```   1/* -*- mode: c; c-basic-offset: 8; -*-
2 * vim: noexpandtab sw=8 ts=8 sts=0:
3 *
4 * blockcheck.c
5 *
6 * Checksum and ECC codes for the OCFS2 userspace library.
7 *
9 *
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17 * General Public License for more details.
18 */
19
20#include <linux/kernel.h>
21#include <linux/types.h>
22#include <linux/crc32.h>
24#include <linux/bitops.h>
25#include <linux/debugfs.h>
26#include <linux/module.h>
27#include <linux/fs.h>
28#include <asm/byteorder.h>
29
31
32#include "ocfs2.h"
33
34#include "blockcheck.h"
35
36
37/*
38 * We use the following conventions:
39 *
40 * d = # data bits
41 * p = # parity bits
42 * c = # total code bits (d + p)
43 */
44
45
46/*
47 * Calculate the bit offset in the hamming code buffer based on the bit's
48 * offset in the data buffer.  Since the hamming code reserves all
49 * power-of-two bits for parity, the data bit number and the code bit
50 * number are offset by all the parity bits beforehand.
51 *
52 * Recall that bit numbers in hamming code are 1-based.  This function
53 * takes the 0-based data bit from the caller.
54 *
55 * An example.  Take bit 1 of the data buffer.  1 is a power of two (2^0),
56 * so it's a parity bit.  2 is a power of two (2^1), so it's a parity bit.
57 * 3 is not a power of two.  So bit 1 of the data buffer ends up as bit 3
58 * in the code buffer.
59 *
60 * The caller can pass in *p if it wants to keep track of the most recent
61 * number of parity bits added.  This allows the function to start the
62 * calculation at the last place.
63 */
64static unsigned int calc_code_bit(unsigned int i, unsigned int *p_cache)
65{
66        unsigned int b, p = 0;
67
68        /*
69         * Data bits are 0-based, but we're talking code bits, which
70         * are 1-based.
71         */
72        b = i + 1;
73
74        /* Use the cache if it is there */
75        if (p_cache)
76                p = *p_cache;
77        b += p;
78
79        /*
80         * For every power of two below our bit number, bump our bit.
81         *
82         * We compare with (b + 1) because we have to compare with what b
83         * would be _if_ it were bumped up by the parity bit.  Capice?
84         *
85         * p is set above.
86         */
87        for (; (1 << p) < (b + 1); p++)
88                b++;
89
90        if (p_cache)
91                *p_cache = p;
92
93        return b;
94}
95
96/*
97 * This is the low level encoder function.  It can be called across
98 * multiple hunks just like the crc32 code.  'd' is the number of bits
99 * _in_this_hunk_.  nr is the bit offset of this hunk.  So, if you had
100 * two 512B buffers, you would do it like so:
101 *
102 * parity = ocfs2_hamming_encode(0, buf1, 512 * 8, 0);
103 * parity = ocfs2_hamming_encode(parity, buf2, 512 * 8, 512 * 8);
104 *
105 * If you just have one buffer, use ocfs2_hamming_encode_block().
106 */
107u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr)
108{
109        unsigned int i, b, p = 0;
110
111        BUG_ON(!d);
112
113        /*
114         * b is the hamming code bit number.  Hamming code specifies a
115         * 1-based array, but C uses 0-based.  So 'i' is for C, and 'b' is
116         * for the algorithm.
117         *
118         * The i++ in the for loop is so that the start offset passed
119         * to ocfs2_find_next_bit_set() is one greater than the previously
120         * found bit.
121         */
122        for (i = 0; (i = ocfs2_find_next_bit(data, d, i)) < d; i++)
123        {
124                /*
125                 * i is the offset in this hunk, nr + i is the total bit
126                 * offset.
127                 */
128                b = calc_code_bit(nr + i, &p);
129
130                /*
131                 * Data bits in the resultant code are checked by
132                 * parity bits that are part of the bit number
133                 * representation.  Huh?
134                 *
135                 * <wikipedia href="http://en.wikipedia.org/wiki/Hamming_code">
136                 * In other words, the parity bit at position 2^k
137                 * checks bits in positions having bit k set in
138                 * their binary representation.  Conversely, for
139                 * instance, bit 13, i.e. 1101(2), is checked by
140                 * bits 1000(2) = 8, 0100(2)=4 and 0001(2) = 1.
141                 * </wikipedia>
142                 *
143                 * Note that 'k' is the _code_ bit number.  'b' in
144                 * our loop.
145                 */
146                parity ^= b;
147        }
148
149        /* While the data buffer was treated as little endian, the
150         * return value is in host endian. */
151        return parity;
152}
153
154u32 ocfs2_hamming_encode_block(void *data, unsigned int blocksize)
155{
156        return ocfs2_hamming_encode(0, data, blocksize * 8, 0);
157}
158
159/*
160 * Like ocfs2_hamming_encode(), this can handle hunks.  nr is the bit
161 * offset of the current hunk.  If bit to be fixed is not part of the
162 * current hunk, this does nothing.
163 *
164 * If you only have one hunk, use ocfs2_hamming_fix_block().
165 */
166void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr,
167                       unsigned int fix)
168{
169        unsigned int i, b;
170
171        BUG_ON(!d);
172
173        /*
174         * If the bit to fix has an hweight of 1, it's a parity bit.  One
175         * busted parity bit is its own error.  Nothing to do here.
176         */
177        if (hweight32(fix) == 1)
178                return;
179
180        /*
181         * nr + d is the bit right past the data hunk we're looking at.
182         * If fix after that, nothing to do
183         */
184        if (fix >= calc_code_bit(nr + d, NULL))
185                return;
186
187        /*
188         * nr is the offset in the data hunk we're starting at.  Let's
189         * start b at the offset in the code buffer.  See hamming_encode()
190         * for a more detailed description of 'b'.
191         */
192        b = calc_code_bit(nr, NULL);
193        /* If the fix is before this hunk, nothing to do */
194        if (fix < b)
195                return;
196
197        for (i = 0; i < d; i++, b++)
198        {
199                /* Skip past parity bits */
200                while (hweight32(b) == 1)
201                        b++;
202
203                /*
204                 * i is the offset in this data hunk.
205                 * nr + i is the offset in the total data buffer.
206                 * b is the offset in the total code buffer.
207                 *
208                 * Thus, when b == fix, bit i in the current hunk needs
209                 * fixing.
210                 */
211                if (b == fix)
212                {
213                        if (ocfs2_test_bit(i, data))
214                                ocfs2_clear_bit(i, data);
215                        else
216                                ocfs2_set_bit(i, data);
217                        break;
218                }
219        }
220}
221
222void ocfs2_hamming_fix_block(void *data, unsigned int blocksize,
223                             unsigned int fix)
224{
225        ocfs2_hamming_fix(data, blocksize * 8, 0, fix);
226}
227
228
229/*
230 * Debugfs handling.
231 */
232
233#ifdef CONFIG_DEBUG_FS
234
235static int blockcheck_u64_get(void *data, u64 *val)
236{
237        *val = *(u64 *)data;
238        return 0;
239}
240DEFINE_SIMPLE_ATTRIBUTE(blockcheck_fops, blockcheck_u64_get, NULL, "%llu\n");
241
242static struct dentry *blockcheck_debugfs_create(const char *name,
243                                                struct dentry *parent,
244                                                u64 *value)
245{
246        return debugfs_create_file(name, S_IFREG | S_IRUSR, parent, value,
247                                   &blockcheck_fops);
248}
249
250static void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats)
251{
252        if (stats) {
253                debugfs_remove(stats->b_debug_check);
254                stats->b_debug_check = NULL;
255                debugfs_remove(stats->b_debug_failure);
256                stats->b_debug_failure = NULL;
257                debugfs_remove(stats->b_debug_recover);
258                stats->b_debug_recover = NULL;
259                debugfs_remove(stats->b_debug_dir);
260                stats->b_debug_dir = NULL;
261        }
262}
263
264static int ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats,
265                                          struct dentry *parent)
266{
267        int rc = -EINVAL;
268
269        if (!stats)
270                goto out;
271
272        stats->b_debug_dir = debugfs_create_dir("blockcheck", parent);
273        if (!stats->b_debug_dir)
274                goto out;
275
276        stats->b_debug_check =
277                blockcheck_debugfs_create("blocks_checked",
278                                          stats->b_debug_dir,
279                                          &stats->b_check_count);
280
281        stats->b_debug_failure =
282                blockcheck_debugfs_create("checksums_failed",
283                                          stats->b_debug_dir,
284                                          &stats->b_failure_count);
285
286        stats->b_debug_recover =
287                blockcheck_debugfs_create("ecc_recoveries",
288                                          stats->b_debug_dir,
289                                          &stats->b_recover_count);
290        if (stats->b_debug_check && stats->b_debug_failure &&
291            stats->b_debug_recover)
292                rc = 0;
293
294out:
295        if (rc)
296                ocfs2_blockcheck_debug_remove(stats);
297        return rc;
298}
299#else
300static inline int ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats,
301                                                 struct dentry *parent)
302{
303        return 0;
304}
305
306static inline void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats)
307{
308}
309#endif  /* CONFIG_DEBUG_FS */
310
311/* Always-called wrappers for starting and stopping the debugfs files */
312int ocfs2_blockcheck_stats_debugfs_install(struct ocfs2_blockcheck_stats *stats,
313                                           struct dentry *parent)
314{
315        return ocfs2_blockcheck_debug_install(stats, parent);
316}
317
318void ocfs2_blockcheck_stats_debugfs_remove(struct ocfs2_blockcheck_stats *stats)
319{
320        ocfs2_blockcheck_debug_remove(stats);
321}
322
323static void ocfs2_blockcheck_inc_check(struct ocfs2_blockcheck_stats *stats)
324{
325        u64 new_count;
326
327        if (!stats)
328                return;
329
330        spin_lock(&stats->b_lock);
331        stats->b_check_count++;
332        new_count = stats->b_check_count;
333        spin_unlock(&stats->b_lock);
334
335        if (!new_count)
336                mlog(ML_NOTICE, "Block check count has wrapped\n");
337}
338
339static void ocfs2_blockcheck_inc_failure(struct ocfs2_blockcheck_stats *stats)
340{
341        u64 new_count;
342
343        if (!stats)
344                return;
345
346        spin_lock(&stats->b_lock);
347        stats->b_failure_count++;
348        new_count = stats->b_failure_count;
349        spin_unlock(&stats->b_lock);
350
351        if (!new_count)
352                mlog(ML_NOTICE, "Checksum failure count has wrapped\n");
353}
354
355static void ocfs2_blockcheck_inc_recover(struct ocfs2_blockcheck_stats *stats)
356{
357        u64 new_count;
358
359        if (!stats)
360                return;
361
362        spin_lock(&stats->b_lock);
363        stats->b_recover_count++;
364        new_count = stats->b_recover_count;
365        spin_unlock(&stats->b_lock);
366
367        if (!new_count)
368                mlog(ML_NOTICE, "ECC recovery count has wrapped\n");
369}
370
371
372
373/*
374 * These are the low-level APIs for using the ocfs2_block_check structure.
375 */
376
377/*
378 * This function generates check information for a block.
379 * data is the block to be checked.  bc is a pointer to the
380 * ocfs2_block_check structure describing the crc32 and the ecc.
381 *
382 * bc should be a pointer inside data, as the function will
383 * take care of zeroing it before calculating the check information.  If
384 * bc does not point inside data, the caller must make sure any inline
385 * ocfs2_block_check structures are zeroed.
386 *
387 * The data buffer must be in on-disk endian (little endian for ocfs2).
388 * bc will be filled with little-endian values and will be ready to go to
389 * disk.
390 */
391void ocfs2_block_check_compute(void *data, size_t blocksize,
392                               struct ocfs2_block_check *bc)
393{
394        u32 crc;
395        u32 ecc;
396
397        memset(bc, 0, sizeof(struct ocfs2_block_check));
398
399        crc = crc32_le(~0, data, blocksize);
400        ecc = ocfs2_hamming_encode_block(data, blocksize);
401
402        /*
403         * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
404         * larger than 16 bits.
405         */
406        BUG_ON(ecc > USHRT_MAX);
407
408        bc->bc_crc32e = cpu_to_le32(crc);
409        bc->bc_ecc = cpu_to_le16((u16)ecc);
410}
411
412/*
413 * This function validates existing check information.  Like _compute,
414 * the function will take care of zeroing bc before calculating check codes.
415 * If bc is not a pointer inside data, the caller must have zeroed any
416 * inline ocfs2_block_check structures.
417 *
418 * Again, the data passed in should be the on-disk endian.
419 */
420int ocfs2_block_check_validate(void *data, size_t blocksize,
421                               struct ocfs2_block_check *bc,
422                               struct ocfs2_blockcheck_stats *stats)
423{
424        int rc = 0;
425        u32 bc_crc32e;
426        u16 bc_ecc;
427        u32 crc, ecc;
428
429        ocfs2_blockcheck_inc_check(stats);
430
431        bc_crc32e = le32_to_cpu(bc->bc_crc32e);
432        bc_ecc = le16_to_cpu(bc->bc_ecc);
433
434        memset(bc, 0, sizeof(struct ocfs2_block_check));
435
436        /* Fast path - if the crc32 validates, we're good to go */
437        crc = crc32_le(~0, data, blocksize);
438        if (crc == bc_crc32e)
439                goto out;
440
441        ocfs2_blockcheck_inc_failure(stats);
442        mlog(ML_ERROR,
443             "CRC32 failed: stored: 0x%x, computed 0x%x. Applying ECC.\n",
444             (unsigned int)bc_crc32e, (unsigned int)crc);
445
446        /* Ok, try ECC fixups */
447        ecc = ocfs2_hamming_encode_block(data, blocksize);
448        ocfs2_hamming_fix_block(data, blocksize, ecc ^ bc_ecc);
449
450        /* And check the crc32 again */
451        crc = crc32_le(~0, data, blocksize);
452        if (crc == bc_crc32e) {
453                ocfs2_blockcheck_inc_recover(stats);
454                goto out;
455        }
456
457        mlog(ML_ERROR, "Fixed CRC32 failed: stored: 0x%x, computed 0x%x\n",
458             (unsigned int)bc_crc32e, (unsigned int)crc);
459
460        rc = -EIO;
461
462out:
463        bc->bc_crc32e = cpu_to_le32(bc_crc32e);
464        bc->bc_ecc = cpu_to_le16(bc_ecc);
465
466        return rc;
467}
468
469/*
470 * This function generates check information for a list of buffer_heads.
471 * bhs is the blocks to be checked.  bc is a pointer to the
472 * ocfs2_block_check structure describing the crc32 and the ecc.
473 *
474 * bc should be a pointer inside data, as the function will
475 * take care of zeroing it before calculating the check information.  If
476 * bc does not point inside data, the caller must make sure any inline
477 * ocfs2_block_check structures are zeroed.
478 *
479 * The data buffer must be in on-disk endian (little endian for ocfs2).
480 * bc will be filled with little-endian values and will be ready to go to
481 * disk.
482 */
483void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr,
484                                   struct ocfs2_block_check *bc)
485{
486        int i;
487        u32 crc, ecc;
488
489        BUG_ON(nr < 0);
490
491        if (!nr)
492                return;
493
494        memset(bc, 0, sizeof(struct ocfs2_block_check));
495
496        for (i = 0, crc = ~0, ecc = 0; i < nr; i++) {
497                crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
498                /*
499                 * The number of bits in a buffer is obviously b_size*8.
500                 * The offset of this buffer is b_size*i, so the bit offset
501                 * of this buffer is b_size*8*i.
502                 */
503                ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
504                                                bhs[i]->b_size * 8,
505                                                bhs[i]->b_size * 8 * i);
506        }
507
508        /*
509         * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
510         * larger than 16 bits.
511         */
512        BUG_ON(ecc > USHRT_MAX);
513
514        bc->bc_crc32e = cpu_to_le32(crc);
515        bc->bc_ecc = cpu_to_le16((u16)ecc);
516}
517
518/*
519 * This function validates existing check information on a list of
520 * buffer_heads.  Like _compute_bhs, the function will take care of
521 * zeroing bc before calculating check codes.  If bc is not a pointer
522 * inside data, the caller must have zeroed any inline
523 * ocfs2_block_check structures.
524 *
525 * Again, the data passed in should be the on-disk endian.
526 */
527int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr,
528                                   struct ocfs2_block_check *bc,
529                                   struct ocfs2_blockcheck_stats *stats)
530{
531        int i, rc = 0;
532        u32 bc_crc32e;
533        u16 bc_ecc;
534        u32 crc, ecc, fix;
535
536        BUG_ON(nr < 0);
537
538        if (!nr)
539                return 0;
540
541        ocfs2_blockcheck_inc_check(stats);
542
543        bc_crc32e = le32_to_cpu(bc->bc_crc32e);
544        bc_ecc = le16_to_cpu(bc->bc_ecc);
545
546        memset(bc, 0, sizeof(struct ocfs2_block_check));
547
548        /* Fast path - if the crc32 validates, we're good to go */
549        for (i = 0, crc = ~0; i < nr; i++)
550                crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
551        if (crc == bc_crc32e)
552                goto out;
553
554        ocfs2_blockcheck_inc_failure(stats);
555        mlog(ML_ERROR,
556             "CRC32 failed: stored: %u, computed %u.  Applying ECC.\n",
557             (unsigned int)bc_crc32e, (unsigned int)crc);
558
559        /* Ok, try ECC fixups */
560        for (i = 0, ecc = 0; i < nr; i++) {
561                /*
562                 * The number of bits in a buffer is obviously b_size*8.
563                 * The offset of this buffer is b_size*i, so the bit offset
564                 * of this buffer is b_size*8*i.
565                 */
566                ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
567                                                bhs[i]->b_size * 8,
568                                                bhs[i]->b_size * 8 * i);
569        }
570        fix = ecc ^ bc_ecc;
571        for (i = 0; i < nr; i++) {
572                /*
573                 * Try the fix against each buffer.  It will only affect
574                 * one of them.
575                 */
576                ocfs2_hamming_fix(bhs[i]->b_data, bhs[i]->b_size * 8,
577                                  bhs[i]->b_size * 8 * i, fix);
578        }
579
580        /* And check the crc32 again */
581        for (i = 0, crc = ~0; i < nr; i++)
582                crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
583        if (crc == bc_crc32e) {
584                ocfs2_blockcheck_inc_recover(stats);
585                goto out;
586        }
587
588        mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n",
589             (unsigned int)bc_crc32e, (unsigned int)crc);
590
591        rc = -EIO;
592
593out:
594        bc->bc_crc32e = cpu_to_le32(bc_crc32e);
595        bc->bc_ecc = cpu_to_le16(bc_ecc);
596
597        return rc;
598}
599
600/*
601 * These are the main API.  They check the superblock flag before
602 * calling the underlying operations.
603 *
604 * They expect the buffer(s) to be in disk format.
605 */
606void ocfs2_compute_meta_ecc(struct super_block *sb, void *data,
607                            struct ocfs2_block_check *bc)
608{
609        if (ocfs2_meta_ecc(OCFS2_SB(sb)))
610                ocfs2_block_check_compute(data, sb->s_blocksize, bc);
611}
612
613int ocfs2_validate_meta_ecc(struct super_block *sb, void *data,
614                            struct ocfs2_block_check *bc)
615{
616        int rc = 0;
617        struct ocfs2_super *osb = OCFS2_SB(sb);
618
619        if (ocfs2_meta_ecc(osb))
620                rc = ocfs2_block_check_validate(data, sb->s_blocksize, bc,
621                                                &osb->osb_ecc_stats);
622
623        return rc;
624}
625
626void ocfs2_compute_meta_ecc_bhs(struct super_block *sb,
627                                struct buffer_head **bhs, int nr,
628                                struct ocfs2_block_check *bc)
629{
630        if (ocfs2_meta_ecc(OCFS2_SB(sb)))
631                ocfs2_block_check_compute_bhs(bhs, nr, bc);
632}
633
634int ocfs2_validate_meta_ecc_bhs(struct super_block *sb,
635                                struct buffer_head **bhs, int nr,
636                                struct ocfs2_block_check *bc)
637{
638        int rc = 0;
639        struct ocfs2_super *osb = OCFS2_SB(sb);
640
641        if (ocfs2_meta_ecc(osb))
642                rc = ocfs2_block_check_validate_bhs(bhs, nr, bc,
643                                                    &osb->osb_ecc_stats);
644
645        return rc;
646}
647
648```
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