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         refcount_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_WORK(&server->initcb_work, afs_server_init_callback_work);
 240         init_waitqueue_head(&server->probe_wq);
 241         INIT_LIST_HEAD(&server->probe_link);
 242         spin_lock_init(&server->probe_lock);
 243         server->cell = cell;
 244         server->rtt = UINT_MAX;
 245
 246         afs_inc_servers_outstanding(net);
 247         trace_afs_server(server->debug_id, 1, 1, afs_server_trace_alloc);
 248         _leave(" = %p", server);
 249         return server;
 250
 251 enomem:
 252         _leave(" = NULL [nomem]");
 253         return NULL;
 254 }
 255
 256 /*
 257  * Look up an address record for a server
 258  */
 259 static struct afs_addr_list *afs_vl_lookup_addrs(struct afs_cell *cell,
 260                                                  struct key *key, const uuid_t *uuid)
 261 {
 262         struct afs_vl_cursor vc;
 263         struct afs_addr_list *alist = NULL;
 264         int ret;
 265
 266         ret = -ERESTARTSYS;
 267         if (afs_begin_vlserver_operation(&vc, cell, key)) {
 268                 while (afs_select_vlserver(&vc)) {
 269                         if (test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags))
 270                                 alist = afs_yfsvl_get_endpoints(&vc, uuid);
 271                         else
 272                                 alist = afs_vl_get_addrs_u(&vc, uuid);
 273                 }
 274
 275                 ret = afs_end_vlserver_operation(&vc);
 276         }
 277
 278         return ret < 0 ? ERR_PTR(ret) : alist;
 279 }
 280
 281 /*
 282  * Get or create a fileserver record.
 283  */
 284 struct afs_server *afs_lookup_server(struct afs_cell *cell, struct key *key,
 285                                      const uuid_t *uuid, u32 addr_version)
 286 {
 287         struct afs_addr_list *alist;
 288         struct afs_server *server, *candidate;
 289
 290         _enter("%p,%pU", cell->net, uuid);
 291
 292         server = afs_find_server_by_uuid(cell->net, uuid);
 293         if (server) {
 294                 if (server->addr_version != addr_version)
 295                         set_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags);
 296                 return server;
 297         }
 298
 299         alist = afs_vl_lookup_addrs(cell, key, uuid);
 300         if (IS_ERR(alist))
 301                 return ERR_CAST(alist);
 302
 303         candidate = afs_alloc_server(cell, uuid, alist);
 304         if (!candidate) {
 305                 afs_put_addrlist(alist);
 306                 return ERR_PTR(-ENOMEM);
 307         }
 308
 309         server = afs_install_server(cell, candidate);
 310         if (server != candidate) {
 311                 afs_put_addrlist(alist);
 312                 kfree(candidate);
 313         } else {
 314                 /* Immediately dispatch an asynchronous probe to each interface
 315                  * on the fileserver.  This will make sure the repeat-probing
 316                  * service is started.
 317                  */
 318                 afs_fs_probe_fileserver(cell->net, server, key, true);
 319         }
 320
 321         return server;
 322 }
 323
 324 /*
 325  * Set the server timer to fire after a given delay, assuming it's not already
 326  * set for an earlier time.
 327  */
 328 static void afs_set_server_timer(struct afs_net *net, time64_t delay)
 329 {
 330         if (net->live) {
 331                 afs_inc_servers_outstanding(net);
 332                 if (timer_reduce(&net->fs_timer, jiffies + delay * HZ))
 333                         afs_dec_servers_outstanding(net);
 334         }
 335 }
 336
 337 /*
 338  * Server management timer.  We have an increment on fs_outstanding that we
 339  * need to pass along to the work item.
 340  */
 341 void afs_servers_timer(struct timer_list *timer)
 342 {
 343         struct afs_net *net = container_of(timer, struct afs_net, fs_timer);
 344
 345         _enter("");
 346         if (!queue_work(afs_wq, &net->fs_manager))
 347                 afs_dec_servers_outstanding(net);
 348 }
 349
 350 /*
 351  * Get a reference on a server object.
 352  */
 353 struct afs_server *afs_get_server(struct afs_server *server,
 354                                   enum afs_server_trace reason)
 355 {
 356         unsigned int a;
 357         int r;
 358
 359         __refcount_inc(&server->ref, &r);
 360         a = atomic_read(&server->active);
 361         trace_afs_server(server->debug_id, r + 1, a, reason);
 362         return server;
 363 }
 364
 365 /*
 366  * Try to get a reference on a server object.
 367  */
 368 static struct afs_server *afs_maybe_use_server(struct afs_server *server,
 369                                                enum afs_server_trace reason)
 370 {
 371         unsigned int a;
 372         int r;
 373
 374         if (!__refcount_inc_not_zero(&server->ref, &r))
 375                 return NULL;
 376
 377         a = atomic_inc_return(&server->active);
 378         trace_afs_server(server->debug_id, r + 1, a, reason);
 379         return server;
 380 }
 381
 382 /*
 383  * Get an active count on a server object.
 384  */
 385 struct afs_server *afs_use_server(struct afs_server *server, enum afs_server_trace reason)
 386 {
 387         unsigned int a;
 388         int r;
 389
 390         __refcount_inc(&server->ref, &r);
 391         a = atomic_inc_return(&server->active);
 392
 393         trace_afs_server(server->debug_id, r + 1, a, reason);
 394         return server;
 395 }
 396
 397 /*
 398  * Release a reference on a server record.
 399  */
 400 void afs_put_server(struct afs_net *net, struct afs_server *server,
 401                     enum afs_server_trace reason)
 402 {
 403         unsigned int a, debug_id = server->debug_id;
 404         bool zero;
 405         int r;
 406
 407         if (!server)
 408                 return;
 409
 410         a = atomic_read(&server->active);
 411         zero = __refcount_dec_and_test(&server->ref, &r);
 412         trace_afs_server(debug_id, r - 1, a, reason);
 413         if (unlikely(zero))
 414                 __afs_put_server(net, server);
 415 }
 416
 417 /*
 418  * Drop an active count on a server object without updating the last-unused
 419  * time.
 420  */
 421 void afs_unuse_server_notime(struct afs_net *net, struct afs_server *server,
 422                              enum afs_server_trace reason)
 423 {
 424         if (server) {
 425                 unsigned int active = atomic_dec_return(&server->active);
 426
 427                 if (active == 0)
 428                         afs_set_server_timer(net, afs_server_gc_delay);
 429                 afs_put_server(net, server, reason);
 430         }
 431 }
 432
 433 /*
 434  * Drop an active count on a server object.
 435  */
 436 void afs_unuse_server(struct afs_net *net, struct afs_server *server,
 437                       enum afs_server_trace reason)
 438 {
 439         if (server) {
 440                 server->unuse_time = ktime_get_real_seconds();
 441                 afs_unuse_server_notime(net, server, reason);
 442         }
 443 }
 444
 445 static void afs_server_rcu(struct rcu_head *rcu)
 446 {
 447         struct afs_server *server = container_of(rcu, struct afs_server, rcu);
 448
 449         trace_afs_server(server->debug_id, refcount_read(&server->ref),
 450                          atomic_read(&server->active), afs_server_trace_free);
 451         afs_put_addrlist(rcu_access_pointer(server->addresses));
 452         kfree(server);
 453 }
 454
 455 static void __afs_put_server(struct afs_net *net, struct afs_server *server)
 456 {
 457         call_rcu(&server->rcu, afs_server_rcu);
 458         afs_dec_servers_outstanding(net);
 459 }
 460
 461 static void afs_give_up_callbacks(struct afs_net *net, struct afs_server *server)
 462 {
 463         struct afs_addr_list *alist = rcu_access_pointer(server->addresses);
 464         struct afs_addr_cursor ac = {
 465                 .alist  = alist,
 466                 .index  = alist->preferred,
 467                 .error  = 0,
 468         };
 469
 470         afs_fs_give_up_all_callbacks(net, server, &ac, NULL);
 471 }
 472
 473 /*
 474  * destroy a dead server
 475  */
 476 static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
 477 {
 478         if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
 479                 afs_give_up_callbacks(net, server);
 480
 481         flush_work(&server->initcb_work);
 482         afs_put_server(net, server, afs_server_trace_destroy);
 483 }
 484
 485 /*
 486  * Garbage collect any expired servers.
 487  */
 488 static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
 489 {
 490         struct afs_server *server, *next, *prev;
 491         int active;
 492
 493         while ((server = gc_list)) {
 494                 gc_list = server->gc_next;
 495
 496                 write_seqlock(&net->fs_lock);
 497
 498                 active = atomic_read(&server->active);
 499                 if (active == 0) {
 500                         trace_afs_server(server->debug_id, refcount_read(&server->ref),
 501                                          active, afs_server_trace_gc);
 502                         next = rcu_dereference_protected(
 503                                 server->uuid_next, lockdep_is_held(&net->fs_lock.lock));
 504                         prev = server->uuid_prev;
 505                         if (!prev) {
 506                                 /* The one at the front is in the tree */
 507                                 if (!next) {
 508                                         rb_erase(&server->uuid_rb, &net->fs_servers);
 509                                 } else {
 510                                         rb_replace_node_rcu(&server->uuid_rb,
 511                                                             &next->uuid_rb,
 512                                                             &net->fs_servers);
 513                                         next->uuid_prev = NULL;
 514                                 }
 515                         } else {
 516                                 /* This server is not at the front */
 517                                 rcu_assign_pointer(prev->uuid_next, next);
 518                                 if (next)
 519                                         next->uuid_prev = prev;
 520                         }
 521
 522                         list_del(&server->probe_link);
 523                         hlist_del_rcu(&server->proc_link);
 524                         if (!hlist_unhashed(&server->addr4_link))
 525                                 hlist_del_rcu(&server->addr4_link);
 526                         if (!hlist_unhashed(&server->addr6_link))
 527                                 hlist_del_rcu(&server->addr6_link);
 528                 }
 529                 write_sequnlock(&net->fs_lock);
 530
 531                 if (active == 0)
 532                         afs_destroy_server(net, server);
 533         }
 534 }
 535
 536 /*
 537  * Manage the records of servers known to be within a network namespace.  This
 538  * includes garbage collecting unused servers.
 539  *
 540  * Note also that we were given an increment on net->servers_outstanding by
 541  * whoever queued us that we need to deal with before returning.
 542  */
 543 void afs_manage_servers(struct work_struct *work)
 544 {
 545         struct afs_net *net = container_of(work, struct afs_net, fs_manager);
 546         struct afs_server *gc_list = NULL;
 547         struct rb_node *cursor;
 548         time64_t now = ktime_get_real_seconds(), next_manage = TIME64_MAX;
 549         bool purging = !net->live;
 550
 551         _enter("");
 552
 553         /* Trawl the server list looking for servers that have expired from
 554          * lack of use.
 555          */
 556         read_seqlock_excl(&net->fs_lock);
 557
 558         for (cursor = rb_first(&net->fs_servers); cursor; cursor = rb_next(cursor)) {
 559                 struct afs_server *server =
 560                         rb_entry(cursor, struct afs_server, uuid_rb);
 561                 int active = atomic_read(&server->active);
 562
 563                 _debug("manage %pU %u", &server->uuid, active);
 564
 565                 if (purging) {
 566                         trace_afs_server(server->debug_id, refcount_read(&server->ref),
 567                                          active, afs_server_trace_purging);
 568                         if (active != 0)
 569                                 pr_notice("Can't purge s=%08x\n", server->debug_id);
 570                 }
 571
 572                 if (active == 0) {
 573                         time64_t expire_at = server->unuse_time;
 574
 575                         if (!test_bit(AFS_SERVER_FL_VL_FAIL, &server->flags) &&
 576                             !test_bit(AFS_SERVER_FL_NOT_FOUND, &server->flags))
 577                                 expire_at += afs_server_gc_delay;
 578                         if (purging || expire_at <= now) {
 579                                 server->gc_next = gc_list;
 580                                 gc_list = server;
 581                         } else if (expire_at < next_manage) {
 582                                 next_manage = expire_at;
 583                         }
 584                 }
 585         }
 586
 587         read_sequnlock_excl(&net->fs_lock);
 588
 589         /* Update the timer on the way out.  We have to pass an increment on
 590          * servers_outstanding in the namespace that we are in to the timer or
 591          * the work scheduler.
 592          */
 593         if (!purging && next_manage < TIME64_MAX) {
 594                 now = ktime_get_real_seconds();
 595
 596                 if (next_manage - now <= 0) {
 597                         if (queue_work(afs_wq, &net->fs_manager))
 598                                 afs_inc_servers_outstanding(net);
 599                 } else {
 600                         afs_set_server_timer(net, next_manage - now);
 601                 }
 602         }
 603
 604         afs_gc_servers(net, gc_list);
 605
 606         afs_dec_servers_outstanding(net);
 607         _leave(" [%d]", atomic_read(&net->servers_outstanding));
 608 }
 609
 610 static void afs_queue_server_manager(struct afs_net *net)
 611 {
 612         afs_inc_servers_outstanding(net);
 613         if (!queue_work(afs_wq, &net->fs_manager))
 614                 afs_dec_servers_outstanding(net);
 615 }
 616
 617 /*
 618  * Purge list of servers.
 619  */
 620 void afs_purge_servers(struct afs_net *net)
 621 {
 622         _enter("");
 623
 624         if (del_timer_sync(&net->fs_timer))
 625                 afs_dec_servers_outstanding(net);
 626
 627         afs_queue_server_manager(net);
 628
 629         _debug("wait");
 630         atomic_dec(&net->servers_outstanding);
 631         wait_var_event(&net->servers_outstanding,
 632                        !atomic_read(&net->servers_outstanding));
 633         _leave("");
 634 }
 635
 636 /*
 637  * Get an update for a server's address list.
 638  */
 639 static noinline bool afs_update_server_record(struct afs_operation *op,
 640                                               struct afs_server *server)
 641 {
 642         struct afs_addr_list *alist, *discard;
 643
 644         _enter("");
 645
 646         trace_afs_server(server->debug_id, refcount_read(&server->ref),
 647                          atomic_read(&server->active),
 648                          afs_server_trace_update);
 649
 650         alist = afs_vl_lookup_addrs(op->volume->cell, op->key, &server->uuid);
 651         if (IS_ERR(alist)) {
 652                 if ((PTR_ERR(alist) == -ERESTARTSYS ||
 653                      PTR_ERR(alist) == -EINTR) &&
 654                     (op->flags & AFS_OPERATION_UNINTR) &&
 655                     server->addresses) {
 656                         _leave(" = t [intr]");
 657                         return true;
 658                 }
 659                 op->error = PTR_ERR(alist);
 660                 _leave(" = f [%d]", op->error);
 661                 return false;
 662         }
 663
 664         discard = alist;
 665         if (server->addr_version != alist->version) {
 666                 write_lock(&server->fs_lock);
 667                 discard = rcu_dereference_protected(server->addresses,
 668                                                     lockdep_is_held(&server->fs_lock));
 669                 rcu_assign_pointer(server->addresses, alist);
 670                 server->addr_version = alist->version;
 671                 write_unlock(&server->fs_lock);
 672         }
 673
 674         afs_put_addrlist(discard);
 675         _leave(" = t");
 676         return true;
 677 }
 678
 679 /*
 680  * See if a server's address list needs updating.
 681  */
 682 bool afs_check_server_record(struct afs_operation *op, struct afs_server *server)
 683 {
 684         bool success;
 685         int ret, retries = 0;
 686
 687         _enter("");
 688
 689         ASSERT(server);
 690
 691 retry:
 692         if (test_bit(AFS_SERVER_FL_UPDATING, &server->flags))
 693                 goto wait;
 694         if (test_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags))
 695                 goto update;
 696         _leave(" = t [good]");
 697         return true;
 698
 699 update:
 700         if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) {
 701                 clear_bit(AFS_SERVER_FL_NEEDS_UPDATE, &server->flags);
 702                 success = afs_update_server_record(op, server);
 703                 clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags);
 704                 wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING);
 705                 _leave(" = %d", success);
 706                 return success;
 707         }
 708
 709 wait:
 710         ret = wait_on_bit(&server->flags, AFS_SERVER_FL_UPDATING,
 711                           (op->flags & AFS_OPERATION_UNINTR) ?
 712                           TASK_UNINTERRUPTIBLE : TASK_INTERRUPTIBLE);
 713         if (ret == -ERESTARTSYS) {
 714                 op->error = ret;
 715                 _leave(" = f [intr]");
 716                 return false;
 717         }
 718
 719         retries++;
 720         if (retries == 4) {
 721                 _leave(" = f [stale]");
 722                 ret = -ESTALE;
 723                 return false;
 724         }
 725         goto retry;
 726 }