fs/bcachefs/bset.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Code for working with individual keys, and sorted sets of keys with in a
   4  * btree node
   5  *
   6  * Copyright 2012 Google, Inc.
   7  */
   8
   9 #include "bcachefs.h"
  10 #include "btree_cache.h"
  11 #include "bset.h"
  12 #include "eytzinger.h"
  13 #include "trace.h"
  14 #include "util.h"
  15
  16 #include <asm/unaligned.h>
  17 #include <linux/console.h>
  18 #include <linux/random.h>
  19 #include <linux/prefetch.h>
  20
  21 static inline void __bch2_btree_node_iter_advance(struct btree_node_iter *,
  22                                                   struct btree *);
  23
  24 static inline unsigned __btree_node_iter_used(struct btree_node_iter *iter)
  25 {
  26         unsigned n = ARRAY_SIZE(iter->data);
  27
  28         while (n && __btree_node_iter_set_end(iter, n - 1))
  29                 --n;
  30
  31         return n;
  32 }
  33
  34 struct bset_tree *bch2_bkey_to_bset(struct btree *b, struct bkey_packed *k)
  35 {
  36         return bch2_bkey_to_bset_inlined(b, k);
  37 }
  38
  39 /*
  40  * There are never duplicate live keys in the btree - but including keys that
  41  * have been flagged as deleted (and will be cleaned up later) we _will_ see
  42  * duplicates.
  43  *
  44  * Thus the sort order is: usual key comparison first, but for keys that compare
  45  * equal the deleted key(s) come first, and the (at most one) live version comes
  46  * last.
  47  *
  48  * The main reason for this is insertion: to handle overwrites, we first iterate
  49  * over keys that compare equal to our insert key, and then insert immediately
  50  * prior to the first key greater than the key we're inserting - our insert
  51  * position will be after all keys that compare equal to our insert key, which
  52  * by the time we actually do the insert will all be deleted.
  53  */
  54
  55 void bch2_dump_bset(struct bch_fs *c, struct btree *b,
  56                     struct bset *i, unsigned set)
  57 {
  58         struct bkey_packed *_k, *_n;
  59         struct bkey uk, n;
  60         struct bkey_s_c k;
  61         struct printbuf buf = PRINTBUF;
  62
  63         if (!i->u64s)
  64                 return;
  65
  66         for (_k = i->start;
  67              _k < vstruct_last(i);
  68              _k = _n) {
  69                 _n = bkey_p_next(_k);
  70
  71                 if (!_k->u64s) {
  72                         printk(KERN_ERR "block %u key %5zu - u64s 0? aieee!\n", set,
  73                                _k->_data - i->_data);
  74                         break;
  75                 }
  76
  77                 k = bkey_disassemble(b, _k, &uk);
  78
  79                 printbuf_reset(&buf);
  80                 if (c)
  81                         bch2_bkey_val_to_text(&buf, c, k);
  82                 else
  83                         bch2_bkey_to_text(&buf, k.k);
  84                 printk(KERN_ERR "block %u key %5zu: %s\n", set,
  85                        _k->_data - i->_data, buf.buf);
  86
  87                 if (_n == vstruct_last(i))
  88                         continue;
  89
  90                 n = bkey_unpack_key(b, _n);
  91
  92                 if (bpos_lt(n.p, k.k->p)) {
  93                         printk(KERN_ERR "Key skipped backwards\n");
  94                         continue;
  95                 }
  96
  97                 if (!bkey_deleted(k.k) && bpos_eq(n.p, k.k->p))
  98                         printk(KERN_ERR "Duplicate keys\n");
  99         }
 100
 101         printbuf_exit(&buf);
 102 }
 103
 104 void bch2_dump_btree_node(struct bch_fs *c, struct btree *b)
 105 {
 106         console_lock();
 107         for_each_bset(b, t)
 108                 bch2_dump_bset(c, b, bset(b, t), t - b->set);
 109         console_unlock();
 110 }
 111
 112 void bch2_dump_btree_node_iter(struct btree *b,
 113                               struct btree_node_iter *iter)
 114 {
 115         struct btree_node_iter_set *set;
 116         struct printbuf buf = PRINTBUF;
 117
 118         printk(KERN_ERR "btree node iter with %u/%u sets:\n",
 119                __btree_node_iter_used(iter), b->nsets);
 120
 121         btree_node_iter_for_each(iter, set) {
 122                 struct bkey_packed *k = __btree_node_offset_to_key(b, set->k);
 123                 struct bset_tree *t = bch2_bkey_to_bset(b, k);
 124                 struct bkey uk = bkey_unpack_key(b, k);
 125
 126                 printbuf_reset(&buf);
 127                 bch2_bkey_to_text(&buf, &uk);
 128                 printk(KERN_ERR "set %zu key %u: %s\n",
 129                        t - b->set, set->k, buf.buf);
 130         }
 131
 132         printbuf_exit(&buf);
 133 }
 134
 135 struct btree_nr_keys bch2_btree_node_count_keys(struct btree *b)
 136 {
 137         struct bkey_packed *k;
 138         struct btree_nr_keys nr = {};
 139
 140         for_each_bset(b, t)
 141                 bset_tree_for_each_key(b, t, k)
 142                         if (!bkey_deleted(k))
 143                                 btree_keys_account_key_add(&nr, t - b->set, k);
 144         return nr;
 145 }
 146
 147 #ifdef CONFIG_BCACHEFS_DEBUG
 148
 149 void __bch2_verify_btree_nr_keys(struct btree *b)
 150 {
 151         struct btree_nr_keys nr = bch2_btree_node_count_keys(b);
 152
 153         BUG_ON(memcmp(&nr, &b->nr, sizeof(nr)));
 154 }
 155
 156 static void bch2_btree_node_iter_next_check(struct btree_node_iter *_iter,
 157                                             struct btree *b)
 158 {
 159         struct btree_node_iter iter = *_iter;
 160         const struct bkey_packed *k, *n;
 161
 162         k = bch2_btree_node_iter_peek_all(&iter, b);
 163         __bch2_btree_node_iter_advance(&iter, b);
 164         n = bch2_btree_node_iter_peek_all(&iter, b);
 165
 166         bkey_unpack_key(b, k);
 167
 168         if (n &&
 169             bkey_iter_cmp(b, k, n) > 0) {
 170                 struct btree_node_iter_set *set;
 171                 struct bkey ku = bkey_unpack_key(b, k);
 172                 struct bkey nu = bkey_unpack_key(b, n);
 173                 struct printbuf buf1 = PRINTBUF;
 174                 struct printbuf buf2 = PRINTBUF;
 175
 176                 bch2_dump_btree_node(NULL, b);
 177                 bch2_bkey_to_text(&buf1, &ku);
 178                 bch2_bkey_to_text(&buf2, &nu);
 179                 printk(KERN_ERR "out of order/overlapping:\n%s\n%s\n",
 180                        buf1.buf, buf2.buf);
 181                 printk(KERN_ERR "iter was:");
 182
 183                 btree_node_iter_for_each(_iter, set) {
 184                         struct bkey_packed *k2 = __btree_node_offset_to_key(b, set->k);
 185                         struct bset_tree *t = bch2_bkey_to_bset(b, k2);
 186                         printk(" [%zi %zi]", t - b->set,
 187                                k2->_data - bset(b, t)->_data);
 188                 }
 189                 panic("\n");
 190         }
 191 }
 192
 193 void bch2_btree_node_iter_verify(struct btree_node_iter *iter,
 194                                  struct btree *b)
 195 {
 196         struct btree_node_iter_set *set, *s2;
 197         struct bkey_packed *k, *p;
 198
 199         if (bch2_btree_node_iter_end(iter))
 200                 return;
 201
 202         /* Verify no duplicates: */
 203         btree_node_iter_for_each(iter, set) {
 204                 BUG_ON(set->k > set->end);
 205                 btree_node_iter_for_each(iter, s2)
 206                         BUG_ON(set != s2 && set->end == s2->end);
 207         }
 208
 209         /* Verify that set->end is correct: */
 210         btree_node_iter_for_each(iter, set) {
 211                 for_each_bset(b, t)
 212                         if (set->end == t->end_offset) {
 213                                 BUG_ON(set->k < btree_bkey_first_offset(t) ||
 214                                        set->k >= t->end_offset);
 215                                 goto found;
 216                         }
 217                 BUG();
 218 found:
 219                 do {} while (0);
 220         }
 221
 222         /* Verify iterator is sorted: */
 223         btree_node_iter_for_each(iter, set)
 224                 BUG_ON(set != iter->data &&
 225                        btree_node_iter_cmp(b, set[-1], set[0]) > 0);
 226
 227         k = bch2_btree_node_iter_peek_all(iter, b);
 228
 229         for_each_bset(b, t) {
 230                 if (iter->data[0].end == t->end_offset)
 231                         continue;
 232
 233                 p = bch2_bkey_prev_all(b, t,
 234                         bch2_btree_node_iter_bset_pos(iter, b, t));
 235
 236                 BUG_ON(p && bkey_iter_cmp(b, k, p) < 0);
 237         }
 238 }
 239
 240 void bch2_verify_insert_pos(struct btree *b, struct bkey_packed *where,
 241                             struct bkey_packed *insert, unsigned clobber_u64s)
 242 {
 243         struct bset_tree *t = bch2_bkey_to_bset(b, where);
 244         struct bkey_packed *prev = bch2_bkey_prev_all(b, t, where);
 245         struct bkey_packed *next = (void *) ((u64 *) where->_data + clobber_u64s);
 246         struct printbuf buf1 = PRINTBUF;
 247         struct printbuf buf2 = PRINTBUF;
 248 #if 0
 249         BUG_ON(prev &&
 250                bkey_iter_cmp(b, prev, insert) > 0);
 251 #else
 252         if (prev &&
 253             bkey_iter_cmp(b, prev, insert) > 0) {
 254                 struct bkey k1 = bkey_unpack_key(b, prev);
 255                 struct bkey k2 = bkey_unpack_key(b, insert);
 256
 257                 bch2_dump_btree_node(NULL, b);
 258                 bch2_bkey_to_text(&buf1, &k1);
 259                 bch2_bkey_to_text(&buf2, &k2);
 260
 261                 panic("prev > insert:\n"
 262                       "prev    key %s\n"
 263                       "insert  key %s\n",
 264                       buf1.buf, buf2.buf);
 265         }
 266 #endif
 267 #if 0
 268         BUG_ON(next != btree_bkey_last(b, t) &&
 269                bkey_iter_cmp(b, insert, next) > 0);
 270 #else
 271         if (next != btree_bkey_last(b, t) &&
 272             bkey_iter_cmp(b, insert, next) > 0) {
 273                 struct bkey k1 = bkey_unpack_key(b, insert);
 274                 struct bkey k2 = bkey_unpack_key(b, next);
 275
 276                 bch2_dump_btree_node(NULL, b);
 277                 bch2_bkey_to_text(&buf1, &k1);
 278                 bch2_bkey_to_text(&buf2, &k2);
 279
 280                 panic("insert > next:\n"
 281                       "insert  key %s\n"
 282                       "next    key %s\n",
 283                       buf1.buf, buf2.buf);
 284         }
 285 #endif
 286 }
 287
 288 #else
 289
 290 static inline void bch2_btree_node_iter_next_check(struct btree_node_iter *iter,
 291                                                    struct btree *b) {}
 292
 293 #endif
 294
 295 /* Auxiliary search trees */
 296
 297 #define BFLOAT_FAILED_UNPACKED  U8_MAX
 298 #define BFLOAT_FAILED           U8_MAX
 299
 300 struct bkey_float {
 301         u8              exponent;
 302         u8              key_offset;
 303         u16             mantissa;
 304 };
 305 #define BKEY_MANTISSA_BITS      16
 306
 307 static unsigned bkey_float_byte_offset(unsigned idx)
 308 {
 309         return idx * sizeof(struct bkey_float);
 310 }
 311
 312 struct ro_aux_tree {
 313         u8                      nothing[0];
 314         struct bkey_float       f[];
 315 };
 316
 317 struct rw_aux_tree {
 318         u16             offset;
 319         struct bpos     k;
 320 };
 321
 322 static unsigned bset_aux_tree_buf_end(const struct bset_tree *t)
 323 {
 324         BUG_ON(t->aux_data_offset == U16_MAX);
 325
 326         switch (bset_aux_tree_type(t)) {
 327         case BSET_NO_AUX_TREE:
 328                 return t->aux_data_offset;
 329         case BSET_RO_AUX_TREE:
 330                 return t->aux_data_offset +
 331                         DIV_ROUND_UP(t->size * sizeof(struct bkey_float) +
 332                                      t->size * sizeof(u8), 8);
 333         case BSET_RW_AUX_TREE:
 334                 return t->aux_data_offset +
 335                         DIV_ROUND_UP(sizeof(struct rw_aux_tree) * t->size, 8);
 336         default:
 337                 BUG();
 338         }
 339 }
 340
 341 static unsigned bset_aux_tree_buf_start(const struct btree *b,
 342                                         const struct bset_tree *t)
 343 {
 344         return t == b->set
 345                 ? DIV_ROUND_UP(b->unpack_fn_len, 8)
 346                 : bset_aux_tree_buf_end(t - 1);
 347 }
 348
 349 static void *__aux_tree_base(const struct btree *b,
 350                              const struct bset_tree *t)
 351 {
 352         return b->aux_data + t->aux_data_offset * 8;
 353 }
 354
 355 static struct ro_aux_tree *ro_aux_tree_base(const struct btree *b,
 356                                             const struct bset_tree *t)
 357 {
 358         EBUG_ON(bset_aux_tree_type(t) != BSET_RO_AUX_TREE);
 359
 360         return __aux_tree_base(b, t);
 361 }
 362
 363 static u8 *ro_aux_tree_prev(const struct btree *b,
 364                             const struct bset_tree *t)
 365 {
 366         EBUG_ON(bset_aux_tree_type(t) != BSET_RO_AUX_TREE);
 367
 368         return __aux_tree_base(b, t) + bkey_float_byte_offset(t->size);
 369 }
 370
 371 static struct bkey_float *bkey_float(const struct btree *b,
 372                                      const struct bset_tree *t,
 373                                      unsigned idx)
 374 {
 375         return ro_aux_tree_base(b, t)->f + idx;
 376 }
 377
 378 static void bset_aux_tree_verify(struct btree *b)
 379 {
 380 #ifdef CONFIG_BCACHEFS_DEBUG
 381         for_each_bset(b, t) {
 382                 if (t->aux_data_offset == U16_MAX)
 383                         continue;
 384
 385                 BUG_ON(t != b->set &&
 386                        t[-1].aux_data_offset == U16_MAX);
 387
 388                 BUG_ON(t->aux_data_offset < bset_aux_tree_buf_start(b, t));
 389                 BUG_ON(t->aux_data_offset > btree_aux_data_u64s(b));
 390                 BUG_ON(bset_aux_tree_buf_end(t) > btree_aux_data_u64s(b));
 391         }
 392 #endif
 393 }
 394
 395 void bch2_btree_keys_init(struct btree *b)
 396 {
 397         unsigned i;
 398
 399         b->nsets                = 0;
 400         memset(&b->nr, 0, sizeof(b->nr));
 401
 402         for (i = 0; i < MAX_BSETS; i++)
 403                 b->set[i].data_offset = U16_MAX;
 404
 405         bch2_bset_set_no_aux_tree(b, b->set);
 406 }
 407
 408 /* Binary tree stuff for auxiliary search trees */
 409
 410 /*
 411  * Cacheline/offset <-> bkey pointer arithmetic:
 412  *
 413  * t->tree is a binary search tree in an array; each node corresponds to a key
 414  * in one cacheline in t->set (BSET_CACHELINE bytes).
 415  *
 416  * This means we don't have to store the full index of the key that a node in
 417  * the binary tree points to; eytzinger1_to_inorder() gives us the cacheline, and
 418  * then bkey_float->m gives us the offset within that cacheline, in units of 8
 419  * bytes.
 420  *
 421  * cacheline_to_bkey() and friends abstract out all the pointer arithmetic to
 422  * make this work.
 423  *
 424  * To construct the bfloat for an arbitrary key we need to know what the key
 425  * immediately preceding it is: we have to check if the two keys differ in the
 426  * bits we're going to store in bkey_float->mantissa. t->prev[j] stores the size
 427  * of the previous key so we can walk backwards to it from t->tree[j]'s key.
 428  */
 429
 430 static inline void *bset_cacheline(const struct btree *b,
 431                                    const struct bset_tree *t,
 432                                    unsigned cacheline)
 433 {
 434         return (void *) round_down((unsigned long) btree_bkey_first(b, t),
 435                                    L1_CACHE_BYTES) +
 436                 cacheline * BSET_CACHELINE;
 437 }
 438
 439 static struct bkey_packed *cacheline_to_bkey(const struct btree *b,
 440                                              const struct bset_tree *t,
 441                                              unsigned cacheline,
 442                                              unsigned offset)
 443 {
 444         return bset_cacheline(b, t, cacheline) + offset * 8;
 445 }
 446
 447 static unsigned bkey_to_cacheline(const struct btree *b,
 448                                   const struct bset_tree *t,
 449                                   const struct bkey_packed *k)
 450 {
 451         return ((void *) k - bset_cacheline(b, t, 0)) / BSET_CACHELINE;
 452 }
 453
 454 static ssize_t __bkey_to_cacheline_offset(const struct btree *b,
 455                                           const struct bset_tree *t,
 456                                           unsigned cacheline,
 457                                           const struct bkey_packed *k)
 458 {
 459         return (u64 *) k - (u64 *) bset_cacheline(b, t, cacheline);
 460 }
 461
 462 static unsigned bkey_to_cacheline_offset(const struct btree *b,
 463                                          const struct bset_tree *t,
 464                                          unsigned cacheline,
 465                                          const struct bkey_packed *k)
 466 {
 467         size_t m = __bkey_to_cacheline_offset(b, t, cacheline, k);
 468
 469         EBUG_ON(m > U8_MAX);
 470         return m;
 471 }
 472
 473 static inline struct bkey_packed *tree_to_bkey(const struct btree *b,
 474                                                const struct bset_tree *t,
 475                                                unsigned j)
 476 {
 477         return cacheline_to_bkey(b, t,
 478                         __eytzinger1_to_inorder(j, t->size - 1, t->extra),
 479                         bkey_float(b, t, j)->key_offset);
 480 }
 481
 482 static struct bkey_packed *tree_to_prev_bkey(const struct btree *b,
 483                                              const struct bset_tree *t,
 484                                              unsigned j)
 485 {
 486         unsigned prev_u64s = ro_aux_tree_prev(b, t)[j];
 487
 488         return (void *) ((u64 *) tree_to_bkey(b, t, j)->_data - prev_u64s);
 489 }
 490
 491 static struct rw_aux_tree *rw_aux_tree(const struct btree *b,
 492                                        const struct bset_tree *t)
 493 {
 494         EBUG_ON(bset_aux_tree_type(t) != BSET_RW_AUX_TREE);
 495
 496         return __aux_tree_base(b, t);
 497 }
 498
 499 /*
 500  * For the write set - the one we're currently inserting keys into - we don't
 501  * maintain a full search tree, we just keep a simple lookup table in t->prev.
 502  */
 503 static struct bkey_packed *rw_aux_to_bkey(const struct btree *b,
 504                                           struct bset_tree *t,
 505                                           unsigned j)
 506 {
 507         return __btree_node_offset_to_key(b, rw_aux_tree(b, t)[j].offset);
 508 }
 509
 510 static void rw_aux_tree_set(const struct btree *b, struct bset_tree *t,
 511                             unsigned j, struct bkey_packed *k)
 512 {
 513         EBUG_ON(k >= btree_bkey_last(b, t));
 514
 515         rw_aux_tree(b, t)[j] = (struct rw_aux_tree) {
 516                 .offset = __btree_node_key_to_offset(b, k),
 517                 .k      = bkey_unpack_pos(b, k),
 518         };
 519 }
 520
 521 static void bch2_bset_verify_rw_aux_tree(struct btree *b,
 522                                         struct bset_tree *t)
 523 {
 524         struct bkey_packed *k = btree_bkey_first(b, t);
 525         unsigned j = 0;
 526
 527         if (!bch2_expensive_debug_checks)
 528                 return;
 529
 530         BUG_ON(bset_has_ro_aux_tree(t));
 531
 532         if (!bset_has_rw_aux_tree(t))
 533                 return;
 534
 535         BUG_ON(t->size < 1);
 536         BUG_ON(rw_aux_to_bkey(b, t, j) != k);
 537
 538         goto start;
 539         while (1) {
 540                 if (rw_aux_to_bkey(b, t, j) == k) {
 541                         BUG_ON(!bpos_eq(rw_aux_tree(b, t)[j].k,
 542                                         bkey_unpack_pos(b, k)));
 543 start:
 544                         if (++j == t->size)
 545                                 break;
 546
 547                         BUG_ON(rw_aux_tree(b, t)[j].offset <=
 548                                rw_aux_tree(b, t)[j - 1].offset);
 549                 }
 550
 551                 k = bkey_p_next(k);
 552                 BUG_ON(k >= btree_bkey_last(b, t));
 553         }
 554 }
 555
 556 /* returns idx of first entry >= offset: */
 557 static unsigned rw_aux_tree_bsearch(struct btree *b,
 558                                     struct bset_tree *t,
 559                                     unsigned offset)
 560 {
 561         unsigned bset_offs = offset - btree_bkey_first_offset(t);
 562         unsigned bset_u64s = t->end_offset - btree_bkey_first_offset(t);
 563         unsigned idx = bset_u64s ? bset_offs * t->size / bset_u64s : 0;
 564
 565         EBUG_ON(bset_aux_tree_type(t) != BSET_RW_AUX_TREE);
 566         EBUG_ON(!t->size);
 567         EBUG_ON(idx > t->size);
 568
 569         while (idx < t->size &&
 570                rw_aux_tree(b, t)[idx].offset < offset)
 571                 idx++;
 572
 573         while (idx &&
 574                rw_aux_tree(b, t)[idx - 1].offset >= offset)
 575                 idx--;
 576
 577         EBUG_ON(idx < t->size &&
 578                 rw_aux_tree(b, t)[idx].offset < offset);
 579         EBUG_ON(idx && rw_aux_tree(b, t)[idx - 1].offset >= offset);
 580         EBUG_ON(idx + 1 < t->size &&
 581                 rw_aux_tree(b, t)[idx].offset ==
 582                 rw_aux_tree(b, t)[idx + 1].offset);
 583
 584         return idx;
 585 }
 586
 587 static inline unsigned bkey_mantissa(const struct bkey_packed *k,
 588                                      const struct bkey_float *f,
 589                                      unsigned idx)
 590 {
 591         u64 v;
 592
 593         EBUG_ON(!bkey_packed(k));
 594
 595         v = get_unaligned((u64 *) (((u8 *) k->_data) + (f->exponent >> 3)));
 596
 597         /*
 598          * In little endian, we're shifting off low bits (and then the bits we
 599          * want are at the low end), in big endian we're shifting off high bits
 600          * (and then the bits we want are at the high end, so we shift them
 601          * back down):
 602          */
 603 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 604         v >>= f->exponent & 7;
 605 #else
 606         v >>= 64 - (f->exponent & 7) - BKEY_MANTISSA_BITS;
 607 #endif
 608         return (u16) v;
 609 }
 610
 611 static __always_inline void make_bfloat(struct btree *b, struct bset_tree *t,
 612                                         unsigned j,
 613                                         struct bkey_packed *min_key,
 614                                         struct bkey_packed *max_key)
 615 {
 616         struct bkey_float *f = bkey_float(b, t, j);
 617         struct bkey_packed *m = tree_to_bkey(b, t, j);
 618         struct bkey_packed *l = is_power_of_2(j)
 619                 ? min_key
 620                 : tree_to_prev_bkey(b, t, j >> ffs(j));
 621         struct bkey_packed *r = is_power_of_2(j + 1)
 622                 ? max_key
 623                 : tree_to_bkey(b, t, j >> (ffz(j) + 1));
 624         unsigned mantissa;
 625         int shift, exponent, high_bit;
 626
 627         /*
 628          * for failed bfloats, the lookup code falls back to comparing against
 629          * the original key.
 630          */
 631
 632         if (!bkey_packed(l) || !bkey_packed(r) || !bkey_packed(m) ||
 633             !b->nr_key_bits) {
 634                 f->exponent = BFLOAT_FAILED_UNPACKED;
 635                 return;
 636         }
 637
 638         /*
 639          * The greatest differing bit of l and r is the first bit we must
 640          * include in the bfloat mantissa we're creating in order to do
 641          * comparisons - that bit always becomes the high bit of
 642          * bfloat->mantissa, and thus the exponent we're calculating here is
 643          * the position of what will become the low bit in bfloat->mantissa:
 644          *
 645          * Note that this may be negative - we may be running off the low end
 646          * of the key: we handle this later:
 647          */
 648         high_bit = max(bch2_bkey_greatest_differing_bit(b, l, r),
 649                        min_t(unsigned, BKEY_MANTISSA_BITS, b->nr_key_bits) - 1);
 650         exponent = high_bit - (BKEY_MANTISSA_BITS - 1);
 651
 652         /*
 653          * Then we calculate the actual shift value, from the start of the key
 654          * (k->_data), to get the key bits starting at exponent:
 655          */
 656 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 657         shift = (int) (b->format.key_u64s * 64 - b->nr_key_bits) + exponent;
 658
 659         EBUG_ON(shift + BKEY_MANTISSA_BITS > b->format.key_u64s * 64);
 660 #else
 661         shift = high_bit_offset +
 662                 b->nr_key_bits -
 663                 exponent -
 664                 BKEY_MANTISSA_BITS;
 665
 666         EBUG_ON(shift < KEY_PACKED_BITS_START);
 667 #endif
 668         EBUG_ON(shift < 0 || shift >= BFLOAT_FAILED);
 669
 670         f->exponent = shift;
 671         mantissa = bkey_mantissa(m, f, j);
 672
 673         /*
 674          * If we've got garbage bits, set them to all 1s - it's legal for the
 675          * bfloat to compare larger than the original key, but not smaller:
 676          */
 677         if (exponent < 0)
 678                 mantissa |= ~(~0U << -exponent);
 679
 680         f->mantissa = mantissa;
 681 }
 682
 683 /* bytes remaining - only valid for last bset: */
 684 static unsigned __bset_tree_capacity(struct btree *b, const struct bset_tree *t)
 685 {
 686         bset_aux_tree_verify(b);
 687
 688         return btree_aux_data_bytes(b) - t->aux_data_offset * sizeof(u64);
 689 }
 690
 691 static unsigned bset_ro_tree_capacity(struct btree *b, const struct bset_tree *t)
 692 {
 693         return __bset_tree_capacity(b, t) /
 694                 (sizeof(struct bkey_float) + sizeof(u8));
 695 }
 696
 697 static unsigned bset_rw_tree_capacity(struct btree *b, const struct bset_tree *t)
 698 {
 699         return __bset_tree_capacity(b, t) / sizeof(struct rw_aux_tree);
 700 }
 701
 702 static noinline void __build_rw_aux_tree(struct btree *b, struct bset_tree *t)
 703 {
 704         struct bkey_packed *k;
 705
 706         t->size = 1;
 707         t->extra = BSET_RW_AUX_TREE_VAL;
 708         rw_aux_tree(b, t)[0].offset =
 709                 __btree_node_key_to_offset(b, btree_bkey_first(b, t));
 710
 711         bset_tree_for_each_key(b, t, k) {
 712                 if (t->size == bset_rw_tree_capacity(b, t))
 713                         break;
 714
 715                 if ((void *) k - (void *) rw_aux_to_bkey(b, t, t->size - 1) >
 716                     L1_CACHE_BYTES)
 717                         rw_aux_tree_set(b, t, t->size++, k);
 718         }
 719 }
 720
 721 static noinline void __build_ro_aux_tree(struct btree *b, struct bset_tree *t)
 722 {
 723         struct bkey_packed *prev = NULL, *k = btree_bkey_first(b, t);
 724         struct bkey_i min_key, max_key;
 725         unsigned cacheline = 1;
 726
 727         t->size = min(bkey_to_cacheline(b, t, btree_bkey_last(b, t)),
 728                       bset_ro_tree_capacity(b, t));
 729 retry:
 730         if (t->size < 2) {
 731                 t->size = 0;
 732                 t->extra = BSET_NO_AUX_TREE_VAL;
 733                 return;
 734         }
 735
 736         t->extra = (t->size - rounddown_pow_of_two(t->size - 1)) << 1;
 737
 738         /* First we figure out where the first key in each cacheline is */
 739         eytzinger1_for_each(j, t->size - 1) {
 740                 while (bkey_to_cacheline(b, t, k) < cacheline)
 741                         prev = k, k = bkey_p_next(k);
 742
 743                 if (k >= btree_bkey_last(b, t)) {
 744                         /* XXX: this path sucks */
 745                         t->size--;
 746                         goto retry;
 747                 }
 748
 749                 ro_aux_tree_prev(b, t)[j] = prev->u64s;
 750                 bkey_float(b, t, j)->key_offset =
 751                         bkey_to_cacheline_offset(b, t, cacheline++, k);
 752
 753                 EBUG_ON(tree_to_prev_bkey(b, t, j) != prev);
 754                 EBUG_ON(tree_to_bkey(b, t, j) != k);
 755         }
 756
 757         while (k != btree_bkey_last(b, t))
 758                 prev = k, k = bkey_p_next(k);
 759
 760         if (!bkey_pack_pos(bkey_to_packed(&min_key), b->data->min_key, b)) {
 761                 bkey_init(&min_key.k);
 762                 min_key.k.p = b->data->min_key;
 763         }
 764
 765         if (!bkey_pack_pos(bkey_to_packed(&max_key), b->data->max_key, b)) {
 766                 bkey_init(&max_key.k);
 767                 max_key.k.p = b->data->max_key;
 768         }
 769
 770         /* Then we build the tree */
 771         eytzinger1_for_each(j, t->size - 1)
 772                 make_bfloat(b, t, j,
 773                             bkey_to_packed(&min_key),
 774                             bkey_to_packed(&max_key));
 775 }
 776
 777 static void bset_alloc_tree(struct btree *b, struct bset_tree *t)
 778 {
 779         struct bset_tree *i;
 780
 781         for (i = b->set; i != t; i++)
 782                 BUG_ON(bset_has_rw_aux_tree(i));
 783
 784         bch2_bset_set_no_aux_tree(b, t);
 785
 786         /* round up to next cacheline: */
 787         t->aux_data_offset = round_up(bset_aux_tree_buf_start(b, t),
 788                                       SMP_CACHE_BYTES / sizeof(u64));
 789
 790         bset_aux_tree_verify(b);
 791 }
 792
 793 void bch2_bset_build_aux_tree(struct btree *b, struct bset_tree *t,
 794                              bool writeable)
 795 {
 796         if (writeable
 797             ? bset_has_rw_aux_tree(t)
 798             : bset_has_ro_aux_tree(t))
 799                 return;
 800
 801         bset_alloc_tree(b, t);
 802
 803         if (!__bset_tree_capacity(b, t))
 804                 return;
 805
 806         if (writeable)
 807                 __build_rw_aux_tree(b, t);
 808         else
 809                 __build_ro_aux_tree(b, t);
 810
 811         bset_aux_tree_verify(b);
 812 }
 813
 814 void bch2_bset_init_first(struct btree *b, struct bset *i)
 815 {
 816         struct bset_tree *t;
 817
 818         BUG_ON(b->nsets);
 819
 820         memset(i, 0, sizeof(*i));
 821         get_random_bytes(&i->seq, sizeof(i->seq));
 822         SET_BSET_BIG_ENDIAN(i, CPU_BIG_ENDIAN);
 823
 824         t = &b->set[b->nsets++];
 825         set_btree_bset(b, t, i);
 826 }
 827
 828 void bch2_bset_init_next(struct btree *b, struct btree_node_entry *bne)
 829 {
 830         struct bset *i = &bne->keys;
 831         struct bset_tree *t;
 832
 833         BUG_ON(bset_byte_offset(b, bne) >= btree_buf_bytes(b));
 834         BUG_ON((void *) bne < (void *) btree_bkey_last(b, bset_tree_last(b)));
 835         BUG_ON(b->nsets >= MAX_BSETS);
 836
 837         memset(i, 0, sizeof(*i));
 838         i->seq = btree_bset_first(b)->seq;
 839         SET_BSET_BIG_ENDIAN(i, CPU_BIG_ENDIAN);
 840
 841         t = &b->set[b->nsets++];
 842         set_btree_bset(b, t, i);
 843 }
 844
 845 /*
 846  * find _some_ key in the same bset as @k that precedes @k - not necessarily the
 847  * immediate predecessor:
 848  */
 849 static struct bkey_packed *__bkey_prev(struct btree *b, struct bset_tree *t,
 850                                        struct bkey_packed *k)
 851 {
 852         struct bkey_packed *p;
 853         unsigned offset;
 854         int j;
 855
 856         EBUG_ON(k < btree_bkey_first(b, t) ||
 857                 k > btree_bkey_last(b, t));
 858
 859         if (k == btree_bkey_first(b, t))
 860                 return NULL;
 861
 862         switch (bset_aux_tree_type(t)) {
 863         case BSET_NO_AUX_TREE:
 864                 p = btree_bkey_first(b, t);
 865                 break;
 866         case BSET_RO_AUX_TREE:
 867                 j = min_t(unsigned, t->size - 1, bkey_to_cacheline(b, t, k));
 868
 869                 do {
 870                         p = j ? tree_to_bkey(b, t,
 871                                         __inorder_to_eytzinger1(j--,
 872                                                         t->size - 1, t->extra))
 873                               : btree_bkey_first(b, t);
 874                 } while (p >= k);
 875                 break;
 876         case BSET_RW_AUX_TREE:
 877                 offset = __btree_node_key_to_offset(b, k);
 878                 j = rw_aux_tree_bsearch(b, t, offset);
 879                 p = j ? rw_aux_to_bkey(b, t, j - 1)
 880                       : btree_bkey_first(b, t);
 881                 break;
 882         }
 883
 884         return p;
 885 }
 886
 887 struct bkey_packed *bch2_bkey_prev_filter(struct btree *b,
 888                                           struct bset_tree *t,
 889                                           struct bkey_packed *k,
 890                                           unsigned min_key_type)
 891 {
 892         struct bkey_packed *p, *i, *ret = NULL, *orig_k = k;
 893
 894         while ((p = __bkey_prev(b, t, k)) && !ret) {
 895                 for (i = p; i != k; i = bkey_p_next(i))
 896                         if (i->type >= min_key_type)
 897                                 ret = i;
 898
 899                 k = p;
 900         }
 901
 902         if (bch2_expensive_debug_checks) {
 903                 BUG_ON(ret >= orig_k);
 904
 905                 for (i = ret
 906                         ? bkey_p_next(ret)
 907                         : btree_bkey_first(b, t);
 908                      i != orig_k;
 909                      i = bkey_p_next(i))
 910                         BUG_ON(i->type >= min_key_type);
 911         }
 912
 913         return ret;
 914 }
 915
 916 /* Insert */
 917
 918 static void bch2_bset_fix_lookup_table(struct btree *b,
 919                                        struct bset_tree *t,
 920                                        struct bkey_packed *_where,
 921                                        unsigned clobber_u64s,
 922                                        unsigned new_u64s)
 923 {
 924         int shift = new_u64s - clobber_u64s;
 925         unsigned l, j, where = __btree_node_key_to_offset(b, _where);
 926
 927         EBUG_ON(bset_has_ro_aux_tree(t));
 928
 929         if (!bset_has_rw_aux_tree(t))
 930                 return;
 931
 932         /* returns first entry >= where */
 933         l = rw_aux_tree_bsearch(b, t, where);
 934
 935         if (!l) /* never delete first entry */
 936                 l++;
 937         else if (l < t->size &&
 938                  where < t->end_offset &&
 939                  rw_aux_tree(b, t)[l].offset == where)
 940                 rw_aux_tree_set(b, t, l++, _where);
 941
 942         /* l now > where */
 943
 944         for (j = l;
 945              j < t->size &&
 946              rw_aux_tree(b, t)[j].offset < where + clobber_u64s;
 947              j++)
 948                 ;
 949
 950         if (j < t->size &&
 951             rw_aux_tree(b, t)[j].offset + shift ==
 952             rw_aux_tree(b, t)[l - 1].offset)
 953                 j++;
 954
 955         memmove(&rw_aux_tree(b, t)[l],
 956                 &rw_aux_tree(b, t)[j],
 957                 (void *) &rw_aux_tree(b, t)[t->size] -
 958                 (void *) &rw_aux_tree(b, t)[j]);
 959         t->size -= j - l;
 960
 961         for (j = l; j < t->size; j++)
 962                 rw_aux_tree(b, t)[j].offset += shift;
 963
 964         EBUG_ON(l < t->size &&
 965                 rw_aux_tree(b, t)[l].offset ==
 966                 rw_aux_tree(b, t)[l - 1].offset);
 967
 968         if (t->size < bset_rw_tree_capacity(b, t) &&
 969             (l < t->size
 970              ? rw_aux_tree(b, t)[l].offset
 971              : t->end_offset) -
 972             rw_aux_tree(b, t)[l - 1].offset >
 973             L1_CACHE_BYTES / sizeof(u64)) {
 974                 struct bkey_packed *start = rw_aux_to_bkey(b, t, l - 1);
 975                 struct bkey_packed *end = l < t->size
 976                         ? rw_aux_to_bkey(b, t, l)
 977                         : btree_bkey_last(b, t);
 978                 struct bkey_packed *k = start;
 979
 980                 while (1) {
 981                         k = bkey_p_next(k);
 982                         if (k == end)
 983                                 break;
 984
 985                         if ((void *) k - (void *) start >= L1_CACHE_BYTES) {
 986                                 memmove(&rw_aux_tree(b, t)[l + 1],
 987                                         &rw_aux_tree(b, t)[l],
 988                                         (void *) &rw_aux_tree(b, t)[t->size] -
 989                                         (void *) &rw_aux_tree(b, t)[l]);
 990                                 t->size++;
 991                                 rw_aux_tree_set(b, t, l, k);
 992                                 break;
 993                         }
 994                 }
 995         }
 996
 997         bch2_bset_verify_rw_aux_tree(b, t);
 998         bset_aux_tree_verify(b);
 999 }
1000
1001 void bch2_bset_insert(struct btree *b,
1002                       struct btree_node_iter *iter,
1003                       struct bkey_packed *where,
1004                       struct bkey_i *insert,
1005                       unsigned clobber_u64s)
1006 {
1007         struct bkey_format *f = &b->format;
1008         struct bset_tree *t = bset_tree_last(b);
1009         struct bkey_packed packed, *src = bkey_to_packed(insert);
1010
1011         bch2_bset_verify_rw_aux_tree(b, t);
1012         bch2_verify_insert_pos(b, where, bkey_to_packed(insert), clobber_u64s);
1013
1014         if (bch2_bkey_pack_key(&packed, &insert->k, f))
1015                 src = &packed;
1016
1017         if (!bkey_deleted(&insert->k))
1018                 btree_keys_account_key_add(&b->nr, t - b->set, src);
1019
1020         if (src->u64s != clobber_u64s) {
1021                 u64 *src_p = (u64 *) where->_data + clobber_u64s;
1022                 u64 *dst_p = (u64 *) where->_data + src->u64s;
1023
1024                 EBUG_ON((int) le16_to_cpu(bset(b, t)->u64s) <
1025                         (int) clobber_u64s - src->u64s);
1026
1027                 memmove_u64s(dst_p, src_p, btree_bkey_last(b, t)->_data - src_p);
1028                 le16_add_cpu(&bset(b, t)->u64s, src->u64s - clobber_u64s);
1029                 set_btree_bset_end(b, t);
1030         }
1031
1032         memcpy_u64s_small(where, src,
1033                     bkeyp_key_u64s(f, src));
1034         memcpy_u64s(bkeyp_val(f, where), &insert->v,
1035                     bkeyp_val_u64s(f, src));
1036
1037         if (src->u64s != clobber_u64s)
1038                 bch2_bset_fix_lookup_table(b, t, where, clobber_u64s, src->u64s);
1039
1040         bch2_verify_btree_nr_keys(b);
1041 }
1042
1043 void bch2_bset_delete(struct btree *b,
1044                       struct bkey_packed *where,
1045                       unsigned clobber_u64s)
1046 {
1047         struct bset_tree *t = bset_tree_last(b);
1048         u64 *src_p = (u64 *) where->_data + clobber_u64s;
1049         u64 *dst_p = where->_data;
1050
1051         bch2_bset_verify_rw_aux_tree(b, t);
1052
1053         EBUG_ON(le16_to_cpu(bset(b, t)->u64s) < clobber_u64s);
1054
1055         memmove_u64s_down(dst_p, src_p, btree_bkey_last(b, t)->_data - src_p);
1056         le16_add_cpu(&bset(b, t)->u64s, -clobber_u64s);
1057         set_btree_bset_end(b, t);
1058
1059         bch2_bset_fix_lookup_table(b, t, where, clobber_u64s, 0);
1060 }
1061
1062 /* Lookup */
1063
1064 __flatten
1065 static struct bkey_packed *bset_search_write_set(const struct btree *b,
1066                                 struct bset_tree *t,
1067                                 struct bpos *search)
1068 {
1069         unsigned l = 0, r = t->size;
1070
1071         while (l + 1 != r) {
1072                 unsigned m = (l + r) >> 1;
1073
1074                 if (bpos_lt(rw_aux_tree(b, t)[m].k, *search))
1075                         l = m;
1076                 else
1077                         r = m;
1078         }
1079
1080         return rw_aux_to_bkey(b, t, l);
1081 }
1082
1083 static inline void prefetch_four_cachelines(void *p)
1084 {
1085 #ifdef CONFIG_X86_64
1086         asm("prefetcht0 (-127 + 64 * 0)(%0);"
1087             "prefetcht0 (-127 + 64 * 1)(%0);"
1088             "prefetcht0 (-127 + 64 * 2)(%0);"
1089             "prefetcht0 (-127 + 64 * 3)(%0);"
1090             :
1091             : "r" (p + 127));
1092 #else
1093         prefetch(p + L1_CACHE_BYTES * 0);
1094         prefetch(p + L1_CACHE_BYTES * 1);
1095         prefetch(p + L1_CACHE_BYTES * 2);
1096         prefetch(p + L1_CACHE_BYTES * 3);
1097 #endif
1098 }
1099
1100 static inline bool bkey_mantissa_bits_dropped(const struct btree *b,
1101                                               const struct bkey_float *f,
1102                                               unsigned idx)
1103 {
1104 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
1105         unsigned key_bits_start = b->format.key_u64s * 64 - b->nr_key_bits;
1106
1107         return f->exponent > key_bits_start;
1108 #else
1109         unsigned key_bits_end = high_bit_offset + b->nr_key_bits;
1110
1111         return f->exponent + BKEY_MANTISSA_BITS < key_bits_end;
1112 #endif
1113 }
1114
1115 __flatten
1116 static struct bkey_packed *bset_search_tree(const struct btree *b,
1117                                 const struct bset_tree *t,
1118                                 const struct bpos *search,
1119                                 const struct bkey_packed *packed_search)
1120 {
1121         struct ro_aux_tree *base = ro_aux_tree_base(b, t);
1122         struct bkey_float *f;
1123         struct bkey_packed *k;
1124         unsigned inorder, n = 1, l, r;
1125         int cmp;
1126
1127         do {
1128                 if (likely(n << 4 < t->size))
1129                         prefetch(&base->f[n << 4]);
1130
1131                 f = &base->f[n];
1132                 if (unlikely(f->exponent >= BFLOAT_FAILED))
1133                         goto slowpath;
1134
1135                 l = f->mantissa;
1136                 r = bkey_mantissa(packed_search, f, n);
1137
1138                 if (unlikely(l == r) && bkey_mantissa_bits_dropped(b, f, n))
1139                         goto slowpath;
1140
1141                 n = n * 2 + (l < r);
1142                 continue;
1143 slowpath:
1144                 k = tree_to_bkey(b, t, n);
1145                 cmp = bkey_cmp_p_or_unp(b, k, packed_search, search);
1146                 if (!cmp)
1147                         return k;
1148
1149                 n = n * 2 + (cmp < 0);
1150         } while (n < t->size);
1151
1152         inorder = __eytzinger1_to_inorder(n >> 1, t->size - 1, t->extra);
1153
1154         /*
1155          * n would have been the node we recursed to - the low bit tells us if
1156          * we recursed left or recursed right.
1157          */
1158         if (likely(!(n & 1))) {
1159                 --inorder;
1160                 if (unlikely(!inorder))
1161                         return btree_bkey_first(b, t);
1162
1163                 f = &base->f[eytzinger1_prev(n >> 1, t->size - 1)];
1164         }
1165
1166         return cacheline_to_bkey(b, t, inorder, f->key_offset);
1167 }
1168
1169 static __always_inline __flatten
1170 struct bkey_packed *__bch2_bset_search(struct btree *b,
1171                                 struct bset_tree *t,
1172                                 struct bpos *search,
1173                                 const struct bkey_packed *lossy_packed_search)
1174 {
1175
1176         /*
1177          * First, we search for a cacheline, then lastly we do a linear search
1178          * within that cacheline.
1179          *
1180          * To search for the cacheline, there's three different possibilities:
1181          *  * The set is too small to have a search tree, so we just do a linear
1182          *    search over the whole set.
1183          *  * The set is the one we're currently inserting into; keeping a full
1184          *    auxiliary search tree up to date would be too expensive, so we
1185          *    use a much simpler lookup table to do a binary search -
1186          *    bset_search_write_set().
1187          *  * Or we use the auxiliary search tree we constructed earlier -
1188          *    bset_search_tree()
1189          */
1190
1191         switch (bset_aux_tree_type(t)) {
1192         case BSET_NO_AUX_TREE:
1193                 return btree_bkey_first(b, t);
1194         case BSET_RW_AUX_TREE:
1195                 return bset_search_write_set(b, t, search);
1196         case BSET_RO_AUX_TREE:
1197                 return bset_search_tree(b, t, search, lossy_packed_search);
1198         default:
1199                 BUG();
1200         }
1201 }
1202
1203 static __always_inline __flatten
1204 struct bkey_packed *bch2_bset_search_linear(struct btree *b,
1205                                 struct bset_tree *t,
1206                                 struct bpos *search,
1207                                 struct bkey_packed *packed_search,
1208                                 const struct bkey_packed *lossy_packed_search,
1209                                 struct bkey_packed *m)
1210 {
1211         if (lossy_packed_search)
1212                 while (m != btree_bkey_last(b, t) &&
1213                        bkey_iter_cmp_p_or_unp(b, m,
1214                                         lossy_packed_search, search) < 0)
1215                         m = bkey_p_next(m);
1216
1217         if (!packed_search)
1218                 while (m != btree_bkey_last(b, t) &&
1219                        bkey_iter_pos_cmp(b, m, search) < 0)
1220                         m = bkey_p_next(m);
1221
1222         if (bch2_expensive_debug_checks) {
1223                 struct bkey_packed *prev = bch2_bkey_prev_all(b, t, m);
1224
1225                 BUG_ON(prev &&
1226                        bkey_iter_cmp_p_or_unp(b, prev,
1227                                         packed_search, search) >= 0);
1228         }
1229
1230         return m;
1231 }
1232
1233 /* Btree node iterator */
1234
1235 static inline void __bch2_btree_node_iter_push(struct btree_node_iter *iter,
1236                               struct btree *b,
1237                               const struct bkey_packed *k,
1238                               const struct bkey_packed *end)
1239 {
1240         if (k != end) {
1241                 struct btree_node_iter_set *pos;
1242
1243                 btree_node_iter_for_each(iter, pos)
1244                         ;
1245
1246                 BUG_ON(pos >= iter->data + ARRAY_SIZE(iter->data));
1247                 *pos = (struct btree_node_iter_set) {
1248                         __btree_node_key_to_offset(b, k),
1249                         __btree_node_key_to_offset(b, end)
1250                 };
1251         }
1252 }
1253
1254 void bch2_btree_node_iter_push(struct btree_node_iter *iter,
1255                                struct btree *b,
1256                                const struct bkey_packed *k,
1257                                const struct bkey_packed *end)
1258 {
1259         __bch2_btree_node_iter_push(iter, b, k, end);
1260         bch2_btree_node_iter_sort(iter, b);
1261 }
1262
1263 noinline __flatten __cold
1264 static void btree_node_iter_init_pack_failed(struct btree_node_iter *iter,
1265                               struct btree *b, struct bpos *search)
1266 {
1267         struct bkey_packed *k;
1268
1269         trace_bkey_pack_pos_fail(search);
1270
1271         bch2_btree_node_iter_init_from_start(iter, b);
1272
1273         while ((k = bch2_btree_node_iter_peek(iter, b)) &&
1274                bkey_iter_pos_cmp(b, k, search) < 0)
1275                 bch2_btree_node_iter_advance(iter, b);
1276 }
1277
1278 /**
1279  * bch2_btree_node_iter_init - initialize a btree node iterator, starting from a
1280  * given position
1281  *
1282  * @iter:       iterator to initialize
1283  * @b:          btree node to search
1284  * @search:     search key
1285  *
1286  * Main entry point to the lookup code for individual btree nodes:
1287  *
1288  * NOTE:
1289  *
1290  * When you don't filter out deleted keys, btree nodes _do_ contain duplicate
1291  * keys. This doesn't matter for most code, but it does matter for lookups.
1292  *
1293  * Some adjacent keys with a string of equal keys:
1294  *      i j k k k k l m
1295  *
1296  * If you search for k, the lookup code isn't guaranteed to return you any
1297  * specific k. The lookup code is conceptually doing a binary search and
1298  * iterating backwards is very expensive so if the pivot happens to land at the
1299  * last k that's what you'll get.
1300  *
1301  * This works out ok, but it's something to be aware of:
1302  *
1303  *  - For non extents, we guarantee that the live key comes last - see
1304  *    btree_node_iter_cmp(), keys_out_of_order(). So the duplicates you don't
1305  *    see will only be deleted keys you don't care about.
1306  *
1307  *  - For extents, deleted keys sort last (see the comment at the top of this
1308  *    file). But when you're searching for extents, you actually want the first
1309  *    key strictly greater than your search key - an extent that compares equal
1310  *    to the search key is going to have 0 sectors after the search key.
1311  *
1312  *    But this does mean that we can't just search for
1313  *    bpos_successor(start_of_range) to get the first extent that overlaps with
1314  *    the range we want - if we're unlucky and there's an extent that ends
1315  *    exactly where we searched, then there could be a deleted key at the same
1316  *    position and we'd get that when we search instead of the preceding extent
1317  *    we needed.
1318  *
1319  *    So we've got to search for start_of_range, then after the lookup iterate
1320  *    past any extents that compare equal to the position we searched for.
1321  */
1322 __flatten
1323 void bch2_btree_node_iter_init(struct btree_node_iter *iter,
1324                                struct btree *b, struct bpos *search)
1325 {
1326         struct bkey_packed p, *packed_search = NULL;
1327         struct btree_node_iter_set *pos = iter->data;
1328         struct bkey_packed *k[MAX_BSETS];
1329         unsigned i;
1330
1331         EBUG_ON(bpos_lt(*search, b->data->min_key));
1332         EBUG_ON(bpos_gt(*search, b->data->max_key));
1333         bset_aux_tree_verify(b);
1334
1335         memset(iter, 0, sizeof(*iter));
1336
1337         switch (bch2_bkey_pack_pos_lossy(&p, *search, b)) {
1338         case BKEY_PACK_POS_EXACT:
1339                 packed_search = &p;
1340                 break;
1341         case BKEY_PACK_POS_SMALLER:
1342                 packed_search = NULL;
1343                 break;
1344         case BKEY_PACK_POS_FAIL:
1345                 btree_node_iter_init_pack_failed(iter, b, search);
1346                 return;
1347         }
1348
1349         for (i = 0; i < b->nsets; i++) {
1350                 k[i] = __bch2_bset_search(b, b->set + i, search, &p);
1351                 prefetch_four_cachelines(k[i]);
1352         }
1353
1354         for (i = 0; i < b->nsets; i++) {
1355                 struct bset_tree *t = b->set + i;
1356                 struct bkey_packed *end = btree_bkey_last(b, t);
1357
1358                 k[i] = bch2_bset_search_linear(b, t, search,
1359                                                packed_search, &p, k[i]);
1360                 if (k[i] != end)
1361                         *pos++ = (struct btree_node_iter_set) {
1362                                 __btree_node_key_to_offset(b, k[i]),
1363                                 __btree_node_key_to_offset(b, end)
1364                         };
1365         }
1366
1367         bch2_btree_node_iter_sort(iter, b);
1368 }
1369
1370 void bch2_btree_node_iter_init_from_start(struct btree_node_iter *iter,
1371                                           struct btree *b)
1372 {
1373         memset(iter, 0, sizeof(*iter));
1374
1375         for_each_bset(b, t)
1376                 __bch2_btree_node_iter_push(iter, b,
1377                                            btree_bkey_first(b, t),
1378                                            btree_bkey_last(b, t));
1379         bch2_btree_node_iter_sort(iter, b);
1380 }
1381
1382 struct bkey_packed *bch2_btree_node_iter_bset_pos(struct btree_node_iter *iter,
1383                                                   struct btree *b,
1384                                                   struct bset_tree *t)
1385 {
1386         struct btree_node_iter_set *set;
1387
1388         btree_node_iter_for_each(iter, set)
1389                 if (set->end == t->end_offset)
1390                         return __btree_node_offset_to_key(b, set->k);
1391
1392         return btree_bkey_last(b, t);
1393 }
1394
1395 static inline bool btree_node_iter_sort_two(struct btree_node_iter *iter,
1396                                             struct btree *b,
1397                                             unsigned first)
1398 {
1399         bool ret;
1400
1401         if ((ret = (btree_node_iter_cmp(b,
1402                                         iter->data[first],
1403                                         iter->data[first + 1]) > 0)))
1404                 swap(iter->data[first], iter->data[first + 1]);
1405         return ret;
1406 }
1407
1408 void bch2_btree_node_iter_sort(struct btree_node_iter *iter,
1409                                struct btree *b)
1410 {
1411         /* unrolled bubble sort: */
1412
1413         if (!__btree_node_iter_set_end(iter, 2)) {
1414                 btree_node_iter_sort_two(iter, b, 0);
1415                 btree_node_iter_sort_two(iter, b, 1);
1416         }
1417
1418         if (!__btree_node_iter_set_end(iter, 1))
1419                 btree_node_iter_sort_two(iter, b, 0);
1420 }
1421
1422 void bch2_btree_node_iter_set_drop(struct btree_node_iter *iter,
1423                                    struct btree_node_iter_set *set)
1424 {
1425         struct btree_node_iter_set *last =
1426                 iter->data + ARRAY_SIZE(iter->data) - 1;
1427
1428         memmove(&set[0], &set[1], (void *) last - (void *) set);
1429         *last = (struct btree_node_iter_set) { 0, 0 };
1430 }
1431
1432 static inline void __bch2_btree_node_iter_advance(struct btree_node_iter *iter,
1433                                                   struct btree *b)
1434 {
1435         iter->data->k += __bch2_btree_node_iter_peek_all(iter, b)->u64s;
1436
1437         EBUG_ON(iter->data->k > iter->data->end);
1438
1439         if (unlikely(__btree_node_iter_set_end(iter, 0))) {
1440                 /* avoid an expensive memmove call: */
1441                 iter->data[0] = iter->data[1];
1442                 iter->data[1] = iter->data[2];
1443                 iter->data[2] = (struct btree_node_iter_set) { 0, 0 };
1444                 return;
1445         }
1446
1447         if (__btree_node_iter_set_end(iter, 1))
1448                 return;
1449
1450         if (!btree_node_iter_sort_two(iter, b, 0))
1451                 return;
1452
1453         if (__btree_node_iter_set_end(iter, 2))
1454                 return;
1455
1456         btree_node_iter_sort_two(iter, b, 1);
1457 }
1458
1459 void bch2_btree_node_iter_advance(struct btree_node_iter *iter,
1460                                   struct btree *b)
1461 {
1462         if (bch2_expensive_debug_checks) {
1463                 bch2_btree_node_iter_verify(iter, b);
1464                 bch2_btree_node_iter_next_check(iter, b);
1465         }
1466
1467         __bch2_btree_node_iter_advance(iter, b);
1468 }
1469
1470 /*
1471  * Expensive:
1472  */
1473 struct bkey_packed *bch2_btree_node_iter_prev_all(struct btree_node_iter *iter,
1474                                                   struct btree *b)
1475 {
1476         struct bkey_packed *k, *prev = NULL;
1477         struct btree_node_iter_set *set;
1478         unsigned end = 0;
1479
1480         if (bch2_expensive_debug_checks)
1481                 bch2_btree_node_iter_verify(iter, b);
1482
1483         for_each_bset(b, t) {
1484                 k = bch2_bkey_prev_all(b, t,
1485                         bch2_btree_node_iter_bset_pos(iter, b, t));
1486                 if (k &&
1487                     (!prev || bkey_iter_cmp(b, k, prev) > 0)) {
1488                         prev = k;
1489                         end = t->end_offset;
1490                 }
1491         }
1492
1493         if (!prev)
1494                 return NULL;
1495
1496         /*
1497          * We're manually memmoving instead of just calling sort() to ensure the
1498          * prev we picked ends up in slot 0 - sort won't necessarily put it
1499          * there because of duplicate deleted keys:
1500          */
1501         btree_node_iter_for_each(iter, set)
1502                 if (set->end == end)
1503                         goto found;
1504
1505         BUG_ON(set != &iter->data[__btree_node_iter_used(iter)]);
1506 found:
1507         BUG_ON(set >= iter->data + ARRAY_SIZE(iter->data));
1508
1509         memmove(&iter->data[1],
1510                 &iter->data[0],
1511                 (void *) set - (void *) &iter->data[0]);
1512
1513         iter->data[0].k = __btree_node_key_to_offset(b, prev);
1514         iter->data[0].end = end;
1515
1516         if (bch2_expensive_debug_checks)
1517                 bch2_btree_node_iter_verify(iter, b);
1518         return prev;
1519 }
1520
1521 struct bkey_packed *bch2_btree_node_iter_prev(struct btree_node_iter *iter,
1522                                               struct btree *b)
1523 {
1524         struct bkey_packed *prev;
1525
1526         do {
1527                 prev = bch2_btree_node_iter_prev_all(iter, b);
1528         } while (prev && bkey_deleted(prev));
1529
1530         return prev;
1531 }
1532
1533 struct bkey_s_c bch2_btree_node_iter_peek_unpack(struct btree_node_iter *iter,
1534                                                  struct btree *b,
1535                                                  struct bkey *u)
1536 {
1537         struct bkey_packed *k = bch2_btree_node_iter_peek(iter, b);
1538
1539         return k ? bkey_disassemble(b, k, u) : bkey_s_c_null;
1540 }
1541
1542 /* Mergesort */
1543
1544 void bch2_btree_keys_stats(const struct btree *b, struct bset_stats *stats)
1545 {
1546         for_each_bset_c(b, t) {
1547                 enum bset_aux_tree_type type = bset_aux_tree_type(t);
1548                 size_t j;
1549
1550                 stats->sets[type].nr++;
1551                 stats->sets[type].bytes += le16_to_cpu(bset(b, t)->u64s) *
1552                         sizeof(u64);
1553
1554                 if (bset_has_ro_aux_tree(t)) {
1555                         stats->floats += t->size - 1;
1556
1557                         for (j = 1; j < t->size; j++)
1558                                 stats->failed +=
1559                                         bkey_float(b, t, j)->exponent ==
1560                                         BFLOAT_FAILED;
1561                 }
1562         }
1563 }
1564
1565 void bch2_bfloat_to_text(struct printbuf *out, struct btree *b,
1566                          struct bkey_packed *k)
1567 {
1568         struct bset_tree *t = bch2_bkey_to_bset(b, k);
1569         struct bkey uk;
1570         unsigned j, inorder;
1571
1572         if (!bset_has_ro_aux_tree(t))
1573                 return;
1574
1575         inorder = bkey_to_cacheline(b, t, k);
1576         if (!inorder || inorder >= t->size)
1577                 return;
1578
1579         j = __inorder_to_eytzinger1(inorder, t->size - 1, t->extra);
1580         if (k != tree_to_bkey(b, t, j))
1581                 return;
1582
1583         switch (bkey_float(b, t, j)->exponent) {
1584         case BFLOAT_FAILED:
1585                 uk = bkey_unpack_key(b, k);
1586                 prt_printf(out,
1587                        "    failed unpacked at depth %u\n"
1588                        "\t",
1589                        ilog2(j));
1590                 bch2_bpos_to_text(out, uk.p);
1591                 prt_printf(out, "\n");
1592                 break;
1593         }
1594 }