fs/bcachefs/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         lockdep_set_notrack_class(&b->lock);
  14 }
  15
  16 /* Btree node locking: */
  17
  18 struct six_lock_count bch2_btree_node_lock_counts(struct btree_trans *trans,
  19                                                   struct btree_path *skip,
  20                                                   struct btree_bkey_cached_common *b,
  21                                                   unsigned level)
  22 {
  23         struct btree_path *path;
  24         struct six_lock_count ret;
  25         unsigned i;
  26
  27         memset(&ret, 0, sizeof(ret));
  28
  29         if (IS_ERR_OR_NULL(b))
  30                 return ret;
  31
  32         trans_for_each_path(trans, path, i)
  33                 if (path != skip && &path->l[level].b->c == b) {
  34                         int t = btree_node_locked_type(path, level);
  35
  36                         if (t != BTREE_NODE_UNLOCKED)
  37                                 ret.n[t]++;
  38                 }
  39
  40         return ret;
  41 }
  42
  43 /* unlock */
  44
  45 void bch2_btree_node_unlock_write(struct btree_trans *trans,
  46                         struct btree_path *path, struct btree *b)
  47 {
  48         bch2_btree_node_unlock_write_inlined(trans, path, b);
  49 }
  50
  51 /* lock */
  52
  53 /*
  54  * @trans wants to lock @b with type @type
  55  */
  56 struct trans_waiting_for_lock {
  57         struct btree_trans              *trans;
  58         struct btree_bkey_cached_common *node_want;
  59         enum six_lock_type              lock_want;
  60
  61         /* for iterating over held locks :*/
  62         u8                              path_idx;
  63         u8                              level;
  64         u64                             lock_start_time;
  65 };
  66
  67 struct lock_graph {
  68         struct trans_waiting_for_lock   g[8];
  69         unsigned                        nr;
  70 };
  71
  72 static noinline void print_cycle(struct printbuf *out, struct lock_graph *g)
  73 {
  74         struct trans_waiting_for_lock *i;
  75
  76         prt_printf(out, "Found lock cycle (%u entries):\n", g->nr);
  77
  78         for (i = g->g; i < g->g + g->nr; i++) {
  79                 struct task_struct *task = READ_ONCE(i->trans->locking_wait.task);
  80                 if (!task)
  81                         continue;
  82
  83                 bch2_btree_trans_to_text(out, i->trans);
  84                 bch2_prt_task_backtrace(out, task, i == g->g ? 5 : 1, GFP_NOWAIT);
  85         }
  86 }
  87
  88 static noinline void print_chain(struct printbuf *out, struct lock_graph *g)
  89 {
  90         struct trans_waiting_for_lock *i;
  91
  92         for (i = g->g; i != g->g + g->nr; i++) {
  93                 struct task_struct *task = i->trans->locking_wait.task;
  94                 if (i != g->g)
  95                         prt_str(out, "<- ");
  96                 prt_printf(out, "%u ", task ?task->pid : 0);
  97         }
  98         prt_newline(out);
  99 }
 100
 101 static void lock_graph_up(struct lock_graph *g)
 102 {
 103         closure_put(&g->g[--g->nr].trans->ref);
 104 }
 105
 106 static noinline void lock_graph_pop_all(struct lock_graph *g)
 107 {
 108         while (g->nr)
 109                 lock_graph_up(g);
 110 }
 111
 112 static void __lock_graph_down(struct lock_graph *g, struct btree_trans *trans)
 113 {
 114         g->g[g->nr++] = (struct trans_waiting_for_lock) {
 115                 .trans          = trans,
 116                 .node_want      = trans->locking,
 117                 .lock_want      = trans->locking_wait.lock_want,
 118         };
 119 }
 120
 121 static void lock_graph_down(struct lock_graph *g, struct btree_trans *trans)
 122 {
 123         closure_get(&trans->ref);
 124         __lock_graph_down(g, trans);
 125 }
 126
 127 static bool lock_graph_remove_non_waiters(struct lock_graph *g)
 128 {
 129         struct trans_waiting_for_lock *i;
 130
 131         for (i = g->g + 1; i < g->g + g->nr; i++)
 132                 if (i->trans->locking != i->node_want ||
 133                     i->trans->locking_wait.start_time != i[-1].lock_start_time) {
 134                         while (g->g + g->nr > i)
 135                                 lock_graph_up(g);
 136                         return true;
 137                 }
 138
 139         return false;
 140 }
 141
 142 static void trace_would_deadlock(struct lock_graph *g, struct btree_trans *trans)
 143 {
 144         struct bch_fs *c = trans->c;
 145
 146         count_event(c, trans_restart_would_deadlock);
 147
 148         if (trace_trans_restart_would_deadlock_enabled()) {
 149                 struct printbuf buf = PRINTBUF;
 150
 151                 buf.atomic++;
 152                 print_cycle(&buf, g);
 153
 154                 trace_trans_restart_would_deadlock(trans, buf.buf);
 155                 printbuf_exit(&buf);
 156         }
 157 }
 158
 159 static int abort_lock(struct lock_graph *g, struct trans_waiting_for_lock *i)
 160 {
 161         if (i == g->g) {
 162                 trace_would_deadlock(g, i->trans);
 163                 return btree_trans_restart(i->trans, BCH_ERR_transaction_restart_would_deadlock);
 164         } else {
 165                 i->trans->lock_must_abort = true;
 166                 wake_up_process(i->trans->locking_wait.task);
 167                 return 0;
 168         }
 169 }
 170
 171 static int btree_trans_abort_preference(struct btree_trans *trans)
 172 {
 173         if (trans->lock_may_not_fail)
 174                 return 0;
 175         if (trans->locking_wait.lock_want == SIX_LOCK_write)
 176                 return 1;
 177         if (!trans->in_traverse_all)
 178                 return 2;
 179         return 3;
 180 }
 181
 182 static noinline int break_cycle(struct lock_graph *g, struct printbuf *cycle)
 183 {
 184         struct trans_waiting_for_lock *i, *abort = NULL;
 185         unsigned best = 0, pref;
 186         int ret;
 187
 188         if (lock_graph_remove_non_waiters(g))
 189                 return 0;
 190
 191         /* Only checking, for debugfs: */
 192         if (cycle) {
 193                 print_cycle(cycle, g);
 194                 ret = -1;
 195                 goto out;
 196         }
 197
 198         for (i = g->g; i < g->g + g->nr; i++) {
 199                 pref = btree_trans_abort_preference(i->trans);
 200                 if (pref > best) {
 201                         abort = i;
 202                         best = pref;
 203                 }
 204         }
 205
 206         if (unlikely(!best)) {
 207                 struct printbuf buf = PRINTBUF;
 208                 buf.atomic++;
 209
 210                 prt_printf(&buf, bch2_fmt(g->g->trans->c, "cycle of nofail locks"));
 211
 212                 for (i = g->g; i < g->g + g->nr; i++) {
 213                         struct btree_trans *trans = i->trans;
 214
 215                         bch2_btree_trans_to_text(&buf, trans);
 216
 217                         prt_printf(&buf, "backtrace:\n");
 218                         printbuf_indent_add(&buf, 2);
 219                         bch2_prt_task_backtrace(&buf, trans->locking_wait.task, 2, GFP_NOWAIT);
 220                         printbuf_indent_sub(&buf, 2);
 221                         prt_newline(&buf);
 222                 }
 223
 224                 bch2_print_string_as_lines_nonblocking(KERN_ERR, buf.buf);
 225                 printbuf_exit(&buf);
 226                 BUG();
 227         }
 228
 229         ret = abort_lock(g, abort);
 230 out:
 231         if (ret)
 232                 while (g->nr)
 233                         lock_graph_up(g);
 234         return ret;
 235 }
 236
 237 static int lock_graph_descend(struct lock_graph *g, struct btree_trans *trans,
 238                               struct printbuf *cycle)
 239 {
 240         struct btree_trans *orig_trans = g->g->trans;
 241         struct trans_waiting_for_lock *i;
 242
 243         for (i = g->g; i < g->g + g->nr; i++)
 244                 if (i->trans == trans) {
 245                         closure_put(&trans->ref);
 246                         return break_cycle(g, cycle);
 247                 }
 248
 249         if (g->nr == ARRAY_SIZE(g->g)) {
 250                 closure_put(&trans->ref);
 251
 252                 if (orig_trans->lock_may_not_fail)
 253                         return 0;
 254
 255                 while (g->nr)
 256                         lock_graph_up(g);
 257
 258                 if (cycle)
 259                         return 0;
 260
 261                 trace_and_count(trans->c, trans_restart_would_deadlock_recursion_limit, trans, _RET_IP_);
 262                 return btree_trans_restart(orig_trans, BCH_ERR_transaction_restart_deadlock_recursion_limit);
 263         }
 264
 265         __lock_graph_down(g, trans);
 266         return 0;
 267 }
 268
 269 static bool lock_type_conflicts(enum six_lock_type t1, enum six_lock_type t2)
 270 {
 271         return t1 + t2 > 1;
 272 }
 273
 274 int bch2_check_for_deadlock(struct btree_trans *trans, struct printbuf *cycle)
 275 {
 276         struct lock_graph g;
 277         struct trans_waiting_for_lock *top;
 278         struct btree_bkey_cached_common *b;
 279         btree_path_idx_t path_idx;
 280         int ret = 0;
 281
 282         g.nr = 0;
 283
 284         if (trans->lock_must_abort) {
 285                 if (cycle)
 286                         return -1;
 287
 288                 trace_would_deadlock(&g, trans);
 289                 return btree_trans_restart(trans, BCH_ERR_transaction_restart_would_deadlock);
 290         }
 291
 292         lock_graph_down(&g, trans);
 293
 294         /* trans->paths is rcu protected vs. freeing */
 295         rcu_read_lock();
 296         if (cycle)
 297                 cycle->atomic++;
 298 next:
 299         if (!g.nr)
 300                 goto out;
 301
 302         top = &g.g[g.nr - 1];
 303
 304         struct btree_path *paths = rcu_dereference(top->trans->paths);
 305         if (!paths)
 306                 goto up;
 307
 308         unsigned long *paths_allocated = trans_paths_allocated(paths);
 309
 310         trans_for_each_path_idx_from(paths_allocated, *trans_paths_nr(paths),
 311                                      path_idx, top->path_idx) {
 312                 struct btree_path *path = paths + path_idx;
 313                 if (!path->nodes_locked)
 314                         continue;
 315
 316                 if (path_idx != top->path_idx) {
 317                         top->path_idx           = path_idx;
 318                         top->level              = 0;
 319                         top->lock_start_time    = 0;
 320                 }
 321
 322                 for (;
 323                      top->level < BTREE_MAX_DEPTH;
 324                      top->level++, top->lock_start_time = 0) {
 325                         int lock_held = btree_node_locked_type(path, top->level);
 326
 327                         if (lock_held == BTREE_NODE_UNLOCKED)
 328                                 continue;
 329
 330                         b = &READ_ONCE(path->l[top->level].b)->c;
 331
 332                         if (IS_ERR_OR_NULL(b)) {
 333                                 /*
 334                                  * If we get here, it means we raced with the
 335                                  * other thread updating its btree_path
 336                                  * structures - which means it can't be blocked
 337                                  * waiting on a lock:
 338                                  */
 339                                 if (!lock_graph_remove_non_waiters(&g)) {
 340                                         /*
 341                                          * If lock_graph_remove_non_waiters()
 342                                          * didn't do anything, it must be
 343                                          * because we're being called by debugfs
 344                                          * checking for lock cycles, which
 345                                          * invokes us on btree_transactions that
 346                                          * aren't actually waiting on anything.
 347                                          * Just bail out:
 348                                          */
 349                                         lock_graph_pop_all(&g);
 350                                 }
 351
 352                                 goto next;
 353                         }
 354
 355                         if (list_empty_careful(&b->lock.wait_list))
 356                                 continue;
 357
 358                         raw_spin_lock(&b->lock.wait_lock);
 359                         list_for_each_entry(trans, &b->lock.wait_list, locking_wait.list) {
 360                                 BUG_ON(b != trans->locking);
 361
 362                                 if (top->lock_start_time &&
 363                                     time_after_eq64(top->lock_start_time, trans->locking_wait.start_time))
 364                                         continue;
 365
 366                                 top->lock_start_time = trans->locking_wait.start_time;
 367
 368                                 /* Don't check for self deadlock: */
 369                                 if (trans == top->trans ||
 370                                     !lock_type_conflicts(lock_held, trans->locking_wait.lock_want))
 371                                         continue;
 372
 373                                 closure_get(&trans->ref);
 374                                 raw_spin_unlock(&b->lock.wait_lock);
 375
 376                                 ret = lock_graph_descend(&g, trans, cycle);
 377                                 if (ret)
 378                                         goto out;
 379                                 goto next;
 380
 381                         }
 382                         raw_spin_unlock(&b->lock.wait_lock);
 383                 }
 384         }
 385 up:
 386         if (g.nr > 1 && cycle)
 387                 print_chain(cycle, &g);
 388         lock_graph_up(&g);
 389         goto next;
 390 out:
 391         if (cycle)
 392                 --cycle->atomic;
 393         rcu_read_unlock();
 394         return ret;
 395 }
 396
 397 int bch2_six_check_for_deadlock(struct six_lock *lock, void *p)
 398 {
 399         struct btree_trans *trans = p;
 400
 401         return bch2_check_for_deadlock(trans, NULL);
 402 }
 403
 404 int __bch2_btree_node_lock_write(struct btree_trans *trans, struct btree_path *path,
 405                                  struct btree_bkey_cached_common *b,
 406                                  bool lock_may_not_fail)
 407 {
 408         int readers = bch2_btree_node_lock_counts(trans, NULL, b, b->level).n[SIX_LOCK_read];
 409         int ret;
 410
 411         /*
 412          * Must drop our read locks before calling six_lock_write() -
 413          * six_unlock() won't do wakeups until the reader count
 414          * goes to 0, and it's safe because we have the node intent
 415          * locked:
 416          */
 417         six_lock_readers_add(&b->lock, -readers);
 418         ret = __btree_node_lock_nopath(trans, b, SIX_LOCK_write,
 419                                        lock_may_not_fail, _RET_IP_);
 420         six_lock_readers_add(&b->lock, readers);
 421
 422         if (ret)
 423                 mark_btree_node_locked_noreset(path, b->level, BTREE_NODE_INTENT_LOCKED);
 424
 425         return ret;
 426 }
 427
 428 void bch2_btree_node_lock_write_nofail(struct btree_trans *trans,
 429                                        struct btree_path *path,
 430                                        struct btree_bkey_cached_common *b)
 431 {
 432         int ret = __btree_node_lock_write(trans, path, b, true);
 433         BUG_ON(ret);
 434 }
 435
 436 /* relock */
 437
 438 static inline bool btree_path_get_locks(struct btree_trans *trans,
 439                                         struct btree_path *path,
 440                                         bool upgrade,
 441                                         struct get_locks_fail *f)
 442 {
 443         unsigned l = path->level;
 444         int fail_idx = -1;
 445
 446         do {
 447                 if (!btree_path_node(path, l))
 448                         break;
 449
 450                 if (!(upgrade
 451                       ? bch2_btree_node_upgrade(trans, path, l)
 452                       : bch2_btree_node_relock(trans, path, l))) {
 453                         fail_idx        = l;
 454
 455                         if (f) {
 456                                 f->l    = l;
 457                                 f->b    = path->l[l].b;
 458                         }
 459                 }
 460
 461                 l++;
 462         } while (l < path->locks_want);
 463
 464         /*
 465          * When we fail to get a lock, we have to ensure that any child nodes
 466          * can't be relocked so bch2_btree_path_traverse has to walk back up to
 467          * the node that we failed to relock:
 468          */
 469         if (fail_idx >= 0) {
 470                 __bch2_btree_path_unlock(trans, path);
 471                 btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 472
 473                 do {
 474                         path->l[fail_idx].b = upgrade
 475                                 ? ERR_PTR(-BCH_ERR_no_btree_node_upgrade)
 476                                 : ERR_PTR(-BCH_ERR_no_btree_node_relock);
 477                         --fail_idx;
 478                 } while (fail_idx >= 0);
 479         }
 480
 481         if (path->uptodate == BTREE_ITER_NEED_RELOCK)
 482                 path->uptodate = BTREE_ITER_UPTODATE;
 483
 484         return path->uptodate < BTREE_ITER_NEED_RELOCK;
 485 }
 486
 487 bool __bch2_btree_node_relock(struct btree_trans *trans,
 488                               struct btree_path *path, unsigned level,
 489                               bool trace)
 490 {
 491         struct btree *b = btree_path_node(path, level);
 492         int want = __btree_lock_want(path, level);
 493
 494         if (race_fault())
 495                 goto fail;
 496
 497         if (six_relock_type(&b->c.lock, want, path->l[level].lock_seq) ||
 498             (btree_node_lock_seq_matches(path, b, level) &&
 499              btree_node_lock_increment(trans, &b->c, level, want))) {
 500                 mark_btree_node_locked(trans, path, level, want);
 501                 return true;
 502         }
 503 fail:
 504         if (trace && !trans->notrace_relock_fail)
 505                 trace_and_count(trans->c, btree_path_relock_fail, trans, _RET_IP_, path, level);
 506         return false;
 507 }
 508
 509 /* upgrade */
 510
 511 bool bch2_btree_node_upgrade(struct btree_trans *trans,
 512                              struct btree_path *path, unsigned level)
 513 {
 514         struct btree *b = path->l[level].b;
 515         struct six_lock_count count = bch2_btree_node_lock_counts(trans, path, &b->c, level);
 516
 517         if (!is_btree_node(path, level))
 518                 return false;
 519
 520         switch (btree_lock_want(path, level)) {
 521         case BTREE_NODE_UNLOCKED:
 522                 BUG_ON(btree_node_locked(path, level));
 523                 return true;
 524         case BTREE_NODE_READ_LOCKED:
 525                 BUG_ON(btree_node_intent_locked(path, level));
 526                 return bch2_btree_node_relock(trans, path, level);
 527         case BTREE_NODE_INTENT_LOCKED:
 528                 break;
 529         case BTREE_NODE_WRITE_LOCKED:
 530                 BUG();
 531         }
 532
 533         if (btree_node_intent_locked(path, level))
 534                 return true;
 535
 536         if (race_fault())
 537                 return false;
 538
 539         if (btree_node_locked(path, level)) {
 540                 bool ret;
 541
 542                 six_lock_readers_add(&b->c.lock, -count.n[SIX_LOCK_read]);
 543                 ret = six_lock_tryupgrade(&b->c.lock);
 544                 six_lock_readers_add(&b->c.lock, count.n[SIX_LOCK_read]);
 545
 546                 if (ret)
 547                         goto success;
 548         } else {
 549                 if (six_relock_type(&b->c.lock, SIX_LOCK_intent, path->l[level].lock_seq))
 550                         goto success;
 551         }
 552
 553         /*
 554          * Do we already have an intent lock via another path? If so, just bump
 555          * lock count:
 556          */
 557         if (btree_node_lock_seq_matches(path, b, level) &&
 558             btree_node_lock_increment(trans, &b->c, level, BTREE_NODE_INTENT_LOCKED)) {
 559                 btree_node_unlock(trans, path, level);
 560                 goto success;
 561         }
 562
 563         trace_and_count(trans->c, btree_path_upgrade_fail, trans, _RET_IP_, path, level);
 564         return false;
 565 success:
 566         mark_btree_node_locked_noreset(path, level, BTREE_NODE_INTENT_LOCKED);
 567         return true;
 568 }
 569
 570 /* Btree path locking: */
 571
 572 /*
 573  * Only for btree_cache.c - only relocks intent locks
 574  */
 575 int bch2_btree_path_relock_intent(struct btree_trans *trans,
 576                                   struct btree_path *path)
 577 {
 578         unsigned l;
 579
 580         for (l = path->level;
 581              l < path->locks_want && btree_path_node(path, l);
 582              l++) {
 583                 if (!bch2_btree_node_relock(trans, path, l)) {
 584                         __bch2_btree_path_unlock(trans, path);
 585                         btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 586                         trace_and_count(trans->c, trans_restart_relock_path_intent, trans, _RET_IP_, path);
 587                         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_path_intent);
 588                 }
 589         }
 590
 591         return 0;
 592 }
 593
 594 __flatten
 595 bool bch2_btree_path_relock_norestart(struct btree_trans *trans, struct btree_path *path)
 596 {
 597         struct get_locks_fail f;
 598
 599         bool ret = btree_path_get_locks(trans, path, false, &f);
 600         bch2_trans_verify_locks(trans);
 601         return ret;
 602 }
 603
 604 int __bch2_btree_path_relock(struct btree_trans *trans,
 605                         struct btree_path *path, unsigned long trace_ip)
 606 {
 607         if (!bch2_btree_path_relock_norestart(trans, path)) {
 608                 trace_and_count(trans->c, trans_restart_relock_path, trans, trace_ip, path);
 609                 return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_path);
 610         }
 611
 612         return 0;
 613 }
 614
 615 bool bch2_btree_path_upgrade_noupgrade_sibs(struct btree_trans *trans,
 616                                struct btree_path *path,
 617                                unsigned new_locks_want,
 618                                struct get_locks_fail *f)
 619 {
 620         EBUG_ON(path->locks_want >= new_locks_want);
 621
 622         path->locks_want = new_locks_want;
 623
 624         bool ret = btree_path_get_locks(trans, path, true, f);
 625         bch2_trans_verify_locks(trans);
 626         return ret;
 627 }
 628
 629 bool __bch2_btree_path_upgrade(struct btree_trans *trans,
 630                                struct btree_path *path,
 631                                unsigned new_locks_want,
 632                                struct get_locks_fail *f)
 633 {
 634         bool ret = bch2_btree_path_upgrade_noupgrade_sibs(trans, path, new_locks_want, f);
 635         if (ret)
 636                 goto out;
 637
 638         /*
 639          * XXX: this is ugly - we'd prefer to not be mucking with other
 640          * iterators in the btree_trans here.
 641          *
 642          * On failure to upgrade the iterator, setting iter->locks_want and
 643          * calling get_locks() is sufficient to make bch2_btree_path_traverse()
 644          * get the locks we want on transaction restart.
 645          *
 646          * But if this iterator was a clone, on transaction restart what we did
 647          * to this iterator isn't going to be preserved.
 648          *
 649          * Possibly we could add an iterator field for the parent iterator when
 650          * an iterator is a copy - for now, we'll just upgrade any other
 651          * iterators with the same btree id.
 652          *
 653          * The code below used to be needed to ensure ancestor nodes get locked
 654          * before interior nodes - now that's handled by
 655          * bch2_btree_path_traverse_all().
 656          */
 657         if (!path->cached && !trans->in_traverse_all) {
 658                 struct btree_path *linked;
 659                 unsigned i;
 660
 661                 trans_for_each_path(trans, linked, i)
 662                         if (linked != path &&
 663                             linked->cached == path->cached &&
 664                             linked->btree_id == path->btree_id &&
 665                             linked->locks_want < new_locks_want) {
 666                                 linked->locks_want = new_locks_want;
 667                                 btree_path_get_locks(trans, linked, true, NULL);
 668                         }
 669         }
 670 out:
 671         bch2_trans_verify_locks(trans);
 672         return ret;
 673 }
 674
 675 void __bch2_btree_path_downgrade(struct btree_trans *trans,
 676                                  struct btree_path *path,
 677                                  unsigned new_locks_want)
 678 {
 679         unsigned l, old_locks_want = path->locks_want;
 680
 681         if (trans->restarted)
 682                 return;
 683
 684         EBUG_ON(path->locks_want < new_locks_want);
 685
 686         path->locks_want = new_locks_want;
 687
 688         while (path->nodes_locked &&
 689                (l = btree_path_highest_level_locked(path)) >= path->locks_want) {
 690                 if (l > path->level) {
 691                         btree_node_unlock(trans, path, l);
 692                 } else {
 693                         if (btree_node_intent_locked(path, l)) {
 694                                 six_lock_downgrade(&path->l[l].b->c.lock);
 695                                 mark_btree_node_locked_noreset(path, l, BTREE_NODE_READ_LOCKED);
 696                         }
 697                         break;
 698                 }
 699         }
 700
 701         bch2_btree_path_verify_locks(path);
 702
 703         trace_path_downgrade(trans, _RET_IP_, path, old_locks_want);
 704 }
 705
 706 /* Btree transaction locking: */
 707
 708 void bch2_trans_downgrade(struct btree_trans *trans)
 709 {
 710         struct btree_path *path;
 711         unsigned i;
 712
 713         if (trans->restarted)
 714                 return;
 715
 716         trans_for_each_path(trans, path, i)
 717                 if (path->ref)
 718                         bch2_btree_path_downgrade(trans, path);
 719 }
 720
 721 static inline void __bch2_trans_unlock(struct btree_trans *trans)
 722 {
 723         struct btree_path *path;
 724         unsigned i;
 725
 726         trans_for_each_path(trans, path, i)
 727                 __bch2_btree_path_unlock(trans, path);
 728 }
 729
 730 static noinline __cold int bch2_trans_relock_fail(struct btree_trans *trans, struct btree_path *path,
 731                                                   struct get_locks_fail *f, bool trace)
 732 {
 733         if (!trace)
 734                 goto out;
 735
 736         if (trace_trans_restart_relock_enabled()) {
 737                 struct printbuf buf = PRINTBUF;
 738
 739                 bch2_bpos_to_text(&buf, path->pos);
 740                 prt_printf(&buf, " l=%u seq=%u node seq=", f->l, path->l[f->l].lock_seq);
 741                 if (IS_ERR_OR_NULL(f->b)) {
 742                         prt_str(&buf, bch2_err_str(PTR_ERR(f->b)));
 743                 } else {
 744                         prt_printf(&buf, "%u", f->b->c.lock.seq);
 745
 746                         struct six_lock_count c =
 747                                 bch2_btree_node_lock_counts(trans, NULL, &f->b->c, f->l);
 748                         prt_printf(&buf, " self locked %u.%u.%u", c.n[0], c.n[1], c.n[2]);
 749
 750                         c = six_lock_counts(&f->b->c.lock);
 751                         prt_printf(&buf, " total locked %u.%u.%u", c.n[0], c.n[1], c.n[2]);
 752                 }
 753
 754                 trace_trans_restart_relock(trans, _RET_IP_, buf.buf);
 755                 printbuf_exit(&buf);
 756         }
 757
 758         count_event(trans->c, trans_restart_relock);
 759 out:
 760         __bch2_trans_unlock(trans);
 761         bch2_trans_verify_locks(trans);
 762         return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock);
 763 }
 764
 765 static inline int __bch2_trans_relock(struct btree_trans *trans, bool trace)
 766 {
 767         bch2_trans_verify_locks(trans);
 768
 769         if (unlikely(trans->restarted))
 770                 return -((int) trans->restarted);
 771         if (unlikely(trans->locked))
 772                 goto out;
 773
 774         struct btree_path *path;
 775         unsigned i;
 776
 777         trans_for_each_path(trans, path, i) {
 778                 struct get_locks_fail f;
 779
 780                 if (path->should_be_locked &&
 781                     !btree_path_get_locks(trans, path, false, &f))
 782                         return bch2_trans_relock_fail(trans, path, &f, trace);
 783         }
 784
 785         trans_set_locked(trans);
 786 out:
 787         bch2_trans_verify_locks(trans);
 788         return 0;
 789 }
 790
 791 int bch2_trans_relock(struct btree_trans *trans)
 792 {
 793         return __bch2_trans_relock(trans, true);
 794 }
 795
 796 int bch2_trans_relock_notrace(struct btree_trans *trans)
 797 {
 798         return __bch2_trans_relock(trans, false);
 799 }
 800
 801 void bch2_trans_unlock_noassert(struct btree_trans *trans)
 802 {
 803         __bch2_trans_unlock(trans);
 804
 805         trans_set_unlocked(trans);
 806 }
 807
 808 void bch2_trans_unlock(struct btree_trans *trans)
 809 {
 810         __bch2_trans_unlock(trans);
 811
 812         trans_set_unlocked(trans);
 813 }
 814
 815 void bch2_trans_unlock_long(struct btree_trans *trans)
 816 {
 817         bch2_trans_unlock(trans);
 818         bch2_trans_srcu_unlock(trans);
 819 }
 820
 821 int __bch2_trans_mutex_lock(struct btree_trans *trans,
 822                             struct mutex *lock)
 823 {
 824         int ret = drop_locks_do(trans, (mutex_lock(lock), 0));
 825
 826         if (ret)
 827                 mutex_unlock(lock);
 828         return ret;
 829 }
 830
 831 /* Debug */
 832
 833 #ifdef CONFIG_BCACHEFS_DEBUG
 834
 835 void bch2_btree_path_verify_locks(struct btree_path *path)
 836 {
 837         /*
 838          * A path may be uptodate and yet have nothing locked if and only if
 839          * there is no node at path->level, which generally means we were
 840          * iterating over all nodes and got to the end of the btree
 841          */
 842         BUG_ON(path->uptodate == BTREE_ITER_UPTODATE &&
 843                btree_path_node(path, path->level) &&
 844                !path->nodes_locked);
 845
 846         if (!path->nodes_locked)
 847                 return;
 848
 849         for (unsigned l = 0; l < BTREE_MAX_DEPTH; l++) {
 850                 int want = btree_lock_want(path, l);
 851                 int have = btree_node_locked_type(path, l);
 852
 853                 BUG_ON(!is_btree_node(path, l) && have != BTREE_NODE_UNLOCKED);
 854
 855                 BUG_ON(is_btree_node(path, l) &&
 856                        (want == BTREE_NODE_UNLOCKED ||
 857                         have != BTREE_NODE_WRITE_LOCKED) &&
 858                        want != have);
 859         }
 860 }
 861
 862 static bool bch2_trans_locked(struct btree_trans *trans)
 863 {
 864         struct btree_path *path;
 865         unsigned i;
 866
 867         trans_for_each_path(trans, path, i)
 868                 if (path->nodes_locked)
 869                         return true;
 870         return false;
 871 }
 872
 873 void bch2_trans_verify_locks(struct btree_trans *trans)
 874 {
 875         if (!trans->locked) {
 876                 BUG_ON(bch2_trans_locked(trans));
 877                 return;
 878         }
 879
 880         struct btree_path *path;
 881         unsigned i;
 882
 883         trans_for_each_path(trans, path, i)
 884                 bch2_btree_path_verify_locks(path);
 885 }
 886
 887 #endif