1// SPDX-License-Identifier: GPL-2.0-only 2/* -*- mode: c; c-basic-offset: 8; -*- 3 * vim: noexpandtab sw=8 ts=8 sts=0: 4 * 5 * blockcheck.c 6 * 7 * Checksum and ECC codes for the OCFS2 userspace library. 8 * 9 * Copyright (C) 2006, 2008 Oracle. All rights reserved. 10 */ 11 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> 19#include <linux/fs.h> 20#include <asm/byteorder.h> 21 22#include <cluster/masklog.h> 23 24#include "ocfs2.h" 25 26#include "blockcheck.h" 27 28 29/* 30 * We use the following conventions: 31 * 32 * d = # data bits 33 * p = # parity bits 34 * c = # total code bits (d + p) 35 */ 36 37 38/* 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. 43 * 44 * Recall that bit numbers in hamming code are 1-based. This function 45 * takes the 0-based data bit from the caller. 46 * 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 50 * in the code buffer. 51 * 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. 55 */ 56static unsigned int calc_code_bit(unsigned int i, unsigned int *p_cache) 57{ 58 unsigned int b, p = 0; 59 60 /* 61 * Data bits are 0-based, but we're talking code bits, which 62 * are 1-based. 63 */ 64 b = i + 1; 65 66 /* Use the cache if it is there */ 67 if (p_cache) 68 p = *p_cache; 69 b += p; 70 71 /* 72 * For every power of two below our bit number, bump our bit. 73 * 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? 76 * 77 * p is set above. 78 */ 79 for (; (1 << p) < (b + 1); p++) 80 b++; 81 82 if (p_cache) 83 *p_cache = p; 84 85 return b; 86} 87 88/* 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: 93 * 94 * parity = ocfs2_hamming_encode(0, buf1, 512 * 8, 0); 95 * parity = ocfs2_hamming_encode(parity, buf2, 512 * 8, 512 * 8); 96 * 97 * If you just have one buffer, use ocfs2_hamming_encode_block(). 98 */ 99u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr) 100{ 101 unsigned int i, b, p = 0; 102 103 BUG_ON(!d); 104 105 /* 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 108 * for the algorithm. 109 * 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 112 * found bit. 113 */ 114 for (i = 0; (i = ocfs2_find_next_bit(data, d, i)) < d; i++) 115 { 116 /* 117 * i is the offset in this hunk, nr + i is the total bit 118 * offset. 119 */ 120 b = calc_code_bit(nr + i, &p); 121 122 /* 123 * Data bits in the resultant code are checked by 124 * parity bits that are part of the bit number 125 * representation. Huh? 126 * 127 * <wikipedia href="https://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. 133 * </wikipedia> 134 * 135 * Note that 'k' is the _code_ bit number. 'b' in 136 * our loop. 137 */ 138 parity ^= b; 139 } 140 141 /* While the data buffer was treated as little endian, the 142 * return value is in host endian. */ 143 return parity; 144} 145 146u32 ocfs2_hamming_encode_block(void *data, unsigned int blocksize) 147{ 148 return ocfs2_hamming_encode(0, data, blocksize * 8, 0); 149} 150 151/* 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. 155 * 156 * If you only have one hunk, use ocfs2_hamming_fix_block(). 157 */ 158void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr, 159 unsigned int fix) 160{ 161 unsigned int i, b; 162 163 BUG_ON(!d); 164 165 /* 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. 168 */ 169 if (hweight32(fix) == 1) 170 return; 171 172 /* 173 * nr + d is the bit right past the data hunk we're looking at. 174 * If fix after that, nothing to do 175 */ 176 if (fix >= calc_code_bit(nr + d, NULL)) 177 return; 178 179 /* 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'. 183 */ 184 b = calc_code_bit(nr, NULL); 185 /* If the fix is before this hunk, nothing to do */ 186 if (fix < b) 187 return; 188 189 for (i = 0; i < d; i++, b++) 190 { 191 /* Skip past parity bits */ 192 while (hweight32(b) == 1) 193 b++; 194 195 /* 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. 199 * 200 * Thus, when b == fix, bit i in the current hunk needs 201 * fixing. 202 */ 203 if (b == fix) 204 { 205 if (ocfs2_test_bit(i, data)) 206 ocfs2_clear_bit(i, data); 207 else 208 ocfs2_set_bit(i, data); 209 break; 210 } 211 } 212} 213 214void ocfs2_hamming_fix_block(void *data, unsigned int blocksize, 215 unsigned int fix) 216{ 217 ocfs2_hamming_fix(data, blocksize * 8, 0, fix); 218} 219 220 221/* 222 * Debugfs handling. 223 */ 224 225#ifdef CONFIG_DEBUG_FS 226 227static int blockcheck_u64_get(void *data, u64 *val) 228{ 229 *val = *(u64 *)data; 230 return 0; 231} 232DEFINE_SIMPLE_ATTRIBUTE(blockcheck_fops, blockcheck_u64_get, NULL, "%llu\n"); 233 234static void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats) 235{ 236 if (stats) { 237 debugfs_remove_recursive(stats->b_debug_dir); 238 stats->b_debug_dir = NULL; 239 } 240} 241 242static void ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats, 243 struct dentry *parent) 244{ 245 struct dentry *dir; 246 247 dir = debugfs_create_dir("blockcheck", parent); 248 stats->b_debug_dir = dir; 249 250 debugfs_create_file("blocks_checked", S_IFREG | S_IRUSR, dir, 251 &stats->b_check_count, &blockcheck_fops); 252 253 debugfs_create_file("checksums_failed", S_IFREG | S_IRUSR, dir, 254 &stats->b_failure_count, &blockcheck_fops); 255 256 debugfs_create_file("ecc_recoveries", S_IFREG | S_IRUSR, dir, 257 &stats->b_recover_count, &blockcheck_fops); 258 259} 260#else 261static inline void ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats, 262 struct dentry *parent) 263{ 264} 265 266static inline void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats) 267{ 268} 269#endif /* CONFIG_DEBUG_FS */ 270 271/* Always-called wrappers for starting and stopping the debugfs files */ 272void ocfs2_blockcheck_stats_debugfs_install(struct ocfs2_blockcheck_stats *stats, 273 struct dentry *parent) 274{ 275 ocfs2_blockcheck_debug_install(stats, parent); 276} 277 278void ocfs2_blockcheck_stats_debugfs_remove(struct ocfs2_blockcheck_stats *stats) 279{ 280 ocfs2_blockcheck_debug_remove(stats); 281} 282 283static void ocfs2_blockcheck_inc_check(struct ocfs2_blockcheck_stats *stats) 284{ 285 u64 new_count; 286 287 if (!stats) 288 return; 289 290 spin_lock(&stats->b_lock); 291 stats->b_check_count++; 292 new_count = stats->b_check_count; 293 spin_unlock(&stats->b_lock); 294 295 if (!new_count) 296 mlog(ML_NOTICE, "Block check count has wrapped\n"); 297} 298 299static void ocfs2_blockcheck_inc_failure(struct ocfs2_blockcheck_stats *stats) 300{ 301 u64 new_count; 302 303 if (!stats) 304 return; 305 306 spin_lock(&stats->b_lock); 307 stats->b_failure_count++; 308 new_count = stats->b_failure_count; 309 spin_unlock(&stats->b_lock); 310 311 if (!new_count) 312 mlog(ML_NOTICE, "Checksum failure count has wrapped\n"); 313} 314 315static void ocfs2_blockcheck_inc_recover(struct ocfs2_blockcheck_stats *stats) 316{ 317 u64 new_count; 318 319 if (!stats) 320 return; 321 322 spin_lock(&stats->b_lock); 323 stats->b_recover_count++; 324 new_count = stats->b_recover_count; 325 spin_unlock(&stats->b_lock); 326 327 if (!new_count) 328 mlog(ML_NOTICE, "ECC recovery count has wrapped\n"); 329} 330 331 332 333/* 334 * These are the low-level APIs for using the ocfs2_block_check structure. 335 */ 336 337/* 338 * This function generates check information for a block. 339 * data is the block to be checked. bc is a pointer to the 340 * ocfs2_block_check structure describing the crc32 and the ecc. 341 * 342 * bc should be a pointer inside data, as the function will 343 * take care of zeroing it before calculating the check information. If 344 * bc does not point inside data, the caller must make sure any inline 345 * ocfs2_block_check structures are zeroed. 346 * 347 * The data buffer must be in on-disk endian (little endian for ocfs2). 348 * bc will be filled with little-endian values and will be ready to go to 349 * disk. 350 */ 351void ocfs2_block_check_compute(void *data, size_t blocksize, 352 struct ocfs2_block_check *bc) 353{ 354 u32 crc; 355 u32 ecc; 356 357 memset(bc, 0, sizeof(struct ocfs2_block_check)); 358 359 crc = crc32_le(~0, data, blocksize); 360 ecc = ocfs2_hamming_encode_block(data, blocksize); 361 362 /* 363 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no 364 * larger than 16 bits. 365 */ 366 BUG_ON(ecc > USHRT_MAX); 367 368 bc->bc_crc32e = cpu_to_le32(crc); 369 bc->bc_ecc = cpu_to_le16((u16)ecc); 370} 371 372/* 373 * This function validates existing check information. Like _compute, 374 * the function will take care of zeroing bc before calculating check codes. 375 * If bc is not a pointer inside data, the caller must have zeroed any 376 * inline ocfs2_block_check structures. 377 * 378 * Again, the data passed in should be the on-disk endian. 379 */ 380int ocfs2_block_check_validate(void *data, size_t blocksize, 381 struct ocfs2_block_check *bc, 382 struct ocfs2_blockcheck_stats *stats) 383{ 384 int rc = 0; 385 u32 bc_crc32e; 386 u16 bc_ecc; 387 u32 crc, ecc; 388 389 ocfs2_blockcheck_inc_check(stats); 390 391 bc_crc32e = le32_to_cpu(bc->bc_crc32e); 392 bc_ecc = le16_to_cpu(bc->bc_ecc); 393 394 memset(bc, 0, sizeof(struct ocfs2_block_check)); 395 396 /* Fast path - if the crc32 validates, we're good to go */ 397 crc = crc32_le(~0, data, blocksize); 398 if (crc == bc_crc32e) 399 goto out; 400 401 ocfs2_blockcheck_inc_failure(stats); 402 mlog(ML_ERROR, 403 "CRC32 failed: stored: 0x%x, computed 0x%x. Applying ECC.\n", 404 (unsigned int)bc_crc32e, (unsigned int)crc); 405 406 /* Ok, try ECC fixups */ 407 ecc = ocfs2_hamming_encode_block(data, blocksize); 408 ocfs2_hamming_fix_block(data, blocksize, ecc ^ bc_ecc); 409 410 /* And check the crc32 again */ 411 crc = crc32_le(~0, data, blocksize); 412 if (crc == bc_crc32e) { 413 ocfs2_blockcheck_inc_recover(stats); 414 goto out; 415 } 416 417 mlog(ML_ERROR, "Fixed CRC32 failed: stored: 0x%x, computed 0x%x\n", 418 (unsigned int)bc_crc32e, (unsigned int)crc); 419 420 rc = -EIO; 421 422out: 423 bc->bc_crc32e = cpu_to_le32(bc_crc32e); 424 bc->bc_ecc = cpu_to_le16(bc_ecc); 425 426 return rc; 427} 428 429/* 430 * This function generates check information for a list of buffer_heads. 431 * bhs is the blocks to be checked. bc is a pointer to the 432 * ocfs2_block_check structure describing the crc32 and the ecc. 433 * 434 * bc should be a pointer inside data, as the function will 435 * take care of zeroing it before calculating the check information. If 436 * bc does not point inside data, the caller must make sure any inline 437 * ocfs2_block_check structures are zeroed. 438 * 439 * The data buffer must be in on-disk endian (little endian for ocfs2). 440 * bc will be filled with little-endian values and will be ready to go to 441 * disk. 442 */ 443void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr, 444 struct ocfs2_block_check *bc) 445{ 446 int i; 447 u32 crc, ecc; 448 449 BUG_ON(nr < 0); 450 451 if (!nr) 452 return; 453 454 memset(bc, 0, sizeof(struct ocfs2_block_check)); 455 456 for (i = 0, crc = ~0, ecc = 0; i < nr; i++) { 457 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size); 458 /* 459 * The number of bits in a buffer is obviously b_size*8. 460 * The offset of this buffer is b_size*i, so the bit offset 461 * of this buffer is b_size*8*i. 462 */ 463 ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data, 464 bhs[i]->b_size * 8, 465 bhs[i]->b_size * 8 * i); 466 } 467 468 /* 469 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no 470 * larger than 16 bits. 471 */ 472 BUG_ON(ecc > USHRT_MAX); 473 474 bc->bc_crc32e = cpu_to_le32(crc); 475 bc->bc_ecc = cpu_to_le16((u16)ecc); 476} 477 478/* 479 * This function validates existing check information on a list of 480 * buffer_heads. Like _compute_bhs, the function will take care of 481 * zeroing bc before calculating check codes. If bc is not a pointer 482 * inside data, the caller must have zeroed any inline 483 * ocfs2_block_check structures. 484 * 485 * Again, the data passed in should be the on-disk endian. 486 */ 487int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr, 488 struct ocfs2_block_check *bc, 489 struct ocfs2_blockcheck_stats *stats) 490{ 491 int i, rc = 0; 492 u32 bc_crc32e; 493 u16 bc_ecc; 494 u32 crc, ecc, fix; 495 496 BUG_ON(nr < 0); 497 498 if (!nr) 499 return 0; 500 501 ocfs2_blockcheck_inc_check(stats); 502 503 bc_crc32e = le32_to_cpu(bc->bc_crc32e); 504 bc_ecc = le16_to_cpu(bc->bc_ecc); 505 506 memset(bc, 0, sizeof(struct ocfs2_block_check)); 507 508 /* Fast path - if the crc32 validates, we're good to go */ 509 for (i = 0, crc = ~0; i < nr; i++) 510 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size); 511 if (crc == bc_crc32e) 512 goto out; 513 514 ocfs2_blockcheck_inc_failure(stats); 515 mlog(ML_ERROR, 516 "CRC32 failed: stored: %u, computed %u. Applying ECC.\n", 517 (unsigned int)bc_crc32e, (unsigned int)crc); 518 519 /* Ok, try ECC fixups */ 520 for (i = 0, ecc = 0; i < nr; i++) { 521 /* 522 * The number of bits in a buffer is obviously b_size*8. 523 * The offset of this buffer is b_size*i, so the bit offset 524 * of this buffer is b_size*8*i. 525 */ 526 ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data, 527 bhs[i]->b_size * 8, 528 bhs[i]->b_size * 8 * i); 529 } 530 fix = ecc ^ bc_ecc; 531 for (i = 0; i < nr; i++) { 532 /* 533 * Try the fix against each buffer. It will only affect 534 * one of them. 535 */ 536 ocfs2_hamming_fix(bhs[i]->b_data, bhs[i]->b_size * 8, 537 bhs[i]->b_size * 8 * i, fix); 538 } 539 540 /* And check the crc32 again */ 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) { 544 ocfs2_blockcheck_inc_recover(stats); 545 goto out; 546 } 547 548 mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n", 549 (unsigned int)bc_crc32e, (unsigned int)crc); 550 551 rc = -EIO; 552 553out: 554 bc->bc_crc32e = cpu_to_le32(bc_crc32e); 555 bc->bc_ecc = cpu_to_le16(bc_ecc); 556 557 return rc; 558} 559 560/* 561 * These are the main API. They check the superblock flag before 562 * calling the underlying operations. 563 * 564 * They expect the buffer(s) to be in disk format. 565 */ 566void ocfs2_compute_meta_ecc(struct super_block *sb, void *data, 567 struct ocfs2_block_check *bc) 568{ 569 if (ocfs2_meta_ecc(OCFS2_SB(sb))) 570 ocfs2_block_check_compute(data, sb->s_blocksize, bc); 571} 572 573int ocfs2_validate_meta_ecc(struct super_block *sb, void *data, 574 struct ocfs2_block_check *bc) 575{ 576 int rc = 0; 577 struct ocfs2_super *osb = OCFS2_SB(sb); 578 579 if (ocfs2_meta_ecc(osb)) 580 rc = ocfs2_block_check_validate(data, sb->s_blocksize, bc, 581 &osb->osb_ecc_stats); 582 583 return rc; 584} 585 586void ocfs2_compute_meta_ecc_bhs(struct super_block *sb, 587 struct buffer_head **bhs, int nr, 588 struct ocfs2_block_check *bc) 589{ 590 if (ocfs2_meta_ecc(OCFS2_SB(sb))) 591 ocfs2_block_check_compute_bhs(bhs, nr, bc); 592} 593 594int ocfs2_validate_meta_ecc_bhs(struct super_block *sb, 595 struct buffer_head **bhs, int nr, 596 struct ocfs2_block_check *bc) 597{ 598 int rc = 0; 599 struct ocfs2_super *osb = OCFS2_SB(sb); 600 601 if (ocfs2_meta_ecc(osb)) 602 rc = ocfs2_block_check_validate_bhs(bhs, nr, bc, 603 &osb->osb_ecc_stats); 604 605 return rc; 606} 607 608