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 void trace_would_deadlock(struct lock_graph *g, struct btree_trans *trans,
 145                                  unsigned long ip)
 146 {
 147         struct bch_fs *c = trans->c;
 148
 149         count_event(c, trans_restart_would_deadlock);
 150
 151         if (trace_trans_restart_would_deadlock_enabled()) {
 152                 struct printbuf buf = PRINTBUF;
 153
 154                 buf.atomic++;
 155                 print_cycle(&buf, g);
 156
 157                 trace_trans_restart_would_deadlock(trans, ip, buf.buf);
 158                 printbuf_exit(&buf);
 159         }
 160 }
 161
 162 static int abort_lock(struct lock_graph *g, struct trans_waiting_for_lock *i)
 163 {
 164         if (i == g->g) {
 165                 trace_would_deadlock(g, i->trans, _RET_IP_);
 166                 return btree_trans_restart(i->trans, BCH_ERR_transaction_restart_would_deadlock);
 167         } else {
 168                 i->trans->lock_must_abort = true;
 169                 wake_up_process(i->trans->locking_wait.task);
 170                 return 0;
 171         }
 172 }
 173
 174 static int btree_trans_abort_preference(struct btree_trans *trans)
 175 {
 176         if (trans->lock_may_not_fail)
 177                 return 0;
 178         if (trans->locking_wait.lock_want == SIX_LOCK_write)
 179                 return 1;
 180         if (!trans->in_traverse_all)
 181                 return 2;
 182         return 3;
 183 }
 184
 185 static noinline int break_cycle(struct lock_graph *g, struct printbuf *cycle)
 186 {
 187         struct trans_waiting_for_lock *i, *abort = NULL;
 188         unsigned best = 0, pref;
 189         int ret;
 190
 191         if (lock_graph_remove_non_waiters(g))
 192                 return 0;
 193
 194         /* Only checking, for debugfs: */
 195         if (cycle) {
 196                 print_cycle(cycle, g);
 197                 ret = -1;
 198                 goto out;
 199         }
 200
 201         for (i = g->g; i < g->g + g->nr; i++) {
 202                 pref = btree_trans_abort_preference(i->trans);
 203                 if (pref > best) {
 204                         abort = i;
 205                         best = pref;
 206                 }
 207         }
 208
 209         if (unlikely(!best)) {
 210                 struct printbuf buf = PRINTBUF;
 211
 212                 prt_printf(&buf, bch2_fmt(g->g->trans->c, "cycle of nofail locks"));
 213
 214                 for (i = g->g; i < g->g + g->nr; i++) {
 215                         struct btree_trans *trans = i->trans;
 216
 217                         bch2_btree_trans_to_text(&buf, trans);
 218
 219                         prt_printf(&buf, "backtrace:");
 220                         prt_newline(&buf);
 221                         printbuf_indent_add(&buf, 2);
 222                         bch2_prt_task_backtrace(&buf, trans->locking_wait.task);
 223                         printbuf_indent_sub(&buf, 2);
 224                         prt_newline(&buf);
 225                 }
 226
 227                 bch2_print_string_as_lines(KERN_ERR, buf.buf);
 228                 printbuf_exit(&buf);
 229                 BUG();
 230         }
 231
 232         ret = abort_lock(g, abort);
 233 out:
 234         if (ret)
 235                 while (g->nr)
 236                         lock_graph_up(g);
 237         return ret;
 238 }
 239
 240 static int lock_graph_descend(struct lock_graph *g, struct btree_trans *trans,
 241                               struct printbuf *cycle)
 242 {
 243         struct btree_trans *orig_trans = g->g->trans;
 244         struct trans_waiting_for_lock *i;
 245
 246         for (i = g->g; i < g->g + g->nr; i++)
 247                 if (i->trans == trans) {
 248                         closure_put(&trans->ref);
 249                         return break_cycle(g, cycle);
 250                 }
 251
 252         if (g->nr == ARRAY_SIZE(g->g)) {
 253                 closure_put(&trans->ref);
 254
 255                 if (orig_trans->lock_may_not_fail)
 256                         return 0;
 257
 258                 while (g->nr)
 259                         lock_graph_up(g);
 260
 261                 if (cycle)
 262                         return 0;
 263
 264                 trace_and_count(trans->c, trans_restart_would_deadlock_recursion_limit, trans, _RET_IP_);
 265                 return btree_trans_restart(orig_trans, BCH_ERR_transaction_restart_deadlock_recursion_limit);
 266         }
 267
 268         __lock_graph_down(g, trans);
 269         return 0;
 270 }
 271
 272 static bool lock_type_conflicts(enum six_lock_type t1, enum six_lock_type t2)
 273 {
 274         return t1 + t2 > 1;
 275 }
 276
 277 int bch2_check_for_deadlock(struct btree_trans *trans, struct printbuf *cycle)
 278 {
 279         struct lock_graph g;
 280         struct trans_waiting_for_lock *top;
 281         struct btree_bkey_cached_common *b;
 282         struct btree_path *path;
 283         unsigned path_idx;
 284         int ret;
 285
 286         g.nr = 0;
 287
 288         if (trans->lock_must_abort) {
 289                 if (cycle)
 290                         return -1;
 291
 292                 trace_would_deadlock(&g, trans, _RET_IP_);
 293                 return btree_trans_restart(trans, BCH_ERR_transaction_restart_would_deadlock);
 294         }
 295
 296         lock_graph_down(&g, trans);
 297 next:
 298         if (!g.nr)
 299                 return 0;
 300
 301         top = &g.g[g.nr - 1];
 302
 303         trans_for_each_path_safe_from(top->trans, path, path_idx, top->path_idx) {
 304                 if (!path->nodes_locked)
 305                         continue;
 306
 307                 if (path_idx != top->path_idx) {
 308                         top->path_idx           = path_idx;
 309                         top->level              = 0;
 310                         top->lock_start_time    = 0;
 311                 }
 312
 313                 for (;
 314                      top->level < BTREE_MAX_DEPTH;
 315                      top->level++, top->lock_start_time = 0) {
 316                         int lock_held = btree_node_locked_type(path, top->level);
 317
 318                         if (lock_held == BTREE_NODE_UNLOCKED)
 319                                 continue;
 320
 321                         b = &READ_ONCE(path->l[top->level].b)->c;
 322
 323                         if (IS_ERR_OR_NULL(b)) {
 324                                 /*
 325                                  * If we get here, it means we raced with the
 326                                  * other thread updating its btree_path
 327                                  * structures - which means it can't be blocked
 328                                  * waiting on a lock:
 329                                  */
 330                                 if (!lock_graph_remove_non_waiters(&g)) {
 331                                         /*
 332                                          * If lock_graph_remove_non_waiters()
 333                                          * didn't do anything, it must be
 334                                          * because we're being called by debugfs
 335                                          * checking for lock cycles, which
 336                                          * invokes us on btree_transactions that
 337                                          * aren't actually waiting on anything.
 338                                          * Just bail out:
 339                                          */
 340                                         lock_graph_pop_all(&g);
 341                                 }
 342
 343                                 goto next;
 344                         }
 345
 346                         if (list_empty_careful(&b->lock.wait_list))
 347                                 continue;
 348
 349                         raw_spin_lock(&b->lock.wait_lock);
 350                         list_for_each_entry(trans, &b->lock.wait_list, locking_wait.list) {
 351                                 BUG_ON(b != trans->locking);
 352
 353                                 if (top->lock_start_time &&
 354                                     time_after_eq64(top->lock_start_time, trans->locking_wait.start_time))
 355                                         continue;
 356
 357                                 top->lock_start_time = trans->locking_wait.start_time;
 358
 359                                 /* Don't check for self deadlock: */
 360                                 if (trans == top->trans ||
 361                                     !lock_type_conflicts(lock_held, trans->locking_wait.lock_want))
 362                                         continue;
 363
 364                                 closure_get(&trans->ref);
 365                                 raw_spin_unlock(&b->lock.wait_lock);
 366
 367                                 ret = lock_graph_descend(&g, trans, cycle);
 368                                 if (ret)
 369                                         return ret;
 370                                 goto next;
 371
 372                         }
 373                         raw_spin_unlock(&b->lock.wait_lock);
 374                 }
 375         }
 376
 377         if (g.nr > 1 && cycle)
 378                 print_chain(cycle, &g);
 379         lock_graph_up(&g);
 380         goto next;
 381 }
 382
 383 int bch2_six_check_for_deadlock(struct six_lock *lock, void *p)
 384 {
 385         struct btree_trans *trans = p;
 386
 387         return bch2_check_for_deadlock(trans, NULL);
 388 }
 389
 390 int __bch2_btree_node_lock_write(struct btree_trans *trans, struct btree_path *path,
 391                                  struct btree_bkey_cached_common *b,
 392                                  bool lock_may_not_fail)
 393 {
 394         int readers = bch2_btree_node_lock_counts(trans, NULL, b, b->level).n[SIX_LOCK_read];
 395         int ret;
 396
 397         /*
 398          * Must drop our read locks before calling six_lock_write() -
 399          * six_unlock() won't do wakeups until the reader count
 400          * goes to 0, and it's safe because we have the node intent
 401          * locked:
 402          */
 403         six_lock_readers_add(&b->lock, -readers);
 404         ret = __btree_node_lock_nopath(trans, b, SIX_LOCK_write,
 405                                        lock_may_not_fail, _RET_IP_);
 406         six_lock_readers_add(&b->lock, readers);
 407
 408         if (ret)
 409                 mark_btree_node_locked_noreset(path, b->level, BTREE_NODE_INTENT_LOCKED);
 410
 411         return ret;
 412 }
 413
 414 void bch2_btree_node_lock_write_nofail(struct btree_trans *trans,
 415                                        struct btree_path *path,
 416                                        struct btree_bkey_cached_common *b)
 417 {
 418         struct btree_path *linked;
 419         unsigned i;
 420         int ret;
 421
 422         /*
 423          * XXX BIG FAT NOTICE
 424          *
 425          * Drop all read locks before taking a write lock:
 426          *
 427          * This is a hack, because bch2_btree_node_lock_write_nofail() is a
 428          * hack - but by dropping read locks first, this should never fail, and
 429          * we only use this in code paths where whatever read locks we've
 430          * already taken are no longer needed:
 431          */
 432
 433         trans_for_each_path(trans, linked) {
 434                 if (!linked->nodes_locked)
 435                         continue;
 436
 437                 for (i = 0; i < BTREE_MAX_DEPTH; i++)
 438                         if (btree_node_read_locked(linked, i)) {
 439                                 btree_node_unlock(trans, linked, i);
 440                                 btree_path_set_dirty(linked, BTREE_ITER_NEED_RELOCK);
 441                         }
 442         }
 443
 444         ret = __btree_node_lock_write(trans, path, b, true);
 445         BUG_ON(ret);
 446 }
 447
 448 /* relock */
 449
 450 static inline bool btree_path_get_locks(struct btree_trans *trans,
 451                                         struct btree_path *path,
 452                                         bool upgrade,
 453                                         struct get_locks_fail *f)
 454 {
 455         unsigned l = path->level;
 456         int fail_idx = -1;
 457
 458         do {
 459                 if (!btree_path_node(path, l))
 460                         break;
 461
 462                 if (!(upgrade
 463                       ? bch2_btree_node_upgrade(trans, path, l)
 464                       : bch2_btree_node_relock(trans, path, l))) {
 465                         fail_idx        = l;
 466
 467                         if (f) {
 468                                 f->l    = l;
 469                                 f->b    = path->l[l].b;
 470                         }
 471                 }
 472
 473                 l++;
 474         } while (l < path->locks_want);
 475
 476         /*
 477          * When we fail to get a lock, we have to ensure that any child nodes
 478          * can't be relocked so bch2_btree_path_traverse has to walk back up to
 479          * the node that we failed to relock:
 480          */
 481         if (fail_idx >= 0) {
 482                 __bch2_btree_path_unlock(trans, path);
 483                 btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 484
 485                 do {
 486                         path->l[fail_idx].b = upgrade
 487                                 ? ERR_PTR(-BCH_ERR_no_btree_node_upgrade)
 488                                 : ERR_PTR(-BCH_ERR_no_btree_node_relock);
 489                         --fail_idx;
 490                 } while (fail_idx >= 0);
 491         }
 492
 493         if (path->uptodate == BTREE_ITER_NEED_RELOCK)
 494                 path->uptodate = BTREE_ITER_UPTODATE;
 495
 496         bch2_trans_verify_locks(trans);
 497
 498         return path->uptodate < BTREE_ITER_NEED_RELOCK;
 499 }
 500
 501 bool __bch2_btree_node_relock(struct btree_trans *trans,
 502                               struct btree_path *path, unsigned level,
 503                               bool trace)
 504 {
 505         struct btree *b = btree_path_node(path, level);
 506         int want = __btree_lock_want(path, level);
 507
 508         if (race_fault())
 509                 goto fail;
 510
 511         if (six_relock_type(&b->c.lock, want, path->l[level].lock_seq) ||
 512             (btree_node_lock_seq_matches(path, b, level) &&
 513              btree_node_lock_increment(trans, &b->c, level, want))) {
 514                 mark_btree_node_locked(trans, path, level, want);
 515                 return true;
 516         }
 517 fail:
 518         if (trace && !trans->notrace_relock_fail)
 519                 trace_and_count(trans->c, btree_path_relock_fail, trans, _RET_IP_, path, level);
 520         return false;
 521 }
 522
 523 /* upgrade */
 524
 525 bool bch2_btree_node_upgrade(struct btree_trans *trans,
 526                              struct btree_path *path, unsigned level)
 527 {
 528         struct btree *b = path->l[level].b;
 529         struct six_lock_count count = bch2_btree_node_lock_counts(trans, path, &b->c, level);
 530
 531         if (!is_btree_node(path, level))
 532                 return false;
 533
 534         switch (btree_lock_want(path, level)) {
 535         case BTREE_NODE_UNLOCKED:
 536                 BUG_ON(btree_node_locked(path, level));
 537                 return true;
 538         case BTREE_NODE_READ_LOCKED:
 539                 BUG_ON(btree_node_intent_locked(path, level));
 540                 return bch2_btree_node_relock(trans, path, level);
 541         case BTREE_NODE_INTENT_LOCKED:
 542                 break;
 543         case BTREE_NODE_WRITE_LOCKED:
 544                 BUG();
 545         }
 546
 547         if (btree_node_intent_locked(path, level))
 548                 return true;
 549
 550         if (race_fault())
 551                 return false;
 552
 553         if (btree_node_locked(path, level)) {
 554                 bool ret;
 555
 556                 six_lock_readers_add(&b->c.lock, -count.n[SIX_LOCK_read]);
 557                 ret = six_lock_tryupgrade(&b->c.lock);
 558                 six_lock_readers_add(&b->c.lock, count.n[SIX_LOCK_read]);
 559
 560                 if (ret)
 561                         goto success;
 562         } else {
 563                 if (six_relock_type(&b->c.lock, SIX_LOCK_intent, path->l[level].lock_seq))
 564                         goto success;
 565         }
 566
 567         /*
 568          * Do we already have an intent lock via another path? If so, just bump
 569          * lock count:
 570          */
 571         if (btree_node_lock_seq_matches(path, b, level) &&
 572             btree_node_lock_increment(trans, &b->c, level, BTREE_NODE_INTENT_LOCKED)) {
 573                 btree_node_unlock(trans, path, level);
 574                 goto success;
 575         }
 576
 577         trace_and_count(trans->c, btree_path_upgrade_fail, trans, _RET_IP_, path, level);
 578         return false;
 579 success:
 580         mark_btree_node_locked_noreset(path, level, BTREE_NODE_INTENT_LOCKED);
 581         return true;
 582 }
 583
 584 /* Btree path locking: */
 585
 586 /*
 587  * Only for btree_cache.c - only relocks intent locks
 588  */
 589 int bch2_btree_path_relock_intent(struct btree_trans *trans,
 590                                   struct btree_path *path)
 591 {
 592         unsigned l;
 593
 594         for (l = path->level;
 595              l < path->locks_want && btree_path_node(path, l);
 596              l++) {
 597                 if (!bch2_btree_node_relock(trans, path, l)) {
 598                         __bch2_btree_path_unlock(trans, path);
 599                         btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 600                         trace_and_count(trans->c, trans_restart_relock_path_intent, trans, _RET_IP_, path);
 601                         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_path_intent);
 602                 }
 603         }
 604
 605         return 0;
 606 }
 607
 608 __flatten
 609 bool bch2_btree_path_relock_norestart(struct btree_trans *trans,
 610                         struct btree_path *path, unsigned long trace_ip)
 611 {
 612         struct get_locks_fail f;
 613
 614         return btree_path_get_locks(trans, path, false, &f);
 615 }
 616
 617 int __bch2_btree_path_relock(struct btree_trans *trans,
 618                         struct btree_path *path, unsigned long trace_ip)
 619 {
 620         if (!bch2_btree_path_relock_norestart(trans, path, trace_ip)) {
 621                 trace_and_count(trans->c, trans_restart_relock_path, trans, trace_ip, path);
 622                 return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_path);
 623         }
 624
 625         return 0;
 626 }
 627
 628 bool bch2_btree_path_upgrade_noupgrade_sibs(struct btree_trans *trans,
 629                                struct btree_path *path,
 630                                unsigned new_locks_want,
 631                                struct get_locks_fail *f)
 632 {
 633         EBUG_ON(path->locks_want >= new_locks_want);
 634
 635         path->locks_want = new_locks_want;
 636
 637         return btree_path_get_locks(trans, path, true, f);
 638 }
 639
 640 bool __bch2_btree_path_upgrade(struct btree_trans *trans,
 641                                struct btree_path *path,
 642                                unsigned new_locks_want,
 643                                struct get_locks_fail *f)
 644 {
 645         struct btree_path *linked;
 646
 647         if (bch2_btree_path_upgrade_noupgrade_sibs(trans, path, new_locks_want, f))
 648                 return true;
 649
 650         /*
 651          * XXX: this is ugly - we'd prefer to not be mucking with other
 652          * iterators in the btree_trans here.
 653          *
 654          * On failure to upgrade the iterator, setting iter->locks_want and
 655          * calling get_locks() is sufficient to make bch2_btree_path_traverse()
 656          * get the locks we want on transaction restart.
 657          *
 658          * But if this iterator was a clone, on transaction restart what we did
 659          * to this iterator isn't going to be preserved.
 660          *
 661          * Possibly we could add an iterator field for the parent iterator when
 662          * an iterator is a copy - for now, we'll just upgrade any other
 663          * iterators with the same btree id.
 664          *
 665          * The code below used to be needed to ensure ancestor nodes get locked
 666          * before interior nodes - now that's handled by
 667          * bch2_btree_path_traverse_all().
 668          */
 669         if (!path->cached && !trans->in_traverse_all)
 670                 trans_for_each_path(trans, linked)
 671                         if (linked != path &&
 672                             linked->cached == path->cached &&
 673                             linked->btree_id == path->btree_id &&
 674                             linked->locks_want < new_locks_want) {
 675                                 linked->locks_want = new_locks_want;
 676                                 btree_path_get_locks(trans, linked, true, NULL);
 677                         }
 678
 679         return false;
 680 }
 681
 682 void __bch2_btree_path_downgrade(struct btree_trans *trans,
 683                                  struct btree_path *path,
 684                                  unsigned new_locks_want)
 685 {
 686         unsigned l, old_locks_want = path->locks_want;
 687
 688         if (trans->restarted)
 689                 return;
 690
 691         EBUG_ON(path->locks_want < new_locks_want);
 692
 693         path->locks_want = new_locks_want;
 694
 695         while (path->nodes_locked &&
 696                (l = btree_path_highest_level_locked(path)) >= path->locks_want) {
 697                 if (l > path->level) {
 698                         btree_node_unlock(trans, path, l);
 699                 } else {
 700                         if (btree_node_intent_locked(path, l)) {
 701                                 six_lock_downgrade(&path->l[l].b->c.lock);
 702                                 mark_btree_node_locked_noreset(path, l, BTREE_NODE_READ_LOCKED);
 703                         }
 704                         break;
 705                 }
 706         }
 707
 708         bch2_btree_path_verify_locks(path);
 709
 710         path->downgrade_seq++;
 711         trace_path_downgrade(trans, _RET_IP_, path, old_locks_want);
 712 }
 713
 714 /* Btree transaction locking: */
 715
 716 void bch2_trans_downgrade(struct btree_trans *trans)
 717 {
 718         struct btree_path *path;
 719
 720         if (trans->restarted)
 721                 return;
 722
 723         trans_for_each_path(trans, path)
 724                 bch2_btree_path_downgrade(trans, path);
 725 }
 726
 727 int bch2_trans_relock(struct btree_trans *trans)
 728 {
 729         struct btree_path *path;
 730
 731         if (unlikely(trans->restarted))
 732                 return -((int) trans->restarted);
 733
 734         trans_for_each_path(trans, path)
 735                 if (path->should_be_locked &&
 736                     !bch2_btree_path_relock_norestart(trans, path, _RET_IP_)) {
 737                         trace_and_count(trans->c, trans_restart_relock, trans, _RET_IP_, path);
 738                         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock);
 739                 }
 740         return 0;
 741 }
 742
 743 int bch2_trans_relock_notrace(struct btree_trans *trans)
 744 {
 745         struct btree_path *path;
 746
 747         if (unlikely(trans->restarted))
 748                 return -((int) trans->restarted);
 749
 750         trans_for_each_path(trans, path)
 751                 if (path->should_be_locked &&
 752                     !bch2_btree_path_relock_norestart(trans, path, _RET_IP_)) {
 753                         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock);
 754                 }
 755         return 0;
 756 }
 757
 758 void bch2_trans_unlock_noassert(struct btree_trans *trans)
 759 {
 760         struct btree_path *path;
 761
 762         trans_for_each_path(trans, path)
 763                 __bch2_btree_path_unlock(trans, path);
 764 }
 765
 766 void bch2_trans_unlock(struct btree_trans *trans)
 767 {
 768         struct btree_path *path;
 769
 770         trans_for_each_path(trans, path)
 771                 __bch2_btree_path_unlock(trans, path);
 772
 773         /*
 774          * bch2_gc_btree_init_recurse() doesn't use btree iterators for walking
 775          * btree nodes, it implements its own walking:
 776          */
 777         if (!trans->is_initial_gc)
 778                 bch2_assert_btree_nodes_not_locked();
 779 }
 780
 781 void bch2_trans_unlock_long(struct btree_trans *trans)
 782 {
 783         bch2_trans_unlock(trans);
 784         bch2_trans_srcu_unlock(trans);
 785 }
 786
 787 bool bch2_trans_locked(struct btree_trans *trans)
 788 {
 789         struct btree_path *path;
 790
 791         trans_for_each_path(trans, path)
 792                 if (path->nodes_locked)
 793                         return true;
 794         return false;
 795 }
 796
 797 int __bch2_trans_mutex_lock(struct btree_trans *trans,
 798                             struct mutex *lock)
 799 {
 800         int ret = drop_locks_do(trans, (mutex_lock(lock), 0));
 801
 802         if (ret)
 803                 mutex_unlock(lock);
 804         return ret;
 805 }
 806
 807 /* Debug */
 808
 809 #ifdef CONFIG_BCACHEFS_DEBUG
 810
 811 void bch2_btree_path_verify_locks(struct btree_path *path)
 812 {
 813         unsigned l;
 814
 815         if (!path->nodes_locked) {
 816                 BUG_ON(path->uptodate == BTREE_ITER_UPTODATE &&
 817                        btree_path_node(path, path->level));
 818                 return;
 819         }
 820
 821         for (l = 0; l < BTREE_MAX_DEPTH; l++) {
 822                 int want = btree_lock_want(path, l);
 823                 int have = btree_node_locked_type(path, l);
 824
 825                 BUG_ON(!is_btree_node(path, l) && have != BTREE_NODE_UNLOCKED);
 826
 827                 BUG_ON(is_btree_node(path, l) &&
 828                        (want == BTREE_NODE_UNLOCKED ||
 829                         have != BTREE_NODE_WRITE_LOCKED) &&
 830                        want != have);
 831         }
 832 }
 833
 834 void bch2_trans_verify_locks(struct btree_trans *trans)
 835 {
 836         struct btree_path *path;
 837
 838         trans_for_each_path(trans, path)
 839                 bch2_btree_path_verify_locks(path);
 840 }
 841
 842 #endif