1// SPDX-License-Identifier: GPL-2.0-only 2/* 3 * blockcheck.c 4 * 5 * Checksum and ECC codes for the OCFS2 userspace library. 6 * 7 * Copyright (C) 2006, 2008 Oracle. All rights reserved. 8 */ 9 10#include <linux/kernel.h> 11#include <linux/types.h> 12#include <linux/crc32.h> 13#include <linux/buffer_head.h> 14#include <linux/bitops.h> 15#include <linux/debugfs.h> 16#include <linux/module.h> 17#include <linux/fs.h> 18#include <asm/byteorder.h> 19 20#include <cluster/masklog.h> 21 22#include "ocfs2.h" 23 24#include "blockcheck.h" 25 26 27/* 28 * We use the following conventions: 29 * 30 * d = # data bits 31 * p = # parity bits 32 * c = # total code bits (d + p) 33 */ 34 35 36/* 37 * Calculate the bit offset in the hamming code buffer based on the bit's 38 * offset in the data buffer. Since the hamming code reserves all 39 * power-of-two bits for parity, the data bit number and the code bit 40 * number are offset by all the parity bits beforehand. 41 * 42 * Recall that bit numbers in hamming code are 1-based. This function 43 * takes the 0-based data bit from the caller. 44 * 45 * An example. Take bit 1 of the data buffer. 1 is a power of two (2^0), 46 * so it's a parity bit. 2 is a power of two (2^1), so it's a parity bit. 47 * 3 is not a power of two. So bit 1 of the data buffer ends up as bit 3 48 * in the code buffer. 49 * 50 * The caller can pass in *p if it wants to keep track of the most recent 51 * number of parity bits added. This allows the function to start the 52 * calculation at the last place. 53 */ 54static unsigned int calc_code_bit(unsigned int i, unsigned int *p_cache) 55{ 56 unsigned int b, p = 0; 57 58 /* 59 * Data bits are 0-based, but we're talking code bits, which 60 * are 1-based. 61 */ 62 b = i + 1; 63 64 /* Use the cache if it is there */ 65 if (p_cache) 66 p = *p_cache; 67 b += p; 68 69 /* 70 * For every power of two below our bit number, bump our bit. 71 * 72 * We compare with (b + 1) because we have to compare with what b 73 * would be _if_ it were bumped up by the parity bit. Capice? 74 * 75 * p is set above. 76 */ 77 for (; (1 << p) < (b + 1); p++) 78 b++; 79 80 if (p_cache) 81 *p_cache = p; 82 83 return b; 84} 85 86/* 87 * This is the low level encoder function. It can be called across 88 * multiple hunks just like the crc32 code. 'd' is the number of bits 89 * _in_this_hunk_. nr is the bit offset of this hunk. So, if you had 90 * two 512B buffers, you would do it like so: 91 * 92 * parity = ocfs2_hamming_encode(0, buf1, 512 * 8, 0); 93 * parity = ocfs2_hamming_encode(parity, buf2, 512 * 8, 512 * 8); 94 * 95 * If you just have one buffer, use ocfs2_hamming_encode_block(). 96 */ 97u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr) 98{ 99 unsigned int i, b, p = 0; 100 101 BUG_ON(!d); 102 103 /* 104 * b is the hamming code bit number. Hamming code specifies a 105 * 1-based array, but C uses 0-based. So 'i' is for C, and 'b' is 106 * for the algorithm. 107 * 108 * The i++ in the for loop is so that the start offset passed 109 * to ocfs2_find_next_bit_set() is one greater than the previously 110 * found bit. 111 */ 112 for (i = 0; (i = ocfs2_find_next_bit(data, d, i)) < d; i++) 113 { 114 /* 115 * i is the offset in this hunk, nr + i is the total bit 116 * offset. 117 */ 118 b = calc_code_bit(nr + i, &p); 119 120 /* 121 * Data bits in the resultant code are checked by 122 * parity bits that are part of the bit number 123 * representation. Huh? 124 * 125 * <wikipedia href="https://en.wikipedia.org/wiki/Hamming_code"> 126 * In other words, the parity bit at position 2^k 127 * checks bits in positions having bit k set in 128 * their binary representation. Conversely, for 129 * instance, bit 13, i.e. 1101(2), is checked by 130 * bits 1000(2) = 8, 0100(2)=4 and 0001(2) = 1. 131 * </wikipedia> 132 * 133 * Note that 'k' is the _code_ bit number. 'b' in 134 * our loop. 135 */ 136 parity ^= b; 137 } 138 139 /* While the data buffer was treated as little endian, the 140 * return value is in host endian. */ 141 return parity; 142} 143 144u32 ocfs2_hamming_encode_block(void *data, unsigned int blocksize) 145{ 146 return ocfs2_hamming_encode(0, data, blocksize * 8, 0); 147} 148 149/* 150 * Like ocfs2_hamming_encode(), this can handle hunks. nr is the bit 151 * offset of the current hunk. If bit to be fixed is not part of the 152 * current hunk, this does nothing. 153 * 154 * If you only have one hunk, use ocfs2_hamming_fix_block(). 155 */ 156void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr, 157 unsigned int fix) 158{ 159 unsigned int i, b; 160 161 BUG_ON(!d); 162 163 /* 164 * If the bit to fix has an hweight of 1, it's a parity bit. One 165 * busted parity bit is its own error. Nothing to do here. 166 */ 167 if (hweight32(fix) == 1) 168 return; 169 170 /* 171 * nr + d is the bit right past the data hunk we're looking at. 172 * If fix after that, nothing to do 173 */ 174 if (fix >= calc_code_bit(nr + d, NULL)) 175 return; 176 177 /* 178 * nr is the offset in the data hunk we're starting at. Let's 179 * start b at the offset in the code buffer. See hamming_encode() 180 * for a more detailed description of 'b'. 181 */ 182 b = calc_code_bit(nr, NULL); 183 /* If the fix is before this hunk, nothing to do */ 184 if (fix < b) 185 return; 186 187 for (i = 0; i < d; i++, b++) 188 { 189 /* Skip past parity bits */ 190 while (hweight32(b) == 1) 191 b++; 192 193 /* 194 * i is the offset in this data hunk. 195 * nr + i is the offset in the total data buffer. 196 * b is the offset in the total code buffer. 197 * 198 * Thus, when b == fix, bit i in the current hunk needs 199 * fixing. 200 */ 201 if (b == fix) 202 { 203 if (ocfs2_test_bit(i, data)) 204 ocfs2_clear_bit(i, data); 205 else 206 ocfs2_set_bit(i, data); 207 break; 208 } 209 } 210} 211 212void ocfs2_hamming_fix_block(void *data, unsigned int blocksize, 213 unsigned int fix) 214{ 215 ocfs2_hamming_fix(data, blocksize * 8, 0, fix); 216} 217 218 219/* 220 * Debugfs handling. 221 */ 222 223#ifdef CONFIG_DEBUG_FS 224 225static int blockcheck_u64_get(void *data, u64 *val) 226{ 227 *val = *(u64 *)data; 228 return 0; 229} 230DEFINE_DEBUGFS_ATTRIBUTE(blockcheck_fops, blockcheck_u64_get, NULL, "%llu\n"); 231 232static void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats) 233{ 234 if (stats) { 235 debugfs_remove_recursive(stats->b_debug_dir); 236 stats->b_debug_dir = NULL; 237 } 238} 239 240static void ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats, 241 struct dentry *parent) 242{ 243 struct dentry *dir; 244 245 dir = debugfs_create_dir("blockcheck", parent); 246 stats->b_debug_dir = dir; 247 248 debugfs_create_file("blocks_checked", S_IFREG | S_IRUSR, dir, 249 &stats->b_check_count, &blockcheck_fops); 250 251 debugfs_create_file("checksums_failed", S_IFREG | S_IRUSR, dir, 252 &stats->b_failure_count, &blockcheck_fops); 253 254 debugfs_create_file("ecc_recoveries", S_IFREG | S_IRUSR, dir, 255 &stats->b_recover_count, &blockcheck_fops); 256 257} 258#else 259static inline void ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats, 260 struct dentry *parent) 261{ 262} 263 264static inline void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats) 265{ 266} 267#endif /* CONFIG_DEBUG_FS */ 268 269/* Always-called wrappers for starting and stopping the debugfs files */ 270void ocfs2_blockcheck_stats_debugfs_install(struct ocfs2_blockcheck_stats *stats, 271 struct dentry *parent) 272{ 273 ocfs2_blockcheck_debug_install(stats, parent); 274} 275 276void ocfs2_blockcheck_stats_debugfs_remove(struct ocfs2_blockcheck_stats *stats) 277{ 278 ocfs2_blockcheck_debug_remove(stats); 279} 280 281static void ocfs2_blockcheck_inc_check(struct ocfs2_blockcheck_stats *stats) 282{ 283 u64 new_count; 284 285 if (!stats) 286 return; 287 288 spin_lock(&stats->b_lock); 289 stats->b_check_count++; 290 new_count = stats->b_check_count; 291 spin_unlock(&stats->b_lock); 292 293 if (!new_count) 294 mlog(ML_NOTICE, "Block check count has wrapped\n"); 295} 296 297static void ocfs2_blockcheck_inc_failure(struct ocfs2_blockcheck_stats *stats) 298{ 299 u64 new_count; 300 301 if (!stats) 302 return; 303 304 spin_lock(&stats->b_lock); 305 stats->b_failure_count++; 306 new_count = stats->b_failure_count; 307 spin_unlock(&stats->b_lock); 308 309 if (!new_count) 310 mlog(ML_NOTICE, "Checksum failure count has wrapped\n"); 311} 312 313static void ocfs2_blockcheck_inc_recover(struct ocfs2_blockcheck_stats *stats) 314{ 315 u64 new_count; 316 317 if (!stats) 318 return; 319 320 spin_lock(&stats->b_lock); 321 stats->b_recover_count++; 322 new_count = stats->b_recover_count; 323 spin_unlock(&stats->b_lock); 324 325 if (!new_count) 326 mlog(ML_NOTICE, "ECC recovery count has wrapped\n"); 327} 328 329 330 331/* 332 * These are the low-level APIs for using the ocfs2_block_check structure. 333 */ 334 335/* 336 * This function generates check information for a block. 337 * data is the block to be checked. bc is a pointer to the 338 * ocfs2_block_check structure describing the crc32 and the ecc. 339 * 340 * bc should be a pointer inside data, as the function will 341 * take care of zeroing it before calculating the check information. If 342 * bc does not point inside data, the caller must make sure any inline 343 * ocfs2_block_check structures are zeroed. 344 * 345 * The data buffer must be in on-disk endian (little endian for ocfs2). 346 * bc will be filled with little-endian values and will be ready to go to 347 * disk. 348 */ 349void ocfs2_block_check_compute(void *data, size_t blocksize, 350 struct ocfs2_block_check *bc) 351{ 352 u32 crc; 353 u32 ecc; 354 355 memset(bc, 0, sizeof(struct ocfs2_block_check)); 356 357 crc = crc32_le(~0, data, blocksize); 358 ecc = ocfs2_hamming_encode_block(data, blocksize); 359 360 /* 361 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no 362 * larger than 16 bits. 363 */ 364 BUG_ON(ecc > USHRT_MAX); 365 366 bc->bc_crc32e = cpu_to_le32(crc); 367 bc->bc_ecc = cpu_to_le16((u16)ecc); 368} 369 370/* 371 * This function validates existing check information. Like _compute, 372 * the function will take care of zeroing bc before calculating check codes. 373 * If bc is not a pointer inside data, the caller must have zeroed any 374 * inline ocfs2_block_check structures. 375 * 376 * Again, the data passed in should be the on-disk endian. 377 */ 378int ocfs2_block_check_validate(void *data, size_t blocksize, 379 struct ocfs2_block_check *bc, 380 struct ocfs2_blockcheck_stats *stats) 381{ 382 int rc = 0; 383 u32 bc_crc32e; 384 u16 bc_ecc; 385 u32 crc, ecc; 386 387 ocfs2_blockcheck_inc_check(stats); 388 389 bc_crc32e = le32_to_cpu(bc->bc_crc32e); 390 bc_ecc = le16_to_cpu(bc->bc_ecc); 391 392 memset(bc, 0, sizeof(struct ocfs2_block_check)); 393 394 /* Fast path - if the crc32 validates, we're good to go */ 395 crc = crc32_le(~0, data, blocksize); 396 if (crc == bc_crc32e) 397 goto out; 398 399 ocfs2_blockcheck_inc_failure(stats); 400 mlog(ML_ERROR, 401 "CRC32 failed: stored: 0x%x, computed 0x%x. Applying ECC.\n", 402 (unsigned int)bc_crc32e, (unsigned int)crc); 403 404 /* Ok, try ECC fixups */ 405 ecc = ocfs2_hamming_encode_block(data, blocksize); 406 ocfs2_hamming_fix_block(data, blocksize, ecc ^ bc_ecc); 407 408 /* And check the crc32 again */ 409 crc = crc32_le(~0, data, blocksize); 410 if (crc == bc_crc32e) { 411 ocfs2_blockcheck_inc_recover(stats); 412 goto out; 413 } 414 415 mlog(ML_ERROR, "Fixed CRC32 failed: stored: 0x%x, computed 0x%x\n", 416 (unsigned int)bc_crc32e, (unsigned int)crc); 417 418 rc = -EIO; 419 420out: 421 bc->bc_crc32e = cpu_to_le32(bc_crc32e); 422 bc->bc_ecc = cpu_to_le16(bc_ecc); 423 424 return rc; 425} 426 427/* 428 * This function generates check information for a list of buffer_heads. 429 * bhs is the blocks to be checked. bc is a pointer to the 430 * ocfs2_block_check structure describing the crc32 and the ecc. 431 * 432 * bc should be a pointer inside data, as the function will 433 * take care of zeroing it before calculating the check information. If 434 * bc does not point inside data, the caller must make sure any inline 435 * ocfs2_block_check structures are zeroed. 436 * 437 * The data buffer must be in on-disk endian (little endian for ocfs2). 438 * bc will be filled with little-endian values and will be ready to go to 439 * disk. 440 */ 441void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr, 442 struct ocfs2_block_check *bc) 443{ 444 int i; 445 u32 crc, ecc; 446 447 BUG_ON(nr < 0); 448 449 if (!nr) 450 return; 451 452 memset(bc, 0, sizeof(struct ocfs2_block_check)); 453 454 for (i = 0, crc = ~0, ecc = 0; i < nr; i++) { 455 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size); 456 /* 457 * The number of bits in a buffer is obviously b_size*8. 458 * The offset of this buffer is b_size*i, so the bit offset 459 * of this buffer is b_size*8*i. 460 */ 461 ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data, 462 bhs[i]->b_size * 8, 463 bhs[i]->b_size * 8 * i); 464 } 465 466 /* 467 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no 468 * larger than 16 bits. 469 */ 470 BUG_ON(ecc > USHRT_MAX); 471 472 bc->bc_crc32e = cpu_to_le32(crc); 473 bc->bc_ecc = cpu_to_le16((u16)ecc); 474} 475 476/* 477 * This function validates existing check information on a list of 478 * buffer_heads. Like _compute_bhs, the function will take care of 479 * zeroing bc before calculating check codes. If bc is not a pointer 480 * inside data, the caller must have zeroed any inline 481 * ocfs2_block_check structures. 482 * 483 * Again, the data passed in should be the on-disk endian. 484 */ 485int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr, 486 struct ocfs2_block_check *bc, 487 struct ocfs2_blockcheck_stats *stats) 488{ 489 int i, rc = 0; 490 u32 bc_crc32e; 491 u16 bc_ecc; 492 u32 crc, ecc, fix; 493 494 BUG_ON(nr < 0); 495 496 if (!nr) 497 return 0; 498 499 ocfs2_blockcheck_inc_check(stats); 500 501 bc_crc32e = le32_to_cpu(bc->bc_crc32e); 502 bc_ecc = le16_to_cpu(bc->bc_ecc); 503 504 memset(bc, 0, sizeof(struct ocfs2_block_check)); 505 506 /* Fast path - if the crc32 validates, we're good to go */ 507 for (i = 0, crc = ~0; i < nr; i++) 508 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size); 509 if (crc == bc_crc32e) 510 goto out; 511 512 ocfs2_blockcheck_inc_failure(stats); 513 mlog(ML_ERROR, 514 "CRC32 failed: stored: %u, computed %u. Applying ECC.\n", 515 (unsigned int)bc_crc32e, (unsigned int)crc); 516 517 /* Ok, try ECC fixups */ 518 for (i = 0, ecc = 0; i < nr; i++) { 519 /* 520 * The number of bits in a buffer is obviously b_size*8. 521 * The offset of this buffer is b_size*i, so the bit offset 522 * of this buffer is b_size*8*i. 523 */ 524 ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data, 525 bhs[i]->b_size * 8, 526 bhs[i]->b_size * 8 * i); 527 } 528 fix = ecc ^ bc_ecc; 529 for (i = 0; i < nr; i++) { 530 /* 531 * Try the fix against each buffer. It will only affect 532 * one of them. 533 */ 534 ocfs2_hamming_fix(bhs[i]->b_data, bhs[i]->b_size * 8, 535 bhs[i]->b_size * 8 * i, fix); 536 } 537 538 /* And check the crc32 again */ 539 for (i = 0, crc = ~0; i < nr; i++) 540 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size); 541 if (crc == bc_crc32e) { 542 ocfs2_blockcheck_inc_recover(stats); 543 goto out; 544 } 545 546 mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n", 547 (unsigned int)bc_crc32e, (unsigned int)crc); 548 549 rc = -EIO; 550 551out: 552 bc->bc_crc32e = cpu_to_le32(bc_crc32e); 553 bc->bc_ecc = cpu_to_le16(bc_ecc); 554 555 return rc; 556} 557 558/* 559 * These are the main API. They check the superblock flag before 560 * calling the underlying operations. 561 * 562 * They expect the buffer(s) to be in disk format. 563 */ 564void ocfs2_compute_meta_ecc(struct super_block *sb, void *data, 565 struct ocfs2_block_check *bc) 566{ 567 if (ocfs2_meta_ecc(OCFS2_SB(sb))) 568 ocfs2_block_check_compute(data, sb->s_blocksize, bc); 569} 570 571int ocfs2_validate_meta_ecc(struct super_block *sb, void *data, 572 struct ocfs2_block_check *bc) 573{ 574 int rc = 0; 575 struct ocfs2_super *osb = OCFS2_SB(sb); 576 577 if (ocfs2_meta_ecc(osb)) 578 rc = ocfs2_block_check_validate(data, sb->s_blocksize, bc, 579 &osb->osb_ecc_stats); 580 581 return rc; 582} 583 584void ocfs2_compute_meta_ecc_bhs(struct super_block *sb, 585 struct buffer_head **bhs, int nr, 586 struct ocfs2_block_check *bc) 587{ 588 if (ocfs2_meta_ecc(OCFS2_SB(sb))) 589 ocfs2_block_check_compute_bhs(bhs, nr, bc); 590} 591 592int ocfs2_validate_meta_ecc_bhs(struct super_block *sb, 593 struct buffer_head **bhs, int nr, 594 struct ocfs2_block_check *bc) 595{ 596 int rc = 0; 597 struct ocfs2_super *osb = OCFS2_SB(sb); 598 599 if (ocfs2_meta_ecc(osb)) 600 rc = ocfs2_block_check_validate_bhs(bhs, nr, bc, 601 &osb->osb_ecc_stats); 602 603 return rc; 604} 605 606