drivers/md/bcache/journal.c

   1 /*
   2  * bcache journalling code, for btree insertions
   3  *
   4  * Copyright 2012 Google, Inc.
   5  */
   6
   7 #include "bcache.h"
   8 #include "btree.h"
   9 #include "debug.h"
  10 #include "request.h"
  11
  12 #include <trace/events/bcache.h>
  13
  14 /*
  15  * Journal replay/recovery:
  16  *
  17  * This code is all driven from run_cache_set(); we first read the journal
  18  * entries, do some other stuff, then we mark all the keys in the journal
  19  * entries (same as garbage collection would), then we replay them - reinserting
  20  * them into the cache in precisely the same order as they appear in the
  21  * journal.
  22  *
  23  * We only journal keys that go in leaf nodes, which simplifies things quite a
  24  * bit.
  25  */
  26
  27 static void journal_read_endio(struct bio *bio, int error)
  28 {
  29         struct closure *cl = bio->bi_private;
  30         closure_put(cl);
  31 }
  32
  33 static int journal_read_bucket(struct cache *ca, struct list_head *list,
  34                                struct btree_op *op, unsigned bucket_index)
  35 {
  36         struct journal_device *ja = &ca->journal;
  37         struct bio *bio = &ja->bio;
  38
  39         struct journal_replay *i;
  40         struct jset *j, *data = ca->set->journal.w[0].data;
  41         unsigned len, left, offset = 0;
  42         int ret = 0;
  43         sector_t bucket = bucket_to_sector(ca->set, ca->sb.d[bucket_index]);
  44
  45         pr_debug("reading %llu", (uint64_t) bucket);
  46
  47         while (offset < ca->sb.bucket_size) {
  48 reread:         left = ca->sb.bucket_size - offset;
  49                 len = min_t(unsigned, left, PAGE_SECTORS * 8);
  50
  51                 bio_reset(bio);
  52                 bio->bi_sector  = bucket + offset;
  53                 bio->bi_bdev    = ca->bdev;
  54                 bio->bi_rw      = READ;
  55                 bio->bi_size    = len << 9;
  56
  57                 bio->bi_end_io  = journal_read_endio;
  58                 bio->bi_private = &op->cl;
  59                 bch_bio_map(bio, data);
  60
  61                 closure_bio_submit(bio, &op->cl, ca);
  62                 closure_sync(&op->cl);
  63
  64                 /* This function could be simpler now since we no longer write
  65                  * journal entries that overlap bucket boundaries; this means
  66                  * the start of a bucket will always have a valid journal entry
  67                  * if it has any journal entries at all.
  68                  */
  69
  70                 j = data;
  71                 while (len) {
  72                         struct list_head *where;
  73                         size_t blocks, bytes = set_bytes(j);
  74
  75                         if (j->magic != jset_magic(ca->set))
  76                                 return ret;
  77
  78                         if (bytes > left << 9)
  79                                 return ret;
  80
  81                         if (bytes > len << 9)
  82                                 goto reread;
  83
  84                         if (j->csum != csum_set(j))
  85                                 return ret;
  86
  87                         blocks = set_blocks(j, ca->set);
  88
  89                         while (!list_empty(list)) {
  90                                 i = list_first_entry(list,
  91                                         struct journal_replay, list);
  92                                 if (i->j.seq >= j->last_seq)
  93                                         break;
  94                                 list_del(&i->list);
  95                                 kfree(i);
  96                         }
  97
  98                         list_for_each_entry_reverse(i, list, list) {
  99                                 if (j->seq == i->j.seq)
 100                                         goto next_set;
 101
 102                                 if (j->seq < i->j.last_seq)
 103                                         goto next_set;
 104
 105                                 if (j->seq > i->j.seq) {
 106                                         where = &i->list;
 107                                         goto add;
 108                                 }
 109                         }
 110
 111                         where = list;
 112 add:
 113                         i = kmalloc(offsetof(struct journal_replay, j) +
 114                                     bytes, GFP_KERNEL);
 115                         if (!i)
 116                                 return -ENOMEM;
 117                         memcpy(&i->j, j, bytes);
 118                         list_add(&i->list, where);
 119                         ret = 1;
 120
 121                         ja->seq[bucket_index] = j->seq;
 122 next_set:
 123                         offset  += blocks * ca->sb.block_size;
 124                         len     -= blocks * ca->sb.block_size;
 125                         j = ((void *) j) + blocks * block_bytes(ca);
 126                 }
 127         }
 128
 129         return ret;
 130 }
 131
 132 int bch_journal_read(struct cache_set *c, struct list_head *list,
 133                         struct btree_op *op)
 134 {
 135 #define read_bucket(b)                                                  \
 136         ({                                                              \
 137                 int ret = journal_read_bucket(ca, list, op, b);         \
 138                 __set_bit(b, bitmap);                                   \
 139                 if (ret < 0)                                            \
 140                         return ret;                                     \
 141                 ret;                                                    \
 142         })
 143
 144         struct cache *ca;
 145         unsigned iter;
 146
 147         for_each_cache(ca, c, iter) {
 148                 struct journal_device *ja = &ca->journal;
 149                 unsigned long bitmap[SB_JOURNAL_BUCKETS / BITS_PER_LONG];
 150                 unsigned i, l, r, m;
 151                 uint64_t seq;
 152
 153                 bitmap_zero(bitmap, SB_JOURNAL_BUCKETS);
 154                 pr_debug("%u journal buckets", ca->sb.njournal_buckets);
 155
 156                 /*
 157                  * Read journal buckets ordered by golden ratio hash to quickly
 158                  * find a sequence of buckets with valid journal entries
 159                  */
 160                 for (i = 0; i < ca->sb.njournal_buckets; i++) {
 161                         l = (i * 2654435769U) % ca->sb.njournal_buckets;
 162
 163                         if (test_bit(l, bitmap))
 164                                 break;
 165
 166                         if (read_bucket(l))
 167                                 goto bsearch;
 168                 }
 169
 170                 /*
 171                  * If that fails, check all the buckets we haven't checked
 172                  * already
 173                  */
 174                 pr_debug("falling back to linear search");
 175
 176                 for (l = find_first_zero_bit(bitmap, ca->sb.njournal_buckets);
 177                      l < ca->sb.njournal_buckets;
 178                      l = find_next_zero_bit(bitmap, ca->sb.njournal_buckets, l + 1))
 179                         if (read_bucket(l))
 180                                 goto bsearch;
 181
 182                 if (list_empty(list))
 183                         continue;
 184 bsearch:
 185                 /* Binary search */
 186                 m = r = find_next_bit(bitmap, ca->sb.njournal_buckets, l + 1);
 187                 pr_debug("starting binary search, l %u r %u", l, r);
 188
 189                 while (l + 1 < r) {
 190                         seq = list_entry(list->prev, struct journal_replay,
 191                                          list)->j.seq;
 192
 193                         m = (l + r) >> 1;
 194                         read_bucket(m);
 195
 196                         if (seq != list_entry(list->prev, struct journal_replay,
 197                                               list)->j.seq)
 198                                 l = m;
 199                         else
 200                                 r = m;
 201                 }
 202
 203                 /*
 204                  * Read buckets in reverse order until we stop finding more
 205                  * journal entries
 206                  */
 207                 pr_debug("finishing up: m %u njournal_buckets %u",
 208                          m, ca->sb.njournal_buckets);
 209                 l = m;
 210
 211                 while (1) {
 212                         if (!l--)
 213                                 l = ca->sb.njournal_buckets - 1;
 214
 215                         if (l == m)
 216                                 break;
 217
 218                         if (test_bit(l, bitmap))
 219                                 continue;
 220
 221                         if (!read_bucket(l))
 222                                 break;
 223                 }
 224
 225                 seq = 0;
 226
 227                 for (i = 0; i < ca->sb.njournal_buckets; i++)
 228                         if (ja->seq[i] > seq) {
 229                                 seq = ja->seq[i];
 230                                 ja->cur_idx = ja->discard_idx =
 231                                         ja->last_idx = i;
 232
 233                         }
 234         }
 235
 236         if (!list_empty(list))
 237                 c->journal.seq = list_entry(list->prev,
 238                                             struct journal_replay,
 239                                             list)->j.seq;
 240
 241         return 0;
 242 #undef read_bucket
 243 }
 244
 245 void bch_journal_mark(struct cache_set *c, struct list_head *list)
 246 {
 247         atomic_t p = { 0 };
 248         struct bkey *k;
 249         struct journal_replay *i;
 250         struct journal *j = &c->journal;
 251         uint64_t last = j->seq;
 252
 253         /*
 254          * journal.pin should never fill up - we never write a journal
 255          * entry when it would fill up. But if for some reason it does, we
 256          * iterate over the list in reverse order so that we can just skip that
 257          * refcount instead of bugging.
 258          */
 259
 260         list_for_each_entry_reverse(i, list, list) {
 261                 BUG_ON(last < i->j.seq);
 262                 i->pin = NULL;
 263
 264                 while (last-- != i->j.seq)
 265                         if (fifo_free(&j->pin) > 1) {
 266                                 fifo_push_front(&j->pin, p);
 267                                 atomic_set(&fifo_front(&j->pin), 0);
 268                         }
 269
 270                 if (fifo_free(&j->pin) > 1) {
 271                         fifo_push_front(&j->pin, p);
 272                         i->pin = &fifo_front(&j->pin);
 273                         atomic_set(i->pin, 1);
 274                 }
 275
 276                 for (k = i->j.start;
 277                      k < end(&i->j);
 278                      k = bkey_next(k)) {
 279                         unsigned j;
 280
 281                         for (j = 0; j < KEY_PTRS(k); j++) {
 282                                 struct bucket *g = PTR_BUCKET(c, k, j);
 283                                 atomic_inc(&g->pin);
 284
 285                                 if (g->prio == BTREE_PRIO &&
 286                                     !ptr_stale(c, k, j))
 287                                         g->prio = INITIAL_PRIO;
 288                         }
 289
 290                         __bch_btree_mark_key(c, 0, k);
 291                 }
 292         }
 293 }
 294
 295 int bch_journal_replay(struct cache_set *s, struct list_head *list,
 296                           struct btree_op *op)
 297 {
 298         int ret = 0, keys = 0, entries = 0;
 299         struct bkey *k;
 300         struct journal_replay *i =
 301                 list_entry(list->prev, struct journal_replay, list);
 302
 303         uint64_t start = i->j.last_seq, end = i->j.seq, n = start;
 304         struct keylist keylist;
 305
 306         bch_keylist_init(&keylist);
 307
 308         list_for_each_entry(i, list, list) {
 309                 BUG_ON(i->pin && atomic_read(i->pin) != 1);
 310
 311                 cache_set_err_on(n != i->j.seq, s,
 312 "bcache: journal entries %llu-%llu missing! (replaying %llu-%llu)",
 313                                  n, i->j.seq - 1, start, end);
 314
 315                 for (k = i->j.start;
 316                      k < end(&i->j);
 317                      k = bkey_next(k)) {
 318                         trace_bcache_journal_replay_key(k);
 319
 320                         bkey_copy(keylist.top, k);
 321                         bch_keylist_push(&keylist);
 322
 323                         op->journal = i->pin;
 324
 325                         ret = bch_btree_insert(op, s, &keylist);
 326                         if (ret)
 327                                 goto err;
 328
 329                         BUG_ON(!bch_keylist_empty(&keylist));
 330                         keys++;
 331
 332                         cond_resched();
 333                 }
 334
 335                 if (i->pin)
 336                         atomic_dec(i->pin);
 337                 n = i->j.seq + 1;
 338                 entries++;
 339         }
 340
 341         pr_info("journal replay done, %i keys in %i entries, seq %llu",
 342                 keys, entries, end);
 343
 344         while (!list_empty(list)) {
 345                 i = list_first_entry(list, struct journal_replay, list);
 346                 list_del(&i->list);
 347                 kfree(i);
 348         }
 349 err:
 350         closure_sync(&op->cl);
 351         return ret;
 352 }
 353
 354 /* Journalling */
 355
 356 static void btree_flush_write(struct cache_set *c)
 357 {
 358         /*
 359          * Try to find the btree node with that references the oldest journal
 360          * entry, best is our current candidate and is locked if non NULL:
 361          */
 362         struct btree *b, *best;
 363         unsigned i;
 364 retry:
 365         best = NULL;
 366
 367         for_each_cached_btree(b, c, i)
 368                 if (btree_current_write(b)->journal) {
 369                         if (!best)
 370                                 best = b;
 371                         else if (journal_pin_cmp(c,
 372                                                  btree_current_write(best),
 373                                                  btree_current_write(b))) {
 374                                 best = b;
 375                         }
 376                 }
 377
 378         b = best;
 379         if (b) {
 380                 rw_lock(true, b, b->level);
 381
 382                 if (!btree_current_write(b)->journal) {
 383                         rw_unlock(true, b);
 384                         /* We raced */
 385                         goto retry;
 386                 }
 387
 388                 bch_btree_node_write(b, NULL);
 389                 rw_unlock(true, b);
 390         }
 391 }
 392
 393 #define last_seq(j)     ((j)->seq - fifo_used(&(j)->pin) + 1)
 394
 395 static void journal_discard_endio(struct bio *bio, int error)
 396 {
 397         struct journal_device *ja =
 398                 container_of(bio, struct journal_device, discard_bio);
 399         struct cache *ca = container_of(ja, struct cache, journal);
 400
 401         atomic_set(&ja->discard_in_flight, DISCARD_DONE);
 402
 403         closure_wake_up(&ca->set->journal.wait);
 404         closure_put(&ca->set->cl);
 405 }
 406
 407 static void journal_discard_work(struct work_struct *work)
 408 {
 409         struct journal_device *ja =
 410                 container_of(work, struct journal_device, discard_work);
 411
 412         submit_bio(0, &ja->discard_bio);
 413 }
 414
 415 static void do_journal_discard(struct cache *ca)
 416 {
 417         struct journal_device *ja = &ca->journal;
 418         struct bio *bio = &ja->discard_bio;
 419
 420         if (!ca->discard) {
 421                 ja->discard_idx = ja->last_idx;
 422                 return;
 423         }
 424
 425         switch (atomic_read(&ja->discard_in_flight)) {
 426         case DISCARD_IN_FLIGHT:
 427                 return;
 428
 429         case DISCARD_DONE:
 430                 ja->discard_idx = (ja->discard_idx + 1) %
 431                         ca->sb.njournal_buckets;
 432
 433                 atomic_set(&ja->discard_in_flight, DISCARD_READY);
 434                 /* fallthrough */
 435
 436         case DISCARD_READY:
 437                 if (ja->discard_idx == ja->last_idx)
 438                         return;
 439
 440                 atomic_set(&ja->discard_in_flight, DISCARD_IN_FLIGHT);
 441
 442                 bio_init(bio);
 443                 bio->bi_sector          = bucket_to_sector(ca->set,
 444                                                 ca->sb.d[ja->discard_idx]);
 445                 bio->bi_bdev            = ca->bdev;
 446                 bio->bi_rw              = REQ_WRITE|REQ_DISCARD;
 447                 bio->bi_max_vecs        = 1;
 448                 bio->bi_io_vec          = bio->bi_inline_vecs;
 449                 bio->bi_size            = bucket_bytes(ca);
 450                 bio->bi_end_io          = journal_discard_endio;
 451
 452                 closure_get(&ca->set->cl);
 453                 INIT_WORK(&ja->discard_work, journal_discard_work);
 454                 schedule_work(&ja->discard_work);
 455         }
 456 }
 457
 458 static void journal_reclaim(struct cache_set *c)
 459 {
 460         struct bkey *k = &c->journal.key;
 461         struct cache *ca;
 462         uint64_t last_seq;
 463         unsigned iter, n = 0;
 464         atomic_t p;
 465
 466         while (!atomic_read(&fifo_front(&c->journal.pin)))
 467                 fifo_pop(&c->journal.pin, p);
 468
 469         last_seq = last_seq(&c->journal);
 470
 471         /* Update last_idx */
 472
 473         for_each_cache(ca, c, iter) {
 474                 struct journal_device *ja = &ca->journal;
 475
 476                 while (ja->last_idx != ja->cur_idx &&
 477                        ja->seq[ja->last_idx] < last_seq)
 478                         ja->last_idx = (ja->last_idx + 1) %
 479                                 ca->sb.njournal_buckets;
 480         }
 481
 482         for_each_cache(ca, c, iter)
 483                 do_journal_discard(ca);
 484
 485         if (c->journal.blocks_free)
 486                 goto out;
 487
 488         /*
 489          * Allocate:
 490          * XXX: Sort by free journal space
 491          */
 492
 493         for_each_cache(ca, c, iter) {
 494                 struct journal_device *ja = &ca->journal;
 495                 unsigned next = (ja->cur_idx + 1) % ca->sb.njournal_buckets;
 496
 497                 /* No space available on this device */
 498                 if (next == ja->discard_idx)
 499                         continue;
 500
 501                 ja->cur_idx = next;
 502                 k->ptr[n++] = PTR(0,
 503                                   bucket_to_sector(c, ca->sb.d[ja->cur_idx]),
 504                                   ca->sb.nr_this_dev);
 505         }
 506
 507         bkey_init(k);
 508         SET_KEY_PTRS(k, n);
 509
 510         if (n)
 511                 c->journal.blocks_free = c->sb.bucket_size >> c->block_bits;
 512 out:
 513         if (!journal_full(&c->journal))
 514                 __closure_wake_up(&c->journal.wait);
 515 }
 516
 517 void bch_journal_next(struct journal *j)
 518 {
 519         atomic_t p = { 1 };
 520
 521         j->cur = (j->cur == j->w)
 522                 ? &j->w[1]
 523                 : &j->w[0];
 524
 525         /*
 526          * The fifo_push() needs to happen at the same time as j->seq is
 527          * incremented for last_seq() to be calculated correctly
 528          */
 529         BUG_ON(!fifo_push(&j->pin, p));
 530         atomic_set(&fifo_back(&j->pin), 1);
 531
 532         j->cur->data->seq       = ++j->seq;
 533         j->cur->need_write      = false;
 534         j->cur->data->keys      = 0;
 535
 536         if (fifo_full(&j->pin))
 537                 pr_debug("journal_pin full (%zu)", fifo_used(&j->pin));
 538 }
 539
 540 static void journal_write_endio(struct bio *bio, int error)
 541 {
 542         struct journal_write *w = bio->bi_private;
 543
 544         cache_set_err_on(error, w->c, "journal io error");
 545         closure_put(&w->c->journal.io);
 546 }
 547
 548 static void journal_write(struct closure *);
 549
 550 static void journal_write_done(struct closure *cl)
 551 {
 552         struct journal *j = container_of(cl, struct journal, io);
 553         struct journal_write *w = (j->cur == j->w)
 554                 ? &j->w[1]
 555                 : &j->w[0];
 556
 557         __closure_wake_up(&w->wait);
 558         continue_at_nobarrier(cl, journal_write, system_wq);
 559 }
 560
 561 static void journal_write_unlocked(struct closure *cl)
 562         __releases(c->journal.lock)
 563 {
 564         struct cache_set *c = container_of(cl, struct cache_set, journal.io);
 565         struct cache *ca;
 566         struct journal_write *w = c->journal.cur;
 567         struct bkey *k = &c->journal.key;
 568         unsigned i, sectors = set_blocks(w->data, c) * c->sb.block_size;
 569
 570         struct bio *bio;
 571         struct bio_list list;
 572         bio_list_init(&list);
 573
 574         if (!w->need_write) {
 575                 /*
 576                  * XXX: have to unlock closure before we unlock journal lock,
 577                  * else we race with bch_journal(). But this way we race
 578                  * against cache set unregister. Doh.
 579                  */
 580                 set_closure_fn(cl, NULL, NULL);
 581                 closure_sub(cl, CLOSURE_RUNNING + 1);
 582                 spin_unlock(&c->journal.lock);
 583                 return;
 584         } else if (journal_full(&c->journal)) {
 585                 journal_reclaim(c);
 586                 spin_unlock(&c->journal.lock);
 587
 588                 btree_flush_write(c);
 589                 continue_at(cl, journal_write, system_wq);
 590         }
 591
 592         c->journal.blocks_free -= set_blocks(w->data, c);
 593
 594         w->data->btree_level = c->root->level;
 595
 596         bkey_copy(&w->data->btree_root, &c->root->key);
 597         bkey_copy(&w->data->uuid_bucket, &c->uuid_bucket);
 598
 599         for_each_cache(ca, c, i)
 600                 w->data->prio_bucket[ca->sb.nr_this_dev] = ca->prio_buckets[0];
 601
 602         w->data->magic          = jset_magic(c);
 603         w->data->version        = BCACHE_JSET_VERSION;
 604         w->data->last_seq       = last_seq(&c->journal);
 605         w->data->csum           = csum_set(w->data);
 606
 607         for (i = 0; i < KEY_PTRS(k); i++) {
 608                 ca = PTR_CACHE(c, k, i);
 609                 bio = &ca->journal.bio;
 610
 611                 atomic_long_add(sectors, &ca->meta_sectors_written);
 612
 613                 bio_reset(bio);
 614                 bio->bi_sector  = PTR_OFFSET(k, i);
 615                 bio->bi_bdev    = ca->bdev;
 616                 bio->bi_rw      = REQ_WRITE|REQ_SYNC|REQ_META|REQ_FLUSH|REQ_FUA;
 617                 bio->bi_size    = sectors << 9;
 618
 619                 bio->bi_end_io  = journal_write_endio;
 620                 bio->bi_private = w;
 621                 bch_bio_map(bio, w->data);
 622
 623                 trace_bcache_journal_write(bio);
 624                 bio_list_add(&list, bio);
 625
 626                 SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + sectors);
 627
 628                 ca->journal.seq[ca->journal.cur_idx] = w->data->seq;
 629         }
 630
 631         atomic_dec_bug(&fifo_back(&c->journal.pin));
 632         bch_journal_next(&c->journal);
 633         journal_reclaim(c);
 634
 635         spin_unlock(&c->journal.lock);
 636
 637         while ((bio = bio_list_pop(&list)))
 638                 closure_bio_submit(bio, cl, c->cache[0]);
 639
 640         continue_at(cl, journal_write_done, NULL);
 641 }
 642
 643 static void journal_write(struct closure *cl)
 644 {
 645         struct cache_set *c = container_of(cl, struct cache_set, journal.io);
 646
 647         spin_lock(&c->journal.lock);
 648         journal_write_unlocked(cl);
 649 }
 650
 651 static void journal_try_write(struct cache_set *c)
 652         __releases(c->journal.lock)
 653 {
 654         struct closure *cl = &c->journal.io;
 655         struct journal_write *w = c->journal.cur;
 656
 657         w->need_write = true;
 658
 659         if (closure_trylock(cl, &c->cl))
 660                 journal_write_unlocked(cl);
 661         else
 662                 spin_unlock(&c->journal.lock);
 663 }
 664
 665 static struct journal_write *journal_wait_for_write(struct cache_set *c,
 666                                                     unsigned nkeys)
 667 {
 668         size_t sectors;
 669         struct closure cl;
 670
 671         closure_init_stack(&cl);
 672
 673         spin_lock(&c->journal.lock);
 674
 675         while (1) {
 676                 struct journal_write *w = c->journal.cur;
 677
 678                 sectors = __set_blocks(w->data, w->data->keys + nkeys,
 679                                        c) * c->sb.block_size;
 680
 681                 if (sectors <= min_t(size_t,
 682                                      c->journal.blocks_free * c->sb.block_size,
 683                                      PAGE_SECTORS << JSET_BITS))
 684                         return w;
 685
 686                 /* XXX: tracepoint */
 687                 if (!journal_full(&c->journal)) {
 688                         trace_bcache_journal_entry_full(c);
 689
 690                         /*
 691                          * XXX: If we were inserting so many keys that they
 692                          * won't fit in an _empty_ journal write, we'll
 693                          * deadlock. For now, handle this in
 694                          * bch_keylist_realloc() - but something to think about.
 695                          */
 696                         BUG_ON(!w->data->keys);
 697
 698                         closure_wait(&w->wait, &cl);
 699                         journal_try_write(c); /* unlocks */
 700                 } else {
 701                         trace_bcache_journal_full(c);
 702
 703                         closure_wait(&c->journal.wait, &cl);
 704                         journal_reclaim(c);
 705                         spin_unlock(&c->journal.lock);
 706
 707                         btree_flush_write(c);
 708                 }
 709
 710                 closure_sync(&cl);
 711                 spin_lock(&c->journal.lock);
 712         }
 713 }
 714
 715 static void journal_write_work(struct work_struct *work)
 716 {
 717         struct cache_set *c = container_of(to_delayed_work(work),
 718                                            struct cache_set,
 719                                            journal.work);
 720         spin_lock(&c->journal.lock);
 721         journal_try_write(c);
 722 }
 723
 724 /*
 725  * Entry point to the journalling code - bio_insert() and btree_invalidate()
 726  * pass bch_journal() a list of keys to be journalled, and then
 727  * bch_journal() hands those same keys off to btree_insert_async()
 728  */
 729
 730 atomic_t *bch_journal(struct cache_set *c,
 731                       struct keylist *keys,
 732                       struct closure *parent)
 733 {
 734         struct journal_write *w;
 735         atomic_t *ret;
 736
 737         if (!CACHE_SYNC(&c->sb))
 738                 return NULL;
 739
 740         w = journal_wait_for_write(c, bch_keylist_nkeys(keys));
 741
 742         memcpy(end(w->data), keys->keys, bch_keylist_bytes(keys));
 743         w->data->keys += bch_keylist_nkeys(keys);
 744
 745         ret = &fifo_back(&c->journal.pin);
 746         atomic_inc(ret);
 747
 748         if (parent) {
 749                 closure_wait(&w->wait, parent);
 750                 journal_try_write(c);
 751         } else if (!w->need_write) {
 752                 schedule_delayed_work(&c->journal.work,
 753                                       msecs_to_jiffies(c->journal_delay_ms));
 754                 spin_unlock(&c->journal.lock);
 755         } else {
 756                 spin_unlock(&c->journal.lock);
 757         }
 758
 759
 760         return ret;
 761 }
 762
 763 void bch_journal_meta(struct cache_set *c, struct closure *cl)
 764 {
 765         struct keylist keys;
 766         atomic_t *ref;
 767
 768         bch_keylist_init(&keys);
 769
 770         ref = bch_journal(c, &keys, cl);
 771         if (ref)
 772                 atomic_dec_bug(ref);
 773 }
 774
 775 void bch_journal_free(struct cache_set *c)
 776 {
 777         free_pages((unsigned long) c->journal.w[1].data, JSET_BITS);
 778         free_pages((unsigned long) c->journal.w[0].data, JSET_BITS);
 779         free_fifo(&c->journal.pin);
 780 }
 781
 782 int bch_journal_alloc(struct cache_set *c)
 783 {
 784         struct journal *j = &c->journal;
 785
 786         closure_init_unlocked(&j->io);
 787         spin_lock_init(&j->lock);
 788         INIT_DELAYED_WORK(&j->work, journal_write_work);
 789
 790         c->journal_delay_ms = 100;
 791
 792         j->w[0].c = c;
 793         j->w[1].c = c;
 794
 795         if (!(init_fifo(&j->pin, JOURNAL_PIN, GFP_KERNEL)) ||
 796             !(j->w[0].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)) ||
 797             !(j->w[1].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)))
 798                 return -ENOMEM;
 799
 800         return 0;
 801 }