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 struct lock_class_key bch2_btree_node_lock_key;
   8
   9 /* Btree node locking: */
  10
  11 static inline void six_lock_readers_add(struct six_lock *lock, int nr)
  12 {
  13         if (lock->readers)
  14                 this_cpu_add(*lock->readers, nr);
  15         else if (nr > 0)
  16                 atomic64_add(__SIX_VAL(read_lock, nr), &lock->state.counter);
  17         else
  18                 atomic64_sub(__SIX_VAL(read_lock, -nr), &lock->state.counter);
  19 }
  20
  21 struct six_lock_count bch2_btree_node_lock_counts(struct btree_trans *trans,
  22                                                   struct btree_path *skip,
  23                                                   struct btree_bkey_cached_common *b,
  24                                                   unsigned level)
  25 {
  26         struct btree_path *path;
  27         struct six_lock_count ret;
  28
  29         memset(&ret, 0, sizeof(ret));
  30
  31         if (IS_ERR_OR_NULL(b))
  32                 return ret;
  33
  34         trans_for_each_path(trans, path)
  35                 if (path != skip && &path->l[level].b->c == b) {
  36                         int t = btree_node_locked_type(path, level);
  37
  38                         if (t != BTREE_NODE_UNLOCKED)
  39                                 ret.n[t]++;
  40                 }
  41
  42         return ret;
  43 }
  44
  45 /* unlock */
  46
  47 void bch2_btree_node_unlock_write(struct btree_trans *trans,
  48                         struct btree_path *path, struct btree *b)
  49 {
  50         bch2_btree_node_unlock_write_inlined(trans, path, b);
  51 }
  52
  53 /* lock */
  54
  55 /*
  56  * @trans wants to lock @b with type @type
  57  */
  58 struct trans_waiting_for_lock {
  59         struct btree_trans              *trans;
  60         struct btree_bkey_cached_common *node_want;
  61         enum six_lock_type              lock_want;
  62
  63         /* for iterating over held locks :*/
  64         u8                              path_idx;
  65         u8                              level;
  66         u64                             lock_start_time;
  67 };
  68
  69 struct lock_graph {
  70         struct trans_waiting_for_lock   g[8];
  71         unsigned                        nr;
  72 };
  73
  74 static noinline void print_cycle(struct printbuf *out, struct lock_graph *g)
  75 {
  76         struct trans_waiting_for_lock *i;
  77
  78         prt_printf(out, "Found lock cycle (%u entries):", g->nr);
  79         prt_newline(out);
  80
  81         for (i = g->g; i < g->g + g->nr; i++)
  82                 bch2_btree_trans_to_text(out, i->trans);
  83 }
  84
  85 static noinline void print_chain(struct printbuf *out, struct lock_graph *g)
  86 {
  87         struct trans_waiting_for_lock *i;
  88
  89         for (i = g->g; i != g->g + g->nr; i++) {
  90                 if (i != g->g)
  91                         prt_str(out, "<- ");
  92                 prt_printf(out, "%u ", i->trans->locking_wait.task->pid);
  93         }
  94         prt_newline(out);
  95 }
  96
  97 static void lock_graph_up(struct lock_graph *g)
  98 {
  99         closure_put(&g->g[--g->nr].trans->ref);
 100 }
 101
 102 static noinline void lock_graph_pop_all(struct lock_graph *g)
 103 {
 104         while (g->nr)
 105                 lock_graph_up(g);
 106 }
 107
 108 static void lock_graph_down(struct lock_graph *g, struct btree_trans *trans)
 109 {
 110         closure_get(&trans->ref);
 111
 112         g->g[g->nr++] = (struct trans_waiting_for_lock) {
 113                 .trans          = trans,
 114                 .node_want      = trans->locking,
 115                 .lock_want      = trans->locking_wait.lock_want,
 116         };
 117 }
 118
 119 static bool lock_graph_remove_non_waiters(struct lock_graph *g)
 120 {
 121         struct trans_waiting_for_lock *i;
 122
 123         for (i = g->g + 1; i < g->g + g->nr; i++)
 124                 if (i->trans->locking != i->node_want ||
 125                     i->trans->locking_wait.start_time != i[-1].lock_start_time) {
 126                         while (g->g + g->nr > i)
 127                                 lock_graph_up(g);
 128                         return true;
 129                 }
 130
 131         return false;
 132 }
 133
 134 static int abort_lock(struct lock_graph *g, struct trans_waiting_for_lock *i)
 135 {
 136         if (i == g->g) {
 137                 trace_and_count(i->trans->c, trans_restart_would_deadlock, i->trans, _RET_IP_);
 138                 return btree_trans_restart(i->trans, BCH_ERR_transaction_restart_would_deadlock);
 139         } else {
 140                 i->trans->lock_must_abort = true;
 141                 wake_up_process(i->trans->locking_wait.task);
 142                 return 0;
 143         }
 144 }
 145
 146 static int btree_trans_abort_preference(struct btree_trans *trans)
 147 {
 148         if (trans->lock_may_not_fail)
 149                 return 0;
 150         if (trans->locking_wait.lock_want == SIX_LOCK_write)
 151                 return 1;
 152         if (!trans->in_traverse_all)
 153                 return 2;
 154         return 3;
 155 }
 156
 157 static noinline int break_cycle(struct lock_graph *g, struct printbuf *cycle)
 158 {
 159         struct trans_waiting_for_lock *i, *abort = NULL;
 160         unsigned best = 0, pref;
 161         int ret;
 162
 163         if (lock_graph_remove_non_waiters(g))
 164                 return 0;
 165
 166         /* Only checking, for debugfs: */
 167         if (cycle) {
 168                 print_cycle(cycle, g);
 169                 ret = -1;
 170                 goto out;
 171         }
 172
 173         for (i = g->g; i < g->g + g->nr; i++) {
 174                 pref = btree_trans_abort_preference(i->trans);
 175                 if (pref > best) {
 176                         abort = i;
 177                         best = pref;
 178                 }
 179         }
 180
 181         if (unlikely(!best)) {
 182                 struct printbuf buf = PRINTBUF;
 183
 184                 prt_printf(&buf, bch2_fmt(g->g->trans->c, "cycle of nofail locks"));
 185
 186                 for (i = g->g; i < g->g + g->nr; i++) {
 187                         struct btree_trans *trans = i->trans;
 188
 189                         bch2_btree_trans_to_text(&buf, trans);
 190
 191                         prt_printf(&buf, "backtrace:");
 192                         prt_newline(&buf);
 193                         printbuf_indent_add(&buf, 2);
 194                         bch2_prt_backtrace(&buf, trans->locking_wait.task);
 195                         printbuf_indent_sub(&buf, 2);
 196                         prt_newline(&buf);
 197                 }
 198
 199                 bch2_print_string_as_lines(KERN_ERR, buf.buf);
 200                 printbuf_exit(&buf);
 201                 BUG();
 202         }
 203
 204         ret = abort_lock(g, abort);
 205 out:
 206         if (ret)
 207                 while (g->nr)
 208                         lock_graph_up(g);
 209         return ret;
 210 }
 211
 212 static int lock_graph_descend(struct lock_graph *g, struct btree_trans *trans,
 213                               struct printbuf *cycle)
 214 {
 215         struct btree_trans *orig_trans = g->g->trans;
 216         struct trans_waiting_for_lock *i;
 217
 218         for (i = g->g; i < g->g + g->nr; i++)
 219                 if (i->trans == trans)
 220                         return break_cycle(g, cycle);
 221
 222         if (g->nr == ARRAY_SIZE(g->g)) {
 223                 if (orig_trans->lock_may_not_fail)
 224                         return 0;
 225
 226                 while (g->nr)
 227                         lock_graph_up(g);
 228                 trace_and_count(trans->c, trans_restart_would_deadlock_recursion_limit, trans, _RET_IP_);
 229                 return btree_trans_restart(orig_trans, BCH_ERR_transaction_restart_deadlock_recursion_limit);
 230         }
 231
 232         lock_graph_down(g, trans);
 233         return 0;
 234 }
 235
 236 static bool lock_type_conflicts(enum six_lock_type t1, enum six_lock_type t2)
 237 {
 238         return t1 + t2 > 1;
 239 }
 240
 241 int bch2_check_for_deadlock(struct btree_trans *trans, struct printbuf *cycle)
 242 {
 243         struct lock_graph g;
 244         struct trans_waiting_for_lock *top;
 245         struct btree_bkey_cached_common *b;
 246         struct btree_path *path;
 247         int ret;
 248
 249         if (trans->lock_must_abort) {
 250                 trace_and_count(trans->c, trans_restart_would_deadlock, trans, _RET_IP_);
 251                 return btree_trans_restart(trans, BCH_ERR_transaction_restart_would_deadlock);
 252         }
 253
 254         g.nr = 0;
 255         lock_graph_down(&g, trans);
 256 next:
 257         if (!g.nr)
 258                 return 0;
 259
 260         top = &g.g[g.nr - 1];
 261
 262         trans_for_each_path_from(top->trans, path, top->path_idx) {
 263                 if (!path->nodes_locked)
 264                         continue;
 265
 266                 if (top->path_idx != path->idx) {
 267                         top->path_idx           = path->idx;
 268                         top->level              = 0;
 269                         top->lock_start_time    = 0;
 270                 }
 271
 272                 for (;
 273                      top->level < BTREE_MAX_DEPTH;
 274                      top->level++, top->lock_start_time = 0) {
 275                         int lock_held = btree_node_locked_type(path, top->level);
 276
 277                         if (lock_held == BTREE_NODE_UNLOCKED)
 278                                 continue;
 279
 280                         b = &READ_ONCE(path->l[top->level].b)->c;
 281
 282                         if (IS_ERR_OR_NULL(b)) {
 283                                 /*
 284                                  * If we get here, it means we raced with the
 285                                  * other thread updating its btree_path
 286                                  * structures - which means it can't be blocked
 287                                  * waiting on a lock:
 288                                  */
 289                                 if (!lock_graph_remove_non_waiters(&g)) {
 290                                         /*
 291                                          * If lock_graph_remove_non_waiters()
 292                                          * didn't do anything, it must be
 293                                          * because we're being called by debugfs
 294                                          * checking for lock cycles, which
 295                                          * invokes us on btree_transactions that
 296                                          * aren't actually waiting on anything.
 297                                          * Just bail out:
 298                                          */
 299                                         lock_graph_pop_all(&g);
 300                                 }
 301
 302                                 goto next;
 303                         }
 304
 305                         if (list_empty_careful(&b->lock.wait_list))
 306                                 continue;
 307
 308                         raw_spin_lock(&b->lock.wait_lock);
 309                         list_for_each_entry(trans, &b->lock.wait_list, locking_wait.list) {
 310                                 BUG_ON(b != trans->locking);
 311
 312                                 if (top->lock_start_time &&
 313                                     time_after_eq64(top->lock_start_time, trans->locking_wait.start_time))
 314                                         continue;
 315
 316                                 top->lock_start_time = trans->locking_wait.start_time;
 317
 318                                 /* Don't check for self deadlock: */
 319                                 if (trans == top->trans ||
 320                                     !lock_type_conflicts(lock_held, trans->locking_wait.lock_want))
 321                                         continue;
 322
 323                                 ret = lock_graph_descend(&g, trans, cycle);
 324                                 raw_spin_unlock(&b->lock.wait_lock);
 325
 326                                 if (ret)
 327                                         return ret;
 328                                 goto next;
 329
 330                         }
 331                         raw_spin_unlock(&b->lock.wait_lock);
 332                 }
 333         }
 334
 335         if (g.nr > 1 && cycle)
 336                 print_chain(cycle, &g);
 337         lock_graph_up(&g);
 338         goto next;
 339 }
 340
 341 int bch2_six_check_for_deadlock(struct six_lock *lock, void *p)
 342 {
 343         struct btree_trans *trans = p;
 344
 345         return bch2_check_for_deadlock(trans, NULL);
 346 }
 347
 348 int __bch2_btree_node_lock_write(struct btree_trans *trans, struct btree_path *path,
 349                                  struct btree_bkey_cached_common *b,
 350                                  bool lock_may_not_fail)
 351 {
 352         int readers = bch2_btree_node_lock_counts(trans, NULL, b, b->level).n[SIX_LOCK_read];
 353         int ret;
 354
 355         /*
 356          * Must drop our read locks before calling six_lock_write() -
 357          * six_unlock() won't do wakeups until the reader count
 358          * goes to 0, and it's safe because we have the node intent
 359          * locked:
 360          */
 361         six_lock_readers_add(&b->lock, -readers);
 362         ret = __btree_node_lock_nopath(trans, b, SIX_LOCK_write,
 363                                        lock_may_not_fail, _RET_IP_);
 364         six_lock_readers_add(&b->lock, readers);
 365
 366         if (ret)
 367                 mark_btree_node_locked_noreset(path, b->level, SIX_LOCK_intent);
 368
 369         return ret;
 370 }
 371
 372 /* relock */
 373
 374 static inline bool btree_path_get_locks(struct btree_trans *trans,
 375                                         struct btree_path *path,
 376                                         bool upgrade)
 377 {
 378         unsigned l = path->level;
 379         int fail_idx = -1;
 380
 381         do {
 382                 if (!btree_path_node(path, l))
 383                         break;
 384
 385                 if (!(upgrade
 386                       ? bch2_btree_node_upgrade(trans, path, l)
 387                       : bch2_btree_node_relock(trans, path, l)))
 388                         fail_idx = l;
 389
 390                 l++;
 391         } while (l < path->locks_want);
 392
 393         /*
 394          * When we fail to get a lock, we have to ensure that any child nodes
 395          * can't be relocked so bch2_btree_path_traverse has to walk back up to
 396          * the node that we failed to relock:
 397          */
 398         if (fail_idx >= 0) {
 399                 __bch2_btree_path_unlock(trans, path);
 400                 btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 401
 402                 do {
 403                         path->l[fail_idx].b = upgrade
 404                                 ? ERR_PTR(-BCH_ERR_no_btree_node_upgrade)
 405                                 : ERR_PTR(-BCH_ERR_no_btree_node_relock);
 406                         --fail_idx;
 407                 } while (fail_idx >= 0);
 408         }
 409
 410         if (path->uptodate == BTREE_ITER_NEED_RELOCK)
 411                 path->uptodate = BTREE_ITER_UPTODATE;
 412
 413         bch2_trans_verify_locks(trans);
 414
 415         return path->uptodate < BTREE_ITER_NEED_RELOCK;
 416 }
 417
 418 bool __bch2_btree_node_relock(struct btree_trans *trans,
 419                               struct btree_path *path, unsigned level,
 420                               bool trace)
 421 {
 422         struct btree *b = btree_path_node(path, level);
 423         int want = __btree_lock_want(path, level);
 424
 425         if (race_fault())
 426                 goto fail;
 427
 428         if (six_relock_type(&b->c.lock, want, path->l[level].lock_seq) ||
 429             (btree_node_lock_seq_matches(path, b, level) &&
 430              btree_node_lock_increment(trans, &b->c, level, want))) {
 431                 mark_btree_node_locked(trans, path, level, want);
 432                 return true;
 433         }
 434 fail:
 435         if (trace && !trans->notrace_relock_fail)
 436                 trace_and_count(trans->c, btree_path_relock_fail, trans, _RET_IP_, path, level);
 437         return false;
 438 }
 439
 440 /* upgrade */
 441
 442 bool bch2_btree_node_upgrade(struct btree_trans *trans,
 443                              struct btree_path *path, unsigned level)
 444 {
 445         struct btree *b = path->l[level].b;
 446         struct six_lock_count count = bch2_btree_node_lock_counts(trans, path, &b->c, level);
 447
 448         if (!is_btree_node(path, level))
 449                 return false;
 450
 451         switch (btree_lock_want(path, level)) {
 452         case BTREE_NODE_UNLOCKED:
 453                 BUG_ON(btree_node_locked(path, level));
 454                 return true;
 455         case BTREE_NODE_READ_LOCKED:
 456                 BUG_ON(btree_node_intent_locked(path, level));
 457                 return bch2_btree_node_relock(trans, path, level);
 458         case BTREE_NODE_INTENT_LOCKED:
 459                 break;
 460         case BTREE_NODE_WRITE_LOCKED:
 461                 BUG();
 462         }
 463
 464         if (btree_node_intent_locked(path, level))
 465                 return true;
 466
 467         if (race_fault())
 468                 return false;
 469
 470         if (btree_node_locked(path, level)) {
 471                 bool ret;
 472
 473                 six_lock_readers_add(&b->c.lock, -count.n[SIX_LOCK_read]);
 474                 ret = six_lock_tryupgrade(&b->c.lock);
 475                 six_lock_readers_add(&b->c.lock, count.n[SIX_LOCK_read]);
 476
 477                 if (ret)
 478                         goto success;
 479         } else {
 480                 if (six_relock_type(&b->c.lock, SIX_LOCK_intent, path->l[level].lock_seq))
 481                         goto success;
 482         }
 483
 484         /*
 485          * Do we already have an intent lock via another path? If so, just bump
 486          * lock count:
 487          */
 488         if (btree_node_lock_seq_matches(path, b, level) &&
 489             btree_node_lock_increment(trans, &b->c, level, BTREE_NODE_INTENT_LOCKED)) {
 490                 btree_node_unlock(trans, path, level);
 491                 goto success;
 492         }
 493
 494         trace_and_count(trans->c, btree_path_upgrade_fail, trans, _RET_IP_, path, level);
 495         return false;
 496 success:
 497         mark_btree_node_locked_noreset(path, level, SIX_LOCK_intent);
 498         return true;
 499 }
 500
 501 /* Btree path locking: */
 502
 503 /*
 504  * Only for btree_cache.c - only relocks intent locks
 505  */
 506 int bch2_btree_path_relock_intent(struct btree_trans *trans,
 507                                   struct btree_path *path)
 508 {
 509         unsigned l;
 510
 511         for (l = path->level;
 512              l < path->locks_want && btree_path_node(path, l);
 513              l++) {
 514                 if (!bch2_btree_node_relock(trans, path, l)) {
 515                         __bch2_btree_path_unlock(trans, path);
 516                         btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 517                         trace_and_count(trans->c, trans_restart_relock_path_intent, trans, _RET_IP_, path);
 518                         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_path_intent);
 519                 }
 520         }
 521
 522         return 0;
 523 }
 524
 525 __flatten
 526 bool bch2_btree_path_relock_norestart(struct btree_trans *trans,
 527                         struct btree_path *path, unsigned long trace_ip)
 528 {
 529         return btree_path_get_locks(trans, path, false);
 530 }
 531
 532 int __bch2_btree_path_relock(struct btree_trans *trans,
 533                         struct btree_path *path, unsigned long trace_ip)
 534 {
 535         if (!bch2_btree_path_relock_norestart(trans, path, trace_ip)) {
 536                 trace_and_count(trans->c, trans_restart_relock_path, trans, trace_ip, path);
 537                 return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_path);
 538         }
 539
 540         return 0;
 541 }
 542
 543 __flatten
 544 bool bch2_btree_path_upgrade_norestart(struct btree_trans *trans,
 545                         struct btree_path *path, unsigned long trace_ip)
 546 {
 547         return btree_path_get_locks(trans, path, true);
 548 }
 549
 550 bool bch2_btree_path_upgrade_noupgrade_sibs(struct btree_trans *trans,
 551                                struct btree_path *path,
 552                                unsigned new_locks_want)
 553 {
 554         EBUG_ON(path->locks_want >= new_locks_want);
 555
 556         path->locks_want = new_locks_want;
 557
 558         return btree_path_get_locks(trans, path, true);
 559 }
 560
 561 bool __bch2_btree_path_upgrade(struct btree_trans *trans,
 562                                struct btree_path *path,
 563                                unsigned new_locks_want)
 564 {
 565         struct btree_path *linked;
 566
 567         if (bch2_btree_path_upgrade_noupgrade_sibs(trans, path, new_locks_want))
 568                 return true;
 569
 570         /*
 571          * XXX: this is ugly - we'd prefer to not be mucking with other
 572          * iterators in the btree_trans here.
 573          *
 574          * On failure to upgrade the iterator, setting iter->locks_want and
 575          * calling get_locks() is sufficient to make bch2_btree_path_traverse()
 576          * get the locks we want on transaction restart.
 577          *
 578          * But if this iterator was a clone, on transaction restart what we did
 579          * to this iterator isn't going to be preserved.
 580          *
 581          * Possibly we could add an iterator field for the parent iterator when
 582          * an iterator is a copy - for now, we'll just upgrade any other
 583          * iterators with the same btree id.
 584          *
 585          * The code below used to be needed to ensure ancestor nodes get locked
 586          * before interior nodes - now that's handled by
 587          * bch2_btree_path_traverse_all().
 588          */
 589         if (!path->cached && !trans->in_traverse_all)
 590                 trans_for_each_path(trans, linked)
 591                         if (linked != path &&
 592                             linked->cached == path->cached &&
 593                             linked->btree_id == path->btree_id &&
 594                             linked->locks_want < new_locks_want) {
 595                                 linked->locks_want = new_locks_want;
 596                                 btree_path_get_locks(trans, linked, true);
 597                         }
 598
 599         return false;
 600 }
 601
 602 void __bch2_btree_path_downgrade(struct btree_trans *trans,
 603                                  struct btree_path *path,
 604                                  unsigned new_locks_want)
 605 {
 606         unsigned l;
 607
 608         EBUG_ON(path->locks_want < new_locks_want);
 609
 610         path->locks_want = new_locks_want;
 611
 612         while (path->nodes_locked &&
 613                (l = btree_path_highest_level_locked(path)) >= path->locks_want) {
 614                 if (l > path->level) {
 615                         btree_node_unlock(trans, path, l);
 616                 } else {
 617                         if (btree_node_intent_locked(path, l)) {
 618                                 six_lock_downgrade(&path->l[l].b->c.lock);
 619                                 mark_btree_node_locked_noreset(path, l, SIX_LOCK_read);
 620                         }
 621                         break;
 622                 }
 623         }
 624
 625         bch2_btree_path_verify_locks(path);
 626 }
 627
 628 /* Btree transaction locking: */
 629
 630 void bch2_trans_downgrade(struct btree_trans *trans)
 631 {
 632         struct btree_path *path;
 633
 634         trans_for_each_path(trans, path)
 635                 bch2_btree_path_downgrade(trans, path);
 636 }
 637
 638 int bch2_trans_relock(struct btree_trans *trans)
 639 {
 640         struct btree_path *path;
 641
 642         if (unlikely(trans->restarted))
 643                 return -((int) trans->restarted);
 644
 645         trans_for_each_path(trans, path)
 646                 if (path->should_be_locked &&
 647                     !bch2_btree_path_relock_norestart(trans, path, _RET_IP_)) {
 648                         trace_and_count(trans->c, trans_restart_relock, trans, _RET_IP_, path);
 649                         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock);
 650                 }
 651         return 0;
 652 }
 653
 654 int bch2_trans_relock_notrace(struct btree_trans *trans)
 655 {
 656         struct btree_path *path;
 657
 658         if (unlikely(trans->restarted))
 659                 return -((int) trans->restarted);
 660
 661         trans_for_each_path(trans, path)
 662                 if (path->should_be_locked &&
 663                     !bch2_btree_path_relock_norestart(trans, path, _RET_IP_)) {
 664                         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock);
 665                 }
 666         return 0;
 667 }
 668
 669 void bch2_trans_unlock(struct btree_trans *trans)
 670 {
 671         struct btree_path *path;
 672
 673         trans_for_each_path(trans, path)
 674                 __bch2_btree_path_unlock(trans, path);
 675
 676         /*
 677          * bch2_gc_btree_init_recurse() doesn't use btree iterators for walking
 678          * btree nodes, it implements its own walking:
 679          */
 680         EBUG_ON(!trans->is_initial_gc &&
 681                 lock_class_is_held(&bch2_btree_node_lock_key));
 682 }
 683
 684 bool bch2_trans_locked(struct btree_trans *trans)
 685 {
 686         struct btree_path *path;
 687
 688         trans_for_each_path(trans, path)
 689                 if (path->nodes_locked)
 690                         return true;
 691         return false;
 692 }
 693
 694 /* Debug */
 695
 696 #ifdef CONFIG_BCACHEFS_DEBUG
 697
 698 void bch2_btree_path_verify_locks(struct btree_path *path)
 699 {
 700         unsigned l;
 701
 702         if (!path->nodes_locked) {
 703                 BUG_ON(path->uptodate == BTREE_ITER_UPTODATE &&
 704                        btree_path_node(path, path->level));
 705                 return;
 706         }
 707
 708         for (l = 0; l < BTREE_MAX_DEPTH; l++) {
 709                 int want = btree_lock_want(path, l);
 710                 int have = btree_node_locked_type(path, l);
 711
 712                 BUG_ON(!is_btree_node(path, l) && have != BTREE_NODE_UNLOCKED);
 713
 714                 BUG_ON(is_btree_node(path, l) &&
 715                        (want == BTREE_NODE_UNLOCKED ||
 716                         have != BTREE_NODE_WRITE_LOCKED) &&
 717                        want != have);
 718         }
 719 }
 720
 721 void bch2_trans_verify_locks(struct btree_trans *trans)
 722 {
 723         struct btree_path *path;
 724
 725         trans_for_each_path(trans, path)
 726                 bch2_btree_path_verify_locks(path);
 727 }
 728
 729 #endif