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