fs/afs/server.c

   1 /* AFS server record management
   2  *
   3  * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/sched.h>
  13 #include <linux/slab.h>
  14 #include "afs_fs.h"
  15 #include "internal.h"
  16 #include "protocol_yfs.h"
  17
  18 static unsigned afs_server_gc_delay = 10;       /* Server record timeout in seconds */
  19 static unsigned afs_server_update_delay = 30;   /* Time till VLDB recheck in secs */
  20
  21 static void afs_inc_servers_outstanding(struct afs_net *net)
  22 {
  23         atomic_inc(&net->servers_outstanding);
  24 }
  25
  26 static void afs_dec_servers_outstanding(struct afs_net *net)
  27 {
  28         if (atomic_dec_and_test(&net->servers_outstanding))
  29                 wake_up_var(&net->servers_outstanding);
  30 }
  31
  32 /*
  33  * Find a server by one of its addresses.
  34  */
  35 struct afs_server *afs_find_server(struct afs_net *net,
  36                                    const struct sockaddr_rxrpc *srx)
  37 {
  38         const struct sockaddr_in6 *a = &srx->transport.sin6, *b;
  39         const struct afs_addr_list *alist;
  40         struct afs_server *server = NULL;
  41         unsigned int i;
  42         bool ipv6 = true;
  43         int seq = 0, diff;
  44
  45         if (srx->transport.sin6.sin6_addr.s6_addr32[0] == 0 ||
  46             srx->transport.sin6.sin6_addr.s6_addr32[1] == 0 ||
  47             srx->transport.sin6.sin6_addr.s6_addr32[2] == htonl(0xffff))
  48                 ipv6 = false;
  49
  50         rcu_read_lock();
  51
  52         do {
  53                 if (server)
  54                         afs_put_server(net, server);
  55                 server = NULL;
  56                 read_seqbegin_or_lock(&net->fs_addr_lock, &seq);
  57
  58                 if (ipv6) {
  59                         hlist_for_each_entry_rcu(server, &net->fs_addresses6, addr6_link) {
  60                                 alist = rcu_dereference(server->addresses);
  61                                 for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
  62                                         b = &alist->addrs[i].transport.sin6;
  63                                         diff = ((u16 __force)a->sin6_port -
  64                                                 (u16 __force)b->sin6_port);
  65                                         if (diff == 0)
  66                                                 diff = memcmp(&a->sin6_addr,
  67                                                               &b->sin6_addr,
  68                                                               sizeof(struct in6_addr));
  69                                         if (diff == 0)
  70                                                 goto found;
  71                                 }
  72                         }
  73                 } else {
  74                         hlist_for_each_entry_rcu(server, &net->fs_addresses4, addr4_link) {
  75                                 alist = rcu_dereference(server->addresses);
  76                                 for (i = 0; i < alist->nr_ipv4; i++) {
  77                                         b = &alist->addrs[i].transport.sin6;
  78                                         diff = ((u16 __force)a->sin6_port -
  79                                                 (u16 __force)b->sin6_port);
  80                                         if (diff == 0)
  81                                                 diff = ((u32 __force)a->sin6_addr.s6_addr32[3] -
  82                                                         (u32 __force)b->sin6_addr.s6_addr32[3]);
  83                                         if (diff == 0)
  84                                                 goto found;
  85                                 }
  86                         }
  87                 }
  88
  89                 server = NULL;
  90         found:
  91                 if (server && !atomic_inc_not_zero(&server->usage))
  92                         server = NULL;
  93
  94         } while (need_seqretry(&net->fs_addr_lock, seq));
  95
  96         done_seqretry(&net->fs_addr_lock, seq);
  97
  98         rcu_read_unlock();
  99         return server;
 100 }
 101
 102 /*
 103  * Look up a server by its UUID
 104  */
 105 struct afs_server *afs_find_server_by_uuid(struct afs_net *net, const uuid_t *uuid)
 106 {
 107         struct afs_server *server = NULL;
 108         struct rb_node *p;
 109         int diff, seq = 0;
 110
 111         _enter("%pU", uuid);
 112
 113         do {
 114                 /* Unfortunately, rbtree walking doesn't give reliable results
 115                  * under just the RCU read lock, so we have to check for
 116                  * changes.
 117                  */
 118                 if (server)
 119                         afs_put_server(net, server);
 120                 server = NULL;
 121
 122                 read_seqbegin_or_lock(&net->fs_lock, &seq);
 123
 124                 p = net->fs_servers.rb_node;
 125                 while (p) {
 126                         server = rb_entry(p, struct afs_server, uuid_rb);
 127
 128                         diff = memcmp(uuid, &server->uuid, sizeof(*uuid));
 129                         if (diff < 0) {
 130                                 p = p->rb_left;
 131                         } else if (diff > 0) {
 132                                 p = p->rb_right;
 133                         } else {
 134                                 afs_get_server(server);
 135                                 break;
 136                         }
 137
 138                         server = NULL;
 139                 }
 140         } while (need_seqretry(&net->fs_lock, seq));
 141
 142         done_seqretry(&net->fs_lock, seq);
 143
 144         _leave(" = %p", server);
 145         return server;
 146 }
 147
 148 /*
 149  * Install a server record in the namespace tree
 150  */
 151 static struct afs_server *afs_install_server(struct afs_net *net,
 152                                              struct afs_server *candidate)
 153 {
 154         const struct afs_addr_list *alist;
 155         struct afs_server *server;
 156         struct rb_node **pp, *p;
 157         int ret = -EEXIST, diff;
 158
 159         _enter("%p", candidate);
 160
 161         write_seqlock(&net->fs_lock);
 162
 163         /* Firstly install the server in the UUID lookup tree */
 164         pp = &net->fs_servers.rb_node;
 165         p = NULL;
 166         while (*pp) {
 167                 p = *pp;
 168                 _debug("- consider %p", p);
 169                 server = rb_entry(p, struct afs_server, uuid_rb);
 170                 diff = memcmp(&candidate->uuid, &server->uuid, sizeof(uuid_t));
 171                 if (diff < 0)
 172                         pp = &(*pp)->rb_left;
 173                 else if (diff > 0)
 174                         pp = &(*pp)->rb_right;
 175                 else
 176                         goto exists;
 177         }
 178
 179         server = candidate;
 180         rb_link_node(&server->uuid_rb, p, pp);
 181         rb_insert_color(&server->uuid_rb, &net->fs_servers);
 182         hlist_add_head_rcu(&server->proc_link, &net->fs_proc);
 183
 184         write_seqlock(&net->fs_addr_lock);
 185         alist = rcu_dereference_protected(server->addresses,
 186                                           lockdep_is_held(&net->fs_addr_lock.lock));
 187
 188         /* Secondly, if the server has any IPv4 and/or IPv6 addresses, install
 189          * it in the IPv4 and/or IPv6 reverse-map lists.
 190          *
 191          * TODO: For speed we want to use something other than a flat list
 192          * here; even sorting the list in terms of lowest address would help a
 193          * bit, but anything we might want to do gets messy and memory
 194          * intensive.
 195          */
 196         if (alist->nr_ipv4 > 0)
 197                 hlist_add_head_rcu(&server->addr4_link, &net->fs_addresses4);
 198         if (alist->nr_addrs > alist->nr_ipv4)
 199                 hlist_add_head_rcu(&server->addr6_link, &net->fs_addresses6);
 200
 201         write_sequnlock(&net->fs_addr_lock);
 202         ret = 0;
 203
 204 exists:
 205         afs_get_server(server);
 206         write_sequnlock(&net->fs_lock);
 207         return server;
 208 }
 209
 210 /*
 211  * allocate a new server record
 212  */
 213 static struct afs_server *afs_alloc_server(struct afs_net *net,
 214                                            const uuid_t *uuid,
 215                                            struct afs_addr_list *alist)
 216 {
 217         struct afs_server *server;
 218
 219         _enter("");
 220
 221         server = kzalloc(sizeof(struct afs_server), GFP_KERNEL);
 222         if (!server)
 223                 goto enomem;
 224
 225         atomic_set(&server->usage, 1);
 226         RCU_INIT_POINTER(server->addresses, alist);
 227         server->addr_version = alist->version;
 228         server->uuid = *uuid;
 229         server->update_at = ktime_get_real_seconds() + afs_server_update_delay;
 230         rwlock_init(&server->fs_lock);
 231         INIT_HLIST_HEAD(&server->cb_volumes);
 232         rwlock_init(&server->cb_break_lock);
 233         init_waitqueue_head(&server->probe_wq);
 234         spin_lock_init(&server->probe_lock);
 235
 236         afs_inc_servers_outstanding(net);
 237         _leave(" = %p", server);
 238         return server;
 239
 240 enomem:
 241         _leave(" = NULL [nomem]");
 242         return NULL;
 243 }
 244
 245 /*
 246  * Look up an address record for a server
 247  */
 248 static struct afs_addr_list *afs_vl_lookup_addrs(struct afs_cell *cell,
 249                                                  struct key *key, const uuid_t *uuid)
 250 {
 251         struct afs_vl_cursor vc;
 252         struct afs_addr_list *alist = NULL;
 253         int ret;
 254
 255         ret = -ERESTARTSYS;
 256         if (afs_begin_vlserver_operation(&vc, cell, key)) {
 257                 while (afs_select_vlserver(&vc)) {
 258                         if (test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags))
 259                                 alist = afs_yfsvl_get_endpoints(&vc, uuid);
 260                         else
 261                                 alist = afs_vl_get_addrs_u(&vc, uuid);
 262                 }
 263
 264                 ret = afs_end_vlserver_operation(&vc);
 265         }
 266
 267         return ret < 0 ? ERR_PTR(ret) : alist;
 268 }
 269
 270 /*
 271  * Get or create a fileserver record.
 272  */
 273 struct afs_server *afs_lookup_server(struct afs_cell *cell, struct key *key,
 274                                      const uuid_t *uuid)
 275 {
 276         struct afs_addr_list *alist;
 277         struct afs_server *server, *candidate;
 278
 279         _enter("%p,%pU", cell->net, uuid);
 280
 281         server = afs_find_server_by_uuid(cell->net, uuid);
 282         if (server)
 283                 return server;
 284
 285         alist = afs_vl_lookup_addrs(cell, key, uuid);
 286         if (IS_ERR(alist))
 287                 return ERR_CAST(alist);
 288
 289         candidate = afs_alloc_server(cell->net, uuid, alist);
 290         if (!candidate) {
 291                 afs_put_addrlist(alist);
 292                 return ERR_PTR(-ENOMEM);
 293         }
 294
 295         server = afs_install_server(cell->net, candidate);
 296         if (server != candidate) {
 297                 afs_put_addrlist(alist);
 298                 kfree(candidate);
 299         }
 300
 301         _leave(" = %p{%d}", server, atomic_read(&server->usage));
 302         return server;
 303 }
 304
 305 /*
 306  * Set the server timer to fire after a given delay, assuming it's not already
 307  * set for an earlier time.
 308  */
 309 static void afs_set_server_timer(struct afs_net *net, time64_t delay)
 310 {
 311         if (net->live) {
 312                 afs_inc_servers_outstanding(net);
 313                 if (timer_reduce(&net->fs_timer, jiffies + delay * HZ))
 314                         afs_dec_servers_outstanding(net);
 315         }
 316 }
 317
 318 /*
 319  * Server management timer.  We have an increment on fs_outstanding that we
 320  * need to pass along to the work item.
 321  */
 322 void afs_servers_timer(struct timer_list *timer)
 323 {
 324         struct afs_net *net = container_of(timer, struct afs_net, fs_timer);
 325
 326         _enter("");
 327         if (!queue_work(afs_wq, &net->fs_manager))
 328                 afs_dec_servers_outstanding(net);
 329 }
 330
 331 /*
 332  * Release a reference on a server record.
 333  */
 334 void afs_put_server(struct afs_net *net, struct afs_server *server)
 335 {
 336         unsigned int usage;
 337
 338         if (!server)
 339                 return;
 340
 341         server->put_time = ktime_get_real_seconds();
 342
 343         usage = atomic_dec_return(&server->usage);
 344
 345         _enter("{%u}", usage);
 346
 347         if (likely(usage > 0))
 348                 return;
 349
 350         afs_set_server_timer(net, afs_server_gc_delay);
 351 }
 352
 353 static void afs_server_rcu(struct rcu_head *rcu)
 354 {
 355         struct afs_server *server = container_of(rcu, struct afs_server, rcu);
 356
 357         afs_put_addrlist(rcu_access_pointer(server->addresses));
 358         kfree(server);
 359 }
 360
 361 /*
 362  * destroy a dead server
 363  */
 364 static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
 365 {
 366         struct afs_addr_list *alist = rcu_access_pointer(server->addresses);
 367         struct afs_addr_cursor ac = {
 368                 .alist  = alist,
 369                 .index  = alist->preferred,
 370                 .error  = 0,
 371         };
 372         _enter("%p", server);
 373
 374         if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
 375                 afs_fs_give_up_all_callbacks(net, server, &ac, NULL);
 376
 377         wait_var_event(&server->probe_outstanding,
 378                        atomic_read(&server->probe_outstanding) == 0);
 379
 380         call_rcu(&server->rcu, afs_server_rcu);
 381         afs_dec_servers_outstanding(net);
 382 }
 383
 384 /*
 385  * Garbage collect any expired servers.
 386  */
 387 static void afs_gc_servers(struct afs_net *net, struct afs_server *gc_list)
 388 {
 389         struct afs_server *server;
 390         bool deleted;
 391         int usage;
 392
 393         while ((server = gc_list)) {
 394                 gc_list = server->gc_next;
 395
 396                 write_seqlock(&net->fs_lock);
 397                 usage = 1;
 398                 deleted = atomic_try_cmpxchg(&server->usage, &usage, 0);
 399                 if (deleted) {
 400                         rb_erase(&server->uuid_rb, &net->fs_servers);
 401                         hlist_del_rcu(&server->proc_link);
 402                 }
 403                 write_sequnlock(&net->fs_lock);
 404
 405                 if (deleted) {
 406                         write_seqlock(&net->fs_addr_lock);
 407                         if (!hlist_unhashed(&server->addr4_link))
 408                                 hlist_del_rcu(&server->addr4_link);
 409                         if (!hlist_unhashed(&server->addr6_link))
 410                                 hlist_del_rcu(&server->addr6_link);
 411                         write_sequnlock(&net->fs_addr_lock);
 412                         afs_destroy_server(net, server);
 413                 }
 414         }
 415 }
 416
 417 /*
 418  * Manage the records of servers known to be within a network namespace.  This
 419  * includes garbage collecting unused servers.
 420  *
 421  * Note also that we were given an increment on net->servers_outstanding by
 422  * whoever queued us that we need to deal with before returning.
 423  */
 424 void afs_manage_servers(struct work_struct *work)
 425 {
 426         struct afs_net *net = container_of(work, struct afs_net, fs_manager);
 427         struct afs_server *gc_list = NULL;
 428         struct rb_node *cursor;
 429         time64_t now = ktime_get_real_seconds(), next_manage = TIME64_MAX;
 430         bool purging = !net->live;
 431
 432         _enter("");
 433
 434         /* Trawl the server list looking for servers that have expired from
 435          * lack of use.
 436          */
 437         read_seqlock_excl(&net->fs_lock);
 438
 439         for (cursor = rb_first(&net->fs_servers); cursor; cursor = rb_next(cursor)) {
 440                 struct afs_server *server =
 441                         rb_entry(cursor, struct afs_server, uuid_rb);
 442                 int usage = atomic_read(&server->usage);
 443
 444                 _debug("manage %pU %u", &server->uuid, usage);
 445
 446                 ASSERTCMP(usage, >=, 1);
 447                 ASSERTIFCMP(purging, usage, ==, 1);
 448
 449                 if (usage == 1) {
 450                         time64_t expire_at = server->put_time;
 451
 452                         if (!test_bit(AFS_SERVER_FL_VL_FAIL, &server->flags) &&
 453                             !test_bit(AFS_SERVER_FL_NOT_FOUND, &server->flags))
 454                                 expire_at += afs_server_gc_delay;
 455                         if (purging || expire_at <= now) {
 456                                 server->gc_next = gc_list;
 457                                 gc_list = server;
 458                         } else if (expire_at < next_manage) {
 459                                 next_manage = expire_at;
 460                         }
 461                 }
 462         }
 463
 464         read_sequnlock_excl(&net->fs_lock);
 465
 466         /* Update the timer on the way out.  We have to pass an increment on
 467          * servers_outstanding in the namespace that we are in to the timer or
 468          * the work scheduler.
 469          */
 470         if (!purging && next_manage < TIME64_MAX) {
 471                 now = ktime_get_real_seconds();
 472
 473                 if (next_manage - now <= 0) {
 474                         if (queue_work(afs_wq, &net->fs_manager))
 475                                 afs_inc_servers_outstanding(net);
 476                 } else {
 477                         afs_set_server_timer(net, next_manage - now);
 478                 }
 479         }
 480
 481         afs_gc_servers(net, gc_list);
 482
 483         afs_dec_servers_outstanding(net);
 484         _leave(" [%d]", atomic_read(&net->servers_outstanding));
 485 }
 486
 487 static void afs_queue_server_manager(struct afs_net *net)
 488 {
 489         afs_inc_servers_outstanding(net);
 490         if (!queue_work(afs_wq, &net->fs_manager))
 491                 afs_dec_servers_outstanding(net);
 492 }
 493
 494 /*
 495  * Purge list of servers.
 496  */
 497 void afs_purge_servers(struct afs_net *net)
 498 {
 499         _enter("");
 500
 501         if (del_timer_sync(&net->fs_timer))
 502                 atomic_dec(&net->servers_outstanding);
 503
 504         afs_queue_server_manager(net);
 505
 506         _debug("wait");
 507         wait_var_event(&net->servers_outstanding,
 508                        !atomic_read(&net->servers_outstanding));
 509         _leave("");
 510 }
 511
 512 /*
 513  * Get an update for a server's address list.
 514  */
 515 static noinline bool afs_update_server_record(struct afs_fs_cursor *fc, struct afs_server *server)
 516 {
 517         struct afs_addr_list *alist, *discard;
 518
 519         _enter("");
 520
 521         alist = afs_vl_lookup_addrs(fc->vnode->volume->cell, fc->key,
 522                                     &server->uuid);
 523         if (IS_ERR(alist)) {
 524                 fc->ac.error = PTR_ERR(alist);
 525                 _leave(" = f [%d]", fc->ac.error);
 526                 return false;
 527         }
 528
 529         discard = alist;
 530         if (server->addr_version != alist->version) {
 531                 write_lock(&server->fs_lock);
 532                 discard = rcu_dereference_protected(server->addresses,
 533                                                     lockdep_is_held(&server->fs_lock));
 534                 rcu_assign_pointer(server->addresses, alist);
 535                 server->addr_version = alist->version;
 536                 write_unlock(&server->fs_lock);
 537         }
 538
 539         server->update_at = ktime_get_real_seconds() + afs_server_update_delay;
 540         afs_put_addrlist(discard);
 541         _leave(" = t");
 542         return true;
 543 }
 544
 545 /*
 546  * See if a server's address list needs updating.
 547  */
 548 bool afs_check_server_record(struct afs_fs_cursor *fc, struct afs_server *server)
 549 {
 550         time64_t now = ktime_get_real_seconds();
 551         long diff;
 552         bool success;
 553         int ret, retries = 0;
 554
 555         _enter("");
 556
 557         ASSERT(server);
 558
 559 retry:
 560         diff = READ_ONCE(server->update_at) - now;
 561         if (diff > 0) {
 562                 _leave(" = t [not now %ld]", diff);
 563                 return true;
 564         }
 565
 566         if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) {
 567                 success = afs_update_server_record(fc, server);
 568                 clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags);
 569                 wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING);
 570                 _leave(" = %d", success);
 571                 return success;
 572         }
 573
 574         ret = wait_on_bit(&server->flags, AFS_SERVER_FL_UPDATING,
 575                           TASK_INTERRUPTIBLE);
 576         if (ret == -ERESTARTSYS) {
 577                 fc->ac.error = ret;
 578                 _leave(" = f [intr]");
 579                 return false;
 580         }
 581
 582         retries++;
 583         if (retries == 4) {
 584                 _leave(" = f [stale]");
 585                 ret = -ESTALE;
 586                 return false;
 587         }
 588         goto retry;
 589 }