Root/fs/ocfs2/blockcheck.c

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 *
8 * Copyright (C) 2006, 2008 Oracle. All rights reserved.
9 *
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public
12 * License, version 2, as published by the Free Software Foundation.
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>
23#include <linux/buffer_head.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
30#include <cluster/masklog.h>
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 > USHORT_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    struct ocfs2_block_check check;
426    u32 crc, ecc;
427
428    ocfs2_blockcheck_inc_check(stats);
429
430    check.bc_crc32e = le32_to_cpu(bc->bc_crc32e);
431    check.bc_ecc = le16_to_cpu(bc->bc_ecc);
432
433    memset(bc, 0, sizeof(struct ocfs2_block_check));
434
435    /* Fast path - if the crc32 validates, we're good to go */
436    crc = crc32_le(~0, data, blocksize);
437    if (crc == check.bc_crc32e)
438        goto out;
439
440    ocfs2_blockcheck_inc_failure(stats);
441    mlog(ML_ERROR,
442         "CRC32 failed: stored: %u, computed %u. Applying ECC.\n",
443         (unsigned int)check.bc_crc32e, (unsigned int)crc);
444
445    /* Ok, try ECC fixups */
446    ecc = ocfs2_hamming_encode_block(data, blocksize);
447    ocfs2_hamming_fix_block(data, blocksize, ecc ^ check.bc_ecc);
448
449    /* And check the crc32 again */
450    crc = crc32_le(~0, data, blocksize);
451    if (crc == check.bc_crc32e) {
452        ocfs2_blockcheck_inc_recover(stats);
453        goto out;
454    }
455
456    mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n",
457         (unsigned int)check.bc_crc32e, (unsigned int)crc);
458
459    rc = -EIO;
460
461out:
462    bc->bc_crc32e = cpu_to_le32(check.bc_crc32e);
463    bc->bc_ecc = cpu_to_le16(check.bc_ecc);
464
465    return rc;
466}
467
468/*
469 * This function generates check information for a list of buffer_heads.
470 * bhs is the blocks to be checked. bc is a pointer to the
471 * ocfs2_block_check structure describing the crc32 and the ecc.
472 *
473 * bc should be a pointer inside data, as the function will
474 * take care of zeroing it before calculating the check information. If
475 * bc does not point inside data, the caller must make sure any inline
476 * ocfs2_block_check structures are zeroed.
477 *
478 * The data buffer must be in on-disk endian (little endian for ocfs2).
479 * bc will be filled with little-endian values and will be ready to go to
480 * disk.
481 */
482void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr,
483                   struct ocfs2_block_check *bc)
484{
485    int i;
486    u32 crc, ecc;
487
488    BUG_ON(nr < 0);
489
490    if (!nr)
491        return;
492
493    memset(bc, 0, sizeof(struct ocfs2_block_check));
494
495    for (i = 0, crc = ~0, ecc = 0; i < nr; i++) {
496        crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
497        /*
498         * The number of bits in a buffer is obviously b_size*8.
499         * The offset of this buffer is b_size*i, so the bit offset
500         * of this buffer is b_size*8*i.
501         */
502        ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
503                        bhs[i]->b_size * 8,
504                        bhs[i]->b_size * 8 * i);
505    }
506
507    /*
508     * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
509     * larger than 16 bits.
510     */
511    BUG_ON(ecc > USHORT_MAX);
512
513    bc->bc_crc32e = cpu_to_le32(crc);
514    bc->bc_ecc = cpu_to_le16((u16)ecc);
515}
516
517/*
518 * This function validates existing check information on a list of
519 * buffer_heads. Like _compute_bhs, the function will take care of
520 * zeroing bc before calculating check codes. If bc is not a pointer
521 * inside data, the caller must have zeroed any inline
522 * ocfs2_block_check structures.
523 *
524 * Again, the data passed in should be the on-disk endian.
525 */
526int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr,
527                   struct ocfs2_block_check *bc,
528                   struct ocfs2_blockcheck_stats *stats)
529{
530    int i, rc = 0;
531    struct ocfs2_block_check check;
532    u32 crc, ecc, fix;
533
534    BUG_ON(nr < 0);
535
536    if (!nr)
537        return 0;
538
539    ocfs2_blockcheck_inc_check(stats);
540
541    check.bc_crc32e = le32_to_cpu(bc->bc_crc32e);
542    check.bc_ecc = le16_to_cpu(bc->bc_ecc);
543
544    memset(bc, 0, sizeof(struct ocfs2_block_check));
545
546    /* Fast path - if the crc32 validates, we're good to go */
547    for (i = 0, crc = ~0; i < nr; i++)
548        crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
549    if (crc == check.bc_crc32e)
550        goto out;
551
552    ocfs2_blockcheck_inc_failure(stats);
553    mlog(ML_ERROR,
554         "CRC32 failed: stored: %u, computed %u. Applying ECC.\n",
555         (unsigned int)check.bc_crc32e, (unsigned int)crc);
556
557    /* Ok, try ECC fixups */
558    for (i = 0, ecc = 0; i < nr; i++) {
559        /*
560         * The number of bits in a buffer is obviously b_size*8.
561         * The offset of this buffer is b_size*i, so the bit offset
562         * of this buffer is b_size*8*i.
563         */
564        ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
565                        bhs[i]->b_size * 8,
566                        bhs[i]->b_size * 8 * i);
567    }
568    fix = ecc ^ check.bc_ecc;
569    for (i = 0; i < nr; i++) {
570        /*
571         * Try the fix against each buffer. It will only affect
572         * one of them.
573         */
574        ocfs2_hamming_fix(bhs[i]->b_data, bhs[i]->b_size * 8,
575                  bhs[i]->b_size * 8 * i, fix);
576    }
577
578    /* And check the crc32 again */
579    for (i = 0, crc = ~0; i < nr; i++)
580        crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
581    if (crc == check.bc_crc32e) {
582        ocfs2_blockcheck_inc_recover(stats);
583        goto out;
584    }
585
586    mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n",
587         (unsigned int)check.bc_crc32e, (unsigned int)crc);
588
589    rc = -EIO;
590
591out:
592    bc->bc_crc32e = cpu_to_le32(check.bc_crc32e);
593    bc->bc_ecc = cpu_to_le16(check.bc_ecc);
594
595    return rc;
596}
597
598/*
599 * These are the main API. They check the superblock flag before
600 * calling the underlying operations.
601 *
602 * They expect the buffer(s) to be in disk format.
603 */
604void ocfs2_compute_meta_ecc(struct super_block *sb, void *data,
605                struct ocfs2_block_check *bc)
606{
607    if (ocfs2_meta_ecc(OCFS2_SB(sb)))
608        ocfs2_block_check_compute(data, sb->s_blocksize, bc);
609}
610
611int ocfs2_validate_meta_ecc(struct super_block *sb, void *data,
612                struct ocfs2_block_check *bc)
613{
614    int rc = 0;
615    struct ocfs2_super *osb = OCFS2_SB(sb);
616
617    if (ocfs2_meta_ecc(osb))
618        rc = ocfs2_block_check_validate(data, sb->s_blocksize, bc,
619                        &osb->osb_ecc_stats);
620
621    return rc;
622}
623
624void ocfs2_compute_meta_ecc_bhs(struct super_block *sb,
625                struct buffer_head **bhs, int nr,
626                struct ocfs2_block_check *bc)
627{
628    if (ocfs2_meta_ecc(OCFS2_SB(sb)))
629        ocfs2_block_check_compute_bhs(bhs, nr, bc);
630}
631
632int ocfs2_validate_meta_ecc_bhs(struct super_block *sb,
633                struct buffer_head **bhs, int nr,
634                struct ocfs2_block_check *bc)
635{
636    int rc = 0;
637    struct ocfs2_super *osb = OCFS2_SB(sb);
638
639    if (ocfs2_meta_ecc(osb))
640        rc = ocfs2_block_check_validate_bhs(bhs, nr, bc,
641                            &osb->osb_ecc_stats);
642
643    return rc;
644}
645
646

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