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1 // SPDX-License-Identifier: GPL-2.0-only
2 /* -*- mode: c; c-basic-offset: 8; -*-
3  * vim: noexpandtab sw=8 ts=8 sts=0:
4  *
5  * blockcheck.c
6  *
7  * Checksum and ECC codes for the OCFS2 userspace library.
8  *
9  * Copyright (C) 2006, 2008 Oracle.  All rights reserved.
10  */
11 
12 #include <linux/kernel.h>
13 #include <linux/types.h>
14 #include <linux/crc32.h>
15 #include <linux/buffer_head.h>
16 #include <linux/bitops.h>
17 #include <linux/debugfs.h>
18 #include <linux/module.h>
19 #include <linux/fs.h>
20 #include <asm/byteorder.h>
21 
22 #include <cluster/masklog.h>
23 
24 #include "ocfs2.h"
25 
26 #include "blockcheck.h"
27 
28 
29 /*
30  * We use the following conventions:
31  *
32  * d = # data bits
33  * p = # parity bits
34  * c = # total code bits (d + p)
35  */
36 
37 
38 /*
39  * Calculate the bit offset in the hamming code buffer based on the bit's
40  * offset in the data buffer.  Since the hamming code reserves all
41  * power-of-two bits for parity, the data bit number and the code bit
42  * number are offset by all the parity bits beforehand.
43  *
44  * Recall that bit numbers in hamming code are 1-based.  This function
45  * takes the 0-based data bit from the caller.
46  *
47  * An example.  Take bit 1 of the data buffer.  1 is a power of two (2^0),
48  * so it's a parity bit.  2 is a power of two (2^1), so it's a parity bit.
49  * 3 is not a power of two.  So bit 1 of the data buffer ends up as bit 3
50  * in the code buffer.
51  *
52  * The caller can pass in *p if it wants to keep track of the most recent
53  * number of parity bits added.  This allows the function to start the
54  * calculation at the last place.
55  */
calc_code_bit(unsigned int i,unsigned int * p_cache)56 static unsigned int calc_code_bit(unsigned int i, unsigned int *p_cache)
57 {
58 	unsigned int b, p = 0;
59 
60 	/*
61 	 * Data bits are 0-based, but we're talking code bits, which
62 	 * are 1-based.
63 	 */
64 	b = i + 1;
65 
66 	/* Use the cache if it is there */
67 	if (p_cache)
68 		p = *p_cache;
69         b += p;
70 
71 	/*
72 	 * For every power of two below our bit number, bump our bit.
73 	 *
74 	 * We compare with (b + 1) because we have to compare with what b
75 	 * would be _if_ it were bumped up by the parity bit.  Capice?
76 	 *
77 	 * p is set above.
78 	 */
79 	for (; (1 << p) < (b + 1); p++)
80 		b++;
81 
82 	if (p_cache)
83 		*p_cache = p;
84 
85 	return b;
86 }
87 
88 /*
89  * This is the low level encoder function.  It can be called across
90  * multiple hunks just like the crc32 code.  'd' is the number of bits
91  * _in_this_hunk_.  nr is the bit offset of this hunk.  So, if you had
92  * two 512B buffers, you would do it like so:
93  *
94  * parity = ocfs2_hamming_encode(0, buf1, 512 * 8, 0);
95  * parity = ocfs2_hamming_encode(parity, buf2, 512 * 8, 512 * 8);
96  *
97  * If you just have one buffer, use ocfs2_hamming_encode_block().
98  */
ocfs2_hamming_encode(u32 parity,void * data,unsigned int d,unsigned int nr)99 u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr)
100 {
101 	unsigned int i, b, p = 0;
102 
103 	BUG_ON(!d);
104 
105 	/*
106 	 * b is the hamming code bit number.  Hamming code specifies a
107 	 * 1-based array, but C uses 0-based.  So 'i' is for C, and 'b' is
108 	 * for the algorithm.
109 	 *
110 	 * The i++ in the for loop is so that the start offset passed
111 	 * to ocfs2_find_next_bit_set() is one greater than the previously
112 	 * found bit.
113 	 */
114 	for (i = 0; (i = ocfs2_find_next_bit(data, d, i)) < d; i++)
115 	{
116 		/*
117 		 * i is the offset in this hunk, nr + i is the total bit
118 		 * offset.
119 		 */
120 		b = calc_code_bit(nr + i, &p);
121 
122 		/*
123 		 * Data bits in the resultant code are checked by
124 		 * parity bits that are part of the bit number
125 		 * representation.  Huh?
126 		 *
127 		 * <wikipedia href="https://en.wikipedia.org/wiki/Hamming_code">
128 		 * In other words, the parity bit at position 2^k
129 		 * checks bits in positions having bit k set in
130 		 * their binary representation.  Conversely, for
131 		 * instance, bit 13, i.e. 1101(2), is checked by
132 		 * bits 1000(2) = 8, 0100(2)=4 and 0001(2) = 1.
133 		 * </wikipedia>
134 		 *
135 		 * Note that 'k' is the _code_ bit number.  'b' in
136 		 * our loop.
137 		 */
138 		parity ^= b;
139 	}
140 
141 	/* While the data buffer was treated as little endian, the
142 	 * return value is in host endian. */
143 	return parity;
144 }
145 
ocfs2_hamming_encode_block(void * data,unsigned int blocksize)146 u32 ocfs2_hamming_encode_block(void *data, unsigned int blocksize)
147 {
148 	return ocfs2_hamming_encode(0, data, blocksize * 8, 0);
149 }
150 
151 /*
152  * Like ocfs2_hamming_encode(), this can handle hunks.  nr is the bit
153  * offset of the current hunk.  If bit to be fixed is not part of the
154  * current hunk, this does nothing.
155  *
156  * If you only have one hunk, use ocfs2_hamming_fix_block().
157  */
ocfs2_hamming_fix(void * data,unsigned int d,unsigned int nr,unsigned int fix)158 void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr,
159 		       unsigned int fix)
160 {
161 	unsigned int i, b;
162 
163 	BUG_ON(!d);
164 
165 	/*
166 	 * If the bit to fix has an hweight of 1, it's a parity bit.  One
167 	 * busted parity bit is its own error.  Nothing to do here.
168 	 */
169 	if (hweight32(fix) == 1)
170 		return;
171 
172 	/*
173 	 * nr + d is the bit right past the data hunk we're looking at.
174 	 * If fix after that, nothing to do
175 	 */
176 	if (fix >= calc_code_bit(nr + d, NULL))
177 		return;
178 
179 	/*
180 	 * nr is the offset in the data hunk we're starting at.  Let's
181 	 * start b at the offset in the code buffer.  See hamming_encode()
182 	 * for a more detailed description of 'b'.
183 	 */
184 	b = calc_code_bit(nr, NULL);
185 	/* If the fix is before this hunk, nothing to do */
186 	if (fix < b)
187 		return;
188 
189 	for (i = 0; i < d; i++, b++)
190 	{
191 		/* Skip past parity bits */
192 		while (hweight32(b) == 1)
193 			b++;
194 
195 		/*
196 		 * i is the offset in this data hunk.
197 		 * nr + i is the offset in the total data buffer.
198 		 * b is the offset in the total code buffer.
199 		 *
200 		 * Thus, when b == fix, bit i in the current hunk needs
201 		 * fixing.
202 		 */
203 		if (b == fix)
204 		{
205 			if (ocfs2_test_bit(i, data))
206 				ocfs2_clear_bit(i, data);
207 			else
208 				ocfs2_set_bit(i, data);
209 			break;
210 		}
211 	}
212 }
213 
ocfs2_hamming_fix_block(void * data,unsigned int blocksize,unsigned int fix)214 void ocfs2_hamming_fix_block(void *data, unsigned int blocksize,
215 			     unsigned int fix)
216 {
217 	ocfs2_hamming_fix(data, blocksize * 8, 0, fix);
218 }
219 
220 
221 /*
222  * Debugfs handling.
223  */
224 
225 #ifdef CONFIG_DEBUG_FS
226 
blockcheck_u64_get(void * data,u64 * val)227 static int blockcheck_u64_get(void *data, u64 *val)
228 {
229 	*val = *(u64 *)data;
230 	return 0;
231 }
232 DEFINE_SIMPLE_ATTRIBUTE(blockcheck_fops, blockcheck_u64_get, NULL, "%llu\n");
233 
ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats * stats)234 static void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats)
235 {
236 	if (stats) {
237 		debugfs_remove_recursive(stats->b_debug_dir);
238 		stats->b_debug_dir = NULL;
239 	}
240 }
241 
ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats * stats,struct dentry * parent)242 static void ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats,
243 					   struct dentry *parent)
244 {
245 	struct dentry *dir;
246 
247 	dir = debugfs_create_dir("blockcheck", parent);
248 	stats->b_debug_dir = dir;
249 
250 	debugfs_create_file("blocks_checked", S_IFREG | S_IRUSR, dir,
251 			    &stats->b_check_count, &blockcheck_fops);
252 
253 	debugfs_create_file("checksums_failed", S_IFREG | S_IRUSR, dir,
254 			    &stats->b_failure_count, &blockcheck_fops);
255 
256 	debugfs_create_file("ecc_recoveries", S_IFREG | S_IRUSR, dir,
257 			    &stats->b_recover_count, &blockcheck_fops);
258 
259 }
260 #else
ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats * stats,struct dentry * parent)261 static inline void ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats,
262 						  struct dentry *parent)
263 {
264 }
265 
ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats * stats)266 static inline void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats)
267 {
268 }
269 #endif  /* CONFIG_DEBUG_FS */
270 
271 /* Always-called wrappers for starting and stopping the debugfs files */
ocfs2_blockcheck_stats_debugfs_install(struct ocfs2_blockcheck_stats * stats,struct dentry * parent)272 void ocfs2_blockcheck_stats_debugfs_install(struct ocfs2_blockcheck_stats *stats,
273 					    struct dentry *parent)
274 {
275 	ocfs2_blockcheck_debug_install(stats, parent);
276 }
277 
ocfs2_blockcheck_stats_debugfs_remove(struct ocfs2_blockcheck_stats * stats)278 void ocfs2_blockcheck_stats_debugfs_remove(struct ocfs2_blockcheck_stats *stats)
279 {
280 	ocfs2_blockcheck_debug_remove(stats);
281 }
282 
ocfs2_blockcheck_inc_check(struct ocfs2_blockcheck_stats * stats)283 static void ocfs2_blockcheck_inc_check(struct ocfs2_blockcheck_stats *stats)
284 {
285 	u64 new_count;
286 
287 	if (!stats)
288 		return;
289 
290 	spin_lock(&stats->b_lock);
291 	stats->b_check_count++;
292 	new_count = stats->b_check_count;
293 	spin_unlock(&stats->b_lock);
294 
295 	if (!new_count)
296 		mlog(ML_NOTICE, "Block check count has wrapped\n");
297 }
298 
ocfs2_blockcheck_inc_failure(struct ocfs2_blockcheck_stats * stats)299 static void ocfs2_blockcheck_inc_failure(struct ocfs2_blockcheck_stats *stats)
300 {
301 	u64 new_count;
302 
303 	if (!stats)
304 		return;
305 
306 	spin_lock(&stats->b_lock);
307 	stats->b_failure_count++;
308 	new_count = stats->b_failure_count;
309 	spin_unlock(&stats->b_lock);
310 
311 	if (!new_count)
312 		mlog(ML_NOTICE, "Checksum failure count has wrapped\n");
313 }
314 
ocfs2_blockcheck_inc_recover(struct ocfs2_blockcheck_stats * stats)315 static void ocfs2_blockcheck_inc_recover(struct ocfs2_blockcheck_stats *stats)
316 {
317 	u64 new_count;
318 
319 	if (!stats)
320 		return;
321 
322 	spin_lock(&stats->b_lock);
323 	stats->b_recover_count++;
324 	new_count = stats->b_recover_count;
325 	spin_unlock(&stats->b_lock);
326 
327 	if (!new_count)
328 		mlog(ML_NOTICE, "ECC recovery count has wrapped\n");
329 }
330 
331 
332 
333 /*
334  * These are the low-level APIs for using the ocfs2_block_check structure.
335  */
336 
337 /*
338  * This function generates check information for a block.
339  * data is the block to be checked.  bc is a pointer to the
340  * ocfs2_block_check structure describing the crc32 and the ecc.
341  *
342  * bc should be a pointer inside data, as the function will
343  * take care of zeroing it before calculating the check information.  If
344  * bc does not point inside data, the caller must make sure any inline
345  * ocfs2_block_check structures are zeroed.
346  *
347  * The data buffer must be in on-disk endian (little endian for ocfs2).
348  * bc will be filled with little-endian values and will be ready to go to
349  * disk.
350  */
ocfs2_block_check_compute(void * data,size_t blocksize,struct ocfs2_block_check * bc)351 void ocfs2_block_check_compute(void *data, size_t blocksize,
352 			       struct ocfs2_block_check *bc)
353 {
354 	u32 crc;
355 	u32 ecc;
356 
357 	memset(bc, 0, sizeof(struct ocfs2_block_check));
358 
359 	crc = crc32_le(~0, data, blocksize);
360 	ecc = ocfs2_hamming_encode_block(data, blocksize);
361 
362 	/*
363 	 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
364 	 * larger than 16 bits.
365 	 */
366 	BUG_ON(ecc > USHRT_MAX);
367 
368 	bc->bc_crc32e = cpu_to_le32(crc);
369 	bc->bc_ecc = cpu_to_le16((u16)ecc);
370 }
371 
372 /*
373  * This function validates existing check information.  Like _compute,
374  * the function will take care of zeroing bc before calculating check codes.
375  * If bc is not a pointer inside data, the caller must have zeroed any
376  * inline ocfs2_block_check structures.
377  *
378  * Again, the data passed in should be the on-disk endian.
379  */
ocfs2_block_check_validate(void * data,size_t blocksize,struct ocfs2_block_check * bc,struct ocfs2_blockcheck_stats * stats)380 int ocfs2_block_check_validate(void *data, size_t blocksize,
381 			       struct ocfs2_block_check *bc,
382 			       struct ocfs2_blockcheck_stats *stats)
383 {
384 	int rc = 0;
385 	u32 bc_crc32e;
386 	u16 bc_ecc;
387 	u32 crc, ecc;
388 
389 	ocfs2_blockcheck_inc_check(stats);
390 
391 	bc_crc32e = le32_to_cpu(bc->bc_crc32e);
392 	bc_ecc = le16_to_cpu(bc->bc_ecc);
393 
394 	memset(bc, 0, sizeof(struct ocfs2_block_check));
395 
396 	/* Fast path - if the crc32 validates, we're good to go */
397 	crc = crc32_le(~0, data, blocksize);
398 	if (crc == bc_crc32e)
399 		goto out;
400 
401 	ocfs2_blockcheck_inc_failure(stats);
402 	mlog(ML_ERROR,
403 	     "CRC32 failed: stored: 0x%x, computed 0x%x. Applying ECC.\n",
404 	     (unsigned int)bc_crc32e, (unsigned int)crc);
405 
406 	/* Ok, try ECC fixups */
407 	ecc = ocfs2_hamming_encode_block(data, blocksize);
408 	ocfs2_hamming_fix_block(data, blocksize, ecc ^ bc_ecc);
409 
410 	/* And check the crc32 again */
411 	crc = crc32_le(~0, data, blocksize);
412 	if (crc == bc_crc32e) {
413 		ocfs2_blockcheck_inc_recover(stats);
414 		goto out;
415 	}
416 
417 	mlog(ML_ERROR, "Fixed CRC32 failed: stored: 0x%x, computed 0x%x\n",
418 	     (unsigned int)bc_crc32e, (unsigned int)crc);
419 
420 	rc = -EIO;
421 
422 out:
423 	bc->bc_crc32e = cpu_to_le32(bc_crc32e);
424 	bc->bc_ecc = cpu_to_le16(bc_ecc);
425 
426 	return rc;
427 }
428 
429 /*
430  * This function generates check information for a list of buffer_heads.
431  * bhs is the blocks to be checked.  bc is a pointer to the
432  * ocfs2_block_check structure describing the crc32 and the ecc.
433  *
434  * bc should be a pointer inside data, as the function will
435  * take care of zeroing it before calculating the check information.  If
436  * bc does not point inside data, the caller must make sure any inline
437  * ocfs2_block_check structures are zeroed.
438  *
439  * The data buffer must be in on-disk endian (little endian for ocfs2).
440  * bc will be filled with little-endian values and will be ready to go to
441  * disk.
442  */
ocfs2_block_check_compute_bhs(struct buffer_head ** bhs,int nr,struct ocfs2_block_check * bc)443 void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr,
444 				   struct ocfs2_block_check *bc)
445 {
446 	int i;
447 	u32 crc, ecc;
448 
449 	BUG_ON(nr < 0);
450 
451 	if (!nr)
452 		return;
453 
454 	memset(bc, 0, sizeof(struct ocfs2_block_check));
455 
456 	for (i = 0, crc = ~0, ecc = 0; i < nr; i++) {
457 		crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
458 		/*
459 		 * The number of bits in a buffer is obviously b_size*8.
460 		 * The offset of this buffer is b_size*i, so the bit offset
461 		 * of this buffer is b_size*8*i.
462 		 */
463 		ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
464 						bhs[i]->b_size * 8,
465 						bhs[i]->b_size * 8 * i);
466 	}
467 
468 	/*
469 	 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
470 	 * larger than 16 bits.
471 	 */
472 	BUG_ON(ecc > USHRT_MAX);
473 
474 	bc->bc_crc32e = cpu_to_le32(crc);
475 	bc->bc_ecc = cpu_to_le16((u16)ecc);
476 }
477 
478 /*
479  * This function validates existing check information on a list of
480  * buffer_heads.  Like _compute_bhs, the function will take care of
481  * zeroing bc before calculating check codes.  If bc is not a pointer
482  * inside data, the caller must have zeroed any inline
483  * ocfs2_block_check structures.
484  *
485  * Again, the data passed in should be the on-disk endian.
486  */
ocfs2_block_check_validate_bhs(struct buffer_head ** bhs,int nr,struct ocfs2_block_check * bc,struct ocfs2_blockcheck_stats * stats)487 int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr,
488 				   struct ocfs2_block_check *bc,
489 				   struct ocfs2_blockcheck_stats *stats)
490 {
491 	int i, rc = 0;
492 	u32 bc_crc32e;
493 	u16 bc_ecc;
494 	u32 crc, ecc, fix;
495 
496 	BUG_ON(nr < 0);
497 
498 	if (!nr)
499 		return 0;
500 
501 	ocfs2_blockcheck_inc_check(stats);
502 
503 	bc_crc32e = le32_to_cpu(bc->bc_crc32e);
504 	bc_ecc = le16_to_cpu(bc->bc_ecc);
505 
506 	memset(bc, 0, sizeof(struct ocfs2_block_check));
507 
508 	/* Fast path - if the crc32 validates, we're good to go */
509 	for (i = 0, crc = ~0; i < nr; i++)
510 		crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
511 	if (crc == bc_crc32e)
512 		goto out;
513 
514 	ocfs2_blockcheck_inc_failure(stats);
515 	mlog(ML_ERROR,
516 	     "CRC32 failed: stored: %u, computed %u.  Applying ECC.\n",
517 	     (unsigned int)bc_crc32e, (unsigned int)crc);
518 
519 	/* Ok, try ECC fixups */
520 	for (i = 0, ecc = 0; i < nr; i++) {
521 		/*
522 		 * The number of bits in a buffer is obviously b_size*8.
523 		 * The offset of this buffer is b_size*i, so the bit offset
524 		 * of this buffer is b_size*8*i.
525 		 */
526 		ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
527 						bhs[i]->b_size * 8,
528 						bhs[i]->b_size * 8 * i);
529 	}
530 	fix = ecc ^ bc_ecc;
531 	for (i = 0; i < nr; i++) {
532 		/*
533 		 * Try the fix against each buffer.  It will only affect
534 		 * one of them.
535 		 */
536 		ocfs2_hamming_fix(bhs[i]->b_data, bhs[i]->b_size * 8,
537 				  bhs[i]->b_size * 8 * i, fix);
538 	}
539 
540 	/* And check the crc32 again */
541 	for (i = 0, crc = ~0; i < nr; i++)
542 		crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
543 	if (crc == bc_crc32e) {
544 		ocfs2_blockcheck_inc_recover(stats);
545 		goto out;
546 	}
547 
548 	mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n",
549 	     (unsigned int)bc_crc32e, (unsigned int)crc);
550 
551 	rc = -EIO;
552 
553 out:
554 	bc->bc_crc32e = cpu_to_le32(bc_crc32e);
555 	bc->bc_ecc = cpu_to_le16(bc_ecc);
556 
557 	return rc;
558 }
559 
560 /*
561  * These are the main API.  They check the superblock flag before
562  * calling the underlying operations.
563  *
564  * They expect the buffer(s) to be in disk format.
565  */
ocfs2_compute_meta_ecc(struct super_block * sb,void * data,struct ocfs2_block_check * bc)566 void ocfs2_compute_meta_ecc(struct super_block *sb, void *data,
567 			    struct ocfs2_block_check *bc)
568 {
569 	if (ocfs2_meta_ecc(OCFS2_SB(sb)))
570 		ocfs2_block_check_compute(data, sb->s_blocksize, bc);
571 }
572 
ocfs2_validate_meta_ecc(struct super_block * sb,void * data,struct ocfs2_block_check * bc)573 int ocfs2_validate_meta_ecc(struct super_block *sb, void *data,
574 			    struct ocfs2_block_check *bc)
575 {
576 	int rc = 0;
577 	struct ocfs2_super *osb = OCFS2_SB(sb);
578 
579 	if (ocfs2_meta_ecc(osb))
580 		rc = ocfs2_block_check_validate(data, sb->s_blocksize, bc,
581 						&osb->osb_ecc_stats);
582 
583 	return rc;
584 }
585 
ocfs2_compute_meta_ecc_bhs(struct super_block * sb,struct buffer_head ** bhs,int nr,struct ocfs2_block_check * bc)586 void ocfs2_compute_meta_ecc_bhs(struct super_block *sb,
587 				struct buffer_head **bhs, int nr,
588 				struct ocfs2_block_check *bc)
589 {
590 	if (ocfs2_meta_ecc(OCFS2_SB(sb)))
591 		ocfs2_block_check_compute_bhs(bhs, nr, bc);
592 }
593 
ocfs2_validate_meta_ecc_bhs(struct super_block * sb,struct buffer_head ** bhs,int nr,struct ocfs2_block_check * bc)594 int ocfs2_validate_meta_ecc_bhs(struct super_block *sb,
595 				struct buffer_head **bhs, int nr,
596 				struct ocfs2_block_check *bc)
597 {
598 	int rc = 0;
599 	struct ocfs2_super *osb = OCFS2_SB(sb);
600 
601 	if (ocfs2_meta_ecc(osb))
602 		rc = ocfs2_block_check_validate_bhs(bhs, nr, bc,
603 						    &osb->osb_ecc_stats);
604 
605 	return rc;
606 }
607 
608