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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:
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
);