blob: 2a947c44e5949173817d36716ffb3c7b8bbdeec8 [file] [log] [blame]
Joel Becker70ad1ba2008-10-16 17:54:25 -07001/* -*- 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 <asm/byteorder.h>
26
Joel Beckerd6b32bb2008-10-17 14:55:01 -070027#include <cluster/masklog.h>
28
Joel Becker70ad1ba2008-10-16 17:54:25 -070029#include "ocfs2.h"
30
31#include "blockcheck.h"
32
33
Joel Becker70ad1ba2008-10-16 17:54:25 -070034/*
35 * We use the following conventions:
36 *
37 * d = # data bits
38 * p = # parity bits
39 * c = # total code bits (d + p)
40 */
Joel Becker70ad1ba2008-10-16 17:54:25 -070041
Joel Becker7bb458a2008-12-15 18:24:33 -080042
43/*
Joel Becker70ad1ba2008-10-16 17:54:25 -070044 * Calculate the bit offset in the hamming code buffer based on the bit's
45 * offset in the data buffer. Since the hamming code reserves all
46 * power-of-two bits for parity, the data bit number and the code bit
47 * number are offest by all the parity bits beforehand.
48 *
49 * Recall that bit numbers in hamming code are 1-based. This function
50 * takes the 0-based data bit from the caller.
51 *
52 * An example. Take bit 1 of the data buffer. 1 is a power of two (2^0),
53 * so it's a parity bit. 2 is a power of two (2^1), so it's a parity bit.
54 * 3 is not a power of two. So bit 1 of the data buffer ends up as bit 3
55 * in the code buffer.
Joel Becker58896c42008-12-16 13:54:40 -080056 *
57 * The caller can pass in *p if it wants to keep track of the most recent
58 * number of parity bits added. This allows the function to start the
59 * calculation at the last place.
Joel Becker70ad1ba2008-10-16 17:54:25 -070060 */
Joel Becker58896c42008-12-16 13:54:40 -080061static unsigned int calc_code_bit(unsigned int i, unsigned int *p_cache)
Joel Becker70ad1ba2008-10-16 17:54:25 -070062{
Joel Becker58896c42008-12-16 13:54:40 -080063 unsigned int b, p = 0;
Joel Becker70ad1ba2008-10-16 17:54:25 -070064
65 /*
66 * Data bits are 0-based, but we're talking code bits, which
67 * are 1-based.
68 */
69 b = i + 1;
70
Joel Becker58896c42008-12-16 13:54:40 -080071 /* Use the cache if it is there */
72 if (p_cache)
73 p = *p_cache;
Joel Becker7bb458a2008-12-15 18:24:33 -080074 b += p;
75
76 /*
Joel Becker70ad1ba2008-10-16 17:54:25 -070077 * For every power of two below our bit number, bump our bit.
78 *
Joel Becker58896c42008-12-16 13:54:40 -080079 * We compare with (b + 1) because we have to compare with what b
Joel Becker70ad1ba2008-10-16 17:54:25 -070080 * would be _if_ it were bumped up by the parity bit. Capice?
Joel Becker7bb458a2008-12-15 18:24:33 -080081 *
Joel Becker58896c42008-12-16 13:54:40 -080082 * p is set above.
Joel Becker70ad1ba2008-10-16 17:54:25 -070083 */
Joel Becker58896c42008-12-16 13:54:40 -080084 for (; (1 << p) < (b + 1); p++)
Joel Becker70ad1ba2008-10-16 17:54:25 -070085 b++;
86
Joel Becker58896c42008-12-16 13:54:40 -080087 if (p_cache)
88 *p_cache = p;
89
Joel Becker70ad1ba2008-10-16 17:54:25 -070090 return b;
91}
92
93/*
94 * This is the low level encoder function. It can be called across
95 * multiple hunks just like the crc32 code. 'd' is the number of bits
96 * _in_this_hunk_. nr is the bit offset of this hunk. So, if you had
97 * two 512B buffers, you would do it like so:
98 *
99 * parity = ocfs2_hamming_encode(0, buf1, 512 * 8, 0);
100 * parity = ocfs2_hamming_encode(parity, buf2, 512 * 8, 512 * 8);
101 *
102 * If you just have one buffer, use ocfs2_hamming_encode_block().
103 */
104u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr)
105{
Joel Becker58896c42008-12-16 13:54:40 -0800106 unsigned int i, b, p = 0;
Joel Becker70ad1ba2008-10-16 17:54:25 -0700107
Joel Beckere798b3f2008-12-15 17:13:48 -0800108 BUG_ON(!d);
Joel Becker70ad1ba2008-10-16 17:54:25 -0700109
110 /*
111 * b is the hamming code bit number. Hamming code specifies a
112 * 1-based array, but C uses 0-based. So 'i' is for C, and 'b' is
113 * for the algorithm.
114 *
115 * The i++ in the for loop is so that the start offset passed
116 * to ocfs2_find_next_bit_set() is one greater than the previously
117 * found bit.
118 */
119 for (i = 0; (i = ocfs2_find_next_bit(data, d, i)) < d; i++)
120 {
121 /*
122 * i is the offset in this hunk, nr + i is the total bit
123 * offset.
124 */
Joel Becker58896c42008-12-16 13:54:40 -0800125 b = calc_code_bit(nr + i, &p);
Joel Becker70ad1ba2008-10-16 17:54:25 -0700126
Joel Beckere798b3f2008-12-15 17:13:48 -0800127 /*
128 * Data bits in the resultant code are checked by
129 * parity bits that are part of the bit number
130 * representation. Huh?
131 *
132 * <wikipedia href="http://en.wikipedia.org/wiki/Hamming_code">
133 * In other words, the parity bit at position 2^k
134 * checks bits in positions having bit k set in
135 * their binary representation. Conversely, for
136 * instance, bit 13, i.e. 1101(2), is checked by
137 * bits 1000(2) = 8, 0100(2)=4 and 0001(2) = 1.
138 * </wikipedia>
139 *
140 * Note that 'k' is the _code_ bit number. 'b' in
141 * our loop.
142 */
143 parity ^= b;
Joel Becker70ad1ba2008-10-16 17:54:25 -0700144 }
145
146 /* While the data buffer was treated as little endian, the
147 * return value is in host endian. */
148 return parity;
149}
150
151u32 ocfs2_hamming_encode_block(void *data, unsigned int blocksize)
152{
153 return ocfs2_hamming_encode(0, data, blocksize * 8, 0);
154}
155
156/*
157 * Like ocfs2_hamming_encode(), this can handle hunks. nr is the bit
158 * offset of the current hunk. If bit to be fixed is not part of the
159 * current hunk, this does nothing.
160 *
161 * If you only have one hunk, use ocfs2_hamming_fix_block().
162 */
163void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr,
164 unsigned int fix)
165{
Joel Becker70ad1ba2008-10-16 17:54:25 -0700166 unsigned int i, b;
167
Joel Beckere798b3f2008-12-15 17:13:48 -0800168 BUG_ON(!d);
Joel Becker70ad1ba2008-10-16 17:54:25 -0700169
170 /*
171 * If the bit to fix has an hweight of 1, it's a parity bit. One
172 * busted parity bit is its own error. Nothing to do here.
173 */
174 if (hweight32(fix) == 1)
175 return;
176
177 /*
178 * nr + d is the bit right past the data hunk we're looking at.
179 * If fix after that, nothing to do
180 */
Joel Becker58896c42008-12-16 13:54:40 -0800181 if (fix >= calc_code_bit(nr + d, NULL))
Joel Becker70ad1ba2008-10-16 17:54:25 -0700182 return;
183
184 /*
185 * nr is the offset in the data hunk we're starting at. Let's
186 * start b at the offset in the code buffer. See hamming_encode()
187 * for a more detailed description of 'b'.
188 */
Joel Becker58896c42008-12-16 13:54:40 -0800189 b = calc_code_bit(nr, NULL);
Joel Becker70ad1ba2008-10-16 17:54:25 -0700190 /* If the fix is before this hunk, nothing to do */
191 if (fix < b)
192 return;
193
194 for (i = 0; i < d; i++, b++)
195 {
196 /* Skip past parity bits */
197 while (hweight32(b) == 1)
198 b++;
199
200 /*
201 * i is the offset in this data hunk.
202 * nr + i is the offset in the total data buffer.
203 * b is the offset in the total code buffer.
204 *
205 * Thus, when b == fix, bit i in the current hunk needs
206 * fixing.
207 */
208 if (b == fix)
209 {
210 if (ocfs2_test_bit(i, data))
211 ocfs2_clear_bit(i, data);
212 else
213 ocfs2_set_bit(i, data);
214 break;
215 }
216 }
217}
218
219void ocfs2_hamming_fix_block(void *data, unsigned int blocksize,
220 unsigned int fix)
221{
222 ocfs2_hamming_fix(data, blocksize * 8, 0, fix);
223}
224
225/*
226 * This function generates check information for a block.
227 * data is the block to be checked. bc is a pointer to the
228 * ocfs2_block_check structure describing the crc32 and the ecc.
229 *
230 * bc should be a pointer inside data, as the function will
231 * take care of zeroing it before calculating the check information. If
232 * bc does not point inside data, the caller must make sure any inline
233 * ocfs2_block_check structures are zeroed.
234 *
235 * The data buffer must be in on-disk endian (little endian for ocfs2).
236 * bc will be filled with little-endian values and will be ready to go to
237 * disk.
238 */
239void ocfs2_block_check_compute(void *data, size_t blocksize,
240 struct ocfs2_block_check *bc)
241{
242 u32 crc;
243 u32 ecc;
244
245 memset(bc, 0, sizeof(struct ocfs2_block_check));
246
247 crc = crc32_le(~0, data, blocksize);
248 ecc = ocfs2_hamming_encode_block(data, blocksize);
249
250 /*
251 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
252 * larger than 16 bits.
253 */
254 BUG_ON(ecc > USHORT_MAX);
255
256 bc->bc_crc32e = cpu_to_le32(crc);
257 bc->bc_ecc = cpu_to_le16((u16)ecc);
258}
259
260/*
261 * This function validates existing check information. Like _compute,
262 * the function will take care of zeroing bc before calculating check codes.
263 * If bc is not a pointer inside data, the caller must have zeroed any
264 * inline ocfs2_block_check structures.
265 *
266 * Again, the data passed in should be the on-disk endian.
267 */
268int ocfs2_block_check_validate(void *data, size_t blocksize,
269 struct ocfs2_block_check *bc)
270{
271 int rc = 0;
272 struct ocfs2_block_check check;
273 u32 crc, ecc;
274
275 check.bc_crc32e = le32_to_cpu(bc->bc_crc32e);
276 check.bc_ecc = le16_to_cpu(bc->bc_ecc);
277
278 memset(bc, 0, sizeof(struct ocfs2_block_check));
279
280 /* Fast path - if the crc32 validates, we're good to go */
281 crc = crc32_le(~0, data, blocksize);
282 if (crc == check.bc_crc32e)
283 goto out;
284
Joel Beckerd6b32bb2008-10-17 14:55:01 -0700285 mlog(ML_ERROR,
286 "CRC32 failed: stored: %u, computed %u. Applying ECC.\n",
287 (unsigned int)check.bc_crc32e, (unsigned int)crc);
288
Joel Becker70ad1ba2008-10-16 17:54:25 -0700289 /* Ok, try ECC fixups */
290 ecc = ocfs2_hamming_encode_block(data, blocksize);
291 ocfs2_hamming_fix_block(data, blocksize, ecc ^ check.bc_ecc);
292
293 /* And check the crc32 again */
294 crc = crc32_le(~0, data, blocksize);
295 if (crc == check.bc_crc32e)
296 goto out;
297
Joel Beckerd6b32bb2008-10-17 14:55:01 -0700298 mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n",
299 (unsigned int)check.bc_crc32e, (unsigned int)crc);
300
Joel Becker70ad1ba2008-10-16 17:54:25 -0700301 rc = -EIO;
302
303out:
304 bc->bc_crc32e = cpu_to_le32(check.bc_crc32e);
305 bc->bc_ecc = cpu_to_le16(check.bc_ecc);
306
307 return rc;
308}
309
310/*
311 * This function generates check information for a list of buffer_heads.
312 * bhs is the blocks to be checked. bc is a pointer to the
313 * ocfs2_block_check structure describing the crc32 and the ecc.
314 *
315 * bc should be a pointer inside data, as the function will
316 * take care of zeroing it before calculating the check information. If
317 * bc does not point inside data, the caller must make sure any inline
318 * ocfs2_block_check structures are zeroed.
319 *
320 * The data buffer must be in on-disk endian (little endian for ocfs2).
321 * bc will be filled with little-endian values and will be ready to go to
322 * disk.
323 */
324void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr,
325 struct ocfs2_block_check *bc)
326{
327 int i;
328 u32 crc, ecc;
329
330 BUG_ON(nr < 0);
331
332 if (!nr)
333 return;
334
335 memset(bc, 0, sizeof(struct ocfs2_block_check));
336
337 for (i = 0, crc = ~0, ecc = 0; i < nr; i++) {
338 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
339 /*
340 * The number of bits in a buffer is obviously b_size*8.
341 * The offset of this buffer is b_size*i, so the bit offset
342 * of this buffer is b_size*8*i.
343 */
344 ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
345 bhs[i]->b_size * 8,
346 bhs[i]->b_size * 8 * i);
347 }
348
349 /*
350 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
351 * larger than 16 bits.
352 */
353 BUG_ON(ecc > USHORT_MAX);
354
355 bc->bc_crc32e = cpu_to_le32(crc);
356 bc->bc_ecc = cpu_to_le16((u16)ecc);
357}
358
359/*
360 * This function validates existing check information on a list of
361 * buffer_heads. Like _compute_bhs, the function will take care of
362 * zeroing bc before calculating check codes. If bc is not a pointer
363 * inside data, the caller must have zeroed any inline
364 * ocfs2_block_check structures.
365 *
366 * Again, the data passed in should be the on-disk endian.
367 */
368int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr,
369 struct ocfs2_block_check *bc)
370{
371 int i, rc = 0;
372 struct ocfs2_block_check check;
373 u32 crc, ecc, fix;
374
375 BUG_ON(nr < 0);
376
377 if (!nr)
378 return 0;
379
380 check.bc_crc32e = le32_to_cpu(bc->bc_crc32e);
381 check.bc_ecc = le16_to_cpu(bc->bc_ecc);
382
383 memset(bc, 0, sizeof(struct ocfs2_block_check));
384
385 /* Fast path - if the crc32 validates, we're good to go */
386 for (i = 0, crc = ~0; i < nr; i++)
387 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
388 if (crc == check.bc_crc32e)
389 goto out;
390
391 mlog(ML_ERROR,
392 "CRC32 failed: stored: %u, computed %u. Applying ECC.\n",
393 (unsigned int)check.bc_crc32e, (unsigned int)crc);
394
395 /* Ok, try ECC fixups */
396 for (i = 0, ecc = 0; i < nr; i++) {
397 /*
398 * The number of bits in a buffer is obviously b_size*8.
399 * The offset of this buffer is b_size*i, so the bit offset
400 * of this buffer is b_size*8*i.
401 */
402 ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
403 bhs[i]->b_size * 8,
404 bhs[i]->b_size * 8 * i);
405 }
406 fix = ecc ^ check.bc_ecc;
407 for (i = 0; i < nr; i++) {
408 /*
409 * Try the fix against each buffer. It will only affect
410 * one of them.
411 */
412 ocfs2_hamming_fix(bhs[i]->b_data, bhs[i]->b_size * 8,
413 bhs[i]->b_size * 8 * i, fix);
414 }
415
416 /* And check the crc32 again */
417 for (i = 0, crc = ~0; i < nr; i++)
418 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
419 if (crc == check.bc_crc32e)
420 goto out;
421
422 mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n",
423 (unsigned int)check.bc_crc32e, (unsigned int)crc);
424
425 rc = -EIO;
426
427out:
428 bc->bc_crc32e = cpu_to_le32(check.bc_crc32e);
429 bc->bc_ecc = cpu_to_le16(check.bc_ecc);
430
431 return rc;
432}
433
434/*
435 * These are the main API. They check the superblock flag before
436 * calling the underlying operations.
437 *
438 * They expect the buffer(s) to be in disk format.
439 */
440void ocfs2_compute_meta_ecc(struct super_block *sb, void *data,
441 struct ocfs2_block_check *bc)
442{
443 if (ocfs2_meta_ecc(OCFS2_SB(sb)))
444 ocfs2_block_check_compute(data, sb->s_blocksize, bc);
445}
446
447int ocfs2_validate_meta_ecc(struct super_block *sb, void *data,
448 struct ocfs2_block_check *bc)
449{
450 int rc = 0;
451
452 if (ocfs2_meta_ecc(OCFS2_SB(sb)))
453 rc = ocfs2_block_check_validate(data, sb->s_blocksize, bc);
454
455 return rc;
456}
457
458void ocfs2_compute_meta_ecc_bhs(struct super_block *sb,
459 struct buffer_head **bhs, int nr,
460 struct ocfs2_block_check *bc)
461{
462 if (ocfs2_meta_ecc(OCFS2_SB(sb)))
463 ocfs2_block_check_compute_bhs(bhs, nr, bc);
464}
465
466int ocfs2_validate_meta_ecc_bhs(struct super_block *sb,
467 struct buffer_head **bhs, int nr,
468 struct ocfs2_block_check *bc)
469{
470 int rc = 0;
471
472 if (ocfs2_meta_ecc(OCFS2_SB(sb)))
473 rc = ocfs2_block_check_validate_bhs(bhs, nr, bc);
474
475 return rc;
476}
477