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Linux/block/badblocks.c

  1 /*
  2  * Bad block management
  3  *
  4  * - Heavily based on MD badblocks code from Neil Brown
  5  *
  6  * Copyright (c) 2015, Intel Corporation.
  7  *
  8  * This program is free software; you can redistribute it and/or modify it
  9  * under the terms and conditions of the GNU General Public License,
 10  * version 2, as published by the Free Software Foundation.
 11  *
 12  * This program is distributed in the hope it will be useful, but WITHOUT
 13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 14  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 15  * more details.
 16  */
 17 
 18 #include <linux/badblocks.h>
 19 #include <linux/seqlock.h>
 20 #include <linux/device.h>
 21 #include <linux/kernel.h>
 22 #include <linux/module.h>
 23 #include <linux/stddef.h>
 24 #include <linux/types.h>
 25 #include <linux/slab.h>
 26 
 27 /**
 28  * badblocks_check() - check a given range for bad sectors
 29  * @bb:         the badblocks structure that holds all badblock information
 30  * @s:          sector (start) at which to check for badblocks
 31  * @sectors:    number of sectors to check for badblocks
 32  * @first_bad:  pointer to store location of the first badblock
 33  * @bad_sectors: pointer to store number of badblocks after @first_bad
 34  *
 35  * We can record which blocks on each device are 'bad' and so just
 36  * fail those blocks, or that stripe, rather than the whole device.
 37  * Entries in the bad-block table are 64bits wide.  This comprises:
 38  * Length of bad-range, in sectors: 0-511 for lengths 1-512
 39  * Start of bad-range, sector offset, 54 bits (allows 8 exbibytes)
 40  *  A 'shift' can be set so that larger blocks are tracked and
 41  *  consequently larger devices can be covered.
 42  * 'Acknowledged' flag - 1 bit. - the most significant bit.
 43  *
 44  * Locking of the bad-block table uses a seqlock so badblocks_check
 45  * might need to retry if it is very unlucky.
 46  * We will sometimes want to check for bad blocks in a bi_end_io function,
 47  * so we use the write_seqlock_irq variant.
 48  *
 49  * When looking for a bad block we specify a range and want to
 50  * know if any block in the range is bad.  So we binary-search
 51  * to the last range that starts at-or-before the given endpoint,
 52  * (or "before the sector after the target range")
 53  * then see if it ends after the given start.
 54  *
 55  * Return:
 56  *  0: there are no known bad blocks in the range
 57  *  1: there are known bad block which are all acknowledged
 58  * -1: there are bad blocks which have not yet been acknowledged in metadata.
 59  * plus the start/length of the first bad section we overlap.
 60  */
 61 int badblocks_check(struct badblocks *bb, sector_t s, int sectors,
 62                         sector_t *first_bad, int *bad_sectors)
 63 {
 64         int hi;
 65         int lo;
 66         u64 *p = bb->page;
 67         int rv;
 68         sector_t target = s + sectors;
 69         unsigned seq;
 70 
 71         if (bb->shift > 0) {
 72                 /* round the start down, and the end up */
 73                 s >>= bb->shift;
 74                 target += (1<<bb->shift) - 1;
 75                 target >>= bb->shift;
 76                 sectors = target - s;
 77         }
 78         /* 'target' is now the first block after the bad range */
 79 
 80 retry:
 81         seq = read_seqbegin(&bb->lock);
 82         lo = 0;
 83         rv = 0;
 84         hi = bb->count;
 85 
 86         /* Binary search between lo and hi for 'target'
 87          * i.e. for the last range that starts before 'target'
 88          */
 89         /* INVARIANT: ranges before 'lo' and at-or-after 'hi'
 90          * are known not to be the last range before target.
 91          * VARIANT: hi-lo is the number of possible
 92          * ranges, and decreases until it reaches 1
 93          */
 94         while (hi - lo > 1) {
 95                 int mid = (lo + hi) / 2;
 96                 sector_t a = BB_OFFSET(p[mid]);
 97 
 98                 if (a < target)
 99                         /* This could still be the one, earlier ranges
100                          * could not.
101                          */
102                         lo = mid;
103                 else
104                         /* This and later ranges are definitely out. */
105                         hi = mid;
106         }
107         /* 'lo' might be the last that started before target, but 'hi' isn't */
108         if (hi > lo) {
109                 /* need to check all range that end after 's' to see if
110                  * any are unacknowledged.
111                  */
112                 while (lo >= 0 &&
113                        BB_OFFSET(p[lo]) + BB_LEN(p[lo]) > s) {
114                         if (BB_OFFSET(p[lo]) < target) {
115                                 /* starts before the end, and finishes after
116                                  * the start, so they must overlap
117                                  */
118                                 if (rv != -1 && BB_ACK(p[lo]))
119                                         rv = 1;
120                                 else
121                                         rv = -1;
122                                 *first_bad = BB_OFFSET(p[lo]);
123                                 *bad_sectors = BB_LEN(p[lo]);
124                         }
125                         lo--;
126                 }
127         }
128 
129         if (read_seqretry(&bb->lock, seq))
130                 goto retry;
131 
132         return rv;
133 }
134 EXPORT_SYMBOL_GPL(badblocks_check);
135 
136 static void badblocks_update_acked(struct badblocks *bb)
137 {
138         u64 *p = bb->page;
139         int i;
140         bool unacked = false;
141 
142         if (!bb->unacked_exist)
143                 return;
144 
145         for (i = 0; i < bb->count ; i++) {
146                 if (!BB_ACK(p[i])) {
147                         unacked = true;
148                         break;
149                 }
150         }
151 
152         if (!unacked)
153                 bb->unacked_exist = 0;
154 }
155 
156 /**
157  * badblocks_set() - Add a range of bad blocks to the table.
158  * @bb:         the badblocks structure that holds all badblock information
159  * @s:          first sector to mark as bad
160  * @sectors:    number of sectors to mark as bad
161  * @acknowledged: weather to mark the bad sectors as acknowledged
162  *
163  * This might extend the table, or might contract it if two adjacent ranges
164  * can be merged. We binary-search to find the 'insertion' point, then
165  * decide how best to handle it.
166  *
167  * Return:
168  *  0: success
169  *  1: failed to set badblocks (out of space)
170  */
171 int badblocks_set(struct badblocks *bb, sector_t s, int sectors,
172                         int acknowledged)
173 {
174         u64 *p;
175         int lo, hi;
176         int rv = 0;
177         unsigned long flags;
178 
179         if (bb->shift < 0)
180                 /* badblocks are disabled */
181                 return 0;
182 
183         if (bb->shift) {
184                 /* round the start down, and the end up */
185                 sector_t next = s + sectors;
186 
187                 s >>= bb->shift;
188                 next += (1<<bb->shift) - 1;
189                 next >>= bb->shift;
190                 sectors = next - s;
191         }
192 
193         write_seqlock_irqsave(&bb->lock, flags);
194 
195         p = bb->page;
196         lo = 0;
197         hi = bb->count;
198         /* Find the last range that starts at-or-before 's' */
199         while (hi - lo > 1) {
200                 int mid = (lo + hi) / 2;
201                 sector_t a = BB_OFFSET(p[mid]);
202 
203                 if (a <= s)
204                         lo = mid;
205                 else
206                         hi = mid;
207         }
208         if (hi > lo && BB_OFFSET(p[lo]) > s)
209                 hi = lo;
210 
211         if (hi > lo) {
212                 /* we found a range that might merge with the start
213                  * of our new range
214                  */
215                 sector_t a = BB_OFFSET(p[lo]);
216                 sector_t e = a + BB_LEN(p[lo]);
217                 int ack = BB_ACK(p[lo]);
218 
219                 if (e >= s) {
220                         /* Yes, we can merge with a previous range */
221                         if (s == a && s + sectors >= e)
222                                 /* new range covers old */
223                                 ack = acknowledged;
224                         else
225                                 ack = ack && acknowledged;
226 
227                         if (e < s + sectors)
228                                 e = s + sectors;
229                         if (e - a <= BB_MAX_LEN) {
230                                 p[lo] = BB_MAKE(a, e-a, ack);
231                                 s = e;
232                         } else {
233                                 /* does not all fit in one range,
234                                  * make p[lo] maximal
235                                  */
236                                 if (BB_LEN(p[lo]) != BB_MAX_LEN)
237                                         p[lo] = BB_MAKE(a, BB_MAX_LEN, ack);
238                                 s = a + BB_MAX_LEN;
239                         }
240                         sectors = e - s;
241                 }
242         }
243         if (sectors && hi < bb->count) {
244                 /* 'hi' points to the first range that starts after 's'.
245                  * Maybe we can merge with the start of that range
246                  */
247                 sector_t a = BB_OFFSET(p[hi]);
248                 sector_t e = a + BB_LEN(p[hi]);
249                 int ack = BB_ACK(p[hi]);
250 
251                 if (a <= s + sectors) {
252                         /* merging is possible */
253                         if (e <= s + sectors) {
254                                 /* full overlap */
255                                 e = s + sectors;
256                                 ack = acknowledged;
257                         } else
258                                 ack = ack && acknowledged;
259 
260                         a = s;
261                         if (e - a <= BB_MAX_LEN) {
262                                 p[hi] = BB_MAKE(a, e-a, ack);
263                                 s = e;
264                         } else {
265                                 p[hi] = BB_MAKE(a, BB_MAX_LEN, ack);
266                                 s = a + BB_MAX_LEN;
267                         }
268                         sectors = e - s;
269                         lo = hi;
270                         hi++;
271                 }
272         }
273         if (sectors == 0 && hi < bb->count) {
274                 /* we might be able to combine lo and hi */
275                 /* Note: 's' is at the end of 'lo' */
276                 sector_t a = BB_OFFSET(p[hi]);
277                 int lolen = BB_LEN(p[lo]);
278                 int hilen = BB_LEN(p[hi]);
279                 int newlen = lolen + hilen - (s - a);
280 
281                 if (s >= a && newlen < BB_MAX_LEN) {
282                         /* yes, we can combine them */
283                         int ack = BB_ACK(p[lo]) && BB_ACK(p[hi]);
284 
285                         p[lo] = BB_MAKE(BB_OFFSET(p[lo]), newlen, ack);
286                         memmove(p + hi, p + hi + 1,
287                                 (bb->count - hi - 1) * 8);
288                         bb->count--;
289                 }
290         }
291         while (sectors) {
292                 /* didn't merge (it all).
293                  * Need to add a range just before 'hi'
294                  */
295                 if (bb->count >= MAX_BADBLOCKS) {
296                         /* No room for more */
297                         rv = 1;
298                         break;
299                 } else {
300                         int this_sectors = sectors;
301 
302                         memmove(p + hi + 1, p + hi,
303                                 (bb->count - hi) * 8);
304                         bb->count++;
305 
306                         if (this_sectors > BB_MAX_LEN)
307                                 this_sectors = BB_MAX_LEN;
308                         p[hi] = BB_MAKE(s, this_sectors, acknowledged);
309                         sectors -= this_sectors;
310                         s += this_sectors;
311                 }
312         }
313 
314         bb->changed = 1;
315         if (!acknowledged)
316                 bb->unacked_exist = 1;
317         else
318                 badblocks_update_acked(bb);
319         write_sequnlock_irqrestore(&bb->lock, flags);
320 
321         return rv;
322 }
323 EXPORT_SYMBOL_GPL(badblocks_set);
324 
325 /**
326  * badblocks_clear() - Remove a range of bad blocks to the table.
327  * @bb:         the badblocks structure that holds all badblock information
328  * @s:          first sector to mark as bad
329  * @sectors:    number of sectors to mark as bad
330  *
331  * This may involve extending the table if we spilt a region,
332  * but it must not fail.  So if the table becomes full, we just
333  * drop the remove request.
334  *
335  * Return:
336  *  0: success
337  *  1: failed to clear badblocks
338  */
339 int badblocks_clear(struct badblocks *bb, sector_t s, int sectors)
340 {
341         u64 *p;
342         int lo, hi;
343         sector_t target = s + sectors;
344         int rv = 0;
345 
346         if (bb->shift > 0) {
347                 /* When clearing we round the start up and the end down.
348                  * This should not matter as the shift should align with
349                  * the block size and no rounding should ever be needed.
350                  * However it is better the think a block is bad when it
351                  * isn't than to think a block is not bad when it is.
352                  */
353                 s += (1<<bb->shift) - 1;
354                 s >>= bb->shift;
355                 target >>= bb->shift;
356                 sectors = target - s;
357         }
358 
359         write_seqlock_irq(&bb->lock);
360 
361         p = bb->page;
362         lo = 0;
363         hi = bb->count;
364         /* Find the last range that starts before 'target' */
365         while (hi - lo > 1) {
366                 int mid = (lo + hi) / 2;
367                 sector_t a = BB_OFFSET(p[mid]);
368 
369                 if (a < target)
370                         lo = mid;
371                 else
372                         hi = mid;
373         }
374         if (hi > lo) {
375                 /* p[lo] is the last range that could overlap the
376                  * current range.  Earlier ranges could also overlap,
377                  * but only this one can overlap the end of the range.
378                  */
379                 if ((BB_OFFSET(p[lo]) + BB_LEN(p[lo]) > target) &&
380                     (BB_OFFSET(p[lo]) < target)) {
381                         /* Partial overlap, leave the tail of this range */
382                         int ack = BB_ACK(p[lo]);
383                         sector_t a = BB_OFFSET(p[lo]);
384                         sector_t end = a + BB_LEN(p[lo]);
385 
386                         if (a < s) {
387                                 /* we need to split this range */
388                                 if (bb->count >= MAX_BADBLOCKS) {
389                                         rv = -ENOSPC;
390                                         goto out;
391                                 }
392                                 memmove(p+lo+1, p+lo, (bb->count - lo) * 8);
393                                 bb->count++;
394                                 p[lo] = BB_MAKE(a, s-a, ack);
395                                 lo++;
396                         }
397                         p[lo] = BB_MAKE(target, end - target, ack);
398                         /* there is no longer an overlap */
399                         hi = lo;
400                         lo--;
401                 }
402                 while (lo >= 0 &&
403                        (BB_OFFSET(p[lo]) + BB_LEN(p[lo]) > s) &&
404                        (BB_OFFSET(p[lo]) < target)) {
405                         /* This range does overlap */
406                         if (BB_OFFSET(p[lo]) < s) {
407                                 /* Keep the early parts of this range. */
408                                 int ack = BB_ACK(p[lo]);
409                                 sector_t start = BB_OFFSET(p[lo]);
410 
411                                 p[lo] = BB_MAKE(start, s - start, ack);
412                                 /* now low doesn't overlap, so.. */
413                                 break;
414                         }
415                         lo--;
416                 }
417                 /* 'lo' is strictly before, 'hi' is strictly after,
418                  * anything between needs to be discarded
419                  */
420                 if (hi - lo > 1) {
421                         memmove(p+lo+1, p+hi, (bb->count - hi) * 8);
422                         bb->count -= (hi - lo - 1);
423                 }
424         }
425 
426         badblocks_update_acked(bb);
427         bb->changed = 1;
428 out:
429         write_sequnlock_irq(&bb->lock);
430         return rv;
431 }
432 EXPORT_SYMBOL_GPL(badblocks_clear);
433 
434 /**
435  * ack_all_badblocks() - Acknowledge all bad blocks in a list.
436  * @bb:         the badblocks structure that holds all badblock information
437  *
438  * This only succeeds if ->changed is clear.  It is used by
439  * in-kernel metadata updates
440  */
441 void ack_all_badblocks(struct badblocks *bb)
442 {
443         if (bb->page == NULL || bb->changed)
444                 /* no point even trying */
445                 return;
446         write_seqlock_irq(&bb->lock);
447 
448         if (bb->changed == 0 && bb->unacked_exist) {
449                 u64 *p = bb->page;
450                 int i;
451 
452                 for (i = 0; i < bb->count ; i++) {
453                         if (!BB_ACK(p[i])) {
454                                 sector_t start = BB_OFFSET(p[i]);
455                                 int len = BB_LEN(p[i]);
456 
457                                 p[i] = BB_MAKE(start, len, 1);
458                         }
459                 }
460                 bb->unacked_exist = 0;
461         }
462         write_sequnlock_irq(&bb->lock);
463 }
464 EXPORT_SYMBOL_GPL(ack_all_badblocks);
465 
466 /**
467  * badblocks_show() - sysfs access to bad-blocks list
468  * @bb:         the badblocks structure that holds all badblock information
469  * @page:       buffer received from sysfs
470  * @unack:      weather to show unacknowledged badblocks
471  *
472  * Return:
473  *  Length of returned data
474  */
475 ssize_t badblocks_show(struct badblocks *bb, char *page, int unack)
476 {
477         size_t len;
478         int i;
479         u64 *p = bb->page;
480         unsigned seq;
481 
482         if (bb->shift < 0)
483                 return 0;
484 
485 retry:
486         seq = read_seqbegin(&bb->lock);
487 
488         len = 0;
489         i = 0;
490 
491         while (len < PAGE_SIZE && i < bb->count) {
492                 sector_t s = BB_OFFSET(p[i]);
493                 unsigned int length = BB_LEN(p[i]);
494                 int ack = BB_ACK(p[i]);
495 
496                 i++;
497 
498                 if (unack && ack)
499                         continue;
500 
501                 len += snprintf(page+len, PAGE_SIZE-len, "%llu %u\n",
502                                 (unsigned long long)s << bb->shift,
503                                 length << bb->shift);
504         }
505         if (unack && len == 0)
506                 bb->unacked_exist = 0;
507 
508         if (read_seqretry(&bb->lock, seq))
509                 goto retry;
510 
511         return len;
512 }
513 EXPORT_SYMBOL_GPL(badblocks_show);
514 
515 /**
516  * badblocks_store() - sysfs access to bad-blocks list
517  * @bb:         the badblocks structure that holds all badblock information
518  * @page:       buffer received from sysfs
519  * @len:        length of data received from sysfs
520  * @unack:      weather to show unacknowledged badblocks
521  *
522  * Return:
523  *  Length of the buffer processed or -ve error.
524  */
525 ssize_t badblocks_store(struct badblocks *bb, const char *page, size_t len,
526                         int unack)
527 {
528         unsigned long long sector;
529         int length;
530         char newline;
531 
532         switch (sscanf(page, "%llu %d%c", &sector, &length, &newline)) {
533         case 3:
534                 if (newline != '\n')
535                         return -EINVAL;
536         case 2:
537                 if (length <= 0)
538                         return -EINVAL;
539                 break;
540         default:
541                 return -EINVAL;
542         }
543 
544         if (badblocks_set(bb, sector, length, !unack))
545                 return -ENOSPC;
546         else
547                 return len;
548 }
549 EXPORT_SYMBOL_GPL(badblocks_store);
550 
551 static int __badblocks_init(struct device *dev, struct badblocks *bb,
552                 int enable)
553 {
554         bb->dev = dev;
555         bb->count = 0;
556         if (enable)
557                 bb->shift = 0;
558         else
559                 bb->shift = -1;
560         if (dev)
561                 bb->page = devm_kzalloc(dev, PAGE_SIZE, GFP_KERNEL);
562         else
563                 bb->page = kzalloc(PAGE_SIZE, GFP_KERNEL);
564         if (!bb->page) {
565                 bb->shift = -1;
566                 return -ENOMEM;
567         }
568         seqlock_init(&bb->lock);
569 
570         return 0;
571 }
572 
573 /**
574  * badblocks_init() - initialize the badblocks structure
575  * @bb:         the badblocks structure that holds all badblock information
576  * @enable:     weather to enable badblocks accounting
577  *
578  * Return:
579  *  0: success
580  *  -ve errno: on error
581  */
582 int badblocks_init(struct badblocks *bb, int enable)
583 {
584         return __badblocks_init(NULL, bb, enable);
585 }
586 EXPORT_SYMBOL_GPL(badblocks_init);
587 
588 int devm_init_badblocks(struct device *dev, struct badblocks *bb)
589 {
590         if (!bb)
591                 return -EINVAL;
592         return __badblocks_init(dev, bb, 1);
593 }
594 EXPORT_SYMBOL_GPL(devm_init_badblocks);
595 
596 /**
597  * badblocks_exit() - free the badblocks structure
598  * @bb:         the badblocks structure that holds all badblock information
599  */
600 void badblocks_exit(struct badblocks *bb)
601 {
602         if (!bb)
603                 return;
604         if (bb->dev)
605                 devm_kfree(bb->dev, bb->page);
606         else
607                 kfree(bb->page);
608         bb->page = NULL;
609 }
610 EXPORT_SYMBOL_GPL(badblocks_exit);
611 

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