link);
 512                         hlist_del_rcu(&server->proc_link);
 513                         if (!hlist_unhashed(&server->addr4_link))
 514                                 hlist_del_rcu(&server->addr4_link);
 515                         if (!hlist_unhashed(&server->addr6_link))
 516                                 hlist_del_rcu(&server->addr6_link);
 517                 }
 518                 write_sequnlock(&net->fs_lock);
 519
 520                 if (active == 0)
 521                         afs_destroy_server(net, server);
 522         }
 523 }
 524
 525 /*
 526  * Manage the records of servers known to be within a network namespace.  This
 527  * includes garbage collecting unused servers.
 528  *
 529  * Note also that we were given an increment on net->servers_outstanding by
 530  * whoever queued us that we need to deal with before returning.
 531  */
 532 void afs_manage_servers(struct work_struct *work)
 533 {
 534         struct afs_net *net = container_of(work, struct afs_net, fs_manager);
 535         struct afs_server *gc_list = NULL;
 536         struct rb_node *cursor;
 537         time64_t now = ktime_get_real_seconds(), next_manage = TIME64_MAX;
 538         bool purging = !net->live;
 539
 540         _enter("");
 541
 542         /* Trawl the server list looking for servers that have expired from
 543          * lack of use.
 544          */
 545         read_seqlock_excl(&net->fs_lock);
 546
 547         for (cursor = rb_first(&net->fs_servers); cursor; cursor = rb_next(cursor)) {
 548                 struct afs_server *server =
 549                         rb_entry(cursor, struct afs_server, uuid_rb);
 550                 int active = atomic_read(&server->active);
 551
 552                 _debug("manage %pU %u", &server->uuid, active);
 553
 554                 if (purging) {
 555                         trace_afs_server(server, atomic_read(&server->ref),
 556                                          active, afs_server_trace_purging);
 557                         if (active != 0)
 558                                 pr_notice("Can't purge s=%08x\n", server->debug_id);
 559                 }
 560
 561                 if (active == 0) {
 562                         time64_t expire_at = server->unuse_time;
 563
 564                         if (!test_bit(AFS_SERVER_FL_VL_FAIL, &server->flags) &&
 565                             !test_bit(AFS_SERVER_FL_NOT_FOUND, &server->flags))
 566                                 expire_at += afs_server_gc_delay;
 567                         if (purging || expire_at <= now) {
 568                                 server->gc_next = gc_list;
 569                                 gc_list = server;
 570                         } else if (expire_at < next_manage) {
 571                                 next_manage = expire_at;
 572                         }
 573                 }
 574         }
 575
 576         read_sequnlock_excl(&net->fs_lock);
 577
 578         /* Update the timer on the way out.  We have to pass an increment on
 579          * servers_outstanding in the namespace that we are in to the timer or
 580          * the work scheduler.
 581          */
 582         if (!purging && next_manage < TIME64_MAX) {
 583                 now = ktime_get_real_seconds();
 584
 585                 if (next_manage - now <= 0) {
 586                         if (queue_work(afs_wq, &net->fs_manager))
 587                                 afs_inc_servers_outstanding(net);
 588                 } else {
 589                         afs_set_server_timer(net, next_manage - now);
 590                 }
 591         }
 592
 593         afs_gc_servers(net, gc_list);
 594
 595         afs_dec_servers_outstanding(net);
 596         _leave(" [%d]", atomic_read(&net->servers_outstanding));
 597 }
 598
 599 static void afs_queue_server_manager(struct afs_net *net)
 600 {
 601         afs_inc_servers_outstanding(net);
 602         if (!queue_work(afs_wq, &net->fs_manager))
 603                 afs_dec_servers_outstanding(net);
 604 }
 605
 606 /*
 607  * Purge list of servers.
 608  */
 609 void afs_purge_servers(struct afs_net *net)
 610 {
 611         _enter("");
 612
 613         if (del_timer_sync(&net->fs_timer))
 614                 afs_dec_servers_outstanding(net);
 615
 616         afs_queue_server_manager(net);
 617
 618         _debug("wait");
 619         atomic_dec(&net->servers_outstanding);
 620         wait_var_event(&net->servers_outstanding,
 621                        !atomic_read(&net->servers_outstanding));
 622         _leave("");
 623 }
 624
 625 /*
 626  * Get an update for a server's address list.
 627  */
 628 static noinline bool afs_update_server_record(struct afs_operation *op,
 629                                               struct afs_server *server)
 630 {
 631         struct afs_addr_list *alist, *discard;
 632
 633         _enter("");
 634
 635         trace_afs_server(server, atomic_read(&server->ref), atomic_read(&server->active),
 636                          afs_server_trace_update);
 637
 638         alist = afs_vl_lookup_addrs(op->volume->cell, op->key, &server->uuid);
 639         if (IS_ERR(alist)) {
 640                 if ((PTR_ERR(alist) == -ERESTARTSYS ||
 641                      PTR_ERR(alist) == -EINTR) &&
 642                     (op->flags & AFS_OPERATION_UNINTR) &&
 643                     server->addresses) {
 644                         _leave(" = t [intr]");
 645                         return true;
 646                 }
 647                 op->error = PTR_ERR(alist);
 648                 _leave(" = f [%d]", op->error);
 649                 return false;
 650         }
 651
 652         discard = alist;
 653         if (server->addr_version != alist->version) {
 654                 write_lock(&server->fs_lock);
 655                 discard = rcu_dereference_protected(server->addresses,
 656                                                     lockdep_is_held(&server->fs_lock));
 657                 rcu_assign_pointer(server->addresses, alist);
 658                 server->addr_version = alist->version;
 659                 write_unlock(&server->fs_lock);
 660         }
 661
 662         afs_put_addrlist(discard);
 663         _leave(" = t");
 664         return true;
 665 }
 666
 667 /*
 668  * See if a server's address list needs updating.
 669  */
 670 bool afs_check_server_record(struct afs_operation *op, struct afs_server *server)
 671 {
 672         bool success;
 673         int ret, retries = 0;
 674
 675         _enter("");
 676
 677         ASSERT(server);
 678
 679 retry:
 680         if (test_bit(AFS_SERVER_FL_UPDATING, &server->flags))
 681                 goto wait;
 682         if (test_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags))
 683                 goto update;
 684         _leave(" = t [good]");
 685         return true;
 686
 687 update:
 688         if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) {
 689                 clear_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags);
 690                 success = afs_update_server_record(op, server);
 691                 clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags);
 692                 wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING);
 693                 _leave(" = %d", success);
 694                 return success;
 695         }
 696
 697 wait:
 698         ret = wait_on_bit(&server->flags, AFS_SERVER_FL_UPDATING,
 699                           (op->flags & AFS_OPERATION_UNINTR) ?
 700                           TASK_UNINTERRUPTIBLE : TASK_INTERRUPTIBLE);
 701         if (ret == -ERESTARTSYS) {
 702                 op->error = ret;
 703                 _leave(" = f [intr]");
 704                 return false;
 705         }
 706
 707         retries++;
 708         if (retries == 4) {
 709                 _leave(" = f [stale]");
 710                 ret = -ESTALE;
 711                 return false;
 712         }
 713         goto retry;
 714 }