1 // SPDX-License-Identifier: GPL-2.0-only
2 /* -*- mode: c; c-basic-offset: 8; -*-
3 * vim: noexpandtab sw=8 ts=8 sts=0:
7 * Checksum and ECC codes for the OCFS2 userspace library.
9 * Copyright (C) 2006, 2008 Oracle. All rights reserved.
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>
20 #include <asm/byteorder.h>
22 #include <cluster/masklog.h>
26 #include "blockcheck.h"
30 * We use the following conventions:
34 * c = # total code bits (d + p)
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.
44 * Recall that bit numbers in hamming code are 1-based. This function
45 * takes the 0-based data bit from the caller.
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
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.
56 static unsigned int calc_code_bit(unsigned int i, unsigned int *p_cache)
58 unsigned int b, p = 0;
61 * Data bits are 0-based, but we're talking code bits, which
66 /* Use the cache if it is there */
72 * For every power of two below our bit number, bump our bit.
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?
79 for (; (1 << p) < (b + 1); p++)
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:
94 * parity = ocfs2_hamming_encode(0, buf1, 512 * 8, 0);
95 * parity = ocfs2_hamming_encode(parity, buf2, 512 * 8, 512 * 8);
97 * If you just have one buffer, use ocfs2_hamming_encode_block().
99 u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr)
101 unsigned int i, b, p = 0;
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
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
114 for (i = 0; (i = ocfs2_find_next_bit(data, d, i)) < d; i++)
117 * i is the offset in this hunk, nr + i is the total bit
120 b = calc_code_bit(nr + i, &p);
123 * Data bits in the resultant code are checked by
124 * parity bits that are part of the bit number
125 * representation. Huh?
127 * <wikipedia href="http://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.
135 * Note that 'k' is the _code_ bit number. 'b' in
141 /* While the data buffer was treated as little endian, the
142 * return value is in host endian. */
146 u32 ocfs2_hamming_encode_block(void *data, unsigned int blocksize)
148 return ocfs2_hamming_encode(0, data, blocksize * 8, 0);
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.
156 * If you only have one hunk, use ocfs2_hamming_fix_block().
158 void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr,
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.
169 if (hweight32(fix) == 1)
173 * nr + d is the bit right past the data hunk we're looking at.
174 * If fix after that, nothing to do
176 if (fix >= calc_code_bit(nr + d, NULL))
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'.
184 b = calc_code_bit(nr, NULL);
185 /* If the fix is before this hunk, nothing to do */
189 for (i = 0; i < d; i++, b++)
191 /* Skip past parity bits */
192 while (hweight32(b) == 1)
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.
200 * Thus, when b == fix, bit i in the current hunk needs
205 if (ocfs2_test_bit(i, data))
206 ocfs2_clear_bit(i, data);
208 ocfs2_set_bit(i, data);
214 void ocfs2_hamming_fix_block(void *data, unsigned int blocksize,
217 ocfs2_hamming_fix(data, blocksize * 8, 0, fix);
225 #ifdef CONFIG_DEBUG_FS
227 static int blockcheck_u64_get(void *data, u64 *val)
232 DEFINE_SIMPLE_ATTRIBUTE(blockcheck_fops, blockcheck_u64_get, NULL, "%llu\n");
234 static struct dentry *blockcheck_debugfs_create(const char *name,
235 struct dentry *parent,
238 return debugfs_create_file(name, S_IFREG | S_IRUSR, parent, value,
242 static void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats)
245 debugfs_remove(stats->b_debug_check);
246 stats->b_debug_check = NULL;
247 debugfs_remove(stats->b_debug_failure);
248 stats->b_debug_failure = NULL;
249 debugfs_remove(stats->b_debug_recover);
250 stats->b_debug_recover = NULL;
251 debugfs_remove(stats->b_debug_dir);
252 stats->b_debug_dir = NULL;
256 static int ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats,
257 struct dentry *parent)
264 stats->b_debug_dir = debugfs_create_dir("blockcheck", parent);
265 if (!stats->b_debug_dir)
268 stats->b_debug_check =
269 blockcheck_debugfs_create("blocks_checked",
271 &stats->b_check_count);
273 stats->b_debug_failure =
274 blockcheck_debugfs_create("checksums_failed",
276 &stats->b_failure_count);
278 stats->b_debug_recover =
279 blockcheck_debugfs_create("ecc_recoveries",
281 &stats->b_recover_count);
282 if (stats->b_debug_check && stats->b_debug_failure &&
283 stats->b_debug_recover)
288 ocfs2_blockcheck_debug_remove(stats);
292 static inline int ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats,
293 struct dentry *parent)
298 static inline void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats)
301 #endif /* CONFIG_DEBUG_FS */
303 /* Always-called wrappers for starting and stopping the debugfs files */
304 int ocfs2_blockcheck_stats_debugfs_install(struct ocfs2_blockcheck_stats *stats,
305 struct dentry *parent)
307 return ocfs2_blockcheck_debug_install(stats, parent);
310 void ocfs2_blockcheck_stats_debugfs_remove(struct ocfs2_blockcheck_stats *stats)
312 ocfs2_blockcheck_debug_remove(stats);
315 static void ocfs2_blockcheck_inc_check(struct ocfs2_blockcheck_stats *stats)
322 spin_lock(&stats->b_lock);
323 stats->b_check_count++;
324 new_count = stats->b_check_count;
325 spin_unlock(&stats->b_lock);
328 mlog(ML_NOTICE, "Block check count has wrapped\n");
331 static void ocfs2_blockcheck_inc_failure(struct ocfs2_blockcheck_stats *stats)
338 spin_lock(&stats->b_lock);
339 stats->b_failure_count++;
340 new_count = stats->b_failure_count;
341 spin_unlock(&stats->b_lock);
344 mlog(ML_NOTICE, "Checksum failure count has wrapped\n");
347 static void ocfs2_blockcheck_inc_recover(struct ocfs2_blockcheck_stats *stats)
354 spin_lock(&stats->b_lock);
355 stats->b_recover_count++;
356 new_count = stats->b_recover_count;
357 spin_unlock(&stats->b_lock);
360 mlog(ML_NOTICE, "ECC recovery count has wrapped\n");
366 * These are the low-level APIs for using the ocfs2_block_check structure.
370 * This function generates check information for a block.
371 * data is the block to be checked. bc is a pointer to the
372 * ocfs2_block_check structure describing the crc32 and the ecc.
374 * bc should be a pointer inside data, as the function will
375 * take care of zeroing it before calculating the check information. If
376 * bc does not point inside data, the caller must make sure any inline
377 * ocfs2_block_check structures are zeroed.
379 * The data buffer must be in on-disk endian (little endian for ocfs2).
380 * bc will be filled with little-endian values and will be ready to go to
383 void ocfs2_block_check_compute(void *data, size_t blocksize,
384 struct ocfs2_block_check *bc)
389 memset(bc, 0, sizeof(struct ocfs2_block_check));
391 crc = crc32_le(~0, data, blocksize);
392 ecc = ocfs2_hamming_encode_block(data, blocksize);
395 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
396 * larger than 16 bits.
398 BUG_ON(ecc > USHRT_MAX);
400 bc->bc_crc32e = cpu_to_le32(crc);
401 bc->bc_ecc = cpu_to_le16((u16)ecc);
405 * This function validates existing check information. Like _compute,
406 * the function will take care of zeroing bc before calculating check codes.
407 * If bc is not a pointer inside data, the caller must have zeroed any
408 * inline ocfs2_block_check structures.
410 * Again, the data passed in should be the on-disk endian.
412 int ocfs2_block_check_validate(void *data, size_t blocksize,
413 struct ocfs2_block_check *bc,
414 struct ocfs2_blockcheck_stats *stats)
421 ocfs2_blockcheck_inc_check(stats);
423 bc_crc32e = le32_to_cpu(bc->bc_crc32e);
424 bc_ecc = le16_to_cpu(bc->bc_ecc);
426 memset(bc, 0, sizeof(struct ocfs2_block_check));
428 /* Fast path - if the crc32 validates, we're good to go */
429 crc = crc32_le(~0, data, blocksize);
430 if (crc == bc_crc32e)
433 ocfs2_blockcheck_inc_failure(stats);
435 "CRC32 failed: stored: 0x%x, computed 0x%x. Applying ECC.\n",
436 (unsigned int)bc_crc32e, (unsigned int)crc);
438 /* Ok, try ECC fixups */
439 ecc = ocfs2_hamming_encode_block(data, blocksize);
440 ocfs2_hamming_fix_block(data, blocksize, ecc ^ bc_ecc);
442 /* And check the crc32 again */
443 crc = crc32_le(~0, data, blocksize);
444 if (crc == bc_crc32e) {
445 ocfs2_blockcheck_inc_recover(stats);
449 mlog(ML_ERROR, "Fixed CRC32 failed: stored: 0x%x, computed 0x%x\n",
450 (unsigned int)bc_crc32e, (unsigned int)crc);
455 bc->bc_crc32e = cpu_to_le32(bc_crc32e);
456 bc->bc_ecc = cpu_to_le16(bc_ecc);
462 * This function generates check information for a list of buffer_heads.
463 * bhs is the blocks to be checked. bc is a pointer to the
464 * ocfs2_block_check structure describing the crc32 and the ecc.
466 * bc should be a pointer inside data, as the function will
467 * take care of zeroing it before calculating the check information. If
468 * bc does not point inside data, the caller must make sure any inline
469 * ocfs2_block_check structures are zeroed.
471 * The data buffer must be in on-disk endian (little endian for ocfs2).
472 * bc will be filled with little-endian values and will be ready to go to
475 void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr,
476 struct ocfs2_block_check *bc)
486 memset(bc, 0, sizeof(struct ocfs2_block_check));
488 for (i = 0, crc = ~0, ecc = 0; i < nr; i++) {
489 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
491 * The number of bits in a buffer is obviously b_size*8.
492 * The offset of this buffer is b_size*i, so the bit offset
493 * of this buffer is b_size*8*i.
495 ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
497 bhs[i]->b_size * 8 * i);
501 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
502 * larger than 16 bits.
504 BUG_ON(ecc > USHRT_MAX);
506 bc->bc_crc32e = cpu_to_le32(crc);
507 bc->bc_ecc = cpu_to_le16((u16)ecc);
511 * This function validates existing check information on a list of
512 * buffer_heads. Like _compute_bhs, the function will take care of
513 * zeroing bc before calculating check codes. If bc is not a pointer
514 * inside data, the caller must have zeroed any inline
515 * ocfs2_block_check structures.
517 * Again, the data passed in should be the on-disk endian.
519 int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr,
520 struct ocfs2_block_check *bc,
521 struct ocfs2_blockcheck_stats *stats)
533 ocfs2_blockcheck_inc_check(stats);
535 bc_crc32e = le32_to_cpu(bc->bc_crc32e);
536 bc_ecc = le16_to_cpu(bc->bc_ecc);
538 memset(bc, 0, sizeof(struct ocfs2_block_check));
540 /* Fast path - if the crc32 validates, we're good to go */
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)
546 ocfs2_blockcheck_inc_failure(stats);
548 "CRC32 failed: stored: %u, computed %u. Applying ECC.\n",
549 (unsigned int)bc_crc32e, (unsigned int)crc);
551 /* Ok, try ECC fixups */
552 for (i = 0, ecc = 0; i < nr; i++) {
554 * The number of bits in a buffer is obviously b_size*8.
555 * The offset of this buffer is b_size*i, so the bit offset
556 * of this buffer is b_size*8*i.
558 ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
560 bhs[i]->b_size * 8 * i);
563 for (i = 0; i < nr; i++) {
565 * Try the fix against each buffer. It will only affect
568 ocfs2_hamming_fix(bhs[i]->b_data, bhs[i]->b_size * 8,
569 bhs[i]->b_size * 8 * i, fix);
572 /* And check the crc32 again */
573 for (i = 0, crc = ~0; i < nr; i++)
574 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
575 if (crc == bc_crc32e) {
576 ocfs2_blockcheck_inc_recover(stats);
580 mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n",
581 (unsigned int)bc_crc32e, (unsigned int)crc);
586 bc->bc_crc32e = cpu_to_le32(bc_crc32e);
587 bc->bc_ecc = cpu_to_le16(bc_ecc);
593 * These are the main API. They check the superblock flag before
594 * calling the underlying operations.
596 * They expect the buffer(s) to be in disk format.
598 void ocfs2_compute_meta_ecc(struct super_block *sb, void *data,
599 struct ocfs2_block_check *bc)
601 if (ocfs2_meta_ecc(OCFS2_SB(sb)))
602 ocfs2_block_check_compute(data, sb->s_blocksize, bc);
605 int ocfs2_validate_meta_ecc(struct super_block *sb, void *data,
606 struct ocfs2_block_check *bc)
609 struct ocfs2_super *osb = OCFS2_SB(sb);
611 if (ocfs2_meta_ecc(osb))
612 rc = ocfs2_block_check_validate(data, sb->s_blocksize, bc,
613 &osb->osb_ecc_stats);
618 void ocfs2_compute_meta_ecc_bhs(struct super_block *sb,
619 struct buffer_head **bhs, int nr,
620 struct ocfs2_block_check *bc)
622 if (ocfs2_meta_ecc(OCFS2_SB(sb)))
623 ocfs2_block_check_compute_bhs(bhs, nr, bc);
626 int ocfs2_validate_meta_ecc_bhs(struct super_block *sb,
627 struct buffer_head **bhs, int nr,
628 struct ocfs2_block_check *bc)
631 struct ocfs2_super *osb = OCFS2_SB(sb);
633 if (ocfs2_meta_ecc(osb))
634 rc = ocfs2_block_check_validate_bhs(bhs, nr, bc,
635 &osb->osb_ecc_stats);