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 flush_workqueue(dc->writeback_write_wq); 806 destroy_workqueue(dc->writeback_write_wq); 807 } 808 cached_dev_put(dc); 809 wait_for_kthread_stop(); 810 811 return 0; 812 } 813 814 /* Init */ 815 #define INIT_KEYS_EACH_TIME 500000 816 817 struct sectors_dirty_init { 818 struct btree_op op; 819 unsigned int inode; 820 size_t count; 821 }; 822 823 static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b, 824 struct bkey *k) 825 { 826 struct sectors_dirty_init *op = container_of(_op, 827 struct sectors_dirty_init, op); 828 if (KEY_INODE(k) > op->inode) 829 return MAP_DONE; 830 831 if (KEY_DIRTY(k)) 832 bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k), 833 KEY_START(k), KEY_SIZE(k)); 834 835 op->count++; 836 if (!(op->count % INIT_KEYS_EACH_TIME)) 837 cond_resched(); 838 839 return MAP_CONTINUE; 840 } 841 842 static int bch_root_node_dirty_init(struct cache_set *c, 843 struct bcache_device *d, 844 struct bkey *k) 845 { 846 struct sectors_dirty_init op; 847 int ret; 848 849 bch_btree_op_init(&op.op, -1); 850 op.inode = d->id; 851 op.count = 0; 852 853 ret = bcache_btree(map_keys_recurse, 854 k, 855 c->root, 856 &op.op, 857 &KEY(op.inode, 0, 0), 858 sectors_dirty_init_fn, 859 0); 860 if (ret < 0) 861 pr_warn("sectors dirty init failed, ret=%d!\n", ret); 862 863 return ret; 864 } 865 866 static int bch_dirty_init_thread(void *arg) 867 { 868 struct dirty_init_thrd_info *info = arg; 869 struct bch_dirty_init_state *state = info->state; 870 struct cache_set *c = state->c; 871 struct btree_iter iter; 872 struct bkey *k, *p; 873 int cur_idx, prev_idx, skip_nr; 874 875 k = p = NULL; 876 cur_idx = prev_idx = 0; 877 878 bch_btree_iter_init(&c->root->keys, &iter, NULL); 879 k = bch_btree_iter_next_filter(&iter, &c->root->keys, bch_ptr_bad); 880 BUG_ON(!k); 881 882 p = k; 883 884 while (k) { 885 spin_lock(&state->idx_lock); 886 cur_idx = state->key_idx; 887 state->key_idx++; 888 spin_unlock(&state->idx_lock); 889 890 skip_nr = cur_idx - prev_idx; 891 892 while (skip_nr) { 893 k = bch_btree_iter_next_filter(&iter, 894 &c->root->keys, 895 bch_ptr_bad); 896 if (k) 897 p = k; 898 else { 899 atomic_set(&state->enough, 1); 900 /* Update state->enough earlier */ 901 smp_mb__after_atomic(); 902 goto out; 903 } 904 skip_nr--; 905 } 906 907 if (p) { 908 if (bch_root_node_dirty_init(c, state->d, p) < 0) 909 goto out; 910 } 911 912 p = NULL; 913 prev_idx = cur_idx; 914 } 915 916 out: 917 /* In order to wake up state->wait in time */ 918 smp_mb__before_atomic(); 919 if (atomic_dec_and_test(&state->started)) 920 wake_up(&state->wait); 921 922 return 0; 923 } 924 925 static int bch_btre_dirty_init_thread_nr(void) 926 { 927 int n = num_online_cpus()/2; 928 929 if (n == 0) 930 n = 1; 931 else if (n > BCH_DIRTY_INIT_THRD_MAX) 932 n = BCH_DIRTY_INIT_THRD_MAX; 933 934 return n; 935 } 936 937 void bch_sectors_dirty_init(struct bcache_device *d) 938 { 939 int i; 940 struct bkey *k = NULL; 941 struct btree_iter iter; 942 struct sectors_dirty_init op; 943 struct cache_set *c = d->c; 944 struct bch_dirty_init_state state; 945 946 /* Just count root keys if no leaf node */ 947 rw_lock(0, c->root, c->root->level); 948 if (c->root->level == 0) { 949 bch_btree_op_init(&op.op, -1); 950 op.inode = d->id; 951 op.count = 0; 952 953 for_each_key_filter(&c->root->keys, 954 k, &iter, bch_ptr_invalid) 955 sectors_dirty_init_fn(&op.op, c->root, k); 956 957 rw_unlock(0, c->root); 958 return; 959 } 960 961 memset(&state, 0, sizeof(struct bch_dirty_init_state)); 962 state.c = c; 963 state.d = d; 964 state.total_threads = bch_btre_dirty_init_thread_nr(); 965 state.key_idx = 0; 966 spin_lock_init(&state.idx_lock); 967 atomic_set(&state.started, 0); 968 atomic_set(&state.enough, 0); 969 init_waitqueue_head(&state.wait); 970 971 for (i = 0; i < state.total_threads; i++) { 972 /* Fetch latest state.enough earlier */ 973 smp_mb__before_atomic(); 974 if (atomic_read(&state.enough)) 975 break; 976 977 state.infos[i].state = &state; 978 state.infos[i].thread = 979 kthread_run(bch_dirty_init_thread, &state.infos[i], 980 "bch_dirtcnt[%d]", i); 981 if (IS_ERR(state.infos[i].thread)) { 982 pr_err("fails to run thread bch_dirty_init[%d]\n", i); 983 for (--i; i >= 0; i--) 984 kthread_stop(state.infos[i].thread); 985 goto out; 986 } 987 atomic_inc(&state.started); 988 } 989 990 out: 991 /* Must wait for all threads to stop. */ 992 wait_event(state.wait, atomic_read(&state.started) == 0); 993 rw_unlock(0, c->root); 994 } 995 996 void bch_cached_dev_writeback_init(struct cached_dev *dc) 997 { 998 sema_init(&dc->in_flight, 64); 999 init_rwsem(&dc->writeback_lock); 1000 bch_keybuf_init(&dc->writeback_keys); 1001 1002 dc->writeback_metadata = true; 1003 dc->writeback_running = false; 1004 dc->writeback_consider_fragment = true; 1005 dc->writeback_percent = 10; 1006 dc->writeback_delay = 30; 1007 atomic_long_set(&dc->writeback_rate.rate, 1024); 1008 dc->writeback_rate_minimum = 8; 1009 1010 dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT; 1011 dc->writeback_rate_p_term_inverse = 40; 1012 dc->writeback_rate_fp_term_low = 1; 1013 dc->writeback_rate_fp_term_mid = 10; 1014 dc->writeback_rate_fp_term_high = 1000; 1015 dc->writeback_rate_i_term_inverse = 10000; 1016 1017 /* For dc->writeback_lock contention in update_writeback_rate() */ 1018 dc->rate_update_retry = 0; 1019 1020 WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags)); 1021 INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate); 1022 } 1023 1024 int bch_cached_dev_writeback_start(struct cached_dev *dc) 1025 { 1026 dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq", 1027 WQ_MEM_RECLAIM, 0); 1028 if (!dc->writeback_write_wq) 1029 return -ENOMEM; 1030 1031 cached_dev_get(dc); 1032 dc->writeback_thread = kthread_create(bch_writeback_thread, dc, 1033 "bcache_writeback"); 1034 if (IS_ERR(dc->writeback_thread)) { 1035 cached_dev_put(dc); 1036 destroy_workqueue(dc->writeback_write_wq); 1037 return PTR_ERR(dc->writeback_thread); 1038 } 1039 dc->writeback_running = true; 1040 1041 WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags)); 1042 schedule_delayed_work(&dc->writeback_rate_update, 1043 dc->writeback_rate_update_seconds * HZ); 1044 1045 bch_writeback_queue(dc); 1046 1047 return 0; 1048 } 1049