drivers/md/bcache/writeback.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * background writeback - scan btree for dirty data and write it to the backing
   4  * device
   5  *
   6  * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
   7  * Copyright 2012 Google, Inc.
   8  */
   9
  10 #include "bcache.h"
  11 #include "btree.h"
  12 #include "debug.h"
  13 #include "writeback.h"
  14
  15 #include <linux/delay.h>
  16 #include <linux/kthread.h>
  17 #include <linux/sched/clock.h>
  18 #include <trace/events/bcache.h>
  19
  20 static void update_gc_after_writeback(struct cache_set *c)
  21 {
  22         if (c->gc_after_writeback != (BCH_ENABLE_AUTO_GC) ||
  23             c->gc_stats.in_use < BCH_AUTO_GC_DIRTY_THRESHOLD)
  24                 return;
  25
  26         c->gc_after_writeback |= BCH_DO_AUTO_GC;
  27 }
  28
  29 /* Rate limiting */
  30 static uint64_t __calc_target_rate(struct cached_dev *dc)
  31 {
  32         struct cache_set *c = dc->disk.c;
  33
  34         /*
  35          * This is the size of the cache, minus the amount used for
  36          * flash-only devices
  37          */
  38         uint64_t cache_sectors = c->nbuckets * c->cache->sb.bucket_size -
  39                                 atomic_long_read(&c->flash_dev_dirty_sectors);
  40
  41         /*
  42          * Unfortunately there is no control of global dirty data.  If the
  43          * user states that they want 10% dirty data in the cache, and has,
  44          * e.g., 5 backing volumes of equal size, we try and ensure each
  45          * backing volume uses about 2% of the cache for dirty data.
  46          */
  47         uint32_t bdev_share =
  48                 div64_u64(bdev_sectors(dc->bdev) << WRITEBACK_SHARE_SHIFT,
  49                                 c->cached_dev_sectors);
  50
  51         uint64_t cache_dirty_target =
  52                 div_u64(cache_sectors * dc->writeback_percent, 100);
  53
  54         /* Ensure each backing dev gets at least one dirty share */
  55         if (bdev_share < 1)
  56                 bdev_share = 1;
  57
  58         return (cache_dirty_target * bdev_share) >> WRITEBACK_SHARE_SHIFT;
  59 }
  60
  61 static void __update_writeback_rate(struct cached_dev *dc)
  62 {
  63         /*
  64          * PI controller:
  65          * Figures out the amount that should be written per second.
  66          *
  67          * First, the error (number of sectors that are dirty beyond our
  68          * target) is calculated.  The error is accumulated (numerically
  69          * integrated).
  70          *
  71          * Then, the proportional value and integral value are scaled
  72          * based on configured values.  These are stored as inverses to
  73          * avoid fixed point math and to make configuration easy-- e.g.
  74          * the default value of 40 for writeback_rate_p_term_inverse
  75          * attempts to write at a rate that would retire all the dirty
  76          * blocks in 40 seconds.
  77          *
  78          * The writeback_rate_i_inverse value of 10000 means that 1/10000th
  79          * of the error is accumulated in the integral term per second.
  80          * This acts as a slow, long-term average that is not subject to
  81          * variations in usage like the p term.
  82          */
  83         int64_t target = __calc_target_rate(dc);
  84         int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);
  85         int64_t error = dirty - target;
  86         int64_t proportional_scaled =
  87                 div_s64(error, dc->writeback_rate_p_term_inverse);
  88         int64_t integral_scaled;
  89         uint32_t new_rate;
  90
  91         if ((error < 0 && dc->writeback_rate_integral > 0) ||
  92             (error > 0 && time_before64(local_clock(),
  93                          dc->writeback_rate.next + NSEC_PER_MSEC))) {
  94                 /*
  95                  * Only decrease the integral term if it's more than
  96                  * zero.  Only increase the integral term if the device
  97                  * is keeping up.  (Don't wind up the integral
  98                  * ineffectively in either case).
  99                  *
 100                  * It's necessary to scale this by
 101                  * writeback_rate_update_seconds to keep the integral
 102                  * term dimensioned properly.
 103                  */
 104                 dc->writeback_rate_integral += error *
 105                         dc->writeback_rate_update_seconds;
 106         }
 107
 108         integral_scaled = div_s64(dc->writeback_rate_integral,
 109                         dc->writeback_rate_i_term_inverse);
 110
 111         new_rate = clamp_t(int32_t, (proportional_scaled + integral_scaled),
 112                         dc->writeback_rate_minimum, NSEC_PER_SEC);
 113
 114         dc->writeback_rate_proportional = proportional_scaled;
 115         dc->writeback_rate_integral_scaled = integral_scaled;
 116         dc->writeback_rate_change = new_rate -
 117                         atomic_long_read(&dc->writeback_rate.rate);
 118         atomic_long_set(&dc->writeback_rate.rate, new_rate);
 119         dc->writeback_rate_target = target;
 120 }
 121
 122 static bool set_at_max_writeback_rate(struct cache_set *c,
 123                                        struct cached_dev *dc)
 124 {
 125         /* Don't sst max writeback rate if it is disabled */
 126         if (!c->idle_max_writeback_rate_enabled)
 127                 return false;
 128
 129         /* Don't set max writeback rate if gc is running */
 130         if (!c->gc_mark_valid)
 131                 return false;
 132         /*
 133          * Idle_counter is increased everytime when update_writeback_rate() is
 134          * called. If all backing devices attached to the same cache set have
 135          * identical dc->writeback_rate_update_seconds values, it is about 6
 136          * rounds of update_writeback_rate() on each backing device before
 137          * c->at_max_writeback_rate is set to 1, and then max wrteback rate set
 138          * to each dc->writeback_rate.rate.
 139          * In order to avoid extra locking cost for counting exact dirty cached
 140          * devices number, c->attached_dev_nr is used to calculate the idle
 141          * throushold. It might be bigger if not all cached device are in write-
 142          * back mode, but it still works well with limited extra rounds of
 143          * update_writeback_rate().
 144          */
 145         if (atomic_inc_return(&c->idle_counter) <
 146             atomic_read(&c->attached_dev_nr) * 6)
 147                 return false;
 148
 149         if (atomic_read(&c->at_max_writeback_rate) != 1)
 150                 atomic_set(&c->at_max_writeback_rate, 1);
 151
 152         atomic_long_set(&dc->writeback_rate.rate, INT_MAX);
 153
 154         /* keep writeback_rate_target as existing value */
 155         dc->writeback_rate_proportional = 0;
 156         dc->writeback_rate_integral_scaled = 0;
 157         dc->writeback_rate_change = 0;
 158
 159         /*
 160          * Check c->idle_counter and c->at_max_writeback_rate agagain in case
 161          * new I/O arrives during before set_at_max_writeback_rate() returns.
 162          * Then the writeback rate is set to 1, and its new value should be
 163          * decided via __update_writeback_rate().
 164          */
 165         if ((atomic_read(&c->idle_counter) <
 166              atomic_read(&c->attached_dev_nr) * 6) ||
 167             !atomic_read(&c->at_max_writeback_rate))
 168                 return false;
 169
 170         return true;
 171 }
 172
 173 static void update_writeback_rate(struct work_struct *work)
 174 {
 175         struct cached_dev *dc = container_of(to_delayed_work(work),
 176                                              struct cached_dev,
 177                                              writeback_rate_update);
 178         struct cache_set *c = dc->disk.c;
 179
 180         /*
 181          * should check BCACHE_DEV_RATE_DW_RUNNING before calling
 182          * cancel_delayed_work_sync().
 183          */
 184         set_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 185         /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 186         smp_mb__after_atomic();
 187
 188         /*
 189          * CACHE_SET_IO_DISABLE might be set via sysfs interface,
 190          * check it here too.
 191          */
 192         if (!test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) ||
 193             test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 194                 clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 195                 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 196                 smp_mb__after_atomic();
 197                 return;
 198         }
 199
 200         if (atomic_read(&dc->has_dirty) && dc->writeback_percent) {
 201                 /*
 202                  * If the whole cache set is idle, set_at_max_writeback_rate()
 203                  * will set writeback rate to a max number. Then it is
 204                  * unncessary to update writeback rate for an idle cache set
 205                  * in maximum writeback rate number(s).
 206                  */
 207                 if (!set_at_max_writeback_rate(c, dc)) {
 208                         down_read(&dc->writeback_lock);
 209                         __update_writeback_rate(dc);
 210                         update_gc_after_writeback(c);
 211                         up_read(&dc->writeback_lock);
 212                 }
 213         }
 214
 215
 216         /*
 217          * CACHE_SET_IO_DISABLE might be set via sysfs interface,
 218          * check it here too.
 219          */
 220         if (test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) &&
 221             !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 222                 schedule_delayed_work(&dc->writeback_rate_update,
 223                               dc->writeback_rate_update_seconds * HZ);
 224         }
 225
 226         /*
 227          * should check BCACHE_DEV_RATE_DW_RUNNING before calling
 228          * cancel_delayed_work_sync().
 229          */
 230         clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 231         /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 232         smp_mb__after_atomic();
 233 }
 234
 235 static unsigned int writeback_delay(struct cached_dev *dc,
 236                                     unsigned int sectors)
 237 {
 238         if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
 239             !dc->writeback_percent)
 240                 return 0;
 241
 242         return bch_next_delay(&dc->writeback_rate, sectors);
 243 }
 244
 245 struct dirty_io {
 246         struct closure          cl;
 247         struct cached_dev       *dc;
 248         uint16_t                sequence;
 249         struct bio              bio;
 250 };
 251
 252 static void dirty_init(struct keybuf_key *w)
 253 {
 254         struct dirty_io *io = w->private;
 255         struct bio *bio = &io->bio;
 256
 257         bio_init(bio, bio->bi_inline_vecs,
 258                  DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS));
 259         if (!io->dc->writeback_percent)
 260                 bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
 261
 262         bio->bi_iter.bi_size    = KEY_SIZE(&w->key) << 9;
 263         bio->bi_private         = w;
 264         bch_bio_map(bio, NULL);
 265 }
 266
 267 static void dirty_io_destructor(struct closure *cl)
 268 {
 269         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 270
 271         kfree(io);
 272 }
 273
 274 static void write_dirty_finish(struct closure *cl)
 275 {
 276         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 277         struct keybuf_key *w = io->bio.bi_private;
 278         struct cached_dev *dc = io->dc;
 279
 280         bio_free_pages(&io->bio);
 281
 282         /* This is kind of a dumb way of signalling errors. */
 283         if (KEY_DIRTY(&w->key)) {
 284                 int ret;
 285                 unsigned int i;
 286                 struct keylist keys;
 287
 288                 bch_keylist_init(&keys);
 289
 290                 bkey_copy(keys.top, &w->key);
 291                 SET_KEY_DIRTY(keys.top, false);
 292                 bch_keylist_push(&keys);
 293
 294                 for (i = 0; i < KEY_PTRS(&w->key); i++)
 295                         atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
 296
 297                 ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);
 298
 299                 if (ret)
 300                         trace_bcache_writeback_collision(&w->key);
 301
 302                 atomic_long_inc(ret
 303                                 ? &dc->disk.c->writeback_keys_failed
 304                                 : &dc->disk.c->writeback_keys_done);
 305         }
 306
 307         bch_keybuf_del(&dc->writeback_keys, w);
 308         up(&dc->in_flight);
 309
 310         closure_return_with_destructor(cl, dirty_io_destructor);
 311 }
 312
 313 static void dirty_endio(struct bio *bio)
 314 {
 315         struct keybuf_key *w = bio->bi_private;
 316         struct dirty_io *io = w->private;
 317
 318         if (bio->bi_status) {
 319                 SET_KEY_DIRTY(&w->key, false);
 320                 bch_count_backing_io_errors(io->dc, bio);
 321         }
 322
 323         closure_put(&io->cl);
 324 }
 325
 326 static void write_dirty(struct closure *cl)
 327 {
 328         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 329         struct keybuf_key *w = io->bio.bi_private;
 330         struct cached_dev *dc = io->dc;
 331
 332         uint16_t next_sequence;
 333
 334         if (atomic_read(&dc->writeback_sequence_next) != io->sequence) {
 335                 /* Not our turn to write; wait for a write to complete */
 336                 closure_wait(&dc->writeback_ordering_wait, cl);
 337
 338                 if (atomic_read(&dc->writeback_sequence_next) == io->sequence) {
 339                         /*
 340                          * Edge case-- it happened in indeterminate order
 341                          * relative to when we were added to wait list..
 342                          */
 343                         closure_wake_up(&dc->writeback_ordering_wait);
 344                 }
 345
 346                 continue_at(cl, write_dirty, io->dc->writeback_write_wq);
 347                 return;
 348         }
 349
 350         next_sequence = io->sequence + 1;
 351
 352         /*
 353          * IO errors are signalled using the dirty bit on the key.
 354          * If we failed to read, we should not attempt to write to the
 355          * backing device.  Instead, immediately go to write_dirty_finish
 356          * to clean up.
 357          */
 358         if (KEY_DIRTY(&w->key)) {
 359                 dirty_init(w);
 360                 bio_set_op_attrs(&io->bio, REQ_OP_WRITE, 0);
 361                 io->bio.bi_iter.bi_sector = KEY_START(&w->key);
 362                 bio_set_dev(&io->bio, io->dc->bdev);
 363                 io->bio.bi_end_io       = dirty_endio;
 364
 365                 /* I/O request sent to backing device */
 366                 closure_bio_submit(io->dc->disk.c, &io->bio, cl);
 367         }
 368
 369         atomic_set(&dc->writeback_sequence_next, next_sequence);
 370         closure_wake_up(&dc->writeback_ordering_wait);
 371
 372         continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq);
 373 }
 374
 375 static void read_dirty_endio(struct bio *bio)
 376 {
 377         struct keybuf_key *w = bio->bi_private;
 378         struct dirty_io *io = w->private;
 379
 380         /* is_read = 1 */
 381         bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0),
 382                             bio->bi_status, 1,
 383                             "reading dirty data from cache");
 384
 385         dirty_endio(bio);
 386 }
 387
 388 static void read_dirty_submit(struct closure *cl)
 389 {
 390         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 391
 392         closure_bio_submit(io->dc->disk.c, &io->bio, cl);
 393
 394         continue_at(cl, write_dirty, io->dc->writeback_write_wq);
 395 }
 396
 397 static void read_dirty(struct cached_dev *dc)
 398 {
 399         unsigned int delay = 0;
 400         struct keybuf_key *next, *keys[MAX_WRITEBACKS_IN_PASS], *w;
 401         size_t size;
 402         int nk, i;
 403         struct dirty_io *io;
 404         struct closure cl;
 405         uint16_t sequence = 0;
 406
 407         BUG_ON(!llist_empty(&dc->writeback_ordering_wait.list));
 408         atomic_set(&dc->writeback_sequence_next, sequence);
 409         closure_init_stack(&cl);
 410
 411         /*
 412          * XXX: if we error, background writeback just spins. Should use some
 413          * mempools.
 414          */
 415
 416         next = bch_keybuf_next(&dc->writeback_keys);
 417
 418         while (!kthread_should_stop() &&
 419                !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
 420                next) {
 421                 size = 0;
 422                 nk = 0;
 423
 424                 do {
 425                         BUG_ON(ptr_stale(dc->disk.c, &next->key, 0));
 426
 427                         /*
 428                          * Don't combine too many operations, even if they
 429                          * are all small.
 430                          */
 431                         if (nk >= MAX_WRITEBACKS_IN_PASS)
 432                                 break;
 433
 434                         /*
 435                          * If the current operation is very large, don't
 436                          * further combine operations.
 437                          */
 438                         if (size >= MAX_WRITESIZE_IN_PASS)
 439                                 break;
 440
 441                         /*
 442                          * Operations are only eligible to be combined
 443                          * if they are contiguous.
 444                          *
 445                          * TODO: add a heuristic willing to fire a
 446                          * certain amount of non-contiguous IO per pass,
 447                          * so that we can benefit from backing device
 448                          * command queueing.
 449                          */
 450                         if ((nk != 0) && bkey_cmp(&keys[nk-1]->key,
 451                                                 &START_KEY(&next->key)))
 452                                 break;
 453
 454                         size += KEY_SIZE(&next->key);
 455                         keys[nk++] = next;
 456                 } while ((next = bch_keybuf_next(&dc->writeback_keys)));
 457
 458                 /* Now we have gathered a set of 1..5 keys to write back. */
 459                 for (i = 0; i < nk; i++) {
 460                         w = keys[i];
 461
 462                         io = kzalloc(struct_size(io, bio.bi_inline_vecs,
 463                                                 DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS)),
 464                                      GFP_KERNEL);
 465                         if (!io)
 466                                 goto err;
 467
 468                         w->private      = io;
 469                         io->dc          = dc;
 470                         io->sequence    = sequence++;
 471
 472                         dirty_init(w);
 473                         bio_set_op_attrs(&io->bio, REQ_OP_READ, 0);
 474                         io->bio.bi_iter.bi_sector = PTR_OFFSET(&w->key, 0);
 475                         bio_set_dev(&io->bio,
 476                                     PTR_CACHE(dc->disk.c, &w->key, 0)->bdev);
 477                         io->bio.bi_end_io       = read_dirty_endio;
 478
 479                         if (bch_bio_alloc_pages(&io->bio, GFP_KERNEL))
 480                                 goto err_free;
 481
 482                         trace_bcache_writeback(&w->key);
 483
 484                         down(&dc->in_flight);
 485
 486                         /*
 487                          * We've acquired a semaphore for the maximum
 488                          * simultaneous number of writebacks; from here
 489                          * everything happens asynchronously.
 490                          */
 491                         closure_call(&io->cl, read_dirty_submit, NULL, &cl);
 492                 }
 493
 494                 delay = writeback_delay(dc, size);
 495
 496                 while (!kthread_should_stop() &&
 497                        !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
 498                        delay) {
 499                         schedule_timeout_interruptible(delay);
 500                         delay = writeback_delay(dc, 0);
 501                 }
 502         }
 503
 504         if (0) {
 505 err_free:
 506                 kfree(w->private);
 507 err:
 508                 bch_keybuf_del(&dc->writeback_keys, w);
 509         }
 510
 511         /*
 512          * Wait for outstanding writeback IOs to finish (and keybuf slots to be
 513          * freed) before refilling again
 514          */
 515         closure_sync(&cl);
 516 }
 517
 518 /* Scan for dirty data */
 519
 520 void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode,
 521                                   uint64_t offset, int nr_sectors)
 522 {
 523         struct bcache_device *d = c->devices[inode];
 524         unsigned int stripe_offset, sectors_dirty;
 525         int stripe;
 526
 527         if (!d)
 528                 return;
 529
 530         stripe = offset_to_stripe(d, offset);
 531         if (stripe < 0)
 532                 return;
 533
 534         if (UUID_FLASH_ONLY(&c->uuids[inode]))
 535                 atomic_long_add(nr_sectors, &c->flash_dev_dirty_sectors);
 536
 537         stripe_offset = offset & (d->stripe_size - 1);
 538
 539         while (nr_sectors) {
 540                 int s = min_t(unsigned int, abs(nr_sectors),
 541                               d->stripe_size - stripe_offset);
 542
 543                 if (nr_sectors < 0)
 544                         s = -s;
 545
 546                 if (stripe >= d->nr_stripes)
 547                         return;
 548
 549                 sectors_dirty = atomic_add_return(s,
 550                                         d->stripe_sectors_dirty + stripe);
 551                 if (sectors_dirty == d->stripe_size)
 552                         set_bit(stripe, d->full_dirty_stripes);
 553                 else
 554                         clear_bit(stripe, d->full_dirty_stripes);
 555
 556                 nr_sectors -= s;
 557                 stripe_offset = 0;
 558                 stripe++;
 559         }
 560 }
 561
 562 static bool dirty_pred(struct keybuf *buf, struct bkey *k)
 563 {
 564         struct cached_dev *dc = container_of(buf,
 565                                              struct cached_dev,
 566                                              writeback_keys);
 567
 568         BUG_ON(KEY_INODE(k) != dc->disk.id);
 569
 570         return KEY_DIRTY(k);
 571 }
 572
 573 static void refill_full_stripes(struct cached_dev *dc)
 574 {
 575         struct keybuf *buf = &dc->writeback_keys;
 576         unsigned int start_stripe, next_stripe;
 577         int stripe;
 578         bool wrapped = false;
 579
 580         stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));
 581         if (stripe < 0)
 582                 stripe = 0;
 583
 584         start_stripe = stripe;
 585
 586         while (1) {
 587                 stripe = find_next_bit(dc->disk.full_dirty_stripes,
 588                                        dc->disk.nr_stripes, stripe);
 589
 590                 if (stripe == dc->disk.nr_stripes)
 591                         goto next;
 592
 593                 next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes,
 594                                                  dc->disk.nr_stripes, stripe);
 595
 596                 buf->last_scanned = KEY(dc->disk.id,
 597                                         stripe * dc->disk.stripe_size, 0);
 598
 599                 bch_refill_keybuf(dc->disk.c, buf,
 600                                   &KEY(dc->disk.id,
 601                                        next_stripe * dc->disk.stripe_size, 0),
 602                                   dirty_pred);
 603
 604                 if (array_freelist_empty(&buf->freelist))
 605                         return;
 606
 607                 stripe = next_stripe;
 608 next:
 609                 if (wrapped && stripe > start_stripe)
 610                         return;
 611
 612                 if (stripe == dc->disk.nr_stripes) {
 613                         stripe = 0;
 614                         wrapped = true;
 615                 }
 616         }
 617 }
 618
 619 /*
 620  * Returns true if we scanned the entire disk
 621  */
 622 static bool refill_dirty(struct cached_dev *dc)
 623 {
 624         struct keybuf *buf = &dc->writeback_keys;
 625         struct bkey start = KEY(dc->disk.id, 0, 0);
 626         struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
 627         struct bkey start_pos;
 628
 629         /*
 630          * make sure keybuf pos is inside the range for this disk - at bringup
 631          * we might not be attached yet so this disk's inode nr isn't
 632          * initialized then
 633          */
 634         if (bkey_cmp(&buf->last_scanned, &start) < 0 ||
 635             bkey_cmp(&buf->last_scanned, &end) > 0)
 636                 buf->last_scanned = start;
 637
 638         if (dc->partial_stripes_expensive) {
 639                 refill_full_stripes(dc);
 640                 if (array_freelist_empty(&buf->freelist))
 641                         return false;
 642         }
 643
 644         start_pos = buf->last_scanned;
 645         bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
 646
 647         if (bkey_cmp(&buf->last_scanned, &end) < 0)
 648                 return false;
 649
 650         /*
 651          * If we get to the end start scanning again from the beginning, and
 652          * only scan up to where we initially started scanning from:
 653          */
 654         buf->last_scanned = start;
 655         bch_refill_keybuf(dc->disk.c, buf, &start_pos, dirty_pred);
 656
 657         return bkey_cmp(&buf->last_scanned, &start_pos) >= 0;
 658 }
 659
 660 static int bch_writeback_thread(void *arg)
 661 {
 662         struct cached_dev *dc = arg;
 663         struct cache_set *c = dc->disk.c;
 664         bool searched_full_index;
 665
 666         bch_ratelimit_reset(&dc->writeback_rate);
 667
 668         while (!kthread_should_stop() &&
 669                !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 670                 down_write(&dc->writeback_lock);
 671                 set_current_state(TASK_INTERRUPTIBLE);
 672                 /*
 673                  * If the bache device is detaching, skip here and continue
 674                  * to perform writeback. Otherwise, if no dirty data on cache,
 675                  * or there is dirty data on cache but writeback is disabled,
 676                  * the writeback thread should sleep here and wait for others
 677                  * to wake up it.
 678                  */
 679                 if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
 680                     (!atomic_read(&dc->has_dirty) || !dc->writeback_running)) {
 681                         up_write(&dc->writeback_lock);
 682
 683                         if (kthread_should_stop() ||
 684                             test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 685                                 set_current_state(TASK_RUNNING);
 686                                 break;
 687                         }
 688
 689                         schedule();
 690                         continue;
 691                 }
 692                 set_current_state(TASK_RUNNING);
 693
 694                 searched_full_index = refill_dirty(dc);
 695
 696                 if (searched_full_index &&
 697                     RB_EMPTY_ROOT(&dc->writeback_keys.keys)) {
 698                         atomic_set(&dc->has_dirty, 0);
 699                         SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
 700                         bch_write_bdev_super(dc, NULL);
 701                         /*
 702                          * If bcache device is detaching via sysfs interface,
 703                          * writeback thread should stop after there is no dirty
 704                          * data on cache. BCACHE_DEV_DETACHING flag is set in
 705                          * bch_cached_dev_detach().
 706                          */
 707                         if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
 708                                 struct closure cl;
 709
 710                                 closure_init_stack(&cl);
 711                                 memset(&dc->sb.set_uuid, 0, 16);
 712                                 SET_BDEV_STATE(&dc->sb, BDEV_STATE_NONE);
 713
 714                                 bch_write_bdev_super(dc, &cl);
 715                                 closure_sync(&cl);
 716
 717                                 up_write(&dc->writeback_lock);
 718                                 break;
 719                         }
 720
 721                         /*
 722                          * When dirty data rate is high (e.g. 50%+), there might
 723                          * be heavy buckets fragmentation after writeback
 724                          * finished, which hurts following write performance.
 725                          * If users really care about write performance they
 726                          * may set BCH_ENABLE_AUTO_GC via sysfs, then when
 727                          * BCH_DO_AUTO_GC is set, garbage collection thread
 728                          * will be wake up here. After moving gc, the shrunk
 729                          * btree and discarded free buckets SSD space may be
 730                          * helpful for following write requests.
 731                          */
 732                         if (c->gc_after_writeback ==
 733                             (BCH_ENABLE_AUTO_GC|BCH_DO_AUTO_GC)) {
 734                                 c->gc_after_writeback &= ~BCH_DO_AUTO_GC;
 735                                 force_wake_up_gc(c);
 736                         }
 737                 }
 738
 739                 up_write(&dc->writeback_lock);
 740
 741                 read_dirty(dc);
 742
 743                 if (searched_full_index) {
 744                         unsigned int delay = dc->writeback_delay * HZ;
 745
 746                         while (delay &&
 747                                !kthread_should_stop() &&
 748                                !test_bit(CACHE_SET_IO_DISABLE, &c->flags) &&
 749                                !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
 750                                 delay = schedule_timeout_interruptible(delay);
 751
 752                         bch_ratelimit_reset(&dc->writeback_rate);
 753                 }
 754         }
 755
 756         if (dc->writeback_write_wq) {
 757                 flush_workqueue(dc->writeback_write_wq);
 758                 destroy_workqueue(dc->writeback_write_wq);
 759         }
 760         cached_dev_put(dc);
 761         wait_for_kthread_stop();
 762
 763         return 0;
 764 }
 765
 766 /* Init */
 767 #define INIT_KEYS_EACH_TIME     500000
 768 #define INIT_KEYS_SLEEP_MS      100
 769
 770 struct sectors_dirty_init {
 771         struct btree_op op;
 772         unsigned int    inode;
 773         size_t          count;
 774         struct bkey     start;
 775 };
 776
 777 static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
 778                                  struct bkey *k)
 779 {
 780         struct sectors_dirty_init *op = container_of(_op,
 781                                                 struct sectors_dirty_init, op);
 782         if (KEY_INODE(k) > op->inode)
 783                 return MAP_DONE;
 784
 785         if (KEY_DIRTY(k))
 786                 bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
 787                                              KEY_START(k), KEY_SIZE(k));
 788
 789         op->count++;
 790         if (atomic_read(&b->c->search_inflight) &&
 791             !(op->count % INIT_KEYS_EACH_TIME)) {
 792                 bkey_copy_key(&op->start, k);
 793                 return -EAGAIN;
 794         }
 795
 796         return MAP_CONTINUE;
 797 }
 798
 799 static int bch_root_node_dirty_init(struct cache_set *c,
 800                                      struct bcache_device *d,
 801                                      struct bkey *k)
 802 {
 803         struct sectors_dirty_init op;
 804         int ret;
 805
 806         bch_btree_op_init(&op.op, -1);
 807         op.inode = d->id;
 808         op.count = 0;
 809         op.start = KEY(op.inode, 0, 0);
 810
 811         do {
 812                 ret = bcache_btree(map_keys_recurse,
 813                                    k,
 814                                    c->root,
 815                                    &op.op,
 816                                    &op.start,
 817                                    sectors_dirty_init_fn,
 818                                    0);
 819                 if (ret == -EAGAIN)
 820                         schedule_timeout_interruptible(
 821                                 msecs_to_jiffies(INIT_KEYS_SLEEP_MS));
 822                 else if (ret < 0) {
 823                         pr_warn("sectors dirty init failed, ret=%d!\n", ret);
 824                         break;
 825                 }
 826         } while (ret == -EAGAIN);
 827
 828         return ret;
 829 }
 830
 831 static int bch_dirty_init_thread(void *arg)
 832 {
 833         struct dirty_init_thrd_info *info = arg;
 834         struct bch_dirty_init_state *state = info->state;
 835         struct cache_set *c = state->c;
 836         struct btree_iter iter;
 837         struct bkey *k, *p;
 838         int cur_idx, prev_idx, skip_nr;
 839
 840         k = p = NULL;
 841         cur_idx = prev_idx = 0;
 842
 843         bch_btree_iter_init(&c->root->keys, &iter, NULL);
 844         k = bch_btree_iter_next_filter(&iter, &c->root->keys, bch_ptr_bad);
 845         BUG_ON(!k);
 846
 847         p = k;
 848
 849         while (k) {
 850                 spin_lock(&state->idx_lock);
 851                 cur_idx = state->key_idx;
 852                 state->key_idx++;
 853                 spin_unlock(&state->idx_lock);
 854
 855                 skip_nr = cur_idx - prev_idx;
 856
 857                 while (skip_nr) {
 858                         k = bch_btree_iter_next_filter(&iter,
 859                                                        &c->root->keys,
 860                                                        bch_ptr_bad);
 861                         if (k)
 862                                 p = k;
 863                         else {
 864                                 atomic_set(&state->enough, 1);
 865                                 /* Update state->enough earlier */
 866                                 smp_mb__after_atomic();
 867                                 goto out;
 868                         }
 869                         skip_nr--;
 870                         cond_resched();
 871                 }
 872
 873                 if (p) {
 874                         if (bch_root_node_dirty_init(c, state->d, p) < 0)
 875                                 goto out;
 876                 }
 877
 878                 p = NULL;
 879                 prev_idx = cur_idx;
 880                 cond_resched();
 881         }
 882
 883 out:
 884         /* In order to wake up state->wait in time */
 885         smp_mb__before_atomic();
 886         if (atomic_dec_and_test(&state->started))
 887                 wake_up(&state->wait);
 888
 889         return 0;
 890 }
 891
 892 static int bch_btre_dirty_init_thread_nr(void)
 893 {
 894         int n = num_online_cpus()/2;
 895
 896         if (n == 0)
 897                 n = 1;
 898         else if (n > BCH_DIRTY_INIT_THRD_MAX)
 899                 n = BCH_DIRTY_INIT_THRD_MAX;
 900
 901         return n;
 902 }
 903
 904 void bch_sectors_dirty_init(struct bcache_device *d)
 905 {
 906         int i;
 907         struct bkey *k = NULL;
 908         struct btree_iter iter;
 909         struct sectors_dirty_init op;
 910         struct cache_set *c = d->c;
 911         struct bch_dirty_init_state *state;
 912         char name[32];
 913
 914         /* Just count root keys if no leaf node */
 915         if (c->root->level == 0) {
 916                 bch_btree_op_init(&op.op, -1);
 917                 op.inode = d->id;
 918                 op.count = 0;
 919                 op.start = KEY(op.inode, 0, 0);
 920
 921                 for_each_key_filter(&c->root->keys,
 922                                     k, &iter, bch_ptr_invalid)
 923                         sectors_dirty_init_fn(&op.op, c->root, k);
 924                 return;
 925         }
 926
 927         state = kzalloc(sizeof(struct bch_dirty_init_state), GFP_KERNEL);
 928         if (!state) {
 929                 pr_warn("sectors dirty init failed: cannot allocate memory\n");
 930                 return;
 931         }
 932
 933         state->c = c;
 934         state->d = d;
 935         state->total_threads = bch_btre_dirty_init_thread_nr();
 936         state->key_idx = 0;
 937         spin_lock_init(&state->idx_lock);
 938         atomic_set(&state->started, 0);
 939         atomic_set(&state->enough, 0);
 940         init_waitqueue_head(&state->wait);
 941
 942         for (i = 0; i < state->total_threads; i++) {
 943                 /* Fetch latest state->enough earlier */
 944                 smp_mb__before_atomic();
 945                 if (atomic_read(&state->enough))
 946                         break;
 947
 948                 state->infos[i].state = state;
 949                 atomic_inc(&state->started);
 950                 snprintf(name, sizeof(name), "bch_dirty_init[%d]", i);
 951
 952                 state->infos[i].thread =
 953                         kthread_run(bch_dirty_init_thread,
 954                                     &state->infos[i],
 955                                     name);
 956                 if (IS_ERR(state->infos[i].thread)) {
 957                         pr_err("fails to run thread bch_dirty_init[%d]\n", i);
 958                         for (--i; i >= 0; i--)
 959                                 kthread_stop(state->infos[i].thread);
 960                         goto out;
 961                 }
 962         }
 963
 964         wait_event_interruptible(state->wait,
 965                  atomic_read(&state->started) == 0 ||
 966                  test_bit(CACHE_SET_IO_DISABLE, &c->flags));
 967
 968 out:
 969         kfree(state);
 970 }
 971
 972 void bch_cached_dev_writeback_init(struct cached_dev *dc)
 973 {
 974         sema_init(&dc->in_flight, 64);
 975         init_rwsem(&dc->writeback_lock);
 976         bch_keybuf_init(&dc->writeback_keys);
 977
 978         dc->writeback_metadata          = true;
 979         dc->writeback_running           = false;
 980         dc->writeback_percent           = 10;
 981         dc->writeback_delay             = 30;
 982         atomic_long_set(&dc->writeback_rate.rate, 1024);
 983         dc->writeback_rate_minimum      = 8;
 984
 985         dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT;
 986         dc->writeback_rate_p_term_inverse = 40;
 987         dc->writeback_rate_i_term_inverse = 10000;
 988
 989         WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
 990         INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
 991 }
 992
 993 int bch_cached_dev_writeback_start(struct cached_dev *dc)
 994 {
 995         dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq",
 996                                                 WQ_MEM_RECLAIM, 0);
 997         if (!dc->writeback_write_wq)
 998                 return -ENOMEM;
 999
1000         cached_dev_get(dc);
1001         dc->writeback_thread = kthread_create(bch_writeback_thread, dc,
1002                                               "bcache_writeback");
1003         if (IS_ERR(dc->writeback_thread)) {
1004                 cached_dev_put(dc);
1005                 destroy_workqueue(dc->writeback_write_wq);
1006                 return PTR_ERR(dc->writeback_thread);
1007         }
1008         dc->writeback_running = true;
1009
1010         WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
1011         schedule_delayed_work(&dc->writeback_rate_update,
1012                               dc->writeback_rate_update_seconds * HZ);
1013
1014         bch_writeback_queue(dc);
1015
1016         return 0;
1017 }