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 idle_counter_exceeded(struct cache_set *c) 161 { 162 int counter, dev_nr; 163 164 /* 165 * If c->idle_counter is overflow (idel for really long time), 166 * reset as 0 and not set maximum rate this time for code 167 * simplicity. 168 */ 169 counter = atomic_inc_return(&c->idle_counter); 170 if (counter <= 0) { 171 atomic_set(&c->idle_counter, 0); 172 return false; 173 } 174 175 dev_nr = atomic_read(&c->attached_dev_nr); 176 if (dev_nr == 0) 177 return false; 178 179 /* 180 * c->idle_counter is increased by writeback thread of all 181 * attached backing devices, in order to represent a rough 182 * time period, counter should be divided by dev_nr. 183 * Otherwise the idle time cannot be larger with more backing 184 * device attached. 185 * The following calculation equals to checking 186 * (counter / dev_nr) < (dev_nr * 6) 187 */ 188 if (counter < (dev_nr * dev_nr * 6)) 189 return false; 190 191 return true; 192 } 193 194 /* 195 * Idle_counter is increased every time when update_writeback_rate() is 196 * called. If all backing devices attached to the same cache set have 197 * identical dc->writeback_rate_update_seconds values, it is about 6 198 * rounds of update_writeback_rate() on each backing device before 199 * c->at_max_writeback_rate is set to 1, and then max wrteback rate set 200 * to each dc->writeback_rate.rate. 201 * In order to avoid extra locking cost for counting exact dirty cached 202 * devices number, c->attached_dev_nr is used to calculate the idle 203 * throushold. It might be bigger if not all cached device are in write- 204 * back mode, but it still works well with limited extra rounds of 205 * update_writeback_rate(). 206 */ 207 static bool set_at_max_writeback_rate(struct cache_set *c, 208 struct cached_dev *dc) 209 { 210 /* Don't sst max writeback rate if it is disabled */ 211 if (!c->idle_max_writeback_rate_enabled) 212 return false; 213 214 /* Don't set max writeback rate if gc is running */ 215 if (!c->gc_mark_valid) 216 return false; 217 218 if (!idle_counter_exceeded(c)) 219 return false; 220 221 if (atomic_read(&c->at_max_writeback_rate) != 1) 222 atomic_set(&c->at_max_writeback_rate, 1); 223 224 atomic_long_set(&dc->writeback_rate.rate, INT_MAX); 225 226 /* keep writeback_rate_target as existing value */ 227 dc->writeback_rate_proportional = 0; 228 dc->writeback_rate_integral_scaled = 0; 229 dc->writeback_rate_change = 0; 230 231 /* 232 * In case new I/O arrives during before 233 * set_at_max_writeback_rate() returns. 234 */ 235 if (!idle_counter_exceeded(c) || 236 !atomic_read(&c->at_max_writeback_rate)) 237 return false; 238 239 return true; 240 } 241 242 static void update_writeback_rate(struct work_struct *work) 243 { 244 struct cached_dev *dc = container_of(to_delayed_work(work), 245 struct cached_dev, 246 writeback_rate_update); 247 struct cache_set *c = dc->disk.c; 248 249 /* 250 * should check BCACHE_DEV_RATE_DW_RUNNING before calling 251 * cancel_delayed_work_sync(). 252 */ 253 set_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags); 254 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */ 255 smp_mb__after_atomic(); 256 257 /* 258 * CACHE_SET_IO_DISABLE might be set via sysfs interface, 259 * check it here too. 260 */ 261 if (!test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) || 262 test_bit(CACHE_SET_IO_DISABLE, &c->flags)) { 263 clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags); 264 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */ 265 smp_mb__after_atomic(); 266 return; 267 } 268 269 /* 270 * If the whole cache set is idle, set_at_max_writeback_rate() 271 * will set writeback rate to a max number. Then it is 272 * unncessary to update writeback rate for an idle cache set 273 * in maximum writeback rate number(s). 274 */ 275 if (atomic_read(&dc->has_dirty) && dc->writeback_percent && 276 !set_at_max_writeback_rate(c, dc)) { 277 do { 278 if (!down_read_trylock((&dc->writeback_lock))) { 279 dc->rate_update_retry++; 280 if (dc->rate_update_retry <= 281 BCH_WBRATE_UPDATE_MAX_SKIPS) 282 break; 283 down_read(&dc->writeback_lock); 284 dc->rate_update_retry = 0; 285 } 286 __update_writeback_rate(dc); 287 update_gc_after_writeback(c); 288 up_read(&dc->writeback_lock); 289 } while (0); 290 } 291 292 293 /* 294 * CACHE_SET_IO_DISABLE might be set via sysfs interface, 295 * check it here too. 296 */ 297 if (test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) && 298 !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) { 299 schedule_delayed_work(&dc->writeback_rate_update, 300 dc->writeback_rate_update_seconds * HZ); 301 } 302 303 /* 304 * should check BCACHE_DEV_RATE_DW_RUNNING before calling 305 * cancel_delayed_work_sync(). 306 */ 307 clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags); 308 /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */ 309 smp_mb__after_atomic(); 310 } 311 312 static unsigned int writeback_delay(struct cached_dev *dc, 313 unsigned int sectors) 314 { 315 if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) || 316 !dc->writeback_percent) 317 return 0; 318 319 return bch_next_delay(&dc->writeback_rate, sectors); 320 } 321 322 struct dirty_io { 323 struct closure cl; 324 struct cached_dev *dc; 325 uint16_t sequence; 326 struct bio bio; 327 }; 328 329 static void dirty_init(struct keybuf_key *w) 330 { 331 struct dirty_io *io = w->private; 332 struct bio *bio = &io->bio; 333 334 bio_init(bio, NULL, bio->bi_inline_vecs, 335 DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS), 0); 336 if (!io->dc->writeback_percent) 337 bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0)); 338 339 bio->bi_iter.bi_size = KEY_SIZE(&w->key) << 9; 340 bio->bi_private = w; 341 bch_bio_map(bio, NULL); 342 } 343 344 static CLOSURE_CALLBACK(dirty_io_destructor) 345 { 346 closure_type(io, struct dirty_io, cl); 347 348 kfree(io); 349 } 350 351 static CLOSURE_CALLBACK(write_dirty_finish) 352 { 353 closure_type(io, struct dirty_io, cl); 354 struct keybuf_key *w = io->bio.bi_private; 355 struct cached_dev *dc = io->dc; 356 357 bio_free_pages(&io->bio); 358 359 /* This is kind of a dumb way of signalling errors. */ 360 if (KEY_DIRTY(&w->key)) { 361 int ret; 362 unsigned int i; 363 struct keylist keys; 364 365 bch_keylist_init(&keys); 366 367 bkey_copy(keys.top, &w->key); 368 SET_KEY_DIRTY(keys.top, false); 369 bch_keylist_push(&keys); 370 371 for (i = 0; i < KEY_PTRS(&w->key); i++) 372 atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin); 373 374 ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key); 375 376 if (ret) 377 trace_bcache_writeback_collision(&w->key); 378 379 atomic_long_inc(ret 380 ? &dc->disk.c->writeback_keys_failed 381 : &dc->disk.c->writeback_keys_done); 382 } 383 384 bch_keybuf_del(&dc->writeback_keys, w); 385 up(&dc->in_flight); 386 387 closure_return_with_destructor(cl, dirty_io_destructor); 388 } 389 390 static void dirty_endio(struct bio *bio) 391 { 392 struct keybuf_key *w = bio->bi_private; 393 struct dirty_io *io = w->private; 394 395 if (bio->bi_status) { 396 SET_KEY_DIRTY(&w->key, false); 397 bch_count_backing_io_errors(io->dc, bio); 398 } 399 400 closure_put(&io->cl); 401 } 402 403 static CLOSURE_CALLBACK(write_dirty) 404 { 405 closure_type(io, struct dirty_io, cl); 406 struct keybuf_key *w = io->bio.bi_private; 407 struct cached_dev *dc = io->dc; 408 409 uint16_t next_sequence; 410 411 if (atomic_read(&dc->writeback_sequence_next) != io->sequence) { 412 /* Not our turn to write; wait for a write to complete */ 413 closure_wait(&dc->writeback_ordering_wait, cl); 414 415 if (atomic_read(&dc->writeback_sequence_next) == io->sequence) { 416 /* 417 * Edge case-- it happened in indeterminate order 418 * relative to when we were added to wait list.. 419 */ 420 closure_wake_up(&dc->writeback_ordering_wait); 421 } 422 423 continue_at(cl, write_dirty, io->dc->writeback_write_wq); 424 return; 425 } 426 427 next_sequence = io->sequence + 1; 428 429 /* 430 * IO errors are signalled using the dirty bit on the key. 431 * If we failed to read, we should not attempt to write to the 432 * backing device. Instead, immediately go to write_dirty_finish 433 * to clean up. 434 */ 435 if (KEY_DIRTY(&w->key)) { 436 dirty_init(w); 437 io->bio.bi_opf = REQ_OP_WRITE; 438 io->bio.bi_iter.bi_sector = KEY_START(&w->key); 439 bio_set_dev(&io->bio, io->dc->bdev); 440 io->bio.bi_end_io = dirty_endio; 441 442 /* I/O request sent to backing device */ 443 closure_bio_submit(io->dc->disk.c, &io->bio, cl); 444 } 445 446 atomic_set(&dc->writeback_sequence_next, next_sequence); 447 closure_wake_up(&dc->writeback_ordering_wait); 448 449 continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq); 450 } 451 452 static void read_dirty_endio(struct bio *bio) 453 { 454 struct keybuf_key *w = bio->bi_private; 455 struct dirty_io *io = w->private; 456 457 /* is_read = 1 */ 458 bch_count_io_errors(io->dc->disk.c->cache, 459 bio->bi_status, 1, 460 "reading dirty data from cache"); 461 462 dirty_endio(bio); 463 } 464 465 static CLOSURE_CALLBACK(read_dirty_submit) 466 { 467 closure_type(io, struct dirty_io, cl); 468 469 closure_bio_submit(io->dc->disk.c, &io->bio, cl); 470 471 continue_at(cl, write_dirty, io->dc->writeback_write_wq); 472 } 473 474 static void read_dirty(struct cached_dev *dc) 475 { 476 unsigned int delay = 0; 477 struct keybuf_key *next, *keys[MAX_WRITEBACKS_IN_PASS], *w; 478 size_t size; 479 int nk, i; 480 struct dirty_io *io; 481 struct closure cl; 482 uint16_t sequence = 0; 483 484 BUG_ON(!llist_empty(&dc->writeback_ordering_wait.list)); 485 atomic_set(&dc->writeback_sequence_next, sequence); 486 closure_init_stack(&cl); 487 488 /* 489 * XXX: if we error, background writeback just spins. Should use some 490 * mempools. 491 */ 492 493 next = bch_keybuf_next(&dc->writeback_keys); 494 495 while (!kthread_should_stop() && 496 !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) && 497 next) { 498 size = 0; 499 nk = 0; 500 501 do { 502 BUG_ON(ptr_stale(dc->disk.c, &next->key, 0)); 503 504 /* 505 * Don't combine too many operations, even if they 506 * are all small. 507 */ 508 if (nk >= MAX_WRITEBACKS_IN_PASS) 509 break; 510 511 /* 512 * If the current operation is very large, don't 513 * further combine operations. 514 */ 515 if (size >= MAX_WRITESIZE_IN_PASS) 516 break; 517 518 /* 519 * Operations are only eligible to be combined 520 * if they are contiguous. 521 * 522 * TODO: add a heuristic willing to fire a 523 * certain amount of non-contiguous IO per pass, 524 * so that we can benefit from backing device 525 * command queueing. 526 */ 527 if ((nk != 0) && bkey_cmp(&keys[nk-1]->key, 528 &START_KEY(&next->key))) 529 break; 530 531 size += KEY_SIZE(&next->key); 532 keys[nk++] = next; 533 } while ((next = bch_keybuf_next(&dc->writeback_keys))); 534 535 /* Now we have gathered a set of 1..5 keys to write back. */ 536 for (i = 0; i < nk; i++) { 537 w = keys[i]; 538 539 io = kzalloc(struct_size(io, bio.bi_inline_vecs, 540 DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS)), 541 GFP_KERNEL); 542 if (!io) 543 goto err; 544 545 w->private = io; 546 io->dc = dc; 547 io->sequence = sequence++; 548 549 dirty_init(w); 550 io->bio.bi_opf = REQ_OP_READ; 551 io->bio.bi_iter.bi_sector = PTR_OFFSET(&w->key, 0); 552 bio_set_dev(&io->bio, dc->disk.c->cache->bdev); 553 io->bio.bi_end_io = read_dirty_endio; 554 555 if (bch_bio_alloc_pages(&io->bio, GFP_KERNEL)) 556 goto err_free; 557 558 trace_bcache_writeback(&w->key); 559 560 down(&dc->in_flight); 561 562 /* 563 * We've acquired a semaphore for the maximum 564 * simultaneous number of writebacks; from here 565 * everything happens asynchronously. 566 */ 567 closure_call(&io->cl, read_dirty_submit, NULL, &cl); 568 } 569 570 delay = writeback_delay(dc, size); 571 572 while (!kthread_should_stop() && 573 !test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) && 574 delay) { 575 schedule_timeout_interruptible(delay); 576 delay = writeback_delay(dc, 0); 577 } 578 } 579 580 if (0) { 581 err_free: 582 kfree(w->private); 583 err: 584 bch_keybuf_del(&dc->writeback_keys, w); 585 } 586 587 /* 588 * Wait for outstanding writeback IOs to finish (and keybuf slots to be 589 * freed) before refilling again 590 */ 591 closure_sync(&cl); 592 } 593 594 /* Scan for dirty data */ 595 596 void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode, 597 uint64_t offset, int nr_sectors) 598 { 599 struct bcache_device *d = c->devices[inode]; 600 unsigned int stripe_offset, sectors_dirty; 601 int stripe; 602 603 if (!d) 604 return; 605 606 stripe = offset_to_stripe(d, offset); 607 if (stripe < 0) 608 return; 609 610 if (UUID_FLASH_ONLY(&c->uuids[inode])) 611 atomic_long_add(nr_sectors, &c->flash_dev_dirty_sectors); 612 613 stripe_offset = offset & (d->stripe_size - 1); 614 615 while (nr_sectors) { 616 int s = min_t(unsigned int, abs(nr_sectors), 617 d->stripe_size - stripe_offset); 618 619 if (nr_sectors < 0) 620 s = -s; 621 622 if (stripe >= d->nr_stripes) 623 return; 624 625 sectors_dirty = atomic_add_return(s, 626 d->stripe_sectors_dirty + stripe); 627 if (sectors_dirty == d->stripe_size) { 628 if (!test_bit(stripe, d->full_dirty_stripes)) 629 set_bit(stripe, d->full_dirty_stripes); 630 } else { 631 if (test_bit(stripe, d->full_dirty_stripes)) 632 clear_bit(stripe, d->full_dirty_stripes); 633 } 634 635 nr_sectors -= s; 636 stripe_offset = 0; 637 stripe++; 638 } 639 } 640 641 static bool dirty_pred(struct keybuf *buf, struct bkey *k) 642 { 643 struct cached_dev *dc = container_of(buf, 644 struct cached_dev, 645 writeback_keys); 646 647 BUG_ON(KEY_INODE(k) != dc->disk.id); 648 649 return KEY_DIRTY(k); 650 } 651 652 static void refill_full_stripes(struct cached_dev *dc) 653 { 654 struct keybuf *buf = &dc->writeback_keys; 655 unsigned int start_stripe, next_stripe; 656 int stripe; 657 bool wrapped = false; 658 659 stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned)); 660 if (stripe < 0) 661 stripe = 0; 662 663 start_stripe = stripe; 664 665 while (1) { 666 stripe = find_next_bit(dc->disk.full_dirty_stripes, 667 dc->disk.nr_stripes, stripe); 668 669 if (stripe == dc->disk.nr_stripes) 670 goto next; 671 672 next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes, 673 dc->disk.nr_stripes, stripe); 674 675 buf->last_scanned = KEY(dc->disk.id, 676 stripe * dc->disk.stripe_size, 0); 677 678 bch_refill_keybuf(dc->disk.c, buf, 679 &KEY(dc->disk.id, 680 next_stripe * dc->disk.stripe_size, 0), 681 dirty_pred); 682 683 if (array_freelist_empty(&buf->freelist)) 684 return; 685 686 stripe = next_stripe; 687 next: 688 if (wrapped && stripe > start_stripe) 689 return; 690 691 if (stripe == dc->disk.nr_stripes) { 692 stripe = 0; 693 wrapped = true; 694 } 695 } 696 } 697 698 /* 699 * Returns true if we scanned the entire disk 700 */ 701 static bool refill_dirty(struct cached_dev *dc) 702 { 703 struct keybuf *buf = &dc->writeback_keys; 704 struct bkey start = KEY(dc->disk.id, 0, 0); 705 struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0); 706 struct bkey start_pos; 707 708 /* 709 * make sure keybuf pos is inside the range for this disk - at bringup 710 * we might not be attached yet so this disk's inode nr isn't 711 * initialized then 712 */ 713 if (bkey_cmp(&buf->last_scanned, &start) < 0 || 714 bkey_cmp(&buf->last_scanned, &end) > 0) 715 buf->last_scanned = start; 716 717 if (dc->partial_stripes_expensive) { 718 refill_full_stripes(dc); 719 if (array_freelist_empty(&buf->freelist)) 720 return false; 721 } 722 723 start_pos = buf->last_scanned; 724 bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred); 725 726 if (bkey_cmp(&buf->last_scanned, &end) < 0) 727 return false; 728 729 /* 730 * If we get to the end start scanning again from the beginning, and 731 * only scan up to where we initially started scanning from: 732 */ 733 buf->last_scanned = start; 734 bch_refill_keybuf(dc->disk.c, buf, &start_pos, dirty_pred); 735 736 return bkey_cmp(&buf->last_scanned, &start_pos) >= 0; 737 } 738 739 static int bch_writeback_thread(void *arg) 740 { 741 struct cached_dev *dc = arg; 742 struct cache_set *c = dc->disk.c; 743 bool searched_full_index; 744 745 bch_ratelimit_reset(&dc->writeback_rate); 746 747 while (!kthread_should_stop() && 748 !test_bit(CACHE_SET_IO_DISABLE, &c->flags)) { 749 down_write(&dc->writeback_lock); 750 set_current_state(TASK_INTERRUPTIBLE); 751 /* 752 * If the bache device is detaching, skip here and continue 753 * to perform writeback. Otherwise, if no dirty data on cache, 754 * or there is dirty data on cache but writeback is disabled, 755 * the writeback thread should sleep here and wait for others 756 * to wake up it. 757 */ 758 if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) && 759 (!atomic_read(&dc->has_dirty) || !dc->writeback_running)) { 760 up_write(&dc->writeback_lock); 761 762 if (kthread_should_stop() || 763 test_bit(CACHE_SET_IO_DISABLE, &c->flags)) { 764 set_current_state(TASK_RUNNING); 765 break; 766 } 767 768 schedule(); 769 continue; 770 } 771 set_current_state(TASK_RUNNING); 772 773 searched_full_index = refill_dirty(dc); 774 775 if (searched_full_index && 776 RB_EMPTY_ROOT(&dc->writeback_keys.keys)) { 777 atomic_set(&dc->has_dirty, 0); 778 SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN); 779 bch_write_bdev_super(dc, NULL); 780 /* 781 * If bcache device is detaching via sysfs interface, 782 * writeback thread should stop after there is no dirty 783 * data on cache. BCACHE_DEV_DETACHING flag is set in 784 * bch_cached_dev_detach(). 785 */ 786 if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) { 787 struct closure cl; 788 789 closure_init_stack(&cl); 790 memset(&dc->sb.set_uuid, 0, 16); 791 SET_BDEV_STATE(&dc->sb, BDEV_STATE_NONE); 792 793 bch_write_bdev_super(dc, &cl); 794 closure_sync(&cl); 795 796 up_write(&dc->writeback_lock); 797 break; 798 } 799 800 /* 801 * When dirty data rate is high (e.g. 50%+), there might 802 * be heavy buckets fragmentation after writeback 803 * finished, which hurts following write performance. 804 * If users really care about write performance they 805 * may set BCH_ENABLE_AUTO_GC via sysfs, then when 806 * BCH_DO_AUTO_GC is set, garbage collection thread 807 * will be wake up here. After moving gc, the shrunk 808 * btree and discarded free buckets SSD space may be 809 * helpful for following write requests. 810 */ 811 if (c->gc_after_writeback == 812 (BCH_ENABLE_AUTO_GC|BCH_DO_AUTO_GC)) { 813 c->gc_after_writeback &= ~BCH_DO_AUTO_GC; 814 force_wake_up_gc(c); 815 } 816 } 817 818 up_write(&dc->writeback_lock); 819 820 read_dirty(dc); 821 822 if (searched_full_index) { 823 unsigned int delay = dc->writeback_delay * HZ; 824 825 while (delay && 826 !kthread_should_stop() && 827 !test_bit(CACHE_SET_IO_DISABLE, &c->flags) && 828 !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) 829 delay = schedule_timeout_interruptible(delay); 830 831 bch_ratelimit_reset(&dc->writeback_rate); 832 } 833 } 834 835 if (dc->writeback_write_wq) 836 destroy_workqueue(dc->writeback_write_wq); 837 838 cached_dev_put(dc); 839 wait_for_kthread_stop(); 840 841 return 0; 842 } 843 844 /* Init */ 845 #define INIT_KEYS_EACH_TIME 500000 846 847 struct sectors_dirty_init { 848 struct btree_op op; 849 unsigned int inode; 850 size_t count; 851 }; 852 853 static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b, 854 struct bkey *k) 855 { 856 struct sectors_dirty_init *op = container_of(_op, 857 struct sectors_dirty_init, op); 858 if (KEY_INODE(k) > op->inode) 859 return MAP_DONE; 860 861 if (KEY_DIRTY(k)) 862 bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k), 863 KEY_START(k), KEY_SIZE(k)); 864 865 op->count++; 866 if (!(op->count % INIT_KEYS_EACH_TIME)) 867 cond_resched(); 868 869 return MAP_CONTINUE; 870 } 871 872 static int bch_root_node_dirty_init(struct cache_set *c, 873 struct bcache_device *d, 874 struct bkey *k) 875 { 876 struct sectors_dirty_init op; 877 int ret; 878 879 bch_btree_op_init(&op.op, -1); 880 op.inode = d->id; 881 op.count = 0; 882 883 ret = bcache_btree(map_keys_recurse, 884 k, 885 c->root, 886 &op.op, 887 &KEY(op.inode, 0, 0), 888 sectors_dirty_init_fn, 889 0); 890 if (ret < 0) 891 pr_warn("sectors dirty init failed, ret=%d!\n", ret); 892 893 /* 894 * The op may be added to cache_set's btree_cache_wait 895 * in mca_cannibalize(), must ensure it is removed from 896 * the list and release btree_cache_alloc_lock before 897 * free op memory. 898 * Otherwise, the btree_cache_wait will be damaged. 899 */ 900 bch_cannibalize_unlock(c); 901 finish_wait(&c->btree_cache_wait, &(&op.op)->wait); 902 903 return ret; 904 } 905 906 static int bch_dirty_init_thread(void *arg) 907 { 908 struct dirty_init_thrd_info *info = arg; 909 struct bch_dirty_init_state *state = info->state; 910 struct cache_set *c = state->c; 911 struct btree_iter iter; 912 struct bkey *k, *p; 913 int cur_idx, prev_idx, skip_nr; 914 915 k = p = NULL; 916 prev_idx = 0; 917 918 min_heap_init(&iter.heap, NULL, MAX_BSETS); 919 bch_btree_iter_init(&c->root->keys, &iter, NULL); 920 k = bch_btree_iter_next_filter(&iter, &c->root->keys, bch_ptr_bad); 921 BUG_ON(!k); 922 923 p = k; 924 925 while (k) { 926 spin_lock(&state->idx_lock); 927 cur_idx = state->key_idx; 928 state->key_idx++; 929 spin_unlock(&state->idx_lock); 930 931 skip_nr = cur_idx - prev_idx; 932 933 while (skip_nr) { 934 k = bch_btree_iter_next_filter(&iter, 935 &c->root->keys, 936 bch_ptr_bad); 937 if (k) 938 p = k; 939 else { 940 atomic_set(&state->enough, 1); 941 /* Update state->enough earlier */ 942 smp_mb__after_atomic(); 943 goto out; 944 } 945 skip_nr--; 946 } 947 948 if (p) { 949 if (bch_root_node_dirty_init(c, state->d, p) < 0) 950 goto out; 951 } 952 953 p = NULL; 954 prev_idx = cur_idx; 955 } 956 957 out: 958 /* In order to wake up state->wait in time */ 959 smp_mb__before_atomic(); 960 if (atomic_dec_and_test(&state->started)) 961 wake_up(&state->wait); 962 963 return 0; 964 } 965 966 static int bch_btre_dirty_init_thread_nr(void) 967 { 968 int n = num_online_cpus()/2; 969 970 if (n == 0) 971 n = 1; 972 else if (n > BCH_DIRTY_INIT_THRD_MAX) 973 n = BCH_DIRTY_INIT_THRD_MAX; 974 975 return n; 976 } 977 978 void bch_sectors_dirty_init(struct bcache_device *d) 979 { 980 int i; 981 struct btree *b = NULL; 982 struct bkey *k = NULL; 983 struct btree_iter iter; 984 struct sectors_dirty_init op; 985 struct cache_set *c = d->c; 986 struct bch_dirty_init_state state; 987 988 min_heap_init(&iter.heap, NULL, MAX_BSETS); 989 990 retry_lock: 991 b = c->root; 992 rw_lock(0, b, b->level); 993 if (b != c->root) { 994 rw_unlock(0, b); 995 goto retry_lock; 996 } 997 998 /* Just count root keys if no leaf node */ 999 if (c->root->level == 0) { 1000 bch_btree_op_init(&op.op, -1); 1001 op.inode = d->id; 1002 op.count = 0; 1003 1004 for_each_key_filter(&c->root->keys, 1005 k, &iter, bch_ptr_invalid) { 1006 if (KEY_INODE(k) != op.inode) 1007 continue; 1008 sectors_dirty_init_fn(&op.op, c->root, k); 1009 } 1010 1011 rw_unlock(0, b); 1012 return; 1013 } 1014 1015 memset(&state, 0, sizeof(struct bch_dirty_init_state)); 1016 state.c = c; 1017 state.d = d; 1018 state.total_threads = bch_btre_dirty_init_thread_nr(); 1019 state.key_idx = 0; 1020 spin_lock_init(&state.idx_lock); 1021 atomic_set(&state.started, 0); 1022 atomic_set(&state.enough, 0); 1023 init_waitqueue_head(&state.wait); 1024 1025 for (i = 0; i < state.total_threads; i++) { 1026 /* Fetch latest state.enough earlier */ 1027 smp_mb__before_atomic(); 1028 if (atomic_read(&state.enough)) 1029 break; 1030 1031 atomic_inc(&state.started); 1032 state.infos[i].state = &state; 1033 state.infos[i].thread = 1034 kthread_run(bch_dirty_init_thread, &state.infos[i], 1035 "bch_dirtcnt[%d]", i); 1036 if (IS_ERR(state.infos[i].thread)) { 1037 pr_err("fails to run thread bch_dirty_init[%d]\n", i); 1038 atomic_dec(&state.started); 1039 for (--i; i >= 0; i--) 1040 kthread_stop(state.infos[i].thread); 1041 goto out; 1042 } 1043 } 1044 1045 out: 1046 /* Must wait for all threads to stop. */ 1047 wait_event(state.wait, atomic_read(&state.started) == 0); 1048 rw_unlock(0, b); 1049 } 1050 1051 void bch_cached_dev_writeback_init(struct cached_dev *dc) 1052 { 1053 sema_init(&dc->in_flight, 64); 1054 init_rwsem(&dc->writeback_lock); 1055 bch_keybuf_init(&dc->writeback_keys); 1056 1057 dc->writeback_metadata = true; 1058 dc->writeback_running = false; 1059 dc->writeback_consider_fragment = true; 1060 dc->writeback_percent = 10; 1061 dc->writeback_delay = 30; 1062 atomic_long_set(&dc->writeback_rate.rate, 1024); 1063 dc->writeback_rate_minimum = 8; 1064 1065 dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT; 1066 dc->writeback_rate_p_term_inverse = 40; 1067 dc->writeback_rate_fp_term_low = 1; 1068 dc->writeback_rate_fp_term_mid = 10; 1069 dc->writeback_rate_fp_term_high = 1000; 1070 dc->writeback_rate_i_term_inverse = 10000; 1071 1072 /* For dc->writeback_lock contention in update_writeback_rate() */ 1073 dc->rate_update_retry = 0; 1074 1075 WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags)); 1076 INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate); 1077 } 1078 1079 int bch_cached_dev_writeback_start(struct cached_dev *dc) 1080 { 1081 dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq", 1082 WQ_MEM_RECLAIM, 0); 1083 if (!dc->writeback_write_wq) 1084 return -ENOMEM; 1085 1086 cached_dev_get(dc); 1087 dc->writeback_thread = kthread_create(bch_writeback_thread, dc, 1088 "bcache_writeback"); 1089 if (IS_ERR(dc->writeback_thread)) { 1090 cached_dev_put(dc); 1091 destroy_workqueue(dc->writeback_write_wq); 1092 return PTR_ERR(dc->writeback_thread); 1093 } 1094 dc->writeback_running = true; 1095 1096 WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags)); 1097 schedule_delayed_work(&dc->writeback_rate_update, 1098 dc->writeback_rate_update_seconds * HZ); 1099 1100 bch_writeback_queue(dc); 1101 1102 return 0; 1103 } 1104