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_nr_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         /*
  92          * We need to consider the number of dirty buckets as well
  93          * when calculating the proportional_scaled, Otherwise we might
  94          * have an unreasonable small writeback rate at a highly fragmented situation
  95          * when very few dirty sectors consumed a lot dirty buckets, the
  96          * worst case is when dirty buckets reached cutoff_writeback_sync and
  97          * dirty data is still not even reached to writeback percent, so the rate
  98          * still will be at the minimum value, which will cause the write
  99          * stuck at a non-writeback mode.
 100          */
 101         struct cache_set *c = dc->disk.c;
 102
 103         int64_t dirty_buckets = c->nbuckets - c->avail_nbuckets;
 104
 105         if (dc->writeback_consider_fragment &&
 106                 c->gc_stats.in_use > BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW && dirty > 0) {
 107                 int64_t fragment =
 108                         div_s64((dirty_buckets *  c->cache->sb.bucket_size), dirty);
 109                 int64_t fp_term;
 110                 int64_t fps;
 111
 112                 if (c->gc_stats.in_use <= BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID) {
 113                         fp_term = (int64_t)dc->writeback_rate_fp_term_low *
 114                         (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW);
 115                 } else if (c->gc_stats.in_use <= BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH) {
 116                         fp_term = (int64_t)dc->writeback_rate_fp_term_mid *
 117                         (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID);
 118                 } else {
 119                         fp_term = (int64_t)dc->writeback_rate_fp_term_high *
 120                         (c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH);
 121                 }
 122                 fps = div_s64(dirty, dirty_buckets) * fp_term;
 123                 if (fragment > 3 && fps > proportional_scaled) {
 124                         /* Only overrite the p when fragment > 3 */
 125                         proportional_scaled = fps;
 126                 }
 127         }
 128
 129         if ((error < 0 && dc->writeback_rate_integral > 0) ||
 130             (error > 0 && time_before64(local_clock(),
 131                          dc->writeback_rate.next + NSEC_PER_MSEC))) {
 132                 /*
 133                  * Only decrease the integral term if it's more than
 134                  * zero.  Only increase the integral term if the device
 135                  * is keeping up.  (Don't wind up the integral
 136                  * ineffectively in either case).
 137                  *
 138                  * It's necessary to scale this by
 139                  * writeback_rate_update_seconds to keep the integral
 140                  * term dimensioned properly.
 141                  */
 142                 dc->writeback_rate_integral += error *
 143                         dc->writeback_rate_update_seconds;
 144         }
 145
 146         integral_scaled = div_s64(dc->writeback_rate_integral,
 147                         dc->writeback_rate_i_term_inverse);
 148
 149         new_rate = clamp_t(int32_t, (proportional_scaled + integral_scaled),
 150                         dc->writeback_rate_minimum, NSEC_PER_SEC);
 151
 152         dc->writeback_rate_proportional = proportional_scaled;
 153         dc->writeback_rate_integral_scaled = integral_scaled;
 154         dc->writeback_rate_change = new_rate -
 155                         atomic_long_read(&dc->writeback_rate.rate);
 156         atomic_long_set(&dc->writeback_rate.rate, new_rate);
 157         dc->writeback_rate_target = target;
 158 }
 159
 160 static bool set_at_max_writeback_rate(struct cache_set *c,
 161                                        struct cached_dev *dc)
 162 {
 163         /* Don't sst max writeback rate if it is disabled */
 164         if (!c->idle_max_writeback_rate_enabled)
 165                 return false;
 166
 167         /* Don't set max writeback rate if gc is running */
 168         if (!c->gc_mark_valid)
 169                 return false;
 170         /*
 171          * Idle_counter is increased everytime when update_writeback_rate() is
 172          * called. If all backing devices attached to the same cache set have
 173          * identical dc->writeback_rate_update_seconds values, it is about 6
 174          * rounds of update_writeback_rate() on each backing device before
 175          * c->at_max_writeback_rate is set to 1, and then max wrteback rate set
 176          * to each dc->writeback_rate.rate.
 177          * In order to avoid extra locking cost for counting exact dirty cached
 178          * devices number, c->attached_dev_nr is used to calculate the idle
 179          * throushold. It might be bigger if not all cached device are in write-
 180          * back mode, but it still works well with limited extra rounds of
 181          * update_writeback_rate().
 182          */
 183         if (atomic_inc_return(&c->idle_counter) <
 184             atomic_read(&c->attached_dev_nr) * 6)
 185                 return false;
 186
 187         if (atomic_read(&c->at_max_writeback_rate) != 1)
 188                 atomic_set(&c->at_max_writeback_rate, 1);
 189
 190         atomic_long_set(&dc->writeback_rate.rate, INT_MAX);
 191
 192         /* keep writeback_rate_target as existing value */
 193         dc->writeback_rate_proportional = 0;
 194         dc->writeback_rate_integral_scaled = 0;
 195         dc->writeback_rate_change = 0;
 196
 197         /*
 198          * Check c->idle_counter and c->at_max_writeback_rate agagain in case
 199          * new I/O arrives during before set_at_max_writeback_rate() returns.
 200          * Then the writeback rate is set to 1, and its new value should be
 201          * decided via __update_writeback_rate().
 202          */
 203         if ((atomic_read(&c->idle_counter) <
 204              atomic_read(&c->attached_dev_nr) * 6) ||
 205             !atomic_read(&c->at_max_writeback_rate))
 206                 return false;
 207
 208         return true;
 209 }
 210
 211 static void update_writeback_rate(struct work_struct *work)
 212 {
 213         struct cached_dev *dc = container_of(to_delayed_work(work),
 214                                              struct cached_dev,
 215                                              writeback_rate_update);
 216         struct cache_set *c = dc->disk.c;
 217
 218         /*
 219          * should check BCACHE_DEV_RATE_DW_RUNNING before calling
 220          * cancel_delayed_work_sync().
 221          */
 222         set_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 223         /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 224         smp_mb__after_atomic();
 225
 226         /*
 227          * CACHE_SET_IO_DISABLE might be set via sysfs interface,
 228          * check it here too.
 229          */
 230         if (!test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) ||
 231             test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 232                 clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 233                 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 234                 smp_mb__after_atomic();
 235                 return;
 236         }
 237
 238         /*
 239          * If the whole cache set is idle, set_at_max_writeback_rate()
 240          * will set writeback rate to a max number. Then it is
 241          * unncessary to update writeback rate for an idle cache set
 242          * in maximum writeback rate number(s).
 243          */
 244         if (atomic_read(&dc->has_dirty) && dc->writeback_percent &&
 245             !set_at_max_writeback_rate(c, dc)) {
 246                 do {
 247                         if (!down_read_trylock((&dc->writeback_lock))) {
 248                                 dc->rate_update_retry++;
 249                                 if (dc->rate_update_retry <=
 250                                     BCH_WBRATE_UPDATE_MAX_SKIPS)
 251                                         break;
 252                                 down_read(&dc->writeback_lock);
 253                                 dc->rate_update_retry = 0;
 254                         }
 255                         __update_writeback_rate(dc);
 256                         update_gc_after_writeback(c);
 257                         up_read(&dc->writeback_lock);
 258                 } while (0);
 259         }
 260
 261
 262         /*
 263          * CACHE_SET_IO_DISABLE might be set via sysfs interface,
 264          * check it here too.
 265          */
 266         if (test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) &&
 267             !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 268                 schedule_delayed_work(&dc->writeback_rate_update,
 269                               dc->writeback_rate_update_seconds * HZ);
 270         }
 271
 272         /*
 273          * should check BCACHE_DEV_RATE_DW_RUNNING before calling
 274          * cancel_delayed_work_sync().
 275          */
 276         clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
 277         /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
 278         smp_mb__after_atomic();
 279 }
 280
 281 static unsigned int writeback_delay(struct cached_dev *dc,
 282                                     unsigned int sectors)
 283 {
 284         if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
 285             !dc->writeback_percent)
 286                 return 0;
 287
 288         return bch_next_delay(&dc->writeback_rate, sectors);
 289 }
 290
 291 struct dirty_io {
 292         struct closure          cl;
 293         struct cached_dev       *dc;
 294         uint16_t                sequence;
 295         struct bio              bio;
 296 };
 297
 298 static void dirty_init(struct keybuf_key *w)
 299 {
 300         struct dirty_io *io = w->private;
 301         struct bio *bio = &io->bio;
 302
 303         bio_init(bio, NULL, bio->bi_inline_vecs,
 304                  DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS), 0);
 305         if (!io->dc->writeback_percent)
 306                 bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
 307
 308         bio->bi_iter.bi_size    = KEY_SIZE(&w->key) << 9;
 309         bio->bi_private         = w;
 310         bch_bio_map(bio, NULL);
 311 }
 312
 313 static void dirty_io_destructor(struct closure *cl)
 314 {
 315         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 316
 317         kfree(io);
 318 }
 319
 320 static void write_dirty_finish(struct closure *cl)
 321 {
 322         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 323         struct keybuf_key *w = io->bio.bi_private;
 324         struct cached_dev *dc = io->dc;
 325
 326         bio_free_pages(&io->bio);
 327
 328         /* This is kind of a dumb way of signalling errors. */
 329         if (KEY_DIRTY(&w->key)) {
 330                 int ret;
 331                 unsigned int i;
 332                 struct keylist keys;
 333
 334                 bch_keylist_init(&keys);
 335
 336                 bkey_copy(keys.top, &w->key);
 337                 SET_KEY_DIRTY(keys.top, false);
 338                 bch_keylist_push(&keys);
 339
 340                 for (i = 0; i < KEY_PTRS(&w->key); i++)
 341                         atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
 342
 343                 ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);
 344
 345                 if (ret)
 346                         trace_bcache_writeback_collision(&w->key);
 347
 348                 atomic_long_inc(ret
 349                                 ? &dc->disk.c->writeback_keys_failed
 350                                 : &dc->disk.c->writeback_keys_done);
 351         }
 352
 353         bch_keybuf_del(&dc->writeback_keys, w);
 354         up(&dc->in_flight);
 355
 356         closure_return_with_destructor(cl, dirty_io_destructor);
 357 }
 358
 359 static void dirty_endio(struct bio *bio)
 360 {
 361         struct keybuf_key *w = bio->bi_private;
 362         struct dirty_io *io = w->private;
 363
 364         if (bio->bi_status) {
 365                 SET_KEY_DIRTY(&w->key, false);
 366                 bch_count_backing_io_errors(io->dc, bio);
 367         }
 368
 369         closure_put(&io->cl);
 370 }
 371
 372 static void write_dirty(struct closure *cl)
 373 {
 374         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 375         struct keybuf_key *w = io->bio.bi_private;
 376         struct cached_dev *dc = io->dc;
 377
 378         uint16_t next_sequence;
 379
 380         if (atomic_read(&dc->writeback_sequence_next) != io->sequence) {
 381                 /* Not our turn to write; wait for a write to complete */
 382                 closure_wait(&dc->writeback_ordering_wait, cl);
 383
 384                 if (atomic_read(&dc->writeback_sequence_next) == io->sequence) {
 385                         /*
 386                          * Edge case-- it happened in indeterminate order
 387                          * relative to when we were added to wait list..
 388                          */
 389                         closure_wake_up(&dc->writeback_ordering_wait);
 390                 }
 391
 392                 continue_at(cl, write_dirty, io->dc->writeback_write_wq);
 393                 return;
 394         }
 395
 396         next_sequence = io->sequence + 1;
 397
 398         /*
 399          * IO errors are signalled using the dirty bit on the key.
 400          * If we failed to read, we should not attempt to write to the
 401          * backing device.  Instead, immediately go to write_dirty_finish
 402          * to clean up.
 403          */
 404         if (KEY_DIRTY(&w->key)) {
 405                 dirty_init(w);
 406                 bio_set_op_attrs(&io->bio, REQ_OP_WRITE, 0);
 407                 io->bio.bi_iter.bi_sector = KEY_START(&w->key);
 408                 bio_set_dev(&io->bio, io->dc->bdev);
 409                 io->bio.bi_end_io       = dirty_endio;
 410
 411                 /* I/O request sent to backing device */
 412                 closure_bio_submit(io->dc->disk.c, &io->bio, cl);
 413         }
 414
 415         atomic_set(&dc->writeback_sequence_next, next_sequence);
 416         closure_wake_up(&dc->writeback_ordering_wait);
 417
 418         continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq);
 419 }
 420
 421 static void read_dirty_endio(struct bio *bio)
 422 {
 423         struct keybuf_key *w = bio->bi_private;
 424         struct dirty_io *io = w->private;
 425
 426         /* is_read = 1 */
 427         bch_count_io_errors(io->dc->disk.c->cache,
 428                             bio->bi_status, 1,
 429                             "reading dirty data from cache");
 430
 431         dirty_endio(bio);
 432 }
 433
 434 static void read_dirty_submit(struct closure *cl)
 435 {
 436         struct dirty_io *io = container_of(cl, struct dirty_io, cl);
 437
 438         closure_bio_submit(io->dc->disk.c, &io->bio, cl);
 439
 440         continue_at(cl, write_dirty, io->dc->writeback_write_wq);
 441 }
 442
 443 static void read_dirty(struct cached_dev *dc)
 444 {
 445         unsigned int delay = 0;
 446         struct keybuf_key *next, *keys[MAX_WRITEBACKS_IN_PASS], *w;
 447         size_t size;
 448         int nk, i;
 449         struct dirty_io *io;
 450         struct closure cl;
 451         uint16_t sequence = 0;
 452
 453         BUG_ON(!llist_empty(&dc->writeback_ordering_wait.list));
 454         atomic_set(&dc->writeback_sequence_next, sequence);
 455         closure_init_stack(&cl);
 456
 457         /*
 458          * XXX: if we error, background writeback just spins. Should use some
 459          * mempools.
 460          */
 461
 462         next = bch_keybuf_next(&dc->writeback_keys);
 463
 464         while (!kthread_should_stop() &&
 465                !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
 466                next) {
 467                 size = 0;
 468                 nk = 0;
 469
 470                 do {
 471                         BUG_ON(ptr_stale(dc->disk.c, &next->key, 0));
 472
 473                         /*
 474                          * Don't combine too many operations, even if they
 475                          * are all small.
 476                          */
 477                         if (nk >= MAX_WRITEBACKS_IN_PASS)
 478                                 break;
 479
 480                         /*
 481                          * If the current operation is very large, don't
 482                          * further combine operations.
 483                          */
 484                         if (size >= MAX_WRITESIZE_IN_PASS)
 485                                 break;
 486
 487                         /*
 488                          * Operations are only eligible to be combined
 489                          * if they are contiguous.
 490                          *
 491                          * TODO: add a heuristic willing to fire a
 492                          * certain amount of non-contiguous IO per pass,
 493                          * so that we can benefit from backing device
 494                          * command queueing.
 495                          */
 496                         if ((nk != 0) && bkey_cmp(&keys[nk-1]->key,
 497                                                 &START_KEY(&next->key)))
 498                                 break;
 499
 500                         size += KEY_SIZE(&next->key);
 501                         keys[nk++] = next;
 502                 } while ((next = bch_keybuf_next(&dc->writeback_keys)));
 503
 504                 /* Now we have gathered a set of 1..5 keys to write back. */
 505                 for (i = 0; i < nk; i++) {
 506                         w = keys[i];
 507
 508                         io = kzalloc(struct_size(io, bio.bi_inline_vecs,
 509                                                 DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS)),
 510                                      GFP_KERNEL);
 511                         if (!io)
 512                                 goto err;
 513
 514                         w->private      = io;
 515                         io->dc          = dc;
 516                         io->sequence    = sequence++;
 517
 518                         dirty_init(w);
 519                         bio_set_op_attrs(&io->bio, REQ_OP_READ, 0);
 520                         io->bio.bi_iter.bi_sector = PTR_OFFSET(&w->key, 0);
 521                         bio_set_dev(&io->bio, dc->disk.c->cache->bdev);
 522                         io->bio.bi_end_io       = read_dirty_endio;
 523
 524                         if (bch_bio_alloc_pages(&io->bio, GFP_KERNEL))
 525                                 goto err_free;
 526
 527                         trace_bcache_writeback(&w->key);
 528
 529                         down(&dc->in_flight);
 530
 531                         /*
 532                          * We've acquired a semaphore for the maximum
 533                          * simultaneous number of writebacks; from here
 534                          * everything happens asynchronously.
 535                          */
 536                         closure_call(&io->cl, read_dirty_submit, NULL, &cl);
 537                 }
 538
 539                 delay = writeback_delay(dc, size);
 540
 541                 while (!kthread_should_stop() &&
 542                        !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
 543                        delay) {
 544                         schedule_timeout_interruptible(delay);
 545                         delay = writeback_delay(dc, 0);
 546                 }
 547         }
 548
 549         if (0) {
 550 err_free:
 551                 kfree(w->private);
 552 err:
 553                 bch_keybuf_del(&dc->writeback_keys, w);
 554         }
 555
 556         /*
 557          * Wait for outstanding writeback IOs to finish (and keybuf slots to be
 558          * freed) before refilling again
 559          */
 560         closure_sync(&cl);
 561 }
 562
 563 /* Scan for dirty data */
 564
 565 void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode,
 566                                   uint64_t offset, int nr_sectors)
 567 {
 568         struct bcache_device *d = c->devices[inode];
 569         unsigned int stripe_offset, sectors_dirty;
 570         int stripe;
 571
 572         if (!d)
 573                 return;
 574
 575         stripe = offset_to_stripe(d, offset);
 576         if (stripe < 0)
 577                 return;
 578
 579         if (UUID_FLASH_ONLY(&c->uuids[inode]))
 580                 atomic_long_add(nr_sectors, &c->flash_dev_dirty_sectors);
 581
 582         stripe_offset = offset & (d->stripe_size - 1);
 583
 584         while (nr_sectors) {
 585                 int s = min_t(unsigned int, abs(nr_sectors),
 586                               d->stripe_size - stripe_offset);
 587
 588                 if (nr_sectors < 0)
 589                         s = -s;
 590
 591                 if (stripe >= d->nr_stripes)
 592                         return;
 593
 594                 sectors_dirty = atomic_add_return(s,
 595                                         d->stripe_sectors_dirty + stripe);
 596                 if (sectors_dirty == d->stripe_size) {
 597                         if (!test_bit(stripe, d->full_dirty_stripes))
 598                                 set_bit(stripe, d->full_dirty_stripes);
 599                 } else {
 600                         if (test_bit(stripe, d->full_dirty_stripes))
 601                                 clear_bit(stripe, d->full_dirty_stripes);
 602                 }
 603
 604                 nr_sectors -= s;
 605                 stripe_offset = 0;
 606                 stripe++;
 607         }
 608 }
 609
 610 static bool dirty_pred(struct keybuf *buf, struct bkey *k)
 611 {
 612         struct cached_dev *dc = container_of(buf,
 613                                              struct cached_dev,
 614                                              writeback_keys);
 615
 616         BUG_ON(KEY_INODE(k) != dc->disk.id);
 617
 618         return KEY_DIRTY(k);
 619 }
 620
 621 static void refill_full_stripes(struct cached_dev *dc)
 622 {
 623         struct keybuf *buf = &dc->writeback_keys;
 624         unsigned int start_stripe, next_stripe;
 625         int stripe;
 626         bool wrapped = false;
 627
 628         stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));
 629         if (stripe < 0)
 630                 stripe = 0;
 631
 632         start_stripe = stripe;
 633
 634         while (1) {
 635                 stripe = find_next_bit(dc->disk.full_dirty_stripes,
 636                                        dc->disk.nr_stripes, stripe);
 637
 638                 if (stripe == dc->disk.nr_stripes)
 639                         goto next;
 640
 641                 next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes,
 642                                                  dc->disk.nr_stripes, stripe);
 643
 644                 buf->last_scanned = KEY(dc->disk.id,
 645                                         stripe * dc->disk.stripe_size, 0);
 646
 647                 bch_refill_keybuf(dc->disk.c, buf,
 648                                   &KEY(dc->disk.id,
 649                                        next_stripe * dc->disk.stripe_size, 0),
 650                                   dirty_pred);
 651
 652                 if (array_freelist_empty(&buf->freelist))
 653                         return;
 654
 655                 stripe = next_stripe;
 656 next:
 657                 if (wrapped && stripe > start_stripe)
 658                         return;
 659
 660                 if (stripe == dc->disk.nr_stripes) {
 661                         stripe = 0;
 662                         wrapped = true;
 663                 }
 664         }
 665 }
 666
 667 /*
 668  * Returns true if we scanned the entire disk
 669  */
 670 static bool refill_dirty(struct cached_dev *dc)
 671 {
 672         struct keybuf *buf = &dc->writeback_keys;
 673         struct bkey start = KEY(dc->disk.id, 0, 0);
 674         struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
 675         struct bkey start_pos;
 676
 677         /*
 678          * make sure keybuf pos is inside the range for this disk - at bringup
 679          * we might not be attached yet so this disk's inode nr isn't
 680          * initialized then
 681          */
 682         if (bkey_cmp(&buf->last_scanned, &start) < 0 ||
 683             bkey_cmp(&buf->last_scanned, &end) > 0)
 684                 buf->last_scanned = start;
 685
 686         if (dc->partial_stripes_expensive) {
 687                 refill_full_stripes(dc);
 688                 if (array_freelist_empty(&buf->freelist))
 689                         return false;
 690         }
 691
 692         start_pos = buf->last_scanned;
 693         bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
 694
 695         if (bkey_cmp(&buf->last_scanned, &end) < 0)
 696                 return false;
 697
 698         /*
 699          * If we get to the end start scanning again from the beginning, and
 700          * only scan up to where we initially started scanning from:
 701          */
 702         buf->last_scanned = start;
 703         bch_refill_keybuf(dc->disk.c, buf, &start_pos, dirty_pred);
 704
 705         return bkey_cmp(&buf->last_scanned, &start_pos) >= 0;
 706 }
 707
 708 static int bch_writeback_thread(void *arg)
 709 {
 710         struct cached_dev *dc = arg;
 711         struct cache_set *c = dc->disk.c;
 712         bool searched_full_index;
 713
 714         bch_ratelimit_reset(&dc->writeback_rate);
 715
 716         while (!kthread_should_stop() &&
 717                !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 718                 down_write(&dc->writeback_lock);
 719                 set_current_state(TASK_INTERRUPTIBLE);
 720                 /*
 721                  * If the bache device is detaching, skip here and continue
 722                  * to perform writeback. Otherwise, if no dirty data on cache,
 723                  * or there is dirty data on cache but writeback is disabled,
 724                  * the writeback thread should sleep here and wait for others
 725                  * to wake up it.
 726                  */
 727                 if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
 728                     (!atomic_read(&dc->has_dirty) || !dc->writeback_running)) {
 729                         up_write(&dc->writeback_lock);
 730
 731                         if (kthread_should_stop() ||
 732                             test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
 733                                 set_current_state(TASK_RUNNING);
 734                                 break;
 735                         }
 736
 737                         schedule();
 738                         continue;
 739                 }
 740                 set_current_state(TASK_RUNNING);
 741
 742                 searched_full_index = refill_dirty(dc);
 743
 744                 if (searched_full_index &&
 745                     RB_EMPTY_ROOT(&dc->writeback_keys.keys)) {
 746                         atomic_set(&dc->has_dirty, 0);
 747                         SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
 748                         bch_write_bdev_super(dc, NULL);
 749                         /*
 750                          * If bcache device is detaching via sysfs interface,
 751                          * writeback thread should stop after there is no dirty
 752                          * data on cache. BCACHE_DEV_DETACHING flag is set in
 753                          * bch_cached_dev_detach().
 754                          */
 755                         if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
 756                                 struct closure cl;
 757
 758                                 closure_init_stack(&cl);
 759                                 memset(&dc->sb.set_uuid, 0, 16);
 760                                 SET_BDEV_STATE(&dc->sb, BDEV_STATE_NONE);
 761
 762                                 bch_write_bdev_super(dc, &cl);
 763                                 closure_sync(&cl);
 764
 765                                 up_write(&dc->writeback_lock);
 766                                 break;
 767                         }
 768
 769                         /*
 770                          * When dirty data rate is high (e.g. 50%+), there might
 771                          * be heavy buckets fragmentation after writeback
 772                          * finished, which hurts following write performance.
 773                          * If users really care about write performance they
 774                          * may set BCH_ENABLE_AUTO_GC via sysfs, then when
 775                          * BCH_DO_AUTO_GC is set, garbage collection thread
 776                          * will be wake up here. After moving gc, the shrunk
 777                          * btree and discarded free buckets SSD space may be
 778                          * helpful for following write requests.
 779                          */
 780                         if (c->gc_after_writeback ==
 781                             (BCH_ENABLE_AUTO_GC|BCH_DO_AUTO_GC)) {
 782                                 c->gc_after_writeback &= ~BCH_DO_AUTO_GC;
 783                                 force_wake_up_gc(c);
 784                         }
 785                 }
 786
 787                 up_write(&dc->writeback_lock);
 788
 789                 read_dirty(dc);
 790
 791                 if (searched_full_index) {
 792                         unsigned int delay = dc->writeback_delay * HZ;
 793
 794                         while (delay &&
 795                                !kthread_should_stop() &&
 796                                !test_bit(CACHE_SET_IO_DISABLE, &c->flags) &&
 797                                !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
 798                                 delay = schedule_timeout_interruptible(delay);
 799
 800                         bch_ratelimit_reset(&dc->writeback_rate);
 801                 }
 802         }
 803
 804         if (dc->writeback_write_wq)
 805                 destroy_workqueue(dc->writeback_write_wq);
 806
 807         cached_dev_put(dc);
 808         wait_for_kthread_stop();
 809
 810         return 0;
 811 }
 812
 813 /* Init */
 814 #define INIT_KEYS_EACH_TIME     500000
 815
 816 struct sectors_dirty_init {
 817         struct btree_op op;
 818         unsigned int    inode;
 819         size_t          count;
 820 };
 821
 822 static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
 823                                  struct bkey *k)
 824 {
 825         struct sectors_dirty_init *op = container_of(_op,
 826                                                 struct sectors_dirty_init, op);
 827         if (KEY_INODE(k) > op->inode)
 828                 return MAP_DONE;
 829
 830         if (KEY_DIRTY(k))
 831                 bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
 832                                              KEY_START(k), KEY_SIZE(k));
 833
 834         op->count++;
 835         if (!(op->count % INIT_KEYS_EACH_TIME))
 836                 cond_resched();
 837
 838         return MAP_CONTINUE;
 839 }
 840
 841 static int bch_root_node_dirty_init(struct cache_set *c,
 842                                      struct bcache_device *d,
 843                                      struct bkey *k)
 844 {
 845         struct sectors_dirty_init op;
 846         int ret;
 847
 848         bch_btree_op_init(&op.op, -1);
 849         op.inode = d->id;
 850         op.count = 0;
 851
 852         ret = bcache_btree(map_keys_recurse,
 853                            k,
 854                            c->root,
 855                            &op.op,
 856                            &KEY(op.inode, 0, 0),
 857                            sectors_dirty_init_fn,
 858                            0);
 859         if (ret < 0)
 860                 pr_warn("sectors dirty init failed, ret=%d!\n", ret);
 861
 862         return ret;
 863 }
 864
 865 static int bch_dirty_init_thread(void *arg)
 866 {
 867         struct dirty_init_thrd_info *info = arg;
 868         struct bch_dirty_init_state *state = info->state;
 869         struct cache_set *c = state->c;
 870         struct btree_iter iter;
 871         struct bkey *k, *p;
 872         int cur_idx, prev_idx, skip_nr;
 873
 874         k = p = NULL;
 875         cur_idx = prev_idx = 0;
 876
 877         bch_btree_iter_init(&c->root->keys, &iter, NULL);
 878         k = bch_btree_iter_next_filter(&iter, &c->root->keys, bch_ptr_bad);
 879         BUG_ON(!k);
 880
 881         p = k;
 882
 883         while (k) {
 884                 spin_lock(&state->idx_lock);
 885                 cur_idx = state->key_idx;
 886                 state->key_idx++;
 887                 spin_unlock(&state->idx_lock);
 888
 889                 skip_nr = cur_idx - prev_idx;
 890
 891                 while (skip_nr) {
 892                         k = bch_btree_iter_next_filter(&iter,
 893                                                        &c->root->keys,
 894                                                        bch_ptr_bad);
 895                         if (k)
 896                                 p = k;
 897                         else {
 898                                 atomic_set(&state->enough, 1);
 899                                 /* Update state->enough earlier */
 900                                 smp_mb__after_atomic();
 901                                 goto out;
 902                         }
 903                         skip_nr--;
 904                 }
 905
 906                 if (p) {
 907                         if (bch_root_node_dirty_init(c, state->d, p) < 0)
 908                                 goto out;
 909                 }
 910
 911                 p = NULL;
 912                 prev_idx = cur_idx;
 913         }
 914
 915 out:
 916         /* In order to wake up state->wait in time */
 917         smp_mb__before_atomic();
 918         if (atomic_dec_and_test(&state->started))
 919                 wake_up(&state->wait);
 920
 921         return 0;
 922 }
 923
 924 static int bch_btre_dirty_init_thread_nr(void)
 925 {
 926         int n = num_online_cpus()/2;
 927
 928         if (n == 0)
 929                 n = 1;
 930         else if (n > BCH_DIRTY_INIT_THRD_MAX)
 931                 n = BCH_DIRTY_INIT_THRD_MAX;
 932
 933         return n;
 934 }
 935
 936 void bch_sectors_dirty_init(struct bcache_device *d)
 937 {
 938         int i;
 939         struct bkey *k = NULL;
 940         struct btree_iter iter;
 941         struct sectors_dirty_init op;
 942         struct cache_set *c = d->c;
 943         struct bch_dirty_init_state state;
 944
 945         /* Just count root keys if no leaf node */
 946         rw_lock(0, c->root, c->root->level);
 947         if (c->root->level == 0) {
 948                 bch_btree_op_init(&op.op, -1);
 949                 op.inode = d->id;
 950                 op.count = 0;
 951
 952                 for_each_key_filter(&c->root->keys,
 953                                     k, &iter, bch_ptr_invalid)
 954                         sectors_dirty_init_fn(&op.op, c->root, k);
 955
 956                 rw_unlock(0, c->root);
 957                 return;
 958         }
 959
 960         memset(&state, 0, sizeof(struct bch_dirty_init_state));
 961         state.c = c;
 962         state.d = d;
 963         state.total_threads = bch_btre_dirty_init_thread_nr();
 964         state.key_idx = 0;
 965         spin_lock_init(&state.idx_lock);
 966         atomic_set(&state.started, 0);
 967         atomic_set(&state.enough, 0);
 968         init_waitqueue_head(&state.wait);
 969
 970         for (i = 0; i < state.total_threads; i++) {
 971                 /* Fetch latest state.enough earlier */
 972                 smp_mb__before_atomic();
 973                 if (atomic_read(&state.enough))
 974                         break;
 975
 976                 state.infos[i].state = &state;
 977                 state.infos[i].thread =
 978                         kthread_run(bch_dirty_init_thread, &state.infos[i],
 979                                     "bch_dirtcnt[%d]", i);
 980                 if (IS_ERR(state.infos[i].thread)) {
 981                         pr_err("fails to run thread bch_dirty_init[%d]\n", i);
 982                         for (--i; i >= 0; i--)
 983                                 kthread_stop(state.infos[i].thread);
 984                         goto out;
 985                 }
 986                 atomic_inc(&state.started);
 987         }
 988
 989 out:
 990         /* Must wait for all threads to stop. */
 991         wait_event(state.wait, atomic_read(&state.started) == 0);
 992         rw_unlock(0, c->root);
 993 }
 994
 995 void bch_cached_dev_writeback_init(struct cached_dev *dc)
 996 {
 997         sema_init(&dc->in_flight, 64);
 998         init_rwsem(&dc->writeback_lock);
 999         bch_keybuf_init(&dc->writeback_keys);
1000
1001         dc->writeback_metadata          = true;
1002         dc->writeback_running           = false;
1003         dc->writeback_consider_fragment = true;
1004         dc->writeback_percent           = 10;
1005         dc->writeback_delay             = 30;
1006         atomic_long_set(&dc->writeback_rate.rate, 1024);
1007         dc->writeback_rate_minimum      = 8;
1008
1009         dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT;
1010         dc->writeback_rate_p_term_inverse = 40;
1011         dc->writeback_rate_fp_term_low = 1;
1012         dc->writeback_rate_fp_term_mid = 10;
1013         dc->writeback_rate_fp_term_high = 1000;
1014         dc->writeback_rate_i_term_inverse = 10000;
1015
1016         /* For dc->writeback_lock contention in update_writeback_rate() */
1017         dc->rate_update_retry = 0;
1018
1019         WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
1020         INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
1021 }
1022
1023 int bch_cached_dev_writeback_start(struct cached_dev *dc)
1024 {
1025         dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq",
1026                                                 WQ_MEM_RECLAIM, 0);
1027         if (!dc->writeback_write_wq)
1028                 return -ENOMEM;
1029
1030         cached_dev_get(dc);
1031         dc->writeback_thread = kthread_create(bch_writeback_thread, dc,
1032                                               "bcache_writeback");
1033         if (IS_ERR(dc->writeback_thread)) {
1034                 cached_dev_put(dc);
1035                 destroy_workqueue(dc->writeback_write_wq);
1036                 return PTR_ERR(dc->writeback_thread);
1037         }
1038         dc->writeback_running = true;
1039
1040         WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
1041         schedule_delayed_work(&dc->writeback_rate_update,
1042                               dc->writeback_rate_update_seconds * HZ);
1043
1044         bch_writeback_queue(dc);
1045
1046         return 0;
1047 }