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

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include "bcachefs.h"
   4 #include "bkey_buf.h"
   5 #include "btree_cache.h"
   6 #include "btree_io.h"
   7 #include "btree_iter.h"
   8 #include "btree_locking.h"
   9 #include "debug.h"
  10 #include "error.h"
  11
  12 #include <linux/prefetch.h>
  13 #include <linux/sched/mm.h>
  14 #include <trace/events/bcachefs.h>
  15
  16 const char * const bch2_btree_ids[] = {
  17 #define x(kwd, val, name) name,
  18         BCH_BTREE_IDS()
  19 #undef x
  20         NULL
  21 };
  22
  23 void bch2_recalc_btree_reserve(struct bch_fs *c)
  24 {
  25         unsigned i, reserve = 16;
  26
  27         if (!c->btree_roots[0].b)
  28                 reserve += 8;
  29
  30         for (i = 0; i < BTREE_ID_NR; i++)
  31                 if (c->btree_roots[i].b)
  32                         reserve += min_t(unsigned, 1,
  33                                          c->btree_roots[i].b->c.level) * 8;
  34
  35         c->btree_cache.reserve = reserve;
  36 }
  37
  38 static inline unsigned btree_cache_can_free(struct btree_cache *bc)
  39 {
  40         return max_t(int, 0, bc->used - bc->reserve);
  41 }
  42
  43 static void __btree_node_data_free(struct bch_fs *c, struct btree *b)
  44 {
  45         EBUG_ON(btree_node_write_in_flight(b));
  46
  47         kvpfree(b->data, btree_bytes(c));
  48         b->data = NULL;
  49         vfree(b->aux_data);
  50         b->aux_data = NULL;
  51 }
  52
  53 static void btree_node_data_free(struct bch_fs *c, struct btree *b)
  54 {
  55         struct btree_cache *bc = &c->btree_cache;
  56
  57         __btree_node_data_free(c, b);
  58         bc->used--;
  59         list_move(&b->list, &bc->freed);
  60 }
  61
  62 static int bch2_btree_cache_cmp_fn(struct rhashtable_compare_arg *arg,
  63                                    const void *obj)
  64 {
  65         const struct btree *b = obj;
  66         const u64 *v = arg->key;
  67
  68         return b->hash_val == *v ? 0 : 1;
  69 }
  70
  71 static const struct rhashtable_params bch_btree_cache_params = {
  72         .head_offset    = offsetof(struct btree, hash),
  73         .key_offset     = offsetof(struct btree, hash_val),
  74         .key_len        = sizeof(u64),
  75         .obj_cmpfn      = bch2_btree_cache_cmp_fn,
  76 };
  77
  78 static int btree_node_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)
  79 {
  80         BUG_ON(b->data || b->aux_data);
  81
  82         b->data = kvpmalloc(btree_bytes(c), gfp);
  83         if (!b->data)
  84                 return -ENOMEM;
  85
  86         b->aux_data = vmalloc_exec(btree_aux_data_bytes(b), gfp);
  87         if (!b->aux_data) {
  88                 kvpfree(b->data, btree_bytes(c));
  89                 b->data = NULL;
  90                 return -ENOMEM;
  91         }
  92
  93         return 0;
  94 }
  95
  96 static struct btree *__btree_node_mem_alloc(struct bch_fs *c)
  97 {
  98         struct btree *b = kzalloc(sizeof(struct btree), GFP_KERNEL);
  99         if (!b)
 100                 return NULL;
 101
 102         bkey_btree_ptr_init(&b->key);
 103         six_lock_init(&b->c.lock);
 104         INIT_LIST_HEAD(&b->list);
 105         INIT_LIST_HEAD(&b->write_blocked);
 106         b->byte_order = ilog2(btree_bytes(c));
 107         return b;
 108 }
 109
 110 static struct btree *btree_node_mem_alloc(struct bch_fs *c)
 111 {
 112         struct btree_cache *bc = &c->btree_cache;
 113         struct btree *b = __btree_node_mem_alloc(c);
 114         if (!b)
 115                 return NULL;
 116
 117         if (btree_node_data_alloc(c, b, GFP_KERNEL)) {
 118                 kfree(b);
 119                 return NULL;
 120         }
 121
 122         bc->used++;
 123         list_add(&b->list, &bc->freeable);
 124         return b;
 125 }
 126
 127 /* Btree in memory cache - hash table */
 128
 129 void bch2_btree_node_hash_remove(struct btree_cache *bc, struct btree *b)
 130 {
 131         rhashtable_remove_fast(&bc->table, &b->hash, bch_btree_cache_params);
 132
 133         /* Cause future lookups for this node to fail: */
 134         b->hash_val = 0;
 135
 136         six_lock_wakeup_all(&b->c.lock);
 137 }
 138
 139 int __bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b)
 140 {
 141         BUG_ON(b->hash_val);
 142         b->hash_val = btree_ptr_hash_val(&b->key);
 143
 144         return rhashtable_lookup_insert_fast(&bc->table, &b->hash,
 145                                              bch_btree_cache_params);
 146 }
 147
 148 int bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b,
 149                                 unsigned level, enum btree_id id)
 150 {
 151         int ret;
 152
 153         b->c.level      = level;
 154         b->c.btree_id   = id;
 155
 156         mutex_lock(&bc->lock);
 157         ret = __bch2_btree_node_hash_insert(bc, b);
 158         if (!ret)
 159                 list_add(&b->list, &bc->live);
 160         mutex_unlock(&bc->lock);
 161
 162         return ret;
 163 }
 164
 165 __flatten
 166 static inline struct btree *btree_cache_find(struct btree_cache *bc,
 167                                      const struct bkey_i *k)
 168 {
 169         u64 v = btree_ptr_hash_val(k);
 170
 171         return rhashtable_lookup_fast(&bc->table, &v, bch_btree_cache_params);
 172 }
 173
 174 /*
 175  * this version is for btree nodes that have already been freed (we're not
 176  * reaping a real btree node)
 177  */
 178 static int __btree_node_reclaim(struct bch_fs *c, struct btree *b, bool flush)
 179 {
 180         struct btree_cache *bc = &c->btree_cache;
 181         int ret = 0;
 182
 183         lockdep_assert_held(&bc->lock);
 184
 185         if (!six_trylock_intent(&b->c.lock))
 186                 return -ENOMEM;
 187
 188         if (!six_trylock_write(&b->c.lock))
 189                 goto out_unlock_intent;
 190
 191         if (btree_node_noevict(b))
 192                 goto out_unlock;
 193
 194         if (!btree_node_may_write(b))
 195                 goto out_unlock;
 196
 197         if (btree_node_dirty(b) &&
 198             test_bit(BCH_FS_HOLD_BTREE_WRITES, &c->flags))
 199                 goto out_unlock;
 200
 201         if (btree_node_dirty(b) ||
 202             btree_node_write_in_flight(b) ||
 203             btree_node_read_in_flight(b)) {
 204                 if (!flush)
 205                         goto out_unlock;
 206
 207                 wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
 208                                TASK_UNINTERRUPTIBLE);
 209
 210                 /*
 211                  * Using the underscore version because we don't want to compact
 212                  * bsets after the write, since this node is about to be evicted
 213                  * - unless btree verify mode is enabled, since it runs out of
 214                  * the post write cleanup:
 215                  */
 216                 if (bch2_verify_btree_ondisk)
 217                         bch2_btree_node_write(c, b, SIX_LOCK_intent);
 218                 else
 219                         __bch2_btree_node_write(c, b, SIX_LOCK_read);
 220
 221                 /* wait for any in flight btree write */
 222                 btree_node_wait_on_io(b);
 223         }
 224 out:
 225         if (b->hash_val && !ret)
 226                 trace_btree_node_reap(c, b);
 227         return ret;
 228 out_unlock:
 229         six_unlock_write(&b->c.lock);
 230 out_unlock_intent:
 231         six_unlock_intent(&b->c.lock);
 232         ret = -ENOMEM;
 233         goto out;
 234 }
 235
 236 static int btree_node_reclaim(struct bch_fs *c, struct btree *b)
 237 {
 238         return __btree_node_reclaim(c, b, false);
 239 }
 240
 241 static int btree_node_write_and_reclaim(struct bch_fs *c, struct btree *b)
 242 {
 243         return __btree_node_reclaim(c, b, true);
 244 }
 245
 246 static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
 247                                            struct shrink_control *sc)
 248 {
 249         struct bch_fs *c = container_of(shrink, struct bch_fs,
 250                                         btree_cache.shrink);
 251         struct btree_cache *bc = &c->btree_cache;
 252         struct btree *b, *t;
 253         unsigned long nr = sc->nr_to_scan;
 254         unsigned long can_free;
 255         unsigned long touched = 0;
 256         unsigned long freed = 0;
 257         unsigned i, flags;
 258
 259         if (bch2_btree_shrinker_disabled)
 260                 return SHRINK_STOP;
 261
 262         /* Return -1 if we can't do anything right now */
 263         if (sc->gfp_mask & __GFP_FS)
 264                 mutex_lock(&bc->lock);
 265         else if (!mutex_trylock(&bc->lock))
 266                 return -1;
 267
 268         flags = memalloc_nofs_save();
 269
 270         /*
 271          * It's _really_ critical that we don't free too many btree nodes - we
 272          * have to always leave ourselves a reserve. The reserve is how we
 273          * guarantee that allocating memory for a new btree node can always
 274          * succeed, so that inserting keys into the btree can always succeed and
 275          * IO can always make forward progress:
 276          */
 277         nr /= btree_pages(c);
 278         can_free = btree_cache_can_free(bc);
 279         nr = min_t(unsigned long, nr, can_free);
 280
 281         i = 0;
 282         list_for_each_entry_safe(b, t, &bc->freeable, list) {
 283                 touched++;
 284
 285                 if (freed >= nr)
 286                         break;
 287
 288                 if (++i > 3 &&
 289                     !btree_node_reclaim(c, b)) {
 290                         btree_node_data_free(c, b);
 291                         six_unlock_write(&b->c.lock);
 292                         six_unlock_intent(&b->c.lock);
 293                         freed++;
 294                 }
 295         }
 296 restart:
 297         list_for_each_entry_safe(b, t, &bc->live, list) {
 298                 touched++;
 299
 300                 if (freed >= nr) {
 301                         /* Save position */
 302                         if (&t->list != &bc->live)
 303                                 list_move_tail(&bc->live, &t->list);
 304                         break;
 305                 }
 306
 307                 if (!btree_node_accessed(b) &&
 308                     !btree_node_reclaim(c, b)) {
 309                         /* can't call bch2_btree_node_hash_remove under lock  */
 310                         freed++;
 311                         if (&t->list != &bc->live)
 312                                 list_move_tail(&bc->live, &t->list);
 313
 314                         btree_node_data_free(c, b);
 315                         mutex_unlock(&bc->lock);
 316
 317                         bch2_btree_node_hash_remove(bc, b);
 318                         six_unlock_write(&b->c.lock);
 319                         six_unlock_intent(&b->c.lock);
 320
 321                         if (freed >= nr)
 322                                 goto out;
 323
 324                         if (sc->gfp_mask & __GFP_FS)
 325                                 mutex_lock(&bc->lock);
 326                         else if (!mutex_trylock(&bc->lock))
 327                                 goto out;
 328                         goto restart;
 329                 } else
 330                         clear_btree_node_accessed(b);
 331         }
 332
 333         mutex_unlock(&bc->lock);
 334 out:
 335         memalloc_nofs_restore(flags);
 336         return (unsigned long) freed * btree_pages(c);
 337 }
 338
 339 static unsigned long bch2_btree_cache_count(struct shrinker *shrink,
 340                                             struct shrink_control *sc)
 341 {
 342         struct bch_fs *c = container_of(shrink, struct bch_fs,
 343                                         btree_cache.shrink);
 344         struct btree_cache *bc = &c->btree_cache;
 345
 346         if (bch2_btree_shrinker_disabled)
 347                 return 0;
 348
 349         return btree_cache_can_free(bc) * btree_pages(c);
 350 }
 351
 352 void bch2_fs_btree_cache_exit(struct bch_fs *c)
 353 {
 354         struct btree_cache *bc = &c->btree_cache;
 355         struct btree *b;
 356         unsigned i, flags;
 357
 358         if (bc->shrink.list.next)
 359                 unregister_shrinker(&bc->shrink);
 360
 361         /* vfree() can allocate memory: */
 362         flags = memalloc_nofs_save();
 363         mutex_lock(&bc->lock);
 364
 365 #ifdef CONFIG_BCACHEFS_DEBUG
 366         if (c->verify_data)
 367                 list_move(&c->verify_data->list, &bc->live);
 368
 369         kvpfree(c->verify_ondisk, btree_bytes(c));
 370 #endif
 371
 372         for (i = 0; i < BTREE_ID_NR; i++)
 373                 if (c->btree_roots[i].b)
 374                         list_add(&c->btree_roots[i].b->list, &bc->live);
 375
 376         list_splice(&bc->freeable, &bc->live);
 377
 378         while (!list_empty(&bc->live)) {
 379                 b = list_first_entry(&bc->live, struct btree, list);
 380
 381                 BUG_ON(btree_node_read_in_flight(b) ||
 382                        btree_node_write_in_flight(b));
 383
 384                 if (btree_node_dirty(b))
 385                         bch2_btree_complete_write(c, b, btree_current_write(b));
 386                 clear_btree_node_dirty(c, b);
 387
 388                 btree_node_data_free(c, b);
 389         }
 390
 391         BUG_ON(atomic_read(&c->btree_cache.dirty));
 392
 393         while (!list_empty(&bc->freed)) {
 394                 b = list_first_entry(&bc->freed, struct btree, list);
 395                 list_del(&b->list);
 396                 kfree(b);
 397         }
 398
 399         mutex_unlock(&bc->lock);
 400         memalloc_nofs_restore(flags);
 401
 402         if (bc->table_init_done)
 403                 rhashtable_destroy(&bc->table);
 404 }
 405
 406 int bch2_fs_btree_cache_init(struct bch_fs *c)
 407 {
 408         struct btree_cache *bc = &c->btree_cache;
 409         unsigned i;
 410         int ret = 0;
 411
 412         pr_verbose_init(c->opts, "");
 413
 414         ret = rhashtable_init(&bc->table, &bch_btree_cache_params);
 415         if (ret)
 416                 goto out;
 417
 418         bc->table_init_done = true;
 419
 420         bch2_recalc_btree_reserve(c);
 421
 422         for (i = 0; i < bc->reserve; i++)
 423                 if (!btree_node_mem_alloc(c)) {
 424                         ret = -ENOMEM;
 425                         goto out;
 426                 }
 427
 428         list_splice_init(&bc->live, &bc->freeable);
 429
 430 #ifdef CONFIG_BCACHEFS_DEBUG
 431         mutex_init(&c->verify_lock);
 432
 433         c->verify_ondisk = kvpmalloc(btree_bytes(c), GFP_KERNEL);
 434         if (!c->verify_ondisk) {
 435                 ret = -ENOMEM;
 436                 goto out;
 437         }
 438
 439         c->verify_data = btree_node_mem_alloc(c);
 440         if (!c->verify_data) {
 441                 ret = -ENOMEM;
 442                 goto out;
 443         }
 444
 445         list_del_init(&c->verify_data->list);
 446 #endif
 447
 448         bc->shrink.count_objects        = bch2_btree_cache_count;
 449         bc->shrink.scan_objects         = bch2_btree_cache_scan;
 450         bc->shrink.seeks                = 4;
 451         bc->shrink.batch                = btree_pages(c) * 2;
 452         ret = register_shrinker(&bc->shrink);
 453 out:
 454         pr_verbose_init(c->opts, "ret %i", ret);
 455         return ret;
 456 }
 457
 458 void bch2_fs_btree_cache_init_early(struct btree_cache *bc)
 459 {
 460         mutex_init(&bc->lock);
 461         INIT_LIST_HEAD(&bc->live);
 462         INIT_LIST_HEAD(&bc->freeable);
 463         INIT_LIST_HEAD(&bc->freed);
 464 }
 465
 466 /*
 467  * We can only have one thread cannibalizing other cached btree nodes at a time,
 468  * or we'll deadlock. We use an open coded mutex to ensure that, which a
 469  * cannibalize_bucket() will take. This means every time we unlock the root of
 470  * the btree, we need to release this lock if we have it held.
 471  */
 472 void bch2_btree_cache_cannibalize_unlock(struct bch_fs *c)
 473 {
 474         struct btree_cache *bc = &c->btree_cache;
 475
 476         if (bc->alloc_lock == current) {
 477                 trace_btree_node_cannibalize_unlock(c);
 478                 bc->alloc_lock = NULL;
 479                 closure_wake_up(&bc->alloc_wait);
 480         }
 481 }
 482
 483 int bch2_btree_cache_cannibalize_lock(struct bch_fs *c, struct closure *cl)
 484 {
 485         struct btree_cache *bc = &c->btree_cache;
 486         struct task_struct *old;
 487
 488         old = cmpxchg(&bc->alloc_lock, NULL, current);
 489         if (old == NULL || old == current)
 490                 goto success;
 491
 492         if (!cl) {
 493                 trace_btree_node_cannibalize_lock_fail(c);
 494                 return -ENOMEM;
 495         }
 496
 497         closure_wait(&bc->alloc_wait, cl);
 498
 499         /* Try again, after adding ourselves to waitlist */
 500         old = cmpxchg(&bc->alloc_lock, NULL, current);
 501         if (old == NULL || old == current) {
 502                 /* We raced */
 503                 closure_wake_up(&bc->alloc_wait);
 504                 goto success;
 505         }
 506
 507         trace_btree_node_cannibalize_lock_fail(c);
 508         return -EAGAIN;
 509
 510 success:
 511         trace_btree_node_cannibalize_lock(c);
 512         return 0;
 513 }
 514
 515 static struct btree *btree_node_cannibalize(struct bch_fs *c)
 516 {
 517         struct btree_cache *bc = &c->btree_cache;
 518         struct btree *b;
 519
 520         list_for_each_entry_reverse(b, &bc->live, list)
 521                 if (!btree_node_reclaim(c, b))
 522                         return b;
 523
 524         while (1) {
 525                 list_for_each_entry_reverse(b, &bc->live, list)
 526                         if (!btree_node_write_and_reclaim(c, b))
 527                                 return b;
 528
 529                 /*
 530                  * Rare case: all nodes were intent-locked.
 531                  * Just busy-wait.
 532                  */
 533                 WARN_ONCE(1, "btree cache cannibalize failed\n");
 534                 cond_resched();
 535         }
 536 }
 537
 538 struct btree *bch2_btree_node_mem_alloc(struct bch_fs *c)
 539 {
 540         struct btree_cache *bc = &c->btree_cache;
 541         struct btree *b;
 542         u64 start_time = local_clock();
 543         unsigned flags;
 544
 545         flags = memalloc_nofs_save();
 546         mutex_lock(&bc->lock);
 547
 548         /*
 549          * btree_free() doesn't free memory; it sticks the node on the end of
 550          * the list. Check if there's any freed nodes there:
 551          */
 552         list_for_each_entry(b, &bc->freeable, list)
 553                 if (!btree_node_reclaim(c, b))
 554                         goto got_node;
 555
 556         /*
 557          * We never free struct btree itself, just the memory that holds the on
 558          * disk node. Check the freed list before allocating a new one:
 559          */
 560         list_for_each_entry(b, &bc->freed, list)
 561                 if (!btree_node_reclaim(c, b))
 562                         goto got_node;
 563
 564         b = NULL;
 565 got_node:
 566         if (b)
 567                 list_del_init(&b->list);
 568         mutex_unlock(&bc->lock);
 569
 570         if (!b) {
 571                 b = __btree_node_mem_alloc(c);
 572                 if (!b)
 573                         goto err;
 574
 575                 BUG_ON(!six_trylock_intent(&b->c.lock));
 576                 BUG_ON(!six_trylock_write(&b->c.lock));
 577         }
 578
 579         if (!b->data) {
 580                 if (btree_node_data_alloc(c, b, __GFP_NOWARN|GFP_KERNEL))
 581                         goto err;
 582
 583                 mutex_lock(&bc->lock);
 584                 bc->used++;
 585                 mutex_unlock(&bc->lock);
 586         }
 587
 588         BUG_ON(btree_node_hashed(b));
 589         BUG_ON(btree_node_write_in_flight(b));
 590 out:
 591         b->flags                = 0;
 592         b->written              = 0;
 593         b->nsets                = 0;
 594         b->sib_u64s[0]          = 0;
 595         b->sib_u64s[1]          = 0;
 596         b->whiteout_u64s        = 0;
 597         bch2_btree_keys_init(b);
 598
 599         bch2_time_stats_update(&c->times[BCH_TIME_btree_node_mem_alloc],
 600                                start_time);
 601
 602         memalloc_nofs_restore(flags);
 603         return b;
 604 err:
 605         mutex_lock(&bc->lock);
 606
 607         if (b) {
 608                 list_add(&b->list, &bc->freed);
 609                 six_unlock_write(&b->c.lock);
 610                 six_unlock_intent(&b->c.lock);
 611         }
 612
 613         /* Try to cannibalize another cached btree node: */
 614         if (bc->alloc_lock == current) {
 615                 b = btree_node_cannibalize(c);
 616                 list_del_init(&b->list);
 617                 mutex_unlock(&bc->lock);
 618
 619                 bch2_btree_node_hash_remove(bc, b);
 620
 621                 trace_btree_node_cannibalize(c);
 622                 goto out;
 623         }
 624
 625         mutex_unlock(&bc->lock);
 626         memalloc_nofs_restore(flags);
 627         return ERR_PTR(-ENOMEM);
 628 }
 629
 630 /* Slowpath, don't want it inlined into btree_iter_traverse() */
 631 static noinline struct btree *bch2_btree_node_fill(struct bch_fs *c,
 632                                 struct btree_iter *iter,
 633                                 const struct bkey_i *k,
 634                                 enum btree_id btree_id,
 635                                 unsigned level,
 636                                 enum six_lock_type lock_type,
 637                                 bool sync)
 638 {
 639         struct btree_cache *bc = &c->btree_cache;
 640         struct btree *b;
 641
 642         BUG_ON(level + 1 >= BTREE_MAX_DEPTH);
 643         /*
 644          * Parent node must be locked, else we could read in a btree node that's
 645          * been freed:
 646          */
 647         if (iter && !bch2_btree_node_relock(iter, level + 1))
 648                 return ERR_PTR(-EINTR);
 649
 650         b = bch2_btree_node_mem_alloc(c);
 651         if (IS_ERR(b))
 652                 return b;
 653
 654         bkey_copy(&b->key, k);
 655         if (bch2_btree_node_hash_insert(bc, b, level, btree_id)) {
 656                 /* raced with another fill: */
 657
 658                 /* mark as unhashed... */
 659                 b->hash_val = 0;
 660
 661                 mutex_lock(&bc->lock);
 662                 list_add(&b->list, &bc->freeable);
 663                 mutex_unlock(&bc->lock);
 664
 665                 six_unlock_write(&b->c.lock);
 666                 six_unlock_intent(&b->c.lock);
 667                 return NULL;
 668         }
 669
 670         /*
 671          * Unlock before doing IO:
 672          *
 673          * XXX: ideally should be dropping all btree node locks here
 674          */
 675         if (iter && btree_node_read_locked(iter, level + 1))
 676                 btree_node_unlock(iter, level + 1);
 677
 678         bch2_btree_node_read(c, b, sync);
 679
 680         six_unlock_write(&b->c.lock);
 681
 682         if (!sync) {
 683                 six_unlock_intent(&b->c.lock);
 684                 return NULL;
 685         }
 686
 687         if (lock_type == SIX_LOCK_read)
 688                 six_lock_downgrade(&b->c.lock);
 689
 690         return b;
 691 }
 692
 693 static int lock_node_check_fn(struct six_lock *lock, void *p)
 694 {
 695         struct btree *b = container_of(lock, struct btree, c.lock);
 696         const struct bkey_i *k = p;
 697
 698         return b->hash_val == btree_ptr_hash_val(k) ? 0 : -1;
 699 }
 700
 701 /**
 702  * bch_btree_node_get - find a btree node in the cache and lock it, reading it
 703  * in from disk if necessary.
 704  *
 705  * If IO is necessary and running under generic_make_request, returns -EAGAIN.
 706  *
 707  * The btree node will have either a read or a write lock held, depending on
 708  * the @write parameter.
 709  */
 710 struct btree *bch2_btree_node_get(struct bch_fs *c, struct btree_iter *iter,
 711                                   const struct bkey_i *k, unsigned level,
 712                                   enum six_lock_type lock_type,
 713                                   unsigned long trace_ip)
 714 {
 715         struct btree_cache *bc = &c->btree_cache;
 716         struct btree *b;
 717         struct bset_tree *t;
 718
 719         EBUG_ON(level >= BTREE_MAX_DEPTH);
 720
 721         b = btree_node_mem_ptr(k);
 722         if (b)
 723                 goto lock_node;
 724 retry:
 725         b = btree_cache_find(bc, k);
 726         if (unlikely(!b)) {
 727                 /*
 728                  * We must have the parent locked to call bch2_btree_node_fill(),
 729                  * else we could read in a btree node from disk that's been
 730                  * freed:
 731                  */
 732                 b = bch2_btree_node_fill(c, iter, k, iter->btree_id,
 733                                          level, lock_type, true);
 734
 735                 /* We raced and found the btree node in the cache */
 736                 if (!b)
 737                         goto retry;
 738
 739                 if (IS_ERR(b))
 740                         return b;
 741         } else {
 742 lock_node:
 743                 /*
 744                  * There's a potential deadlock with splits and insertions into
 745                  * interior nodes we have to avoid:
 746                  *
 747                  * The other thread might be holding an intent lock on the node
 748                  * we want, and they want to update its parent node so they're
 749                  * going to upgrade their intent lock on the parent node to a
 750                  * write lock.
 751                  *
 752                  * But if we're holding a read lock on the parent, and we're
 753                  * trying to get the intent lock they're holding, we deadlock.
 754                  *
 755                  * So to avoid this we drop the read locks on parent nodes when
 756                  * we're starting to take intent locks - and handle the race.
 757                  *
 758                  * The race is that they might be about to free the node we
 759                  * want, and dropping our read lock on the parent node lets them
 760                  * update the parent marking the node we want as freed, and then
 761                  * free it:
 762                  *
 763                  * To guard against this, btree nodes are evicted from the cache
 764                  * when they're freed - and b->hash_val is zeroed out, which we
 765                  * check for after we lock the node.
 766                  *
 767                  * Then, bch2_btree_node_relock() on the parent will fail - because
 768                  * the parent was modified, when the pointer to the node we want
 769                  * was removed - and we'll bail out:
 770                  */
 771                 if (btree_node_read_locked(iter, level + 1))
 772                         btree_node_unlock(iter, level + 1);
 773
 774                 if (!btree_node_lock(b, k->k.p, level, iter, lock_type,
 775                                      lock_node_check_fn, (void *) k, trace_ip)) {
 776                         if (b->hash_val != btree_ptr_hash_val(k))
 777                                 goto retry;
 778                         return ERR_PTR(-EINTR);
 779                 }
 780
 781                 if (unlikely(b->hash_val != btree_ptr_hash_val(k) ||
 782                              b->c.level != level ||
 783                              race_fault())) {
 784                         six_unlock_type(&b->c.lock, lock_type);
 785                         if (bch2_btree_node_relock(iter, level + 1))
 786                                 goto retry;
 787
 788                         trace_trans_restart_btree_node_reused(iter->trans->ip);
 789                         return ERR_PTR(-EINTR);
 790                 }
 791         }
 792
 793         /* XXX: waiting on IO with btree locks held: */
 794         wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
 795                        TASK_UNINTERRUPTIBLE);
 796
 797         prefetch(b->aux_data);
 798
 799         for_each_bset(b, t) {
 800                 void *p = (u64 *) b->aux_data + t->aux_data_offset;
 801
 802                 prefetch(p + L1_CACHE_BYTES * 0);
 803                 prefetch(p + L1_CACHE_BYTES * 1);
 804                 prefetch(p + L1_CACHE_BYTES * 2);
 805         }
 806
 807         /* avoid atomic set bit if it's not needed: */
 808         if (!btree_node_accessed(b))
 809                 set_btree_node_accessed(b);
 810
 811         if (unlikely(btree_node_read_error(b))) {
 812                 six_unlock_type(&b->c.lock, lock_type);
 813                 return ERR_PTR(-EIO);
 814         }
 815
 816         EBUG_ON(b->c.btree_id != iter->btree_id);
 817         EBUG_ON(BTREE_NODE_LEVEL(b->data) != level);
 818         EBUG_ON(bkey_cmp(b->data->max_key, k->k.p));
 819         EBUG_ON(b->key.k.type == KEY_TYPE_btree_ptr_v2 &&
 820                 bkey_cmp(b->data->min_key,
 821                          bkey_i_to_btree_ptr_v2(&b->key)->v.min_key));
 822
 823         return b;
 824 }
 825
 826 struct btree *bch2_btree_node_get_noiter(struct bch_fs *c,
 827                                          const struct bkey_i *k,
 828                                          enum btree_id btree_id,
 829                                          unsigned level,
 830                                          bool nofill)
 831 {
 832         struct btree_cache *bc = &c->btree_cache;
 833         struct btree *b;
 834         struct bset_tree *t;
 835         int ret;
 836
 837         EBUG_ON(level >= BTREE_MAX_DEPTH);
 838
 839         b = btree_node_mem_ptr(k);
 840         if (b)
 841                 goto lock_node;
 842 retry:
 843         b = btree_cache_find(bc, k);
 844         if (unlikely(!b)) {
 845                 if (nofill)
 846                         return NULL;
 847
 848                 b = bch2_btree_node_fill(c, NULL, k, btree_id,
 849                                          level, SIX_LOCK_read, true);
 850
 851                 /* We raced and found the btree node in the cache */
 852                 if (!b)
 853                         goto retry;
 854
 855                 if (IS_ERR(b))
 856                         return b;
 857         } else {
 858 lock_node:
 859                 ret = six_lock_read(&b->c.lock, lock_node_check_fn, (void *) k);
 860                 if (ret)
 861                         goto retry;
 862
 863                 if (unlikely(b->hash_val != btree_ptr_hash_val(k) ||
 864                              b->c.btree_id != btree_id ||
 865                              b->c.level != level)) {
 866                         six_unlock_read(&b->c.lock);
 867                         goto retry;
 868                 }
 869         }
 870
 871         /* XXX: waiting on IO with btree locks held: */
 872         wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
 873                        TASK_UNINTERRUPTIBLE);
 874
 875         prefetch(b->aux_data);
 876
 877         for_each_bset(b, t) {
 878                 void *p = (u64 *) b->aux_data + t->aux_data_offset;
 879
 880                 prefetch(p + L1_CACHE_BYTES * 0);
 881                 prefetch(p + L1_CACHE_BYTES * 1);
 882                 prefetch(p + L1_CACHE_BYTES * 2);
 883         }
 884
 885         /* avoid atomic set bit if it's not needed: */
 886         if (!btree_node_accessed(b))
 887                 set_btree_node_accessed(b);
 888
 889         if (unlikely(btree_node_read_error(b))) {
 890                 six_unlock_read(&b->c.lock);
 891                 return ERR_PTR(-EIO);
 892         }
 893
 894         EBUG_ON(b->c.btree_id != btree_id);
 895         EBUG_ON(BTREE_NODE_LEVEL(b->data) != level);
 896         EBUG_ON(bkey_cmp(b->data->max_key, k->k.p));
 897         EBUG_ON(b->key.k.type == KEY_TYPE_btree_ptr_v2 &&
 898                 bkey_cmp(b->data->min_key,
 899                          bkey_i_to_btree_ptr_v2(&b->key)->v.min_key));
 900
 901         return b;
 902 }
 903
 904 struct btree *bch2_btree_node_get_sibling(struct bch_fs *c,
 905                                           struct btree_iter *iter,
 906                                           struct btree *b,
 907                                           enum btree_node_sibling sib)
 908 {
 909         struct btree_trans *trans = iter->trans;
 910         struct btree *parent;
 911         struct btree_node_iter node_iter;
 912         struct bkey_packed *k;
 913         struct bkey_buf tmp;
 914         struct btree *ret = NULL;
 915         unsigned level = b->c.level;
 916
 917         bch2_bkey_buf_init(&tmp);
 918
 919         parent = btree_iter_node(iter, level + 1);
 920         if (!parent)
 921                 return NULL;
 922
 923         /*
 924          * There's a corner case where a btree_iter might have a node locked
 925          * that is just outside its current pos - when
 926          * bch2_btree_iter_set_pos_same_leaf() gets to the end of the node.
 927          *
 928          * But the lock ordering checks in __bch2_btree_node_lock() go off of
 929          * iter->pos, not the node's key: so if the iterator is marked as
 930          * needing to be traversed, we risk deadlock if we don't bail out here:
 931          */
 932         if (iter->uptodate >= BTREE_ITER_NEED_TRAVERSE)
 933                 return ERR_PTR(-EINTR);
 934
 935         if (!bch2_btree_node_relock(iter, level + 1)) {
 936                 ret = ERR_PTR(-EINTR);
 937                 goto out;
 938         }
 939
 940         node_iter = iter->l[parent->c.level].iter;
 941
 942         k = bch2_btree_node_iter_peek_all(&node_iter, parent);
 943         BUG_ON(bkey_cmp_left_packed(parent, k, &b->key.k.p));
 944
 945         k = sib == btree_prev_sib
 946                 ? bch2_btree_node_iter_prev(&node_iter, parent)
 947                 : (bch2_btree_node_iter_advance(&node_iter, parent),
 948                    bch2_btree_node_iter_peek(&node_iter, parent));
 949         if (!k)
 950                 goto out;
 951
 952         bch2_bkey_buf_unpack(&tmp, c, parent, k);
 953
 954         ret = bch2_btree_node_get(c, iter, tmp.k, level,
 955                                   SIX_LOCK_intent, _THIS_IP_);
 956
 957         if (PTR_ERR_OR_ZERO(ret) == -EINTR && !trans->nounlock) {
 958                 struct btree_iter *linked;
 959
 960                 if (!bch2_btree_node_relock(iter, level + 1))
 961                         goto out;
 962
 963                 /*
 964                  * We might have got -EINTR because trylock failed, and we're
 965                  * holding other locks that would cause us to deadlock:
 966                  */
 967                 trans_for_each_iter(trans, linked)
 968                         if (btree_iter_lock_cmp(iter, linked) < 0)
 969                                 __bch2_btree_iter_unlock(linked);
 970
 971                 if (sib == btree_prev_sib)
 972                         btree_node_unlock(iter, level);
 973
 974                 ret = bch2_btree_node_get(c, iter, tmp.k, level,
 975                                           SIX_LOCK_intent, _THIS_IP_);
 976
 977                 /*
 978                  * before btree_iter_relock() calls btree_iter_verify_locks():
 979                  */
 980                 if (btree_lock_want(iter, level + 1) == BTREE_NODE_UNLOCKED)
 981                         btree_node_unlock(iter, level + 1);
 982
 983                 if (!bch2_btree_node_relock(iter, level)) {
 984                         btree_iter_set_dirty(iter, BTREE_ITER_NEED_RELOCK);
 985
 986                         if (!IS_ERR(ret)) {
 987                                 six_unlock_intent(&ret->c.lock);
 988                                 ret = ERR_PTR(-EINTR);
 989                         }
 990                 }
 991
 992                 bch2_trans_relock(trans);
 993         }
 994 out:
 995         if (btree_lock_want(iter, level + 1) == BTREE_NODE_UNLOCKED)
 996                 btree_node_unlock(iter, level + 1);
 997
 998         if (PTR_ERR_OR_ZERO(ret) == -EINTR)
 999                 bch2_btree_iter_upgrade(iter, level + 2);
1000
1001         BUG_ON(!IS_ERR(ret) && !btree_node_locked(iter, level));
1002
1003         if (!IS_ERR_OR_NULL(ret)) {
1004                 struct btree *n1 = ret, *n2 = b;
1005
1006                 if (sib != btree_prev_sib)
1007                         swap(n1, n2);
1008
1009                 if (bkey_cmp(bkey_successor(n1->key.k.p),
1010                              n2->data->min_key)) {
1011                         char buf1[200], buf2[200];
1012
1013                         bch2_bkey_val_to_text(&PBUF(buf1), c, bkey_i_to_s_c(&n1->key));
1014                         bch2_bkey_val_to_text(&PBUF(buf2), c, bkey_i_to_s_c(&n2->key));
1015
1016                         bch2_fs_inconsistent(c, "btree topology error at btree %s level %u:\n"
1017                                              "prev: %s\n"
1018                                              "next: %s\n",
1019                                              bch2_btree_ids[iter->btree_id], level,
1020                                              buf1, buf2);
1021
1022                         six_unlock_intent(&ret->c.lock);
1023                         ret = NULL;
1024                 }
1025         }
1026
1027         bch2_btree_trans_verify_locks(trans);
1028
1029         bch2_bkey_buf_exit(&tmp, c);
1030
1031         return ret;
1032 }
1033
1034 void bch2_btree_node_prefetch(struct bch_fs *c, struct btree_iter *iter,
1035                               const struct bkey_i *k,
1036                               enum btree_id btree_id, unsigned level)
1037 {
1038         struct btree_cache *bc = &c->btree_cache;
1039         struct btree *b;
1040
1041         BUG_ON(iter && !btree_node_locked(iter, level + 1));
1042         BUG_ON(level >= BTREE_MAX_DEPTH);
1043
1044         b = btree_cache_find(bc, k);
1045         if (b)
1046                 return;
1047
1048         bch2_btree_node_fill(c, iter, k, btree_id, level, SIX_LOCK_read, false);
1049 }
1050
1051 void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c,
1052                              struct btree *b)
1053 {
1054         const struct bkey_format *f = &b->format;
1055         struct bset_stats stats;
1056
1057         memset(&stats, 0, sizeof(stats));
1058
1059         bch2_btree_keys_stats(b, &stats);
1060
1061         pr_buf(out,
1062                "l %u %llu:%llu - %llu:%llu:\n"
1063                "    ptrs: ",
1064                b->c.level,
1065                b->data->min_key.inode,
1066                b->data->min_key.offset,
1067                b->data->max_key.inode,
1068                b->data->max_key.offset);
1069         bch2_val_to_text(out, c, bkey_i_to_s_c(&b->key));
1070         pr_buf(out, "\n"
1071                "    format: u64s %u fields %u %u %u %u %u\n"
1072                "    unpack fn len: %u\n"
1073                "    bytes used %zu/%zu (%zu%% full)\n"
1074                "    sib u64s: %u, %u (merge threshold %zu)\n"
1075                "    nr packed keys %u\n"
1076                "    nr unpacked keys %u\n"
1077                "    floats %zu\n"
1078                "    failed unpacked %zu\n",
1079                f->key_u64s,
1080                f->bits_per_field[0],
1081                f->bits_per_field[1],
1082                f->bits_per_field[2],
1083                f->bits_per_field[3],
1084                f->bits_per_field[4],
1085                b->unpack_fn_len,
1086                b->nr.live_u64s * sizeof(u64),
1087                btree_bytes(c) - sizeof(struct btree_node),
1088                b->nr.live_u64s * 100 / btree_max_u64s(c),
1089                b->sib_u64s[0],
1090                b->sib_u64s[1],
1091                BTREE_FOREGROUND_MERGE_THRESHOLD(c),
1092                b->nr.packed_keys,
1093                b->nr.unpacked_keys,
1094                stats.floats,
1095                stats.failed);
1096 }
1097
1098 void bch2_btree_cache_to_text(struct printbuf *out, struct bch_fs *c)
1099 {
1100         pr_buf(out, "nr nodes:\t\t%u\n", c->btree_cache.used);
1101         pr_buf(out, "nr dirty:\t\t%u\n", atomic_read(&c->btree_cache.dirty));
1102         pr_buf(out, "cannibalize lock:\t%p\n", c->btree_cache.alloc_lock);
1103 }