summaryrefslogtreecommitdiff
path: root/block/badblocks.c
blob: 96aeb9194a2ef0d72c149b54d834bb810126779e (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
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
/*
 * Bad block management
 *
 * - Heavily based on MD badblocks code from Neil Brown
 *
 * Copyright (c) 2015, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */

#include <linux/badblocks.h>
#include <linux/seqlock.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/stddef.h>
#include <linux/types.h>
#include <linux/slab.h>

/**
 * badblocks_check() - check a given range for bad sectors
 * @bb:		the badblocks structure that holds all badblock information
 * @s:		sector (start) at which to check for badblocks
 * @sectors:	number of sectors to check for badblocks
 * @first_bad:	pointer to store location of the first badblock
 * @bad_sectors: pointer to store number of badblocks after @first_bad
 *
 * We can record which blocks on each device are 'bad' and so just
 * fail those blocks, or that stripe, rather than the whole device.
 * Entries in the bad-block table are 64bits wide.  This comprises:
 * Length of bad-range, in sectors: 0-511 for lengths 1-512
 * Start of bad-range, sector offset, 54 bits (allows 8 exbibytes)
 *  A 'shift' can be set so that larger blocks are tracked and
 *  consequently larger devices can be covered.
 * 'Acknowledged' flag - 1 bit. - the most significant bit.
 *
 * Locking of the bad-block table uses a seqlock so badblocks_check
 * might need to retry if it is very unlucky.
 * We will sometimes want to check for bad blocks in a bi_end_io function,
 * so we use the write_seqlock_irq variant.
 *
 * When looking for a bad block we specify a range and want to
 * know if any block in the range is bad.  So we binary-search
 * to the last range that starts at-or-before the given endpoint,
 * (or "before the sector after the target range")
 * then see if it ends after the given start.
 *
 * Return:
 *  0: there are no known bad blocks in the range
 *  1: there are known bad block which are all acknowledged
 * -1: there are bad blocks which have not yet been acknowledged in metadata.
 * plus the start/length of the first bad section we overlap.
 */
int badblocks_check(struct badblocks *bb, sector_t s, int sectors,
			sector_t *first_bad, int *bad_sectors)
{
	int hi;
	int lo;
	u64 *p = bb->page;
	int rv;
	sector_t target = s + sectors;
	unsigned seq;

	if (bb->shift > 0) {
		/* round the start down, and the end up */
		s >>= bb->shift;
		target += (1<<bb->shift) - 1;
		target >>= bb->shift;
		sectors = target - s;
	}
	/* 'target' is now the first block after the bad range */

retry:
	seq = read_seqbegin(&bb->lock);
	lo = 0;
	rv = 0;
	hi = bb->count;

	/* Binary search between lo and hi for 'target'
	 * i.e. for the last range that starts before 'target'
	 */
	/* INVARIANT: ranges before 'lo' and at-or-after 'hi'
	 * are known not to be the last range before target.
	 * VARIANT: hi-lo is the number of possible
	 * ranges, and decreases until it reaches 1
	 */
	while (hi - lo > 1) {
		int mid = (lo + hi) / 2;
		sector_t a = BB_OFFSET(p[mid]);

		if (a < target)
			/* This could still be the one, earlier ranges
			 * could not.
			 */
			lo = mid;
		else
			/* This and later ranges are definitely out. */
			hi = mid;
	}
	/* 'lo' might be the last that started before target, but 'hi' isn't */
	if (hi > lo) {
		/* need to check all range that end after 's' to see if
		 * any are unacknowledged.
		 */
		while (lo >= 0 &&
		       BB_OFFSET(p[lo]) + BB_LEN(p[lo]) > s) {
			if (BB_OFFSET(p[lo]) < target) {
				/* starts before the end, and finishes after
				 * the start, so they must overlap
				 */
				if (rv != -1 && BB_ACK(p[lo]))
					rv = 1;
				else
					rv = -1;
				*first_bad = BB_OFFSET(p[lo]);
				*bad_sectors = BB_LEN(p[lo]);
			}
			lo--;
		}
	}

	if (read_seqretry(&bb->lock, seq))
		goto retry;

	return rv;
}
EXPORT_SYMBOL_GPL(badblocks_check);

/**
 * badblocks_set() - Add a range of bad blocks to the table.
 * @bb:		the badblocks structure that holds all badblock information
 * @s:		first sector to mark as bad
 * @sectors:	number of sectors to mark as bad
 * @acknowledged: weather to mark the bad sectors as acknowledged
 *
 * This might extend the table, or might contract it if two adjacent ranges
 * can be merged. We binary-search to find the 'insertion' point, then
 * decide how best to handle it.
 *
 * Return:
 *  0: success
 *  1: failed to set badblocks (out of space)
 */
int badblocks_set(struct badblocks *bb, sector_t s, int sectors,
			int acknowledged)
{
	u64 *p;
	int lo, hi;
	int rv = 0;
	unsigned long flags;

	if (bb->shift < 0)
		/* badblocks are disabled */
		return 0;

	if (bb->shift) {
		/* round the start down, and the end up */
		sector_t next = s + sectors;

		s >>= bb->shift;
		next += (1<<bb->shift) - 1;
		next >>= bb->shift;
		sectors = next - s;
	}

	write_seqlock_irqsave(&bb->lock, flags);

	p = bb->page;
	lo = 0;
	hi = bb->count;
	/* Find the last range that starts at-or-before 's' */
	while (hi - lo > 1) {
		int mid = (lo + hi) / 2;
		sector_t a = BB_OFFSET(p[mid]);

		if (a <= s)
			lo = mid;
		else
			hi = mid;
	}
	if (hi > lo && BB_OFFSET(p[lo]) > s)
		hi = lo;

	if (hi > lo) {
		/* we found a range that might merge with the start
		 * of our new range
		 */
		sector_t a = BB_OFFSET(p[lo]);
		sector_t e = a + BB_LEN(p[lo]);
		int ack = BB_ACK(p[lo]);

		if (e >= s) {
			/* Yes, we can merge with a previous range */
			if (s == a && s + sectors >= e)
				/* new range covers old */
				ack = acknowledged;
			else
				ack = ack && acknowledged;

			if (e < s + sectors)
				e = s + sectors;
			if (e - a <= BB_MAX_LEN) {
				p[lo] = BB_MAKE(a, e-a, ack);
				s = e;
			} else {
				/* does not all fit in one range,
				 * make p[lo] maximal
				 */
				if (BB_LEN(p[lo]) != BB_MAX_LEN)
					p[lo] = BB_MAKE(a, BB_MAX_LEN, ack);
				s = a + BB_MAX_LEN;
			}
			sectors = e - s;
		}
	}
	if (sectors && hi < bb->count) {
		/* 'hi' points to the first range that starts after 's'.
		 * Maybe we can merge with the start of that range
		 */
		sector_t a = BB_OFFSET(p[hi]);
		sector_t e = a + BB_LEN(p[hi]);
		int ack = BB_ACK(p[hi]);

		if (a <= s + sectors) {
			/* merging is possible */
			if (e <= s + sectors) {
				/* full overlap */
				e = s + sectors;
				ack = acknowledged;
			} else
				ack = ack && acknowledged;

			a = s;
			if (e - a <= BB_MAX_LEN) {
				p[hi] = BB_MAKE(a, e-a, ack);
				s = e;
			} else {
				p[hi] = BB_MAKE(a, BB_MAX_LEN, ack);
				s = a + BB_MAX_LEN;
			}
			sectors = e - s;
			lo = hi;
			hi++;
		}
	}
	if (sectors == 0 && hi < bb->count) {
		/* we might be able to combine lo and hi */
		/* Note: 's' is at the end of 'lo' */
		sector_t a = BB_OFFSET(p[hi]);
		int lolen = BB_LEN(p[lo]);
		int hilen = BB_LEN(p[hi]);
		int newlen = lolen + hilen - (s - a);

		if (s >= a && newlen < BB_MAX_LEN) {
			/* yes, we can combine them */
			int ack = BB_ACK(p[lo]) && BB_ACK(p[hi]);

			p[lo] = BB_MAKE(BB_OFFSET(p[lo]), newlen, ack);
			memmove(p + hi, p + hi + 1,
				(bb->count - hi - 1) * 8);
			bb->count--;
		}
	}
	while (sectors) {
		/* didn't merge (it all).
		 * Need to add a range just before 'hi'
		 */
		if (bb->count >= MAX_BADBLOCKS) {
			/* No room for more */
			rv = 1;
			break;
		} else {
			int this_sectors = sectors;

			memmove(p + hi + 1, p + hi,
				(bb->count - hi) * 8);
			bb->count++;

			if (this_sectors > BB_MAX_LEN)
				this_sectors = BB_MAX_LEN;
			p[hi] = BB_MAKE(s, this_sectors, acknowledged);
			sectors -= this_sectors;
			s += this_sectors;
		}
	}

	bb->changed = 1;
	if (!acknowledged)
		bb->unacked_exist = 1;
	write_sequnlock_irqrestore(&bb->lock, flags);

	return rv;
}
EXPORT_SYMBOL_GPL(badblocks_set);

/**
 * badblocks_clear() - Remove a range of bad blocks to the table.
 * @bb:		the badblocks structure that holds all badblock information
 * @s:		first sector to mark as bad
 * @sectors:	number of sectors to mark as bad
 *
 * This may involve extending the table if we spilt a region,
 * but it must not fail.  So if the table becomes full, we just
 * drop the remove request.
 *
 * Return:
 *  0: success
 *  1: failed to clear badblocks
 */
int badblocks_clear(struct badblocks *bb, sector_t s, int sectors)
{
	u64 *p;
	int lo, hi;
	sector_t target = s + sectors;
	int rv = 0;

	if (bb->shift > 0) {
		/* When clearing we round the start up and the end down.
		 * This should not matter as the shift should align with
		 * the block size and no rounding should ever be needed.
		 * However it is better the think a block is bad when it
		 * isn't than to think a block is not bad when it is.
		 */
		s += (1<<bb->shift) - 1;
		s >>= bb->shift;
		target >>= bb->shift;
		sectors = target - s;
	}

	write_seqlock_irq(&bb->lock);

	p = bb->page;
	lo = 0;
	hi = bb->count;
	/* Find the last range that starts before 'target' */
	while (hi - lo > 1) {
		int mid = (lo + hi) / 2;
		sector_t a = BB_OFFSET(p[mid]);

		if (a < target)
			lo = mid;
		else
			hi = mid;
	}
	if (hi > lo) {
		/* p[lo] is the last range that could overlap the
		 * current range.  Earlier ranges could also overlap,
		 * but only this one can overlap the end of the range.
		 */
		if (BB_OFFSET(p[lo]) + BB_LEN(p[lo]) > target) {
			/* Partial overlap, leave the tail of this range */
			int ack = BB_ACK(p[lo]);
			sector_t a = BB_OFFSET(p[lo]);
			sector_t end = a + BB_LEN(p[lo]);

			if (a < s) {
				/* we need to split this range */
				if (bb->count >= MAX_BADBLOCKS) {
					rv = -ENOSPC;
					goto out;
				}
				memmove(p+lo+1, p+lo, (bb->count - lo) * 8);
				bb->count++;
				p[lo] = BB_MAKE(a, s-a, ack);
				lo++;
			}
			p[lo] = BB_MAKE(target, end - target, ack);
			/* there is no longer an overlap */
			hi = lo;
			lo--;
		}
		while (lo >= 0 &&
		       BB_OFFSET(p[lo]) + BB_LEN(p[lo]) > s) {
			/* This range does overlap */
			if (BB_OFFSET(p[lo]) < s) {
				/* Keep the early parts of this range. */
				int ack = BB_ACK(p[lo]);
				sector_t start = BB_OFFSET(p[lo]);

				p[lo] = BB_MAKE(start, s - start, ack);
				/* now low doesn't overlap, so.. */
				break;
			}
			lo--;
		}
		/* 'lo' is strictly before, 'hi' is strictly after,
		 * anything between needs to be discarded
		 */
		if (hi - lo > 1) {
			memmove(p+lo+1, p+hi, (bb->count - hi) * 8);
			bb->count -= (hi - lo - 1);
		}
	}

	bb->changed = 1;
out:
	write_sequnlock_irq(&bb->lock);
	return rv;
}
EXPORT_SYMBOL_GPL(badblocks_clear);

/**
 * ack_all_badblocks() - Acknowledge all bad blocks in a list.
 * @bb:		the badblocks structure that holds all badblock information
 *
 * This only succeeds if ->changed is clear.  It is used by
 * in-kernel metadata updates
 */
void ack_all_badblocks(struct badblocks *bb)
{
	if (bb->page == NULL || bb->changed)
		/* no point even trying */
		return;
	write_seqlock_irq(&bb->lock);

	if (bb->changed == 0 && bb->unacked_exist) {
		u64 *p = bb->page;
		int i;

		for (i = 0; i < bb->count ; i++) {
			if (!BB_ACK(p[i])) {
				sector_t start = BB_OFFSET(p[i]);
				int len = BB_LEN(p[i]);

				p[i] = BB_MAKE(start, len, 1);
			}
		}
		bb->unacked_exist = 0;
	}
	write_sequnlock_irq(&bb->lock);
}
EXPORT_SYMBOL_GPL(ack_all_badblocks);

/**
 * badblocks_show() - sysfs access to bad-blocks list
 * @bb:		the badblocks structure that holds all badblock information
 * @page:	buffer received from sysfs
 * @unack:	weather to show unacknowledged badblocks
 *
 * Return:
 *  Length of returned data
 */
ssize_t badblocks_show(struct badblocks *bb, char *page, int unack)
{
	size_t len;
	int i;
	u64 *p = bb->page;
	unsigned seq;

	if (bb->shift < 0)
		return 0;

retry:
	seq = read_seqbegin(&bb->lock);

	len = 0;
	i = 0;

	while (len < PAGE_SIZE && i < bb->count) {
		sector_t s = BB_OFFSET(p[i]);
		unsigned int length = BB_LEN(p[i]);
		int ack = BB_ACK(p[i]);

		i++;

		if (unack && ack)
			continue;

		len += snprintf(page+len, PAGE_SIZE-len, "%llu %u\n",
				(unsigned long long)s << bb->shift,
				length << bb->shift);
	}
	if (unack && len == 0)
		bb->unacked_exist = 0;

	if (read_seqretry(&bb->lock, seq))
		goto retry;

	return len;
}
EXPORT_SYMBOL_GPL(badblocks_show);

/**
 * badblocks_store() - sysfs access to bad-blocks list
 * @bb:		the badblocks structure that holds all badblock information
 * @page:	buffer received from sysfs
 * @len:	length of data received from sysfs
 * @unack:	weather to show unacknowledged badblocks
 *
 * Return:
 *  Length of the buffer processed or -ve error.
 */
ssize_t badblocks_store(struct badblocks *bb, const char *page, size_t len,
			int unack)
{
	unsigned long long sector;
	int length;
	char newline;

	switch (sscanf(page, "%llu %d%c", &sector, &length, &newline)) {
	case 3:
		if (newline != '\n')
			return -EINVAL;
	case 2:
		if (length <= 0)
			return -EINVAL;
		break;
	default:
		return -EINVAL;
	}

	if (badblocks_set(bb, sector, length, !unack))
		return -ENOSPC;
	else
		return len;
}
EXPORT_SYMBOL_GPL(badblocks_store);

/**
 * badblocks_init() - initialize the badblocks structure
 * @bb:		the badblocks structure that holds all badblock information
 * @enable:	weather to enable badblocks accounting
 *
 * Return:
 *  0: success
 *  -ve errno: on error
 */
int badblocks_init(struct badblocks *bb, int enable)
{
	bb->count = 0;
	if (enable)
		bb->shift = 0;
	else
		bb->shift = -1;
	bb->page = kzalloc(PAGE_SIZE, GFP_KERNEL);
	if (bb->page == (u64 *)0) {
		bb->shift = -1;
		return -ENOMEM;
	}
	seqlock_init(&bb->lock);

	return 0;
}
EXPORT_SYMBOL_GPL(badblocks_init);

/**
 * badblocks_free() - free the badblocks structure
 * @bb:		the badblocks structure that holds all badblock information
 */
void badblocks_free(struct badblocks *bb)
{
	kfree(bb->page);
	bb->page = NULL;
}
EXPORT_SYMBOL_GPL(badblocks_free);