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 = 0, 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                 read_seqbegin_or_lock(&net->fs_addr_lock, &seq);
  39
  40                 if (srx->transport.family == AF_INET6) {
  41                         const struct sockaddr_in6 *a = &srx->transport.sin6, *b;
  42                         hlist_for_each_entry_rcu(server, &net->fs_addresses6, addr6_link) {
  43                                 alist = rcu_dereference(server->addresses);
  44                                 for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
  45                                         b = &alist->addrs[i].transport.sin6;
  46                                         diff = ((u16 __force)a->sin6_port -
  47                                                 (u16 __force)b->sin6_port);
  48                                         if (diff == 0)
  49                                                 diff = memcmp(&a->sin6_addr,
  50                                                               &b->sin6_addr,
  51                                                               sizeof(struct in6_addr));
  52                                         if (diff == 0)
  53                                                 goto found;
  54                                 }
  55                         }
  56                 } else {
  57                         const struct sockaddr_in *a = &srx->transport.sin, *b;
  58                         hlist_for_each_entry_rcu(server, &net->fs_addresses4, addr4_link) {
  59                                 alist = rcu_dereference(server->addresses);
  60                                 for (i = 0; i < alist->nr_ipv4; i++) {
  61                                         b = &alist->addrs[i].transport.sin;
  62                                         diff = ((u16 __force)a->sin_port -
  63                                                 (u16 __force)b->sin_port);
  64                                         if (diff == 0)
  65                                                 diff = ((u32 __force)a->sin_addr.s_addr -
  66                                                         (u32 __force)b->sin_addr.s_addr);
  67                                         if (diff == 0)
  68                                                 goto found;
  69                                 }
  70                         }
  71                 }
  72
  73                 server = NULL;
  74                 continue;
  75         found:
  76                 server = afs_maybe_use_server(server, afs_server_trace_get_by_addr);
  77
  78         } while (need_seqretry(&net->fs_addr_lock, seq));
  79
  80         done_seqretry(&net->fs_addr_lock, seq);
  81
  82         rcu_read_unlock();
  83         return server;
  84 }
  85
  86 /*
  87  * Look up a server by its UUID and mark it active.
  88  */
  89 struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uuid)
  90 {
  91         struct afs_server *server = NULL;
  92         struct rb_node *p;
  93         int diff, seq = 0;
  94
  95         _enter("%pU", uuid);
  96
  97         do {
  98                 /* Unfortunately, rbtree walking doesn't give reliable results
  99                  * under just the RCU read lock, so we have to check for
 100                  * changes.
 101                  */
 102                 if (server)
 103                         afs_unuse_server(net, server, afs_server_trace_put_uuid_rsq);
 104                 server = NULL;
 105
 106                 read_seqbegin_or_lock(&net->fs_lock, &seq);
 107
 108                 p = net->fs_servers.rb_node;
 109                 while (p) {
 110                         server = rb_entry(p, struct afs_server, uuid_rb);
 111
 112                         diff = memcmp(uuid, &server->uuid, sizeof(*uuid));
 113                         if (diff < 0) {
 114                                 p = p->rb_left;
 115                         } else if (diff > 0) {
 116                                 p = p->rb_right;
 117                         } else {
 118                                 afs_use_server(server, afs_server_trace_get_by_uuid);
 119                                 break;
 120                         }
 121
 122                         server = NULL;
 123                 }
 124         } while (need_seqretry(&net->fs_lock, seq));
 125
 126         done_seqretry(&net->fs_lock, seq);
 127
 128         _leave(" = %p", server);
 129         return server;
 130 }
 131
 132 /*
 133  * Install a server record in the namespace tree.  If there's a clash, we stick
 134  * it into a list anchored on whichever afs_server struct is actually in the
 135  * tree.
 136  */
 137 static struct afs_server *afs_install_server(struct afs_cell *cell,
 138                                              struct afs_server *candidate)
 139 {
 140         const struct afs_addr_list *alist;
 141         struct afs_server *server, *next;
 142         struct afs_net *net = cell->net;
 143         struct rb_node **pp, *p;
 144         int diff;
 145
 146         _enter("%p", candidate);
 147
 148         write_seqlock(&net->fs_lock);
 149
 150         /* Firstly install the server in the UUID lookup tree */
 151         pp = &net->fs_servers.rb_node;
 152         p = NULL;
 153         while (*pp) {
 154                 p = *pp;
 155                 _debug("- consider %p", p);
 156                 server = rb_entry(p, struct afs_server, uuid_rb);
 157                 diff = memcmp(&candidate->uuid, &server->uuid, sizeof(uuid_t));
 158                 if (diff < 0) {
 159                         pp = &(*pp)->rb_left;
 160                 } else if (diff > 0) {
 161                         pp = &(*pp)->rb_right;
 162                 } else {
 163                         if (server->cell == cell)
 164                                 goto exists;
 165
 166                         /* We have the same UUID representing servers in
 167                          * different cells.  Append the new server to the list.
 168                          */
 169                         for (;;) {
 170                                 next = rcu_dereference_protected(
 171                                         server->uuid_next,
 172                                         lockdep_is_held(&net->fs_lock.lock));
 173                                 if (!next)
 174                                         break;
 175                                 server = next;
 176                         }
 177                         rcu_assign_pointer(server->uuid_next, candidate);
 178                         candidate->uuid_prev = server;
 179                         server = candidate;
 180                         goto added_dup;
 181                 }
 182         }
 183
 184         server = candidate;
 185         rb_link_node(&server->uuid_rb, p, pp);
 186         rb_insert_color(&server->uuid_rb, &net->fs_servers);
 187         hlist_add_head_rcu(&server->proc_link, &net->fs_proc);
 188
 189 added_dup:
 190         write_seqlock(&net->fs_addr_lock);
 191         alist = rcu_dereference_protected(server->addresses,
 192                                           lockdep_is_held(&net->fs_addr_lock.lock));
 193
 194         /* Secondly, if the server has any IPv4 and/or IPv6 addresses, install
 195          * it in the IPv4 and/or IPv6 reverse-map lists.
 196          *
 197          * TODO: For speed we want to use something other than a flat list
 198          * here; even sorting the list in terms of lowest address would help a
 199          * bit, but anything we might want to do gets messy and memory
 200          * intensive.
 201          */
 202         if (alist->nr_ipv4 > 0)
 203                 hlist_add_head_rcu(&server->addr4_link, &net->fs_addresses4);
 204         if (alist->nr_addrs > alist->nr_ipv4)
 205                 hlist_add_head_rcu(&server->addr6_link, &net->fs_addresses6);
 206
 207         write_sequnlock(&net->fs_addr_lock);
 208
 209 exists:
 210         afs_get_server(server, afs_server_trace_get_install);
 211         write_sequnlock(&net->fs_lock);
 212         return server;
 213 }
 214
 215 /*
 216  * Allocate a new server record and mark it active.
 217  */
 218 static struct afs_server *afs_alloc_server(struct afs_cell *cell,
 219                                            const uuid_t *uuid,
 220                                            struct afs_addr_list *alist)
 221 {
 222         struct afs_server *server;
 223         struct afs_net *net = cell->net;
 224
 225         _enter("");
 226
 227         server = kzalloc(sizeof(struct afs_server), GFP_KERNEL);
 228         if (!server)
 229                 goto enomem;
 230
 231         refcount_set(&server->ref, 1);
 232         atomic_set(&server->active, 1);
 233         server->debug_id = atomic_inc_return(&afs_server_debug_id);
 234         RCU_INIT_POINTER(server->addresses, alist);
 235         server->addr_version = alist->version;
 236         server->uuid = *uuid;
 237         rwlock_init(&server->fs_lock);
 238         INIT_WORK(&server->initcb_work, afs_server_init_callback_work);
 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->debug_id, 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 a;
 356         int r;
 357
 358         __refcount_inc(&server->ref, &r);
 359         a = atomic_read(&server->active);
 360         trace_afs_server(server->debug_id, r + 1, a, reason);
 361         return server;
 362 }
 363
 364 /*
 365  * Try to get a reference on a server object.
 366  */
 367 static struct afs_server *afs_maybe_use_server(struct afs_server *server,
 368                                                enum afs_server_trace reason)
 369 {
 370         unsigned int a;
 371         int r;
 372
 373         if (!__refcount_inc_not_zero(&server->ref, &r))
 374                 return NULL;
 375
 376         a = atomic_inc_return(&server->active);
 377         trace_afs_server(server->debug_id, r + 1, a, reason);
 378         return server;
 379 }
 380
 381 /*
 382  * Get an active count on a server object.
 383  */
 384 struct afs_server *afs_use_server(struct afs_server *server, enum afs_server_trace reason)
 385 {
 386         unsigned int a;
 387         int r;
 388
 389         __refcount_inc(&server->ref, &r);
 390         a = atomic_inc_return(&server->active);
 391
 392         trace_afs_server(server->debug_id, r + 1, a, reason);
 393         return server;
 394 }
 395
 396 /*
 397  * Release a reference on a server record.
 398  */
 399 void afs_put_server(struct afs_net *net, struct afs_server *server,
 400                     enum afs_server_trace reason)
 401 {
 402         unsigned int a, debug_id = server->debug_id;
 403         bool zero;
 404         int r;
 405
 406         if (!server)
 407                 return;
 408
 409         a = atomic_read(&server->active);
 410         zero = __refcount_dec_and_test(&server->ref, &r);
 411         trace_afs_server(debug_id, r - 1, a, reason);
 412         if (unlikely(zero))
 413                 __afs_put_server(net, server);
 414 }
 415
 416 /*
 417  * Drop an active count on a server object without updating the last-unused
 418  * time.
 419  */
 420 void afs_unuse_server_notime(struct afs_net *net, struct afs_server *server,
 421                              enum afs_server_trace reason)
 422 {
 423         if (server) {
 424                 unsigned int active = atomic_dec_return(&server->active);
 425
 426                 if (active == 0)
 427                         afs_set_server_timer(net, afs_server_gc_delay);
 428                 afs_put_server(net, server, reason);
 429         }
 430 }
 431
 432 /*
 433  * Drop an active count on a server object.
 434  */
 435 void afs_unuse_server(struct afs_net *net, struct afs_server *server,
 436                       enum afs_server_trace reason)
 437 {
 438         if (server) {
 439                 server->unuse_time = ktime_get_real_seconds();
 440                 afs_unuse_server_notime(net, server, reason);
 441         }
 442 }
 443
 444 static void afs_server_rcu(struct rcu_head *rcu)
 445 {
 446         struct afs_server *server = container_of(rcu, struct afs_server, rcu);
 447
 448         trace_afs_server(server->debug_id, refcount_read(&server->ref),
 449                          atomic_read(&server->active), afs_server_trace_free);
 450         afs_put_addrlist(rcu_access_pointer(server->addresses));
 451         kfree(server);
 452 }
 453
 454 static void __afs_put_server(struct afs_net *net, struct afs_server *server)
 455 {
 456         call_rcu(&server->rcu, afs_server_rcu);
 457         afs_dec_servers_outstanding(net);
 458 }
 459
 460 static void afs_give_up_callbacks(struct afs_net *net, struct afs_server *server)
 461 {
 462         struct afs_addr_list *alist = rcu_access_pointer(server->addresses);
 463         struct afs_addr_cursor ac = {
 464                 .alist  = alist,
 465                 .index  = alist->preferred,
 466                 .error  = 0,
 467         };
 468
 469         afs_fs_give_up_all_callbacks(net, server, &ac, NULL);
 470 }
 471
 472 /*
 473  * destroy a dead server
 474  */
 475 static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
 476 {
 477         if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
 478                 afs_give_up_callbacks(net, server);
 479
 480         flush_work(&server->initcb_work);
 481         afs_put_server(net, server, afs_server_trace_destroy);
 482 }
 483
 484 /*
 485  * Garbage collect any expired servers.
 486  */
 487 static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
 488 {
 489         struct afs_server *server, *next, *prev;
 490         int active;
 491
 492         while ((server = gc_list)) {
 493                 gc_list = server->gc_next;
 494
 495                 write_seqlock(&net->fs_lock);
 496
 497                 active = atomic_read(&server->active);
 498                 if (active == 0) {
 499                         trace_afs_server(server->debug_id, refcount_read(&server->ref),
 500                                          active, afs_server_trace_gc);
 501                         next = rcu_dereference_protected(
 502                                 server->uuid_next, lockdep_is_held(&net->fs_lock.lock));
 503                         prev = server->uuid_prev;
 504                         if (!prev) {
 505                                 /* The one at the front is in the tree */
 506                                 if (!next) {
 507                                         rb_erase(&server->uuid_rb, &net->fs_servers);
 508                                 } else {
 509                                         rb_replace_node_rcu(&server->uuid_rb,
 510                                                             &next->uuid_rb,
 511                                                             &net->fs_servers);
 512                                         next->uuid_prev = NULL;
 513                                 }
 514                         } else {
 515                                 /* This server is not at the front */
 516                                 rcu_assign_pointer(prev->uuid_next, next);
 517                                 if (next)
 518                                         next->uuid_prev = prev;
 519                         }
 520
 521                         list_del(&server->probe_link);
 522                         hlist_del_rcu(&server->proc_link);
 523                         if (!hlist_unhashed(&server->addr4_link))
 524                                 hlist_del_rcu(&server->addr4_link);
 525                         if (!hlist_unhashed(&server->addr6_link))
 526                                 hlist_del_rcu(&server->addr6_link);
 527                 }
 528                 write_sequnlock(&net->fs_lock);
 529
 530                 if (active == 0)
 531                         afs_destroy_server(net, server);
 532         }
 533 }
 534
 535 /*
 536  * Manage the records of servers known to be within a network namespace.  This
 537  * includes garbage collecting unused servers.
 538  *
 539  * Note also that we were given an increment on net->servers_outstanding by
 540  * whoever queued us that we need to deal with before returning.
 541  */
 542 void afs_manage_servers(struct work_struct *work)
 543 {
 544         struct afs_net *net = container_of(work, struct afs_net, fs_manager);
 545         struct afs_server *gc_list = NULL;
 546         struct rb_node *cursor;
 547         time64_t now = ktime_get_real_seconds(), next_manage = TIME64_MAX;
 548         bool purging = !net->live;
 549
 550         _enter("");
 551
 552         /* Trawl the server list looking for servers that have expired from
 553          * lack of use.
 554          */
 555         read_seqlock_excl(&net->fs_lock);
 556
 557         for (cursor = rb_first(&net->fs_servers); cursor; cursor = rb_next(cursor)) {
 558                 struct afs_server *server =
 559                         rb_entry(cursor, struct afs_server, uuid_rb);
 560                 int active = atomic_read(&server->active);
 561
 562                 _debug("manage %pU %u", &server->uuid, active);
 563
 564                 if (purging) {
 565                         trace_afs_server(server->debug_id, refcount_read(&server->ref),
 566                                          active, afs_server_trace_purging);
 567                         if (active != 0)
 568                                 pr_notice("Can't purge s=%08x\n", server->debug_id);
 569                 }
 570
 571                 if (active == 0) {
 572                         time64_t expire_at = server->unuse_time;
 573
 574                         if (!test_bit(AFS_SERVER_FL_VL_FAIL, &server->flags) &&
 575                             !test_bit(AFS_SERVER_FL_NOT_FOUND, &server->flags))
 576                                 expire_at += afs_server_gc_delay;
 577                         if (purging || expire_at <= now) {
 578                                 server->gc_next = gc_list;
 579                                 gc_list = server;
 580                         } else if (expire_at < next_manage) {
 581                                 next_manage = expire_at;
 582                         }
 583                 }
 584         }
 585
 586         read_sequnlock_excl(&net->fs_lock);
 587
 588         /* Update the timer on the way out.  We have to pass an increment on
 589          * servers_outstanding in the namespace that we are in to the timer or
 590          * the work scheduler.
 591          */
 592         if (!purging && next_manage < TIME64_MAX) {
 593                 now = ktime_get_real_seconds();
 594
 595                 if (next_manage - now <= 0) {
 596                         if (queue_work(afs_wq, &net->fs_manager))
 597                                 afs_inc_servers_outstanding(net);
 598                 } else {
 599                         afs_set_server_timer(net, next_manage - now);
 600                 }
 601         }
 602
 603         afs_gc_servers(net, gc_list);
 604
 605         afs_dec_servers_outstanding(net);
 606         _leave(" [%d]", atomic_read(&net->servers_outstanding));
 607 }
 608
 609 static void afs_queue_server_manager(struct afs_net *net)
 610 {
 611         afs_inc_servers_outstanding(net);
 612         if (!queue_work(afs_wq, &net->fs_manager))
 613                 afs_dec_servers_outstanding(net);
 614 }
 615
 616 /*
 617  * Purge list of servers.
 618  */
 619 void afs_purge_servers(struct afs_net *net)
 620 {
 621         _enter("");
 622
 623         if (del_timer_sync(&net->fs_timer))
 624                 afs_dec_servers_outstanding(net);
 625
 626         afs_queue_server_manager(net);
 627
 628         _debug("wait");
 629         atomic_dec(&net->servers_outstanding);
 630         wait_var_event(&net->servers_outstanding,
 631                        !atomic_read(&net->servers_outstanding));
 632         _leave("");
 633 }
 634
 635 /*
 636  * Get an update for a server's address list.
 637  */
 638 static noinline bool afs_update_server_record(struct afs_operation *op,
 639                                               struct afs_server *server)
 640 {
 641         struct afs_addr_list *alist, *discard;
 642
 643         _enter("");
 644
 645         trace_afs_server(server->debug_id, refcount_read(&server->ref),
 646                          atomic_read(&server->active),
 647                          afs_server_trace_update);
 648
 649         alist = afs_vl_lookup_addrs(op->volume->cell, op->key, &server->uuid);
 650         if (IS_ERR(alist)) {
 651                 if ((PTR_ERR(alist) == -ERESTARTSYS ||
 652                      PTR_ERR(alist) == -EINTR) &&
 653                     (op->flags & AFS_OPERATION_UNINTR) &&
 654                     server->addresses) {
 655                         _leave(" = t [intr]");
 656                         return true;
 657                 }
 658                 op->error = PTR_ERR(alist);
 659                 _leave(" = f [%d]", op->error);
 660                 return false;
 661         }
 662
 663         discard = alist;
 664         if (server->addr_version != alist->version) {
 665                 write_lock(&server->fs_lock);
 666                 discard = rcu_dereference_protected(server->addresses,
 667                                                     lockdep_is_held(&server->fs_lock));
 668                 rcu_assign_pointer(server->addresses, alist);
 669                 server->addr_version = alist->version;
 670                 write_unlock(&server->fs_lock);
 671         }
 672
 673         afs_put_addrlist(discard);
 674         _leave(" = t");
 675         return true;
 676 }
 677
 678 /*
 679  * See if a server's address list needs updating.
 680  */
 681 bool afs_check_server_record(struct afs_operation *op, struct afs_server *server)
 682 {
 683         bool success;
 684         int ret, retries = 0;
 685
 686         _enter("");
 687
 688         ASSERT(server);
 689
 690 retry:
 691         if (test_bit(AFS_SERVER_FL_UPDATING, &server->flags))
 692                 goto wait;
 693         if (test_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags))
 694                 goto update;
 695         _leave(" = t [good]");
 696         return true;
 697
 698 update:
 699         if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) {
 700                 clear_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags);
 701                 success = afs_update_server_record(op, server);
 702                 clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags);
 703                 wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING);
 704                 _leave(" = %d", success);
 705                 return success;
 706         }
 707
 708 wait:
 709         ret = wait_on_bit(&server->flags, AFS_SERVER_FL_UPDATING,
 710                           (op->flags & AFS_OPERATION_UNINTR) ?
 711                           TASK_UNINTERRUPTIBLE : TASK_INTERRUPTIBLE);
 712         if (ret == -ERESTARTSYS) {
 713                 op->error = ret;
 714                 _leave(" = f [intr]");
 715                 return false;
 716         }
 717
 718         retries++;
 719         if (retries == 4) {
 720                 _leave(" = f [stale]");
 721                 ret = -ESTALE;
 722                 return false;
 723         }
 724         goto retry;
 725 }