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         atomic_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_waitqueue_head(&server->probe_wq);
 239         INIT_LIST_HEAD(&server->probe_link);
 240         spin_lock_init(&server->probe_lock);
 241         server->cell = cell;
 242         server->rtt = UINT_MAX;
 243
 244         afs_inc_servers_outstanding(net);
 245         trace_afs_server(server, 1, 1, afs_server_trace_alloc);
 246         _leave(" = %p", server);
 247         return server;
 248
 249 enomem:
 250         _leave(" = NULL [nomem]");
 251         return NULL;
 252 }
 253
 254 /*
 255  * Look up an address record for a server
 256  */
 257 static struct afs_addr_list *afs_vl_lookup_addrs(struct afs_cell *cell,
 258                                                  struct key *key, const uuid_t *uuid)
 259 {
 260         struct afs_vl_cursor vc;
 261         struct afs_addr_list *alist = NULL;
 262         int ret;
 263
 264         ret = -ERESTARTSYS;
 265         if (afs_begin_vlserver_operation(&vc, cell, key)) {
 266                 while (afs_select_vlserver(&vc)) {
 267                         if (test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags))
 268                                 alist = afs_yfsvl_get_endpoints(&vc, uuid);
 269                         else
 270                                 alist = afs_vl_get_addrs_u(&vc, uuid);
 271                 }
 272
 273                 ret = afs_end_vlserver_operation(&vc);
 274         }
 275
 276         return ret < 0 ? ERR_PTR(ret) : alist;
 277 }
 278
 279 /*
 280  * Get or create a fileserver record.
 281  */
 282 struct afs_server *afs_lookup_server(struct afs_cell *cell, struct key *key,
 283                                      const uuid_t *uuid, u32 addr_version)
 284 {
 285         struct afs_addr_list *alist;
 286         struct afs_server *server, *candidate;
 287
 288         _enter("%p,%pU", cell->net, uuid);
 289
 290         server = afs_find_server_by_uuid(cell->net, uuid);
 291         if (server) {
 292                 if (server->addr_version != addr_version)
 293                         set_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags);
 294                 return server;
 295         }
 296
 297         alist = afs_vl_lookup_addrs(cell, key, uuid);
 298         if (IS_ERR(alist))
 299                 return ERR_CAST(alist);
 300
 301         candidate = afs_alloc_server(cell, uuid, alist);
 302         if (!candidate) {
 303                 afs_put_addrlist(alist);
 304                 return ERR_PTR(-ENOMEM);
 305         }
 306
 307         server = afs_install_server(cell, candidate);
 308         if (server != candidate) {
 309                 afs_put_addrlist(alist);
 310                 kfree(candidate);
 311         } else {
 312                 /* Immediately dispatch an asynchronous probe to each interface
 313                  * on the fileserver.  This will make sure the repeat-probing
 314                  * service is started.
 315                  */
 316                 afs_fs_probe_fileserver(cell->net, server, key, true);
 317         }
 318
 319         return server;
 320 }
 321
 322 /*
 323  * Set the server timer to fire after a given delay, assuming it's not already
 324  * set for an earlier time.
 325  */
 326 static void afs_set_server_timer(struct afs_net *net, time64_t delay)
 327 {
 328         if (net->live) {
 329                 afs_inc_servers_outstanding(net);
 330                 if (timer_reduce(&net->fs_timer, jiffies + delay * HZ))
 331                         afs_dec_servers_outstanding(net);
 332         }
 333 }
 334
 335 /*
 336  * Server management timer.  We have an increment on fs_outstanding that we
 337  * need to pass along to the work item.
 338  */
 339 void afs_servers_timer(struct timer_list *timer)
 340 {
 341         struct afs_net *net = container_of(timer, struct afs_net, fs_timer);
 342
 343         _enter("");
 344         if (!queue_work(afs_wq, &net->fs_manager))
 345                 afs_dec_servers_outstanding(net);
 346 }
 347
 348 /*
 349  * Get a reference on a server object.
 350  */
 351 struct afs_server *afs_get_server(struct afs_server *server,
 352                                   enum afs_server_trace reason)
 353 {
 354         unsigned int u = atomic_inc_return(&server->ref);
 355
 356         trace_afs_server(server, u, atomic_read(&server->active), reason);
 357         return server;
 358 }
 359
 360 /*
 361  * Try to get a reference on a server object.
 362  */
 363 static struct afs_server *afs_maybe_use_server(struct afs_server *server,
 364                                                enum afs_server_trace reason)
 365 {
 366         unsigned int r = atomic_fetch_add_unless(&server->ref, 1, 0);
 367         unsigned int a;
 368
 369         if (r == 0)
 370                 return NULL;
 371
 372         a = atomic_inc_return(&server->active);
 373         trace_afs_server(server, r, a, reason);
 374         return server;
 375 }
 376
 377 /*
 378  * Get an active count on a server object.
 379  */
 380 struct afs_server *afs_use_server(struct afs_server *server, enum afs_server_trace reason)
 381 {
 382         unsigned int r = atomic_inc_return(&server->ref);
 383         unsigned int a = atomic_inc_return(&server->active);
 384
 385         trace_afs_server(server, r, a, reason);
 386         return server;
 387 }
 388
 389 /*
 390  * Release a reference on a server record.
 391  */
 392 void afs_put_server(struct afs_net *net, struct afs_server *server,
 393                     enum afs_server_trace reason)
 394 {
 395         unsigned int usage;
 396
 397         if (!server)
 398                 return;
 399
 400         usage = atomic_dec_return(&server->ref);
 401         trace_afs_server(server, usage, atomic_read(&server->active), reason);
 402         if (unlikely(usage == 0))
 403                 __afs_put_server(net, server);
 404 }
 405
 406 /*
 407  * Drop an active count on a server object without updating the last-unused
 408  * time.
 409  */
 410 void afs_unuse_server_notime(struct afs_net *net, struct afs_server *server,
 411                              enum afs_server_trace reason)
 412 {
 413         if (server) {
 414                 unsigned int active = atomic_dec_return(&server->active);
 415
 416                 if (active == 0)
 417                         afs_set_server_timer(net, afs_server_gc_delay);
 418                 afs_put_server(net, server, reason);
 419         }
 420 }
 421
 422 /*
 423  * Drop an active count on a server object.
 424  */
 425 void afs_unuse_server(struct afs_net *net, struct afs_server *server,
 426                       enum afs_server_trace reason)
 427 {
 428         if (server) {
 429                 server->unuse_time = ktime_get_real_seconds();
 430                 afs_unuse_server_notime(net, server, reason);
 431         }
 432 }
 433
 434 static void afs_server_rcu(struct rcu_head *rcu)
 435 {
 436         struct afs_server *server = container_of(rcu, struct afs_server, rcu);
 437
 438         trace_afs_server(server, atomic_read(&server->ref),
 439                          atomic_read(&server->active), afs_server_trace_free);
 440         afs_put_addrlist(rcu_access_pointer(server->addresses));
 441         kfree(server);
 442 }
 443
 444 static void __afs_put_server(struct afs_net *net, struct afs_server *server)
 445 {
 446         call_rcu(&server->rcu, afs_server_rcu);
 447         afs_dec_servers_outstanding(net);
 448 }
 449
 450 static void afs_give_up_callbacks(struct afs_net *net, struct afs_server *server)
 451 {
 452         struct afs_addr_list *alist = rcu_access_pointer(server->addresses);
 453         struct afs_addr_cursor ac = {
 454                 .alist  = alist,
 455                 .index  = alist->preferred,
 456                 .error  = 0,
 457         };
 458
 459         afs_fs_give_up_all_callbacks(net, server, &ac, NULL);
 460 }
 461
 462 /*
 463  * destroy a dead server
 464  */
 465 static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
 466 {
 467         if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
 468                 afs_give_up_callbacks(net, server);
 469
 470         afs_put_server(net, server, afs_server_trace_destroy);
 471 }
 472
 473 /*
 474  * Garbage collect any expired servers.
 475  */
 476 static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
 477 {
 478         struct afs_server *server, *next, *prev;
 479         int active;
 480
 481         while ((server = gc_list)) {
 482                 gc_list = server->gc_next;
 483
 484                 write_seqlock(&net->fs_lock);
 485
 486                 active = atomic_read(&server->active);
 487                 if (active == 0) {
 488                         trace_afs_server(server, atomic_read(&server->ref),
 489                                          active, afs_server_trace_gc);
 490                         next = rcu_dereference_protected(
 491                                 server->uuid_next, lockdep_is_held(&net->fs_lock.lock));
 492                         prev = server->uuid_prev;
 493                         if (!prev) {
 494                                 /* The one at the front is in the tree */
 495                                 if (!next) {
 496                                         rb_erase(&server->uuid_rb, &net->fs_servers);
 497                                 } else {
 498                                         rb_replace_node_rcu(&server->uuid_rb,
 499                                                             &next->uuid_rb,
 500                                                             &net->fs_servers);
 501                                         next->uuid_prev = NULL;
 502                                 }
 503                         } else {
 504                                 /* This server is not at the front */
 505                                 rcu_assign_pointer(prev->uuid_next, next);
 506                                 if (next)
 507                                         next->uuid_prev = prev;
 508                         }
 509
 510                         list_del(&server->probe_link);
 511                         hlist_del_rcu(&server->proc_link);
 512                         if (!hlist_unhashed(&server->addr4_link))
 513                                 hlist_del_rcu(&server->addr4_link);
 514                         if (!hlist_unhashed(&server->addr6_link))
 515                                 hlist_del_rcu(&server->addr6_link);
 516                 }
 517                 write_sequnlock(&net->fs_lock);
 518
 519                 if (active == 0)
 520                         afs_destroy_server(net, server);
 521         }
 522 }
 523
 524 /*
 525  * Manage the records of servers known to be within a network namespace.  This
 526  * includes garbage collecting unused servers.
 527  *
 528  * Note also that we were given an increment on net->servers_outstanding by
 529  * whoever queued us that we need to deal with before returning.
 530  */
 531 void afs_manage_servers(struct work_struct *work)
 532 {
 533         struct afs_net *net = container_of(work, struct afs_net, fs_manager);
 534         struct afs_server *gc_list = NULL;
 535         struct rb_node *cursor;
 536         time64_t now = ktime_get_real_seconds(), next_manage = TIME64_MAX;
 537         bool purging = !net->live;
 538
 539         _enter("");
 540
 541         /* Trawl the server list looking for servers that have expired from
 542          * lack of use.
 543          */
 544         read_seqlock_excl(&net->fs_lock);
 545
 546         for (cursor = rb_first(&net->fs_servers); cursor; cursor = rb_next(cursor)) {
 547                 struct afs_server *server =
 548                         rb_entry(cursor, struct afs_server, uuid_rb);
 549                 int active = atomic_read(&server->active);
 550
 551                 _debug("manage %pU %u", &server->uuid, active);
 552
 553                 if (purging) {
 554                         trace_afs_server(server, atomic_read(&server->ref),
 555                                          active, afs_server_trace_purging);
 556                         if (active != 0)
 557                                 pr_notice("Can't purge s=%08x\n", server->debug_id);
 558                 }
 559
 560                 if (active == 0) {
 561                         time64_t expire_at = server->unuse_time;
 562
 563                         if (!test_bit(AFS_SERVER_FL_VL_FAIL, &server->flags) &&
 564                             !test_bit(AFS_SERVER_FL_NOT_FOUND, &server->flags))
 565                                 expire_at += afs_server_gc_delay;
 566                         if (purging || expire_at <= now) {
 567                                 server->gc_next = gc_list;
 568                                 gc_list = server;
 569                         } else if (expire_at < next_manage) {
 570                                 next_manage = expire_at;
 571                         }
 572                 }
 573         }
 574
 575         read_sequnlock_excl(&net->fs_lock);
 576
 577         /* Update the timer on the way out.  We have to pass an increment on
 578          * servers_outstanding in the namespace that we are in to the timer or
 579          * the work scheduler.
 580          */
 581         if (!purging && next_manage < TIME64_MAX) {
 582                 now = ktime_get_real_seconds();
 583
 584                 if (next_manage - now <= 0) {
 585                         if (queue_work(afs_wq, &net->fs_manager))
 586                                 afs_inc_servers_outstanding(net);
 587                 } else {
 588                         afs_set_server_timer(net, next_manage - now);
 589                 }
 590         }
 591
 592         afs_gc_servers(net, gc_list);
 593
 594         afs_dec_servers_outstanding(net);
 595         _leave(" [%d]", atomic_read(&net->servers_outstanding));
 596 }
 597
 598 static void afs_queue_server_manager(struct afs_net *net)
 599 {
 600         afs_inc_servers_outstanding(net);
 601         if (!queue_work(afs_wq, &net->fs_manager))
 602                 afs_dec_servers_outstanding(net);
 603 }
 604
 605 /*
 606  * Purge list of servers.
 607  */
 608 void afs_purge_servers(struct afs_net *net)
 609 {
 610         _enter("");
 611
 612         if (del_timer_sync(&net->fs_timer))
 613                 afs_dec_servers_outstanding(net);
 614
 615         afs_queue_server_manager(net);
 616
 617         _debug("wait");
 618         atomic_dec(&net->servers_outstanding);
 619         wait_var_event(&net->servers_outstanding,
 620                        !atomic_read(&net->servers_outstanding));
 621         _leave("");
 622 }
 623
 624 /*
 625  * Get an update for a server's address list.
 626  */
 627 static noinline bool afs_update_server_record(struct afs_operation *op,
 628                                               struct afs_server *server)
 629 {
 630         struct afs_addr_list *alist, *discard;
 631
 632         _enter("");
 633
 634         trace_afs_server(server, atomic_read(&server->ref), atomic_read(&server->active),
 635                          afs_server_trace_update);
 636
 637         alist = afs_vl_lookup_addrs(op->volume->cell, op->key, &server->uuid);
 638         if (IS_ERR(alist)) {
 639                 if ((PTR_ERR(alist) == -ERESTARTSYS ||
 640                      PTR_ERR(alist) == -EINTR) &&
 641                     (op->flags & AFS_OPERATION_UNINTR) &&
 642                     server->addresses) {
 643                         _leave(" = t [intr]");
 644                         return true;
 645                 }
 646                 op->error = PTR_ERR(alist);
 647                 _leave(" = f [%d]", op->error);
 648                 return false;
 649         }
 650
 651         discard = alist;
 652         if (server->addr_version != alist->version) {
 653                 write_lock(&server->fs_lock);
 654                 discard = rcu_dereference_protected(server->addresses,
 655                                                     lockdep_is_held(&server->fs_lock));
 656                 rcu_assign_pointer(server->addresses, alist);
 657                 server->addr_version = alist->version;
 658                 write_unlock(&server->fs_lock);
 659         }
 660
 661         afs_put_addrlist(discard);
 662         _leave(" = t");
 663         return true;
 664 }
 665
 666 /*
 667  * See if a server's address list needs updating.
 668  */
 669 bool afs_check_server_record(struct afs_operation *op, struct afs_server *server)
 670 {
 671         bool success;
 672         int ret, retries = 0;
 673
 674         _enter("");
 675
 676         ASSERT(server);
 677
 678 retry:
 679         if (test_bit(AFS_SERVER_FL_UPDATING, &server->flags))
 680                 goto wait;
 681         if (test_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags))
 682                 goto update;
 683         _leave(" = t [good]");
 684         return true;
 685
 686 update:
 687         if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) {
 688                 clear_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags);
 689                 success = afs_update_server_record(op, server);
 690                 clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags);
 691                 wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING);
 692                 _leave(" = %d", success);
 693                 return success;
 694         }
 695
 696 wait:
 697         ret = wait_on_bit(&server->flags, AFS_SERVER_FL_UPDATING,
 698                           (op->flags & AFS_OPERATION_UNINTR) ?
 699                           TASK_UNINTERRUPTIBLE : TASK_INTERRUPTIBLE);
 700         if (ret == -ERESTARTSYS) {
 701                 op->error = ret;
 702                 _leave(" = f [intr]");
 703                 return false;
 704         }
 705
 706         retries++;
 707         if (retries == 4) {
 708                 _leave(" = f [stale]");
 709                 ret = -ESTALE;
 710                 return false;
 711         }
 712         goto retry;
 713 }