git.sesse.net Git - bcachefs-tools-debian/blob - libbcachefs/btree_locking.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include "bcachefs.h"
   4 #include "btree_locking.h"
   5 #include "btree_types.h"
   6
   7 static struct lock_class_key bch2_btree_node_lock_key;
   8
   9 void bch2_btree_lock_init(struct btree_bkey_cached_common *b,
  10                           enum six_lock_init_flags flags)
  11 {
  12         __six_lock_init(&b->lock, "b->c.lock", &bch2_btree_node_lock_key, flags);
  13 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  14         lockdep_set_no_check_recursion(&b->lock.dep_map);
  15 #endif
  16 }
  17
  18 #ifdef CONFIG_LOCKDEP
  19 void bch2_assert_btree_nodes_not_locked(void)
  20 {
  21         BUG_ON(lock_class_is_held(&bch2_btree_node_lock_key));
  22 }
  23 #endif
  24
  25 /* Btree node locking: */
  26
  27 struct six_lock_count bch2_btree_node_lock_counts(struct btree_trans *trans,
  28                                                   struct btree_path *skip,
  29                                                   struct btree_bkey_cached_common *b,
  30                                                   unsigned level)
  31 {
  32         struct btree_path *path;
  33         struct six_lock_count ret;
  34
  35         memset(&ret, 0, sizeof(ret));
  36
  37         if (IS_ERR_OR_NULL(b))
  38                 return ret;
  39
  40         trans_for_each_path(trans, path)
  41                 if (path != skip && &path->l[level].b->c == b) {
  42                         int t = btree_node_locked_type(path, level);
  43
  44                         if (t != BTREE_NODE_UNLOCKED)
  45                                 ret.n[t]++;
  46                 }
  47
  48         return ret;
  49 }
  50
  51 /* unlock */
  52
  53 void bch2_btree_node_unlock_write(struct btree_trans *trans,
  54                         struct btree_path *path, struct btree *b)
  55 {
  56         bch2_btree_node_unlock_write_inlined(trans, path, b);
  57 }
  58
  59 /* lock */
  60
  61 /*
  62  * @trans wants to lock @b with type @type
  63  */
  64 struct trans_waiting_for_lock {
  65         struct btree_trans              *trans;
  66         struct btree_bkey_cached_common *node_want;
  67         enum six_lock_type              lock_want;
  68
  69         /* for iterating over held locks :*/
  70         u8                              path_idx;
  71         u8                              level;
  72         u64                             lock_start_time;
  73 };
  74
  75 struct lock_graph {
  76         struct trans_waiting_for_lock   g[8];
  77         unsigned                        nr;
  78 };
  79
  80 static noinline void print_cycle(struct printbuf *out, struct lock_graph *g)
  81 {
  82         struct trans_waiting_for_lock *i;
  83
  84         prt_printf(out, "Found lock cycle (%u entries):", g->nr);
  85         prt_newline(out);
  86
  87         for (i = g->g; i < g->g + g->nr; i++)
  88                 bch2_btree_trans_to_text(out, i->trans);
  89 }
  90
  91 static noinline void print_chain(struct printbuf *out, struct lock_graph *g)
  92 {
  93         struct trans_waiting_for_lock *i;
  94
  95         for (i = g->g; i != g->g + g->nr; i++) {
  96                 if (i != g->g)
  97                         prt_str(out, "<- ");
  98                 prt_printf(out, "%u ", i->trans->locking_wait.task->pid);
  99         }
 100         prt_newline(out);
 101 }
 102
 103 static void lock_graph_up(struct lock_graph *g)
 104 {
 105         closure_put(&g->g[--g->nr].trans->ref);
 106 }
 107
 108 static noinline void lock_graph_pop_all(struct lock_graph *g)
 109 {
 110         while (g->nr)
 111                 lock_graph_up(g);
 112 }
 113
 114 static void __lock_graph_down(struct lock_graph *g, struct btree_trans *trans)
 115 {
 116         g->g[g->nr++] = (struct trans_waiting_for_lock) {
 117                 .trans          = trans,
 118                 .node_want      = trans->locking,
 119                 .lock_want      = trans->locking_wait.lock_want,
 120         };
 121 }
 122
 123 static void lock_graph_down(struct lock_graph *g, struct btree_trans *trans)
 124 {
 125         closure_get(&trans->ref);
 126         __lock_graph_down(g, trans);
 127 }
 128
 129 static bool lock_graph_remove_non_waiters(struct lock_graph *g)
 130 {
 131         struct trans_waiting_for_lock *i;
 132
 133         for (i = g->g + 1; i < g->g + g->nr; i++)
 134                 if (i->trans->locking != i->node_want ||
 135                     i->trans->locking_wait.start_time != i[-1].lock_start_time) {
 136                         while (g->g + g->nr > i)
 137                                 lock_graph_up(g);
 138                         return true;
 139                 }
 140
 141         return false;
 142 }
 143
 144 static int abort_lock(struct lock_graph *g, struct trans_waiting_for_lock *i)
 145 {
 146         if (i == g->g) {
 147                 trace_and_count(i->trans->c, trans_restart_would_deadlock, i->trans, _RET_IP_);
 148                 return btree_trans_restart(i->trans, BCH_ERR_transaction_restart_would_deadlock);
 149         } else {
 150                 i->trans->lock_must_abort = true;
 151                 wake_up_process(i->trans->locking_wait.task);
 152                 return 0;
 153         }
 154 }
 155
 156 static int btree_trans_abort_preference(struct btree_trans *trans)
 157 {
 158         if (trans->lock_may_not_fail)
 159                 return 0;
 160         if (trans->locking_wait.lock_want == SIX_LOCK_write)
 161                 return 1;
 162         if (!trans->in_traverse_all)
 163                 return 2;
 164         return 3;
 165 }
 166
 167 static noinline int break_cycle(struct lock_graph *g, struct printbuf *cycle)
 168 {
 169         struct trans_waiting_for_lock *i, *abort = NULL;
 170         unsigned best = 0, pref;
 171         int ret;
 172
 173         if (lock_graph_remove_non_waiters(g))
 174                 return 0;
 175
 176         /* Only checking, for debugfs: */
 177         if (cycle) {
 178                 print_cycle(cycle, g);
 179                 ret = -1;
 180                 goto out;
 181         }
 182
 183         for (i = g->g; i < g->g + g->nr; i++) {
 184                 pref = btree_trans_abort_preference(i->trans);
 185                 if (pref > best) {
 186                         abort = i;
 187                         best = pref;
 188                 }
 189         }
 190
 191         if (unlikely(!best)) {
 192                 struct printbuf buf = PRINTBUF;
 193
 194                 prt_printf(&buf, bch2_fmt(g->g->trans->c, "cycle of nofail locks"));
 195
 196                 for (i = g->g; i < g->g + g->nr; i++) {
 197                         struct btree_trans *trans = i->trans;
 198
 199                         bch2_btree_trans_to_text(&buf, trans);
 200
 201                         prt_printf(&buf, "backtrace:");
 202                         prt_newline(&buf);
 203                         printbuf_indent_add(&buf, 2);
 204                         bch2_prt_task_backtrace(&buf, trans->locking_wait.task);
 205                         printbuf_indent_sub(&buf, 2);
 206                         prt_newline(&buf);
 207                 }
 208
 209                 bch2_print_string_as_lines(KERN_ERR, buf.buf);
 210                 printbuf_exit(&buf);
 211                 BUG();
 212         }
 213
 214         ret = abort_lock(g, abort);
 215 out:
 216         if (ret)
 217                 while (g->nr)
 218                         lock_graph_up(g);
 219         return ret;
 220 }
 221
 222 static int lock_graph_descend(struct lock_graph *g, struct btree_trans *trans,
 223                               struct printbuf *cycle)
 224 {
 225         struct btree_trans *orig_trans = g->g->trans;
 226         struct trans_waiting_for_lock *i;
 227
 228         for (i = g->g; i < g->g + g->nr; i++)
 229                 if (i->trans == trans) {
 230                         closure_put(&trans->ref);
 231                         return break_cycle(g, cycle);
 232                 }
 233
 234         if (g->nr == ARRAY_SIZE(g->g)) {
 235                 closure_put(&trans->ref);
 236
 237                 if (orig_trans->lock_may_not_fail)
 238                         return 0;
 239
 240                 while (g->nr)
 241                         lock_graph_up(g);
 242
 243                 if (cycle)
 244                         return 0;
 245
 246                 trace_and_count(trans->c, trans_restart_would_deadlock_recursion_limit, trans, _RET_IP_);
 247                 return btree_trans_restart(orig_trans, BCH_ERR_transaction_restart_deadlock_recursion_limit);
 248         }
 249
 250         __lock_graph_down(g, trans);
 251         return 0;
 252 }
 253
 254 static bool lock_type_conflicts(enum six_lock_type t1, enum six_lock_type t2)
 255 {
 256         return t1 + t2 > 1;
 257 }
 258
 259 int bch2_check_for_deadlock(struct btree_trans *trans, struct printbuf *cycle)
 260 {
 261         struct lock_graph g;
 262         struct trans_waiting_for_lock *top;
 263         struct btree_bkey_cached_common *b;
 264         struct btree_path *path;
 265         unsigned path_idx;
 266         int ret;
 267
 268         if (trans->lock_must_abort) {
 269                 if (cycle)
 270                         return -1;
 271
 272                 trace_and_count(trans->c, trans_restart_would_deadlock, trans, _RET_IP_);
 273                 return btree_trans_restart(trans, BCH_ERR_transaction_restart_would_deadlock);
 274         }
 275
 276         g.nr = 0;
 277         lock_graph_down(&g, trans);
 278 next:
 279         if (!g.nr)
 280                 return 0;
 281
 282         top = &g.g[g.nr - 1];
 283
 284         trans_for_each_path_safe_from(top->trans, path, path_idx, top->path_idx) {
 285                 if (!path->nodes_locked)
 286                         continue;
 287
 288                 if (path_idx != top->path_idx) {
 289                         top->path_idx           = path_idx;
 290                         top->level              = 0;
 291                         top->lock_start_time    = 0;
 292                 }
 293
 294                 for (;
 295                      top->level < BTREE_MAX_DEPTH;
 296                      top->level++, top->lock_start_time = 0) {
 297                         int lock_held = btree_node_locked_type(path, top->level);
 298
 299                         if (lock_held == BTREE_NODE_UNLOCKED)
 300                                 continue;
 301
 302                         b = &READ_ONCE(path->l[top->level].b)->c;
 303
 304                         if (IS_ERR_OR_NULL(b)) {
 305                                 /*
 306                                  * If we get here, it means we raced with the
 307                                  * other thread updating its btree_path
 308                                  * structures - which means it can't be blocked
 309                                  * waiting on a lock:
 310                                  */
 311                                 if (!lock_graph_remove_non_waiters(&g)) {
 312                                         /*
 313                                          * If lock_graph_remove_non_waiters()
 314                                          * didn't do anything, it must be
 315                                          * because we're being called by debugfs
 316                                          * checking for lock cycles, which
 317                                          * invokes us on btree_transactions that
 318                                          * aren't actually waiting on anything.
 319                                          * Just bail out:
 320                                          */
 321                                         lock_graph_pop_all(&g);
 322                                 }
 323
 324                                 goto next;
 325                         }
 326
 327                         if (list_empty_careful(&b->lock.wait_list))
 328                                 continue;
 329
 330                         raw_spin_lock(&b->lock.wait_lock);
 331                         list_for_each_entry(trans, &b->lock.wait_list, locking_wait.list) {
 332                                 BUG_ON(b != trans->locking);
 333
 334                                 if (top->lock_start_time &&
 335                                     time_after_eq64(top->lock_start_time, trans->locking_wait.start_time))
 336                                         continue;
 337
 338                                 top->lock_start_time = trans->locking_wait.start_time;
 339
 340                                 /* Don't check for self deadlock: */
 341                                 if (trans == top->trans ||
 342                                     !lock_type_conflicts(lock_held, trans->locking_wait.lock_want))
 343                                         continue;
 344
 345                                 closure_get(&trans->ref);
 346                                 raw_spin_unlock(&b->lock.wait_lock);
 347
 348                                 ret = lock_graph_descend(&g, trans, cycle);
 349                                 if (ret)
 350                                         return ret;
 351                                 goto next;
 352
 353                         }
 354                         raw_spin_unlock(&b->lock.wait_lock);
 355                 }
 356         }
 357
 358         if (g.nr > 1 && cycle)
 359                 print_chain(cycle, &g);
 360         lock_graph_up(&g);
 361         goto next;
 362 }
 363
 364 int bch2_six_check_for_deadlock(struct six_lock *lock, void *p)
 365 {
 366         struct btree_trans *trans = p;
 367
 368         return bch2_check_for_deadlock(trans, NULL);
 369 }
 370
 371 int __bch2_btree_node_lock_write(struct btree_trans *trans, struct btree_path *path,
 372                                  struct btree_bkey_cached_common *b,
 373                                  bool lock_may_not_fail)
 374 {
 375         int readers = bch2_btree_node_lock_counts(trans, NULL, b, b->level).n[SIX_LOCK_read];
 376         int ret;
 377
 378         /*
 379          * Must drop our read locks before calling six_lock_write() -
 380          * six_unlock() won't do wakeups until the reader count
 381          * goes to 0, and it's safe because we have the node intent
 382          * locked:
 383          */
 384         six_lock_readers_add(&b->lock, -readers);
 385         ret = __btree_node_lock_nopath(trans, b, SIX_LOCK_write,
 386                                        lock_may_not_fail, _RET_IP_);
 387         six_lock_readers_add(&b->lock, readers);
 388
 389         if (ret)
 390                 mark_btree_node_locked_noreset(path, b->level, BTREE_NODE_INTENT_LOCKED);
 391
 392         return ret;
 393 }
 394
 395 void bch2_btree_node_lock_write_nofail(struct btree_trans *trans,
 396                                        struct btree_path *path,
 397                                        struct btree_bkey_cached_common *b)
 398 {
 399         struct btree_path *linked;
 400         unsigned i;
 401         int ret;
 402
 403         /*
 404          * XXX BIG FAT NOTICE
 405          *
 406          * Drop all read locks before taking a write lock:
 407          *
 408          * This is a hack, because bch2_btree_node_lock_write_nofail() is a
 409          * hack - but by dropping read locks first, this should never fail, and
 410          * we only use this in code paths where whatever read locks we've
 411          * already taken are no longer needed:
 412          */
 413
 414         trans_for_each_path(trans, linked) {
 415                 if (!linked->nodes_locked)
 416                         continue;
 417
 418                 for (i = 0; i < BTREE_MAX_DEPTH; i++)
 419                         if (btree_node_read_locked(linked, i)) {
 420                                 btree_node_unlock(trans, linked, i);
 421                                 btree_path_set_dirty(linked, BTREE_ITER_NEED_RELOCK);
 422                         }
 423         }
 424
 425         ret = __btree_node_lock_write(trans, path, b, true);
 426         BUG_ON(ret);
 427 }
 428
 429 /* relock */
 430
 431 static inline bool btree_path_get_locks(struct btree_trans *trans,
 432                                         struct btree_path *path,
 433                                         bool upgrade,
 434                                         struct get_locks_fail *f)
 435 {
 436         unsigned l = path->level;
 437         int fail_idx = -1;
 438
 439         do {
 440                 if (!btree_path_node(path, l))
 441                         break;
 442
 443                 if (!(upgrade
 444                       ? bch2_btree_node_upgrade(trans, path, l)
 445                       : bch2_btree_node_relock(trans, path, l))) {
 446                         fail_idx        = l;
 447
 448                         if (f) {
 449                                 f->l    = l;
 450                                 f->b    = path->l[l].b;
 451                         }
 452                 }
 453
 454                 l++;
 455         } while (l < path->locks_want);
 456
 457         /*
 458          * When we fail to get a lock, we have to ensure that any child nodes
 459          * can't be relocked so bch2_btree_path_traverse has to walk back up to
 460          * the node that we failed to relock:
 461          */
 462         if (fail_idx >= 0) {
 463                 __bch2_btree_path_unlock(trans, path);
 464                 btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 465
 466                 do {
 467                         path->l[fail_idx].b = upgrade
 468                                 ? ERR_PTR(-BCH_ERR_no_btree_node_upgrade)
 469                                 : ERR_PTR(-BCH_ERR_no_btree_node_relock);
 470                         --fail_idx;
 471                 } while (fail_idx >= 0);
 472         }
 473
 474         if (path->uptodate == BTREE_ITER_NEED_RELOCK)
 475                 path->uptodate = BTREE_ITER_UPTODATE;
 476
 477         bch2_trans_verify_locks(trans);
 478
 479         return path->uptodate < BTREE_ITER_NEED_RELOCK;
 480 }
 481
 482 bool __bch2_btree_node_relock(struct btree_trans *trans,
 483                               struct btree_path *path, unsigned level,
 484                               bool trace)
 485 {
 486         struct btree *b = btree_path_node(path, level);
 487         int want = __btree_lock_want(path, level);
 488
 489         if (race_fault())
 490                 goto fail;
 491
 492         if (six_relock_type(&b->c.lock, want, path->l[level].lock_seq) ||
 493             (btree_node_lock_seq_matches(path, b, level) &&
 494              btree_node_lock_increment(trans, &b->c, level, want))) {
 495                 mark_btree_node_locked(trans, path, level, want);
 496                 return true;
 497         }
 498 fail:
 499         if (trace && !trans->notrace_relock_fail)
 500                 trace_and_count(trans->c, btree_path_relock_fail, trans, _RET_IP_, path, level);
 501         return false;
 502 }
 503
 504 /* upgrade */
 505
 506 bool bch2_btree_node_upgrade(struct btree_trans *trans,
 507                              struct btree_path *path, unsigned level)
 508 {
 509         struct btree *b = path->l[level].b;
 510         struct six_lock_count count = bch2_btree_node_lock_counts(trans, path, &b->c, level);
 511
 512         if (!is_btree_node(path, level))
 513                 return false;
 514
 515         switch (btree_lock_want(path, level)) {
 516         case BTREE_NODE_UNLOCKED:
 517                 BUG_ON(btree_node_locked(path, level));
 518                 return true;
 519         case BTREE_NODE_READ_LOCKED:
 520                 BUG_ON(btree_node_intent_locked(path, level));
 521                 return bch2_btree_node_relock(trans, path, level);
 522         case BTREE_NODE_INTENT_LOCKED:
 523                 break;
 524         case BTREE_NODE_WRITE_LOCKED:
 525                 BUG();
 526         }
 527
 528         if (btree_node_intent_locked(path, level))
 529                 return true;
 530
 531         if (race_fault())
 532                 return false;
 533
 534         if (btree_node_locked(path, level)) {
 535                 bool ret;
 536
 537                 six_lock_readers_add(&b->c.lock, -count.n[SIX_LOCK_read]);
 538                 ret = six_lock_tryupgrade(&b->c.lock);
 539                 six_lock_readers_add(&b->c.lock, count.n[SIX_LOCK_read]);
 540
 541                 if (ret)
 542                         goto success;
 543         } else {
 544                 if (six_relock_type(&b->c.lock, SIX_LOCK_intent, path->l[level].lock_seq))
 545                         goto success;
 546         }
 547
 548         /*
 549          * Do we already have an intent lock via another path? If so, just bump
 550          * lock count:
 551          */
 552         if (btree_node_lock_seq_matches(path, b, level) &&
 553             btree_node_lock_increment(trans, &b->c, level, BTREE_NODE_INTENT_LOCKED)) {
 554                 btree_node_unlock(trans, path, level);
 555                 goto success;
 556         }
 557
 558         trace_and_count(trans->c, btree_path_upgrade_fail, trans, _RET_IP_, path, level);
 559         return false;
 560 success:
 561         mark_btree_node_locked_noreset(path, level, BTREE_NODE_INTENT_LOCKED);
 562         return true;
 563 }
 564
 565 /* Btree path locking: */
 566
 567 /*
 568  * Only for btree_cache.c - only relocks intent locks
 569  */
 570 int bch2_btree_path_relock_intent(struct btree_trans *trans,
 571                                   struct btree_path *path)
 572 {
 573         unsigned l;
 574
 575         for (l = path->level;
 576              l < path->locks_want && btree_path_node(path, l);
 577              l++) {
 578                 if (!bch2_btree_node_relock(trans, path, l)) {
 579                         __bch2_btree_path_unlock(trans, path);
 580                         btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 581                         trace_and_count(trans->c, trans_restart_relock_path_intent, trans, _RET_IP_, path);
 582                         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_path_intent);
 583                 }
 584         }
 585
 586         return 0;
 587 }
 588
 589 __flatten
 590 bool bch2_btree_path_relock_norestart(struct btree_trans *trans,
 591                         struct btree_path *path, unsigned long trace_ip)
 592 {
 593         struct get_locks_fail f;
 594
 595         return btree_path_get_locks(trans, path, false, &f);
 596 }
 597
 598 int __bch2_btree_path_relock(struct btree_trans *trans,
 599                         struct btree_path *path, unsigned long trace_ip)
 600 {
 601         if (!bch2_btree_path_relock_norestart(trans, path, trace_ip)) {
 602                 trace_and_count(trans->c, trans_restart_relock_path, trans, trace_ip, path);
 603                 return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_path);
 604         }
 605
 606         return 0;
 607 }
 608
 609 bool bch2_btree_path_upgrade_noupgrade_sibs(struct btree_trans *trans,
 610                                struct btree_path *path,
 611                                unsigned new_locks_want,
 612                                struct get_locks_fail *f)
 613 {
 614         EBUG_ON(path->locks_want >= new_locks_want);
 615
 616         path->locks_want = new_locks_want;
 617
 618         return btree_path_get_locks(trans, path, true, f);
 619 }
 620
 621 bool __bch2_btree_path_upgrade(struct btree_trans *trans,
 622                                struct btree_path *path,
 623                                unsigned new_locks_want,
 624                                struct get_locks_fail *f)
 625 {
 626         struct btree_path *linked;
 627
 628         if (bch2_btree_path_upgrade_noupgrade_sibs(trans, path, new_locks_want, f))
 629                 return true;
 630
 631         /*
 632          * XXX: this is ugly - we'd prefer to not be mucking with other
 633          * iterators in the btree_trans here.
 634          *
 635          * On failure to upgrade the iterator, setting iter->locks_want and
 636          * calling get_locks() is sufficient to make bch2_btree_path_traverse()
 637          * get the locks we want on transaction restart.
 638          *
 639          * But if this iterator was a clone, on transaction restart what we did
 640          * to this iterator isn't going to be preserved.
 641          *
 642          * Possibly we could add an iterator field for the parent iterator when
 643          * an iterator is a copy - for now, we'll just upgrade any other
 644          * iterators with the same btree id.
 645          *
 646          * The code below used to be needed to ensure ancestor nodes get locked
 647          * before interior nodes - now that's handled by
 648          * bch2_btree_path_traverse_all().
 649          */
 650         if (!path->cached && !trans->in_traverse_all)
 651                 trans_for_each_path(trans, linked)
 652                         if (linked != path &&
 653                             linked->cached == path->cached &&
 654                             linked->btree_id == path->btree_id &&
 655                             linked->locks_want < new_locks_want) {
 656                                 linked->locks_want = new_locks_want;
 657                                 btree_path_get_locks(trans, linked, true, NULL);
 658                         }
 659
 660         return false;
 661 }
 662
 663 void __bch2_btree_path_downgrade(struct btree_trans *trans,
 664                                  struct btree_path *path,
 665                                  unsigned new_locks_want)
 666 {
 667         unsigned l, old_locks_want = path->locks_want;
 668
 669         if (trans->restarted)
 670                 return;
 671
 672         EBUG_ON(path->locks_want < new_locks_want);
 673
 674         path->locks_want = new_locks_want;
 675
 676         while (path->nodes_locked &&
 677                (l = btree_path_highest_level_locked(path)) >= path->locks_want) {
 678                 if (l > path->level) {
 679                         btree_node_unlock(trans, path, l);
 680                 } else {
 681                         if (btree_node_intent_locked(path, l)) {
 682                                 six_lock_downgrade(&path->l[l].b->c.lock);
 683                                 mark_btree_node_locked_noreset(path, l, BTREE_NODE_READ_LOCKED);
 684                         }
 685                         break;
 686                 }
 687         }
 688
 689         bch2_btree_path_verify_locks(path);
 690
 691         path->downgrade_seq++;
 692         trace_path_downgrade(trans, _RET_IP_, path, old_locks_want);
 693 }
 694
 695 /* Btree transaction locking: */
 696
 697 void bch2_trans_downgrade(struct btree_trans *trans)
 698 {
 699         struct btree_path *path;
 700
 701         if (trans->restarted)
 702                 return;
 703
 704         trans_for_each_path(trans, path)
 705                 bch2_btree_path_downgrade(trans, path);
 706 }
 707
 708 int bch2_trans_relock(struct btree_trans *trans)
 709 {
 710         struct btree_path *path;
 711
 712         if (unlikely(trans->restarted))
 713                 return -((int) trans->restarted);
 714
 715         trans_for_each_path(trans, path)
 716                 if (path->should_be_locked &&
 717                     !bch2_btree_path_relock_norestart(trans, path, _RET_IP_)) {
 718                         trace_and_count(trans->c, trans_restart_relock, trans, _RET_IP_, path);
 719                         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock);
 720                 }
 721         return 0;
 722 }
 723
 724 int bch2_trans_relock_notrace(struct btree_trans *trans)
 725 {
 726         struct btree_path *path;
 727
 728         if (unlikely(trans->restarted))
 729                 return -((int) trans->restarted);
 730
 731         trans_for_each_path(trans, path)
 732                 if (path->should_be_locked &&
 733                     !bch2_btree_path_relock_norestart(trans, path, _RET_IP_)) {
 734                         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock);
 735                 }
 736         return 0;
 737 }
 738
 739 void bch2_trans_unlock_noassert(struct btree_trans *trans)
 740 {
 741         struct btree_path *path;
 742
 743         trans_for_each_path(trans, path)
 744                 __bch2_btree_path_unlock(trans, path);
 745 }
 746
 747 void bch2_trans_unlock(struct btree_trans *trans)
 748 {
 749         struct btree_path *path;
 750
 751         trans_for_each_path(trans, path)
 752                 __bch2_btree_path_unlock(trans, path);
 753
 754         /*
 755          * bch2_gc_btree_init_recurse() doesn't use btree iterators for walking
 756          * btree nodes, it implements its own walking:
 757          */
 758         if (!trans->is_initial_gc)
 759                 bch2_assert_btree_nodes_not_locked();
 760 }
 761
 762 void bch2_trans_unlock_long(struct btree_trans *trans)
 763 {
 764         bch2_trans_unlock(trans);
 765         bch2_trans_srcu_unlock(trans);
 766 }
 767
 768 bool bch2_trans_locked(struct btree_trans *trans)
 769 {
 770         struct btree_path *path;
 771
 772         trans_for_each_path(trans, path)
 773                 if (path->nodes_locked)
 774                         return true;
 775         return false;
 776 }
 777
 778 int __bch2_trans_mutex_lock(struct btree_trans *trans,
 779                             struct mutex *lock)
 780 {
 781         int ret = drop_locks_do(trans, (mutex_lock(lock), 0));
 782
 783         if (ret)
 784                 mutex_unlock(lock);
 785         return ret;
 786 }
 787
 788 /* Debug */
 789
 790 #ifdef CONFIG_BCACHEFS_DEBUG
 791
 792 void bch2_btree_path_verify_locks(struct btree_path *path)
 793 {
 794         unsigned l;
 795
 796         if (!path->nodes_locked) {
 797                 BUG_ON(path->uptodate == BTREE_ITER_UPTODATE &&
 798                        btree_path_node(path, path->level));
 799                 return;
 800         }
 801
 802         for (l = 0; l < BTREE_MAX_DEPTH; l++) {
 803                 int want = btree_lock_want(path, l);
 804                 int have = btree_node_locked_type(path, l);
 805
 806                 BUG_ON(!is_btree_node(path, l) && have != BTREE_NODE_UNLOCKED);
 807
 808                 BUG_ON(is_btree_node(path, l) &&
 809                        (want == BTREE_NODE_UNLOCKED ||
 810                         have != BTREE_NODE_WRITE_LOCKED) &&
 811                        want != have);
 812         }
 813 }
 814
 815 void bch2_trans_verify_locks(struct btree_trans *trans)
 816 {
 817         struct btree_path *path;
 818
 819         trans_for_each_path(trans, path)
 820                 bch2_btree_path_verify_locks(path);
 821 }
 822
 823 #endif