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 > 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 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: 0x%x, computed 0x%x. 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: 0x%x, computed 0x%x\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 > USHRT_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