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 struct lock_class_key bch2_btree_node_lock_key;
  17
  18 void bch2_recalc_btree_reserve(struct bch_fs *c)
  19 {
  20         unsigned i, reserve = 16;
  21
  22         if (!c->btree_roots[0].b)
  23                 reserve += 8;
  24
  25         for (i = 0; i < BTREE_ID_NR; i++)
  26                 if (c->btree_roots[i].b)
  27                         reserve += min_t(unsigned, 1,
  28                                          c->btree_roots[i].b->c.level) * 8;
  29
  30         c->btree_cache.reserve = reserve;
  31 }
  32
  33 static inline unsigned btree_cache_can_free(struct btree_cache *bc)
  34 {
  35         return max_t(int, 0, bc->used - bc->reserve);
  36 }
  37
  38 static void btree_node_data_free(struct bch_fs *c, struct btree *b)
  39 {
  40         struct btree_cache *bc = &c->btree_cache;
  41
  42         EBUG_ON(btree_node_write_in_flight(b));
  43
  44         kvpfree(b->data, btree_bytes(c));
  45         b->data = NULL;
  46 #ifdef __KERNEL__
  47         vfree(b->aux_data);
  48 #else
  49         munmap(b->aux_data, btree_aux_data_bytes(b));
  50 #endif
  51         b->aux_data = NULL;
  52
  53         bc->used--;
  54         list_move(&b->list, &bc->freed);
  55 }
  56
  57 static int bch2_btree_cache_cmp_fn(struct rhashtable_compare_arg *arg,
  58                                    const void *obj)
  59 {
  60         const struct btree *b = obj;
  61         const u64 *v = arg->key;
  62
  63         return b->hash_val == *v ? 0 : 1;
  64 }
  65
  66 static const struct rhashtable_params bch_btree_cache_params = {
  67         .head_offset    = offsetof(struct btree, hash),
  68         .key_offset     = offsetof(struct btree, hash_val),
  69         .key_len        = sizeof(u64),
  70         .obj_cmpfn      = bch2_btree_cache_cmp_fn,
  71 };
  72
  73 static int btree_node_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)
  74 {
  75         BUG_ON(b->data || b->aux_data);
  76
  77         b->data = kvpmalloc(btree_bytes(c), gfp);
  78         if (!b->data)
  79                 return -ENOMEM;
  80 #ifdef __KERNEL__
  81         b->aux_data = vmalloc_exec(btree_aux_data_bytes(b), gfp);
  82 #else
  83         b->aux_data = mmap(NULL, btree_aux_data_bytes(b),
  84                            PROT_READ|PROT_WRITE|PROT_EXEC,
  85                            MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
  86         if (b->aux_data == MAP_FAILED)
  87                 b->aux_data = NULL;
  88 #endif
  89         if (!b->aux_data) {
  90                 kvpfree(b->data, btree_bytes(c));
  91                 b->data = NULL;
  92                 return -ENOMEM;
  93         }
  94
  95         return 0;
  96 }
  97
  98 static struct btree *__btree_node_mem_alloc(struct bch_fs *c)
  99 {
 100         struct btree *b = kzalloc(sizeof(struct btree), GFP_KERNEL);
 101         if (!b)
 102                 return NULL;
 103
 104         bkey_btree_ptr_init(&b->key);
 105         __six_lock_init(&b->c.lock, "b->c.lock", &bch2_btree_node_lock_key);
 106         INIT_LIST_HEAD(&b->list);
 107         INIT_LIST_HEAD(&b->write_blocked);
 108         b->byte_order = ilog2(btree_bytes(c));
 109         return b;
 110 }
 111
 112 struct btree *__bch2_btree_node_mem_alloc(struct bch_fs *c)
 113 {
 114         struct btree_cache *bc = &c->btree_cache;
 115         struct btree *b = __btree_node_mem_alloc(c);
 116         if (!b)
 117                 return NULL;
 118
 119         if (btree_node_data_alloc(c, b, GFP_KERNEL)) {
 120                 kfree(b);
 121                 return NULL;
 122         }
 123
 124         bc->used++;
 125         list_add(&b->list, &bc->freeable);
 126         return b;
 127 }
 128
 129 /* Btree in memory cache - hash table */
 130
 131 void bch2_btree_node_hash_remove(struct btree_cache *bc, struct btree *b)
 132 {
 133         int ret = rhashtable_remove_fast(&bc->table, &b->hash, bch_btree_cache_params);
 134         BUG_ON(ret);
 135
 136         /* Cause future lookups for this node to fail: */
 137         b->hash_val = 0;
 138
 139         six_lock_wakeup_all(&b->c.lock);
 140 }
 141
 142 int __bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b)
 143 {
 144         BUG_ON(b->hash_val);
 145         b->hash_val = btree_ptr_hash_val(&b->key);
 146
 147         return rhashtable_lookup_insert_fast(&bc->table, &b->hash,
 148                                              bch_btree_cache_params);
 149 }
 150
 151 int bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b,
 152                                 unsigned level, enum btree_id id)
 153 {
 154         int ret;
 155
 156         b->c.level      = level;
 157         b->c.btree_id   = id;
 158
 159         if (level)
 160                 six_lock_pcpu_alloc(&b->c.lock);
 161         else
 162                 six_lock_pcpu_free_rcu(&b->c.lock);
 163
 164         mutex_lock(&bc->lock);
 165         ret = __bch2_btree_node_hash_insert(bc, b);
 166         if (!ret)
 167                 list_add(&b->list, &bc->live);
 168         mutex_unlock(&bc->lock);
 169
 170         return ret;
 171 }
 172
 173 __flatten
 174 static inline struct btree *btree_cache_find(struct btree_cache *bc,
 175                                      const struct bkey_i *k)
 176 {
 177         u64 v = btree_ptr_hash_val(k);
 178
 179         return rhashtable_lookup_fast(&bc->table, &v, bch_btree_cache_params);
 180 }
 181
 182 /*
 183  * this version is for btree nodes that have already been freed (we're not
 184  * reaping a real btree node)
 185  */
 186 static int __btree_node_reclaim(struct bch_fs *c, struct btree *b, bool flush)
 187 {
 188         struct btree_cache *bc = &c->btree_cache;
 189         int ret = 0;
 190
 191         lockdep_assert_held(&bc->lock);
 192 wait_on_io:
 193         if (b->flags & ((1U << BTREE_NODE_dirty)|
 194                         (1U << BTREE_NODE_read_in_flight)|
 195                         (1U << BTREE_NODE_write_in_flight))) {
 196                 if (!flush)
 197                         return -ENOMEM;
 198
 199                 /* XXX: waiting on IO with btree cache lock held */
 200                 bch2_btree_node_wait_on_read(b);
 201                 bch2_btree_node_wait_on_write(b);
 202         }
 203
 204         if (!six_trylock_intent(&b->c.lock))
 205                 return -ENOMEM;
 206
 207         if (!six_trylock_write(&b->c.lock))
 208                 goto out_unlock_intent;
 209
 210         /* recheck under lock */
 211         if (b->flags & ((1U << BTREE_NODE_read_in_flight)|
 212                         (1U << BTREE_NODE_write_in_flight))) {
 213                 if (!flush)
 214                         goto out_unlock;
 215                 six_unlock_write(&b->c.lock);
 216                 six_unlock_intent(&b->c.lock);
 217                 goto wait_on_io;
 218         }
 219
 220         if (btree_node_noevict(b))
 221                 goto out_unlock;
 222
 223         if (!btree_node_may_write(b))
 224                 goto out_unlock;
 225
 226         if (btree_node_dirty(b)) {
 227                 if (!flush ||
 228                     test_bit(BCH_FS_HOLD_BTREE_WRITES, &c->flags))
 229                         goto out_unlock;
 230                 /*
 231                  * Using the underscore version because we don't want to compact
 232                  * bsets after the write, since this node is about to be evicted
 233                  * - unless btree verify mode is enabled, since it runs out of
 234                  * the post write cleanup:
 235                  */
 236                 if (bch2_verify_btree_ondisk)
 237                         bch2_btree_node_write(c, b, SIX_LOCK_intent);
 238                 else
 239                         __bch2_btree_node_write(c, b, false);
 240
 241                 six_unlock_write(&b->c.lock);
 242                 six_unlock_intent(&b->c.lock);
 243                 goto wait_on_io;
 244         }
 245 out:
 246         if (b->hash_val && !ret)
 247                 trace_btree_node_reap(c, b);
 248         return ret;
 249 out_unlock:
 250         six_unlock_write(&b->c.lock);
 251 out_unlock_intent:
 252         six_unlock_intent(&b->c.lock);
 253         ret = -ENOMEM;
 254         goto out;
 255 }
 256
 257 static int btree_node_reclaim(struct bch_fs *c, struct btree *b)
 258 {
 259         return __btree_node_reclaim(c, b, false);
 260 }
 261
 262 static int btree_node_write_and_reclaim(struct bch_fs *c, struct btree *b)
 263 {
 264         return __btree_node_reclaim(c, b, true);
 265 }
 266
 267 static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
 268                                            struct shrink_control *sc)
 269 {
 270         struct bch_fs *c = container_of(shrink, struct bch_fs,
 271                                         btree_cache.shrink);
 272         struct btree_cache *bc = &c->btree_cache;
 273         struct btree *b, *t;
 274         unsigned long nr = sc->nr_to_scan;
 275         unsigned long can_free;
 276         unsigned long touched = 0;
 277         unsigned long freed = 0;
 278         unsigned i, flags;
 279         unsigned long ret = SHRINK_STOP;
 280
 281         if (bch2_btree_shrinker_disabled)
 282                 return SHRINK_STOP;
 283
 284         /* Return -1 if we can't do anything right now */
 285         if (sc->gfp_mask & __GFP_FS)
 286                 mutex_lock(&bc->lock);
 287         else if (!mutex_trylock(&bc->lock))
 288                 goto out_norestore;
 289
 290         flags = memalloc_nofs_save();
 291
 292         /*
 293          * It's _really_ critical that we don't free too many btree nodes - we
 294          * have to always leave ourselves a reserve. The reserve is how we
 295          * guarantee that allocating memory for a new btree node can always
 296          * succeed, so that inserting keys into the btree can always succeed and
 297          * IO can always make forward progress:
 298          */
 299         nr /= btree_pages(c);
 300         can_free = btree_cache_can_free(bc);
 301         nr = min_t(unsigned long, nr, can_free);
 302
 303         i = 0;
 304         list_for_each_entry_safe(b, t, &bc->freeable, list) {
 305                 /*
 306                  * Leave a few nodes on the freeable list, so that a btree split
 307                  * won't have to hit the system allocator:
 308                  */
 309                 if (++i <= 3)
 310                         continue;
 311
 312                 touched++;
 313
 314                 if (touched >= nr)
 315                         break;
 316
 317                 if (!btree_node_reclaim(c, b)) {
 318                         btree_node_data_free(c, b);
 319                         six_unlock_write(&b->c.lock);
 320                         six_unlock_intent(&b->c.lock);
 321                         freed++;
 322                 }
 323         }
 324 restart:
 325         list_for_each_entry_safe(b, t, &bc->live, list) {
 326                 touched++;
 327
 328                 if (touched >= nr) {
 329                         /* Save position */
 330                         if (&t->list != &bc->live)
 331                                 list_move_tail(&bc->live, &t->list);
 332                         break;
 333                 }
 334
 335                 if (!btree_node_accessed(b) &&
 336                     !btree_node_reclaim(c, b)) {
 337                         /* can't call bch2_btree_node_hash_remove under lock  */
 338                         freed++;
 339                         if (&t->list != &bc->live)
 340                                 list_move_tail(&bc->live, &t->list);
 341
 342                         btree_node_data_free(c, b);
 343                         mutex_unlock(&bc->lock);
 344
 345                         bch2_btree_node_hash_remove(bc, b);
 346                         six_unlock_write(&b->c.lock);
 347                         six_unlock_intent(&b->c.lock);
 348
 349                         if (freed >= nr)
 350                                 goto out;
 351
 352                         if (sc->gfp_mask & __GFP_FS)
 353                                 mutex_lock(&bc->lock);
 354                         else if (!mutex_trylock(&bc->lock))
 355                                 goto out;
 356                         goto restart;
 357                 } else
 358                         clear_btree_node_accessed(b);
 359         }
 360
 361         mutex_unlock(&bc->lock);
 362 out:
 363         ret = (unsigned long) freed * btree_pages(c);
 364         memalloc_nofs_restore(flags);
 365 out_norestore:
 366         trace_btree_cache_scan(sc->nr_to_scan,
 367                                sc->nr_to_scan / btree_pages(c),
 368                                btree_cache_can_free(bc),
 369                                ret);
 370         return ret;
 371 }
 372
 373 static unsigned long bch2_btree_cache_count(struct shrinker *shrink,
 374                                             struct shrink_control *sc)
 375 {
 376         struct bch_fs *c = container_of(shrink, struct bch_fs,
 377                                         btree_cache.shrink);
 378         struct btree_cache *bc = &c->btree_cache;
 379
 380         if (bch2_btree_shrinker_disabled)
 381                 return 0;
 382
 383         return btree_cache_can_free(bc) * btree_pages(c);
 384 }
 385
 386 void bch2_fs_btree_cache_exit(struct bch_fs *c)
 387 {
 388         struct btree_cache *bc = &c->btree_cache;
 389         struct btree *b;
 390         unsigned i, flags;
 391
 392         if (bc->shrink.list.next)
 393                 unregister_shrinker(&bc->shrink);
 394
 395         /* vfree() can allocate memory: */
 396         flags = memalloc_nofs_save();
 397         mutex_lock(&bc->lock);
 398
 399         if (c->verify_data)
 400                 list_move(&c->verify_data->list, &bc->live);
 401
 402         kvpfree(c->verify_ondisk, btree_bytes(c));
 403
 404         for (i = 0; i < BTREE_ID_NR; i++)
 405                 if (c->btree_roots[i].b)
 406                         list_add(&c->btree_roots[i].b->list, &bc->live);
 407
 408         list_splice(&bc->freeable, &bc->live);
 409
 410         while (!list_empty(&bc->live)) {
 411                 b = list_first_entry(&bc->live, struct btree, list);
 412
 413                 BUG_ON(btree_node_read_in_flight(b) ||
 414                        btree_node_write_in_flight(b));
 415
 416                 if (btree_node_dirty(b))
 417                         bch2_btree_complete_write(c, b, btree_current_write(b));
 418                 clear_btree_node_dirty(c, b);
 419
 420                 btree_node_data_free(c, b);
 421         }
 422
 423         BUG_ON(atomic_read(&c->btree_cache.dirty));
 424
 425         while (!list_empty(&bc->freed)) {
 426                 b = list_first_entry(&bc->freed, struct btree, list);
 427                 list_del(&b->list);
 428                 six_lock_pcpu_free(&b->c.lock);
 429                 kfree(b);
 430         }
 431
 432         mutex_unlock(&bc->lock);
 433         memalloc_nofs_restore(flags);
 434
 435         if (bc->table_init_done)
 436                 rhashtable_destroy(&bc->table);
 437 }
 438
 439 int bch2_fs_btree_cache_init(struct bch_fs *c)
 440 {
 441         struct btree_cache *bc = &c->btree_cache;
 442         unsigned i;
 443         int ret = 0;
 444
 445         pr_verbose_init(c->opts, "");
 446
 447         ret = rhashtable_init(&bc->table, &bch_btree_cache_params);
 448         if (ret)
 449                 goto out;
 450
 451         bc->table_init_done = true;
 452
 453         bch2_recalc_btree_reserve(c);
 454
 455         for (i = 0; i < bc->reserve; i++)
 456                 if (!__bch2_btree_node_mem_alloc(c)) {
 457                         ret = -ENOMEM;
 458                         goto out;
 459                 }
 460
 461         list_splice_init(&bc->live, &bc->freeable);
 462
 463         mutex_init(&c->verify_lock);
 464
 465         bc->shrink.count_objects        = bch2_btree_cache_count;
 466         bc->shrink.scan_objects         = bch2_btree_cache_scan;
 467         bc->shrink.seeks                = 4;
 468         bc->shrink.batch                = btree_pages(c) * 2;
 469         ret = register_shrinker(&bc->shrink);
 470 out:
 471         pr_verbose_init(c->opts, "ret %i", ret);
 472         return ret;
 473 }
 474
 475 void bch2_fs_btree_cache_init_early(struct btree_cache *bc)
 476 {
 477         mutex_init(&bc->lock);
 478         INIT_LIST_HEAD(&bc->live);
 479         INIT_LIST_HEAD(&bc->freeable);
 480         INIT_LIST_HEAD(&bc->freed);
 481 }
 482
 483 /*
 484  * We can only have one thread cannibalizing other cached btree nodes at a time,
 485  * or we'll deadlock. We use an open coded mutex to ensure that, which a
 486  * cannibalize_bucket() will take. This means every time we unlock the root of
 487  * the btree, we need to release this lock if we have it held.
 488  */
 489 void bch2_btree_cache_cannibalize_unlock(struct bch_fs *c)
 490 {
 491         struct btree_cache *bc = &c->btree_cache;
 492
 493         if (bc->alloc_lock == current) {
 494                 trace_btree_node_cannibalize_unlock(c);
 495                 bc->alloc_lock = NULL;
 496                 closure_wake_up(&bc->alloc_wait);
 497         }
 498 }
 499
 500 int bch2_btree_cache_cannibalize_lock(struct bch_fs *c, struct closure *cl)
 501 {
 502         struct btree_cache *bc = &c->btree_cache;
 503         struct task_struct *old;
 504
 505         old = cmpxchg(&bc->alloc_lock, NULL, current);
 506         if (old == NULL || old == current)
 507                 goto success;
 508
 509         if (!cl) {
 510                 trace_btree_node_cannibalize_lock_fail(c);
 511                 return -ENOMEM;
 512         }
 513
 514         closure_wait(&bc->alloc_wait, cl);
 515
 516         /* Try again, after adding ourselves to waitlist */
 517         old = cmpxchg(&bc->alloc_lock, NULL, current);
 518         if (old == NULL || old == current) {
 519                 /* We raced */
 520                 closure_wake_up(&bc->alloc_wait);
 521                 goto success;
 522         }
 523
 524         trace_btree_node_cannibalize_lock_fail(c);
 525         return -EAGAIN;
 526
 527 success:
 528         trace_btree_node_cannibalize_lock(c);
 529         return 0;
 530 }
 531
 532 static struct btree *btree_node_cannibalize(struct bch_fs *c)
 533 {
 534         struct btree_cache *bc = &c->btree_cache;
 535         struct btree *b;
 536
 537         list_for_each_entry_reverse(b, &bc->live, list)
 538                 if (!btree_node_reclaim(c, b))
 539                         return b;
 540
 541         while (1) {
 542                 list_for_each_entry_reverse(b, &bc->live, list)
 543                         if (!btree_node_write_and_reclaim(c, b))
 544                                 return b;
 545
 546                 /*
 547                  * Rare case: all nodes were intent-locked.
 548                  * Just busy-wait.
 549                  */
 550                 WARN_ONCE(1, "btree cache cannibalize failed\n");
 551                 cond_resched();
 552         }
 553 }
 554
 555 struct btree *bch2_btree_node_mem_alloc(struct bch_fs *c)
 556 {
 557         struct btree_cache *bc = &c->btree_cache;
 558         struct btree *b;
 559         u64 start_time = local_clock();
 560         unsigned flags;
 561
 562         flags = memalloc_nofs_save();
 563         mutex_lock(&bc->lock);
 564
 565         /*
 566          * btree_free() doesn't free memory; it sticks the node on the end of
 567          * the list. Check if there's any freed nodes there:
 568          */
 569         list_for_each_entry(b, &bc->freeable, list)
 570                 if (!btree_node_reclaim(c, b))
 571                         goto got_node;
 572
 573         /*
 574          * We never free struct btree itself, just the memory that holds the on
 575          * disk node. Check the freed list before allocating a new one:
 576          */
 577         list_for_each_entry(b, &bc->freed, list)
 578                 if (!btree_node_reclaim(c, b))
 579                         goto got_node;
 580
 581         b = NULL;
 582 got_node:
 583         if (b)
 584                 list_del_init(&b->list);
 585         mutex_unlock(&bc->lock);
 586
 587         if (!b) {
 588                 b = __btree_node_mem_alloc(c);
 589                 if (!b)
 590                         goto err;
 591
 592                 BUG_ON(!six_trylock_intent(&b->c.lock));
 593                 BUG_ON(!six_trylock_write(&b->c.lock));
 594         }
 595
 596         if (!b->data) {
 597                 if (btree_node_data_alloc(c, b, __GFP_NOWARN|GFP_KERNEL))
 598                         goto err;
 599
 600                 mutex_lock(&bc->lock);
 601                 bc->used++;
 602                 mutex_unlock(&bc->lock);
 603         }
 604
 605         BUG_ON(btree_node_hashed(b));
 606         BUG_ON(btree_node_dirty(b));
 607         BUG_ON(btree_node_write_in_flight(b));
 608 out:
 609         b->flags                = 0;
 610         b->written              = 0;
 611         b->nsets                = 0;
 612         b->sib_u64s[0]          = 0;
 613         b->sib_u64s[1]          = 0;
 614         b->whiteout_u64s        = 0;
 615         bch2_btree_keys_init(b);
 616         set_btree_node_accessed(b);
 617
 618         bch2_time_stats_update(&c->times[BCH_TIME_btree_node_mem_alloc],
 619                                start_time);
 620
 621         memalloc_nofs_restore(flags);
 622         return b;
 623 err:
 624         mutex_lock(&bc->lock);
 625
 626         if (b) {
 627                 list_add(&b->list, &bc->freed);
 628                 six_unlock_write(&b->c.lock);
 629                 six_unlock_intent(&b->c.lock);
 630         }
 631
 632         /* Try to cannibalize another cached btree node: */
 633         if (bc->alloc_lock == current) {
 634                 b = btree_node_cannibalize(c);
 635                 list_del_init(&b->list);
 636                 mutex_unlock(&bc->lock);
 637
 638                 bch2_btree_node_hash_remove(bc, b);
 639
 640                 trace_btree_node_cannibalize(c);
 641                 goto out;
 642         }
 643
 644         mutex_unlock(&bc->lock);
 645         memalloc_nofs_restore(flags);
 646         return ERR_PTR(-ENOMEM);
 647 }
 648
 649 /* Slowpath, don't want it inlined into btree_iter_traverse() */
 650 static noinline struct btree *bch2_btree_node_fill(struct bch_fs *c,
 651                                 struct btree_trans *trans,
 652                                 struct btree_path *path,
 653                                 const struct bkey_i *k,
 654                                 enum btree_id btree_id,
 655                                 unsigned level,
 656                                 enum six_lock_type lock_type,
 657                                 bool sync)
 658 {
 659         struct btree_cache *bc = &c->btree_cache;
 660         struct btree *b;
 661         u32 seq;
 662
 663         BUG_ON(level + 1 >= BTREE_MAX_DEPTH);
 664         /*
 665          * Parent node must be locked, else we could read in a btree node that's
 666          * been freed:
 667          */
 668         if (trans && !bch2_btree_node_relock(trans, path, level + 1)) {
 669                 btree_trans_restart(trans);
 670                 return ERR_PTR(-EINTR);
 671         }
 672
 673         b = bch2_btree_node_mem_alloc(c);
 674         if (IS_ERR(b))
 675                 return b;
 676
 677         bkey_copy(&b->key, k);
 678         if (bch2_btree_node_hash_insert(bc, b, level, btree_id)) {
 679                 /* raced with another fill: */
 680
 681                 /* mark as unhashed... */
 682                 b->hash_val = 0;
 683
 684                 mutex_lock(&bc->lock);
 685                 list_add(&b->list, &bc->freeable);
 686                 mutex_unlock(&bc->lock);
 687
 688                 six_unlock_write(&b->c.lock);
 689                 six_unlock_intent(&b->c.lock);
 690                 return NULL;
 691         }
 692
 693         set_btree_node_read_in_flight(b);
 694
 695         six_unlock_write(&b->c.lock);
 696         seq = b->c.lock.state.seq;
 697         six_unlock_intent(&b->c.lock);
 698
 699         /* Unlock before doing IO: */
 700         if (trans && sync)
 701                 bch2_trans_unlock(trans);
 702
 703         bch2_btree_node_read(c, b, sync);
 704
 705         if (!sync)
 706                 return NULL;
 707
 708         if (trans &&
 709             (!bch2_trans_relock(trans) ||
 710              !bch2_btree_path_relock_intent(trans, path))) {
 711                 BUG_ON(!trans->restarted);
 712                 return ERR_PTR(-EINTR);
 713         }
 714
 715         if (!six_relock_type(&b->c.lock, lock_type, seq)) {
 716                 btree_trans_restart(trans);
 717                 return ERR_PTR(-EINTR);
 718         }
 719
 720         return b;
 721 }
 722
 723 static int lock_node_check_fn(struct six_lock *lock, void *p)
 724 {
 725         struct btree *b = container_of(lock, struct btree, c.lock);
 726         const struct bkey_i *k = p;
 727
 728         return b->hash_val == btree_ptr_hash_val(k) ? 0 : -1;
 729 }
 730
 731 static noinline void btree_bad_header(struct bch_fs *c, struct btree *b)
 732 {
 733         char buf1[200], buf2[100], buf3[100];
 734
 735         if (!test_bit(BCH_FS_INITIAL_GC_DONE, &c->flags))
 736                 return;
 737
 738         bch2_bkey_val_to_text(&PBUF(buf1), c, bkey_i_to_s_c(&b->key));
 739         bch2_bpos_to_text(&PBUF(buf2), b->data->min_key);
 740         bch2_bpos_to_text(&PBUF(buf3), b->data->max_key);
 741
 742         bch2_fs_inconsistent(c, "btree node header doesn't match ptr\n"
 743                              "btree %s level %u\n"
 744                              "ptr: %s\n"
 745                              "header: btree %s level %llu\n"
 746                              "min %s max %s\n",
 747                              bch2_btree_ids[b->c.btree_id], b->c.level,
 748                              buf1,
 749                              bch2_btree_ids[BTREE_NODE_ID(b->data)],
 750                              BTREE_NODE_LEVEL(b->data),
 751                              buf2, buf3);
 752 }
 753
 754 static inline void btree_check_header(struct bch_fs *c, struct btree *b)
 755 {
 756         if (b->c.btree_id != BTREE_NODE_ID(b->data) ||
 757             b->c.level != BTREE_NODE_LEVEL(b->data) ||
 758             bpos_cmp(b->data->max_key, b->key.k.p) ||
 759             (b->key.k.type == KEY_TYPE_btree_ptr_v2 &&
 760              bpos_cmp(b->data->min_key,
 761                       bkey_i_to_btree_ptr_v2(&b->key)->v.min_key)))
 762                 btree_bad_header(c, b);
 763 }
 764
 765 /**
 766  * bch_btree_node_get - find a btree node in the cache and lock it, reading it
 767  * in from disk if necessary.
 768  *
 769  * If IO is necessary and running under generic_make_request, returns -EAGAIN.
 770  *
 771  * The btree node will have either a read or a write lock held, depending on
 772  * the @write parameter.
 773  */
 774 struct btree *bch2_btree_node_get(struct btree_trans *trans, struct btree_path *path,
 775                                   const struct bkey_i *k, unsigned level,
 776                                   enum six_lock_type lock_type,
 777                                   unsigned long trace_ip)
 778 {
 779         struct bch_fs *c = trans->c;
 780         struct btree_cache *bc = &c->btree_cache;
 781         struct btree *b;
 782         struct bset_tree *t;
 783
 784         EBUG_ON(level >= BTREE_MAX_DEPTH);
 785
 786         b = btree_node_mem_ptr(k);
 787
 788         /*
 789          * Check b->hash_val _before_ calling btree_node_lock() - this might not
 790          * be the node we want anymore, and trying to lock the wrong node could
 791          * cause an unneccessary transaction restart:
 792          */
 793         if (likely(c->opts.btree_node_mem_ptr_optimization &&
 794                    b &&
 795                    b->hash_val == btree_ptr_hash_val(k)))
 796                         goto lock_node;
 797 retry:
 798         b = btree_cache_find(bc, k);
 799         if (unlikely(!b)) {
 800                 /*
 801                  * We must have the parent locked to call bch2_btree_node_fill(),
 802                  * else we could read in a btree node from disk that's been
 803                  * freed:
 804                  */
 805                 b = bch2_btree_node_fill(c, trans, path, k, path->btree_id,
 806                                          level, lock_type, true);
 807
 808                 /* We raced and found the btree node in the cache */
 809                 if (!b)
 810                         goto retry;
 811
 812                 if (IS_ERR(b))
 813                         return b;
 814         } else {
 815 lock_node:
 816                 /*
 817                  * There's a potential deadlock with splits and insertions into
 818                  * interior nodes we have to avoid:
 819                  *
 820                  * The other thread might be holding an intent lock on the node
 821                  * we want, and they want to update its parent node so they're
 822                  * going to upgrade their intent lock on the parent node to a
 823                  * write lock.
 824                  *
 825                  * But if we're holding a read lock on the parent, and we're
 826                  * trying to get the intent lock they're holding, we deadlock.
 827                  *
 828                  * So to avoid this we drop the read locks on parent nodes when
 829                  * we're starting to take intent locks - and handle the race.
 830                  *
 831                  * The race is that they might be about to free the node we
 832                  * want, and dropping our read lock on the parent node lets them
 833                  * update the parent marking the node we want as freed, and then
 834                  * free it:
 835                  *
 836                  * To guard against this, btree nodes are evicted from the cache
 837                  * when they're freed - and b->hash_val is zeroed out, which we
 838                  * check for after we lock the node.
 839                  *
 840                  * Then, bch2_btree_node_relock() on the parent will fail - because
 841                  * the parent was modified, when the pointer to the node we want
 842                  * was removed - and we'll bail out:
 843                  */
 844                 if (btree_node_read_locked(path, level + 1))
 845                         btree_node_unlock(path, level + 1);
 846
 847                 if (!btree_node_lock(trans, path, b, k->k.p, level, lock_type,
 848                                      lock_node_check_fn, (void *) k, trace_ip)) {
 849                         if (!trans->restarted)
 850                                 goto retry;
 851                         return ERR_PTR(-EINTR);
 852                 }
 853
 854                 if (unlikely(b->hash_val != btree_ptr_hash_val(k) ||
 855                              b->c.level != level ||
 856                              race_fault())) {
 857                         six_unlock_type(&b->c.lock, lock_type);
 858                         if (bch2_btree_node_relock(trans, path, level + 1))
 859                                 goto retry;
 860
 861                         trace_trans_restart_btree_node_reused(trans->ip,
 862                                                               trace_ip,
 863                                                               path->btree_id,
 864                                                               &path->pos);
 865                         btree_trans_restart(trans);
 866                         return ERR_PTR(-EINTR);
 867                 }
 868         }
 869
 870         if (unlikely(btree_node_read_in_flight(b))) {
 871                 u32 seq = b->c.lock.state.seq;
 872
 873                 six_unlock_type(&b->c.lock, lock_type);
 874                 bch2_trans_unlock(trans);
 875
 876                 bch2_btree_node_wait_on_read(b);
 877
 878                 /*
 879                  * should_be_locked is not set on this path yet, so we need to
 880                  * relock it specifically:
 881                  */
 882                 if (trans &&
 883                     (!bch2_trans_relock(trans) ||
 884                      !bch2_btree_path_relock_intent(trans, path))) {
 885                         BUG_ON(!trans->restarted);
 886                         return ERR_PTR(-EINTR);
 887                 }
 888
 889                 if (!six_relock_type(&b->c.lock, lock_type, seq))
 890                         goto retry;
 891         }
 892
 893         prefetch(b->aux_data);
 894
 895         for_each_bset(b, t) {
 896                 void *p = (u64 *) b->aux_data + t->aux_data_offset;
 897
 898                 prefetch(p + L1_CACHE_BYTES * 0);
 899                 prefetch(p + L1_CACHE_BYTES * 1);
 900                 prefetch(p + L1_CACHE_BYTES * 2);
 901         }
 902
 903         /* avoid atomic set bit if it's not needed: */
 904         if (!btree_node_accessed(b))
 905                 set_btree_node_accessed(b);
 906
 907         if (unlikely(btree_node_read_error(b))) {
 908                 six_unlock_type(&b->c.lock, lock_type);
 909                 return ERR_PTR(-EIO);
 910         }
 911
 912         EBUG_ON(b->c.btree_id != path->btree_id);
 913         EBUG_ON(BTREE_NODE_LEVEL(b->data) != level);
 914         btree_check_header(c, b);
 915
 916         return b;
 917 }
 918
 919 struct btree *bch2_btree_node_get_noiter(struct bch_fs *c,
 920                                          const struct bkey_i *k,
 921                                          enum btree_id btree_id,
 922                                          unsigned level,
 923                                          bool nofill)
 924 {
 925         struct btree_cache *bc = &c->btree_cache;
 926         struct btree *b;
 927         struct bset_tree *t;
 928         int ret;
 929
 930         EBUG_ON(level >= BTREE_MAX_DEPTH);
 931
 932         if (c->opts.btree_node_mem_ptr_optimization) {
 933                 b = btree_node_mem_ptr(k);
 934                 if (b)
 935                         goto lock_node;
 936         }
 937 retry:
 938         b = btree_cache_find(bc, k);
 939         if (unlikely(!b)) {
 940                 if (nofill)
 941                         goto out;
 942
 943                 b = bch2_btree_node_fill(c, NULL, NULL, k, btree_id,
 944                                          level, SIX_LOCK_read, true);
 945
 946                 /* We raced and found the btree node in the cache */
 947                 if (!b)
 948                         goto retry;
 949
 950                 if (IS_ERR(b) &&
 951                     !bch2_btree_cache_cannibalize_lock(c, NULL))
 952                         goto retry;
 953
 954                 if (IS_ERR(b))
 955                         goto out;
 956         } else {
 957 lock_node:
 958                 ret = six_lock_read(&b->c.lock, lock_node_check_fn, (void *) k);
 959                 if (ret)
 960                         goto retry;
 961
 962                 if (unlikely(b->hash_val != btree_ptr_hash_val(k) ||
 963                              b->c.btree_id != btree_id ||
 964                              b->c.level != level)) {
 965                         six_unlock_read(&b->c.lock);
 966                         goto retry;
 967                 }
 968         }
 969
 970         /* XXX: waiting on IO with btree locks held: */
 971         __bch2_btree_node_wait_on_read(b);
 972
 973         prefetch(b->aux_data);
 974
 975         for_each_bset(b, t) {
 976                 void *p = (u64 *) b->aux_data + t->aux_data_offset;
 977
 978                 prefetch(p + L1_CACHE_BYTES * 0);
 979                 prefetch(p + L1_CACHE_BYTES * 1);
 980                 prefetch(p + L1_CACHE_BYTES * 2);
 981         }
 982
 983         /* avoid atomic set bit if it's not needed: */
 984         if (!btree_node_accessed(b))
 985                 set_btree_node_accessed(b);
 986
 987         if (unlikely(btree_node_read_error(b))) {
 988                 six_unlock_read(&b->c.lock);
 989                 b = ERR_PTR(-EIO);
 990                 goto out;
 991         }
 992
 993         EBUG_ON(b->c.btree_id != btree_id);
 994         EBUG_ON(BTREE_NODE_LEVEL(b->data) != level);
 995         btree_check_header(c, b);
 996 out:
 997         bch2_btree_cache_cannibalize_unlock(c);
 998         return b;
 999 }
1000
1001 int bch2_btree_node_prefetch(struct bch_fs *c,
1002                              struct btree_trans *trans,
1003                              struct btree_path *path,
1004                              const struct bkey_i *k,
1005                              enum btree_id btree_id, unsigned level)
1006 {
1007         struct btree_cache *bc = &c->btree_cache;
1008         struct btree *b;
1009
1010         BUG_ON(trans && !btree_node_locked(path, level + 1));
1011         BUG_ON(level >= BTREE_MAX_DEPTH);
1012
1013         b = btree_cache_find(bc, k);
1014         if (b)
1015                 return 0;
1016
1017         b = bch2_btree_node_fill(c, trans, path, k, btree_id,
1018                                  level, SIX_LOCK_read, false);
1019         return PTR_ERR_OR_ZERO(b);
1020 }
1021
1022 void bch2_btree_node_evict(struct bch_fs *c, const struct bkey_i *k)
1023 {
1024         struct btree_cache *bc = &c->btree_cache;
1025         struct btree *b;
1026
1027         b = btree_cache_find(bc, k);
1028         if (!b)
1029                 return;
1030 wait_on_io:
1031         /* not allowed to wait on io with btree locks held: */
1032
1033         /* XXX we're called from btree_gc which will be holding other btree
1034          * nodes locked
1035          * */
1036         __bch2_btree_node_wait_on_read(b);
1037         __bch2_btree_node_wait_on_write(b);
1038
1039         six_lock_intent(&b->c.lock, NULL, NULL);
1040         six_lock_write(&b->c.lock, NULL, NULL);
1041
1042         if (btree_node_dirty(b)) {
1043                 __bch2_btree_node_write(c, b, false);
1044                 six_unlock_write(&b->c.lock);
1045                 six_unlock_intent(&b->c.lock);
1046                 goto wait_on_io;
1047         }
1048
1049         BUG_ON(btree_node_dirty(b));
1050
1051         mutex_lock(&bc->lock);
1052         btree_node_data_free(c, b);
1053         bch2_btree_node_hash_remove(bc, b);
1054         mutex_unlock(&bc->lock);
1055
1056         six_unlock_write(&b->c.lock);
1057         six_unlock_intent(&b->c.lock);
1058 }
1059
1060 void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c,
1061                              struct btree *b)
1062 {
1063         const struct bkey_format *f = &b->format;
1064         struct bset_stats stats;
1065
1066         memset(&stats, 0, sizeof(stats));
1067
1068         bch2_btree_keys_stats(b, &stats);
1069
1070         pr_buf(out, "l %u ", b->c.level);
1071         bch2_bpos_to_text(out, b->data->min_key);
1072         pr_buf(out, " - ");
1073         bch2_bpos_to_text(out, b->data->max_key);
1074         pr_buf(out, ":\n"
1075                "    ptrs: ");
1076         bch2_val_to_text(out, c, bkey_i_to_s_c(&b->key));
1077
1078         pr_buf(out, "\n"
1079                "    format: u64s %u fields %u %u %u %u %u\n"
1080                "    unpack fn len: %u\n"
1081                "    bytes used %zu/%zu (%zu%% full)\n"
1082                "    sib u64s: %u, %u (merge threshold %u)\n"
1083                "    nr packed keys %u\n"
1084                "    nr unpacked keys %u\n"
1085                "    floats %zu\n"
1086                "    failed unpacked %zu\n",
1087                f->key_u64s,
1088                f->bits_per_field[0],
1089                f->bits_per_field[1],
1090                f->bits_per_field[2],
1091                f->bits_per_field[3],
1092                f->bits_per_field[4],
1093                b->unpack_fn_len,
1094                b->nr.live_u64s * sizeof(u64),
1095                btree_bytes(c) - sizeof(struct btree_node),
1096                b->nr.live_u64s * 100 / btree_max_u64s(c),
1097                b->sib_u64s[0],
1098                b->sib_u64s[1],
1099                c->btree_foreground_merge_threshold,
1100                b->nr.packed_keys,
1101                b->nr.unpacked_keys,
1102                stats.floats,
1103                stats.failed);
1104 }
1105
1106 void bch2_btree_cache_to_text(struct printbuf *out, struct bch_fs *c)
1107 {
1108         pr_buf(out, "nr nodes:\t\t%u\n", c->btree_cache.used);
1109         pr_buf(out, "nr dirty:\t\t%u\n", atomic_read(&c->btree_cache.dirty));
1110         pr_buf(out, "cannibalize lock:\t%p\n", c->btree_cache.alloc_lock);
1111 }