summaryrefslogtreecommitdiff
path: root/drivers/md/bcache/writeback.c
blob: ba3ee48320f2a38509adb2603f766c55e67f1da1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
/*
 * background writeback - scan btree for dirty data and write it to the backing
 * device
 *
 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
 * Copyright 2012 Google, Inc.
 */

#include "bcache.h"
#include "btree.h"
#include "debug.h"
#include "writeback.h"

#include <trace/events/bcache.h>

static struct workqueue_struct *dirty_wq;

static void read_dirty(struct closure *);

struct dirty_io {
	struct closure		cl;
	struct cached_dev	*dc;
	struct bio		bio;
};

/* Rate limiting */

static void __update_writeback_rate(struct cached_dev *dc)
{
	struct cache_set *c = dc->disk.c;
	uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size;
	uint64_t cache_dirty_target =
		div_u64(cache_sectors * dc->writeback_percent, 100);

	int64_t target = div64_u64(cache_dirty_target * bdev_sectors(dc->bdev),
				   c->cached_dev_sectors);

	/* PD controller */

	int change = 0;
	int64_t error;
	int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);
	int64_t derivative = dirty - dc->disk.sectors_dirty_last;

	dc->disk.sectors_dirty_last = dirty;

	derivative *= dc->writeback_rate_d_term;
	derivative = clamp(derivative, -dirty, dirty);

	derivative = ewma_add(dc->disk.sectors_dirty_derivative, derivative,
			      dc->writeback_rate_d_smooth, 0);

	/* Avoid divide by zero */
	if (!target)
		goto out;

	error = div64_s64((dirty + derivative - target) << 8, target);

	change = div_s64((dc->writeback_rate.rate * error) >> 8,
			 dc->writeback_rate_p_term_inverse);

	/* Don't increase writeback rate if the device isn't keeping up */
	if (change > 0 &&
	    time_after64(local_clock(),
			 dc->writeback_rate.next + 10 * NSEC_PER_MSEC))
		change = 0;

	dc->writeback_rate.rate =
		clamp_t(int64_t, dc->writeback_rate.rate + change,
			1, NSEC_PER_MSEC);
out:
	dc->writeback_rate_derivative = derivative;
	dc->writeback_rate_change = change;
	dc->writeback_rate_target = target;

	schedule_delayed_work(&dc->writeback_rate_update,
			      dc->writeback_rate_update_seconds * HZ);
}

static void update_writeback_rate(struct work_struct *work)
{
	struct cached_dev *dc = container_of(to_delayed_work(work),
					     struct cached_dev,
					     writeback_rate_update);

	down_read(&dc->writeback_lock);

	if (atomic_read(&dc->has_dirty) &&
	    dc->writeback_percent)
		__update_writeback_rate(dc);

	up_read(&dc->writeback_lock);
}

static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors)
{
	uint64_t ret;

	if (atomic_read(&dc->disk.detaching) ||
	    !dc->writeback_percent)
		return 0;

	ret = bch_next_delay(&dc->writeback_rate, sectors * 10000000ULL);

	return min_t(uint64_t, ret, HZ);
}

/* Background writeback */

static bool dirty_pred(struct keybuf *buf, struct bkey *k)
{
	return KEY_DIRTY(k);
}

static bool dirty_full_stripe_pred(struct keybuf *buf, struct bkey *k)
{
	uint64_t stripe;
	unsigned nr_sectors = KEY_SIZE(k);
	struct cached_dev *dc = container_of(buf, struct cached_dev,
					     writeback_keys);
	unsigned stripe_size = 1 << dc->disk.stripe_size_bits;

	if (!KEY_DIRTY(k))
		return false;

	stripe = KEY_START(k) >> dc->disk.stripe_size_bits;
	while (1) {
		if (atomic_read(dc->disk.stripe_sectors_dirty + stripe) !=
		    stripe_size)
			return false;

		if (nr_sectors <= stripe_size)
			return true;

		nr_sectors -= stripe_size;
		stripe++;
	}
}

static void dirty_init(struct keybuf_key *w)
{
	struct dirty_io *io = w->private;
	struct bio *bio = &io->bio;

	bio_init(bio);
	if (!io->dc->writeback_percent)
		bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));

	bio->bi_size		= KEY_SIZE(&w->key) << 9;
	bio->bi_max_vecs	= DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS);
	bio->bi_private		= w;
	bio->bi_io_vec		= bio->bi_inline_vecs;
	bch_bio_map(bio, NULL);
}

static void refill_dirty(struct closure *cl)
{
	struct cached_dev *dc = container_of(cl, struct cached_dev,
					     writeback.cl);
	struct keybuf *buf = &dc->writeback_keys;
	bool searched_from_start = false;
	struct bkey end = MAX_KEY;
	SET_KEY_INODE(&end, dc->disk.id);

	if (!atomic_read(&dc->disk.detaching) &&
	    !dc->writeback_running)
		closure_return(cl);

	down_write(&dc->writeback_lock);

	if (!atomic_read(&dc->has_dirty)) {
		SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
		bch_write_bdev_super(dc, NULL);

		up_write(&dc->writeback_lock);
		closure_return(cl);
	}

	if (bkey_cmp(&buf->last_scanned, &end) >= 0) {
		buf->last_scanned = KEY(dc->disk.id, 0, 0);
		searched_from_start = true;
	}

	if (dc->partial_stripes_expensive) {
		uint64_t i;

		for (i = 0; i < dc->disk.nr_stripes; i++)
			if (atomic_read(dc->disk.stripe_sectors_dirty + i) ==
			    1 << dc->disk.stripe_size_bits)
				goto full_stripes;

		goto normal_refill;
full_stripes:
		bch_refill_keybuf(dc->disk.c, buf, &end,
				  dirty_full_stripe_pred);
	} else {
normal_refill:
		bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
	}

	if (bkey_cmp(&buf->last_scanned, &end) >= 0 && searched_from_start) {
		/* Searched the entire btree  - delay awhile */

		if (RB_EMPTY_ROOT(&buf->keys)) {
			atomic_set(&dc->has_dirty, 0);
			cached_dev_put(dc);
		}

		if (!atomic_read(&dc->disk.detaching))
			closure_delay(&dc->writeback, dc->writeback_delay * HZ);
	}

	up_write(&dc->writeback_lock);

	bch_ratelimit_reset(&dc->writeback_rate);

	/* Punt to workqueue only so we don't recurse and blow the stack */
	continue_at(cl, read_dirty, dirty_wq);
}

void bch_writeback_queue(struct cached_dev *dc)
{
	if (closure_trylock(&dc->writeback.cl, &dc->disk.cl)) {
		if (!atomic_read(&dc->disk.detaching))
			closure_delay(&dc->writeback, dc->writeback_delay * HZ);

		continue_at(&dc->writeback.cl, refill_dirty, dirty_wq);
	}
}

void bch_writeback_add(struct cached_dev *dc)
{
	if (!atomic_read(&dc->has_dirty) &&
	    !atomic_xchg(&dc->has_dirty, 1)) {
		atomic_inc(&dc->count);

		if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) {
			SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY);
			/* XXX: should do this synchronously */
			bch_write_bdev_super(dc, NULL);
		}

		bch_writeback_queue(dc);

		if (dc->writeback_percent)
			schedule_delayed_work(&dc->writeback_rate_update,
				      dc->writeback_rate_update_seconds * HZ);
	}
}

void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned inode,
				  uint64_t offset, int nr_sectors)
{
	struct bcache_device *d = c->devices[inode];
	unsigned stripe_size, stripe_offset;
	uint64_t stripe;

	if (!d)
		return;

	stripe_size = 1 << d->stripe_size_bits;
	stripe = offset >> d->stripe_size_bits;
	stripe_offset = offset & (stripe_size - 1);

	while (nr_sectors) {
		int s = min_t(unsigned, abs(nr_sectors),
			      stripe_size - stripe_offset);

		if (nr_sectors < 0)
			s = -s;

		atomic_add(s, d->stripe_sectors_dirty + stripe);
		nr_sectors -= s;
		stripe_offset = 0;
		stripe++;
	}
}

/* Background writeback - IO loop */

static void dirty_io_destructor(struct closure *cl)
{
	struct dirty_io *io = container_of(cl, struct dirty_io, cl);
	kfree(io);
}

static void write_dirty_finish(struct closure *cl)
{
	struct dirty_io *io = container_of(cl, struct dirty_io, cl);
	struct keybuf_key *w = io->bio.bi_private;
	struct cached_dev *dc = io->dc;
	struct bio_vec *bv;
	int i;

	bio_for_each_segment_all(bv, &io->bio, i)
		__free_page(bv->bv_page);

	/* This is kind of a dumb way of signalling errors. */
	if (KEY_DIRTY(&w->key)) {
		unsigned i;
		struct btree_op op;
		bch_btree_op_init_stack(&op);

		op.type = BTREE_REPLACE;
		bkey_copy(&op.replace, &w->key);

		SET_KEY_DIRTY(&w->key, false);
		bch_keylist_add(&op.keys, &w->key);

		for (i = 0; i < KEY_PTRS(&w->key); i++)
			atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);

		bch_btree_insert(&op, dc->disk.c);
		closure_sync(&op.cl);

		if (op.insert_collision)
			trace_bcache_writeback_collision(&w->key);

		atomic_long_inc(op.insert_collision
				? &dc->disk.c->writeback_keys_failed
				: &dc->disk.c->writeback_keys_done);
	}

	bch_keybuf_del(&dc->writeback_keys, w);
	up(&dc->in_flight);

	closure_return_with_destructor(cl, dirty_io_destructor);
}

static void dirty_endio(struct bio *bio, int error)
{
	struct keybuf_key *w = bio->bi_private;
	struct dirty_io *io = w->private;

	if (error)
		SET_KEY_DIRTY(&w->key, false);

	closure_put(&io->cl);
}

static void write_dirty(struct closure *cl)
{
	struct dirty_io *io = container_of(cl, struct dirty_io, cl);
	struct keybuf_key *w = io->bio.bi_private;

	dirty_init(w);
	io->bio.bi_rw		= WRITE;
	io->bio.bi_sector	= KEY_START(&w->key);
	io->bio.bi_bdev		= io->dc->bdev;
	io->bio.bi_end_io	= dirty_endio;

	closure_bio_submit(&io->bio, cl, &io->dc->disk);

	continue_at(cl, write_dirty_finish, system_wq);
}

static void read_dirty_endio(struct bio *bio, int error)
{
	struct keybuf_key *w = bio->bi_private;
	struct dirty_io *io = w->private;

	bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0),
			    error, "reading dirty data from cache");

	dirty_endio(bio, error);
}

static void read_dirty_submit(struct closure *cl)
{
	struct dirty_io *io = container_of(cl, struct dirty_io, cl);

	closure_bio_submit(&io->bio, cl, &io->dc->disk);

	continue_at(cl, write_dirty, system_wq);
}

static void read_dirty(struct closure *cl)
{
	struct cached_dev *dc = container_of(cl, struct cached_dev,
					     writeback.cl);
	unsigned delay = writeback_delay(dc, 0);
	struct keybuf_key *w;
	struct dirty_io *io;

	/*
	 * XXX: if we error, background writeback just spins. Should use some
	 * mempools.
	 */

	while (1) {
		w = bch_keybuf_next(&dc->writeback_keys);
		if (!w)
			break;

		BUG_ON(ptr_stale(dc->disk.c, &w->key, 0));

		if (delay > 0 &&
		    (KEY_START(&w->key) != dc->last_read ||
		     jiffies_to_msecs(delay) > 50))
			delay = schedule_timeout_uninterruptible(delay);

		dc->last_read	= KEY_OFFSET(&w->key);

		io = kzalloc(sizeof(struct dirty_io) + sizeof(struct bio_vec)
			     * DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),
			     GFP_KERNEL);
		if (!io)
			goto err;

		w->private	= io;
		io->dc		= dc;

		dirty_init(w);
		io->bio.bi_sector	= PTR_OFFSET(&w->key, 0);
		io->bio.bi_bdev		= PTR_CACHE(dc->disk.c,
						    &w->key, 0)->bdev;
		io->bio.bi_rw		= READ;
		io->bio.bi_end_io	= read_dirty_endio;

		if (bio_alloc_pages(&io->bio, GFP_KERNEL))
			goto err_free;

		trace_bcache_writeback(&w->key);

		down(&dc->in_flight);
		closure_call(&io->cl, read_dirty_submit, NULL, cl);

		delay = writeback_delay(dc, KEY_SIZE(&w->key));
	}

	if (0) {
err_free:
		kfree(w->private);
err:
		bch_keybuf_del(&dc->writeback_keys, w);
	}

	/*
	 * Wait for outstanding writeback IOs to finish (and keybuf slots to be
	 * freed) before refilling again
	 */
	continue_at(cl, refill_dirty, dirty_wq);
}

/* Init */

static int bch_btree_sectors_dirty_init(struct btree *b, struct btree_op *op,
					struct cached_dev *dc)
{
	struct bkey *k;
	struct btree_iter iter;

	bch_btree_iter_init(b, &iter, &KEY(dc->disk.id, 0, 0));
	while ((k = bch_btree_iter_next_filter(&iter, b, bch_ptr_bad)))
		if (!b->level) {
			if (KEY_INODE(k) > dc->disk.id)
				break;

			if (KEY_DIRTY(k))
				bcache_dev_sectors_dirty_add(b->c, dc->disk.id,
							     KEY_START(k),
							     KEY_SIZE(k));
		} else {
			btree(sectors_dirty_init, k, b, op, dc);
			if (KEY_INODE(k) > dc->disk.id)
				break;

			cond_resched();
		}

	return 0;
}

void bch_sectors_dirty_init(struct cached_dev *dc)
{
	struct btree_op op;

	bch_btree_op_init_stack(&op);
	btree_root(sectors_dirty_init, dc->disk.c, &op, dc);
}

void bch_cached_dev_writeback_init(struct cached_dev *dc)
{
	sema_init(&dc->in_flight, 64);
	closure_init_unlocked(&dc->writeback);
	init_rwsem(&dc->writeback_lock);

	bch_keybuf_init(&dc->writeback_keys);

	dc->writeback_metadata		= true;
	dc->writeback_running		= true;
	dc->writeback_percent		= 10;
	dc->writeback_delay		= 30;
	dc->writeback_rate.rate		= 1024;

	dc->writeback_rate_update_seconds = 30;
	dc->writeback_rate_d_term	= 16;
	dc->writeback_rate_p_term_inverse = 64;
	dc->writeback_rate_d_smooth	= 8;

	INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
	schedule_delayed_work(&dc->writeback_rate_update,
			      dc->writeback_rate_update_seconds * HZ);
}

void bch_writeback_exit(void)
{
	if (dirty_wq)
		destroy_workqueue(dirty_wq);
}

int __init bch_writeback_init(void)
{
	dirty_wq = create_workqueue("bcache_writeback");
	if (!dirty_wq)
		return -ENOMEM;

	return 0;
}