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 */ 64 static 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 */ 107 u32 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 } 153 154 u32 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 */ 166 void 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 } 221 222 void 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 234 235 static int blockcheck_u64_get(void *data, u64 *val) 236 { 237 *val = *(u64 *)data; 238 return 0; 239 } 240 DEFINE_SIMPLE_ATTRIBUTE(blockcheck_fops, blockcheck_u64_get, NULL, "%llu\n"); 241 242 static 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 } 249 250 static 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 } 263 264 static 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; 293 294 out: 295 if (rc) 296 ocfs2_blockcheck_debug_remove(stats); 297 return rc; 298 } 299 #else 300 static inline int ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats, 301 struct dentry *parent) 302 { 303 return 0; 304 } 305 306 static 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 */ 312 int ocfs2_blockcheck_stats_debugfs_install(struct ocfs2_blockcheck_stats *stats, 313 struct dentry *parent) 314 { 315 return ocfs2_blockcheck_debug_install(stats, parent); 316 } 317 318 void ocfs2_blockcheck_stats_debugfs_remove(struct ocfs2_blockcheck_stats *stats) 319 { 320 ocfs2_blockcheck_debug_remove(stats); 321 } 322 323 static 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 } 338 339 static 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 } 354 355 static 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 */ 391 void 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 */ 420 int 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 u32 bc_crc32e; 426 u16 bc_ecc; 427 u32 crc, ecc; 428 429 ocfs2_blockcheck_inc_check(stats); 430 431 bc_crc32e = le32_to_cpu(bc->bc_crc32e); 432 bc_ecc = le16_to_cpu(bc->bc_ecc); 433 434 memset(bc, 0, sizeof(struct ocfs2_block_check)); 435 436 /* Fast path - if the crc32 validates, we're good to go */ 437 crc = crc32_le(~0, data, blocksize); 438 if (crc == bc_crc32e) 439 goto out; 440 441 ocfs2_blockcheck_inc_failure(stats); 442 mlog(ML_ERROR, 443 "CRC32 failed: stored: 0x%x, computed 0x%x. Applying ECC.\n", 444 (unsigned int)bc_crc32e, (unsigned int)crc); 445 446 /* Ok, try ECC fixups */ 447 ecc = ocfs2_hamming_encode_block(data, blocksize); 448 ocfs2_hamming_fix_block(data, blocksize, ecc ^ bc_ecc); 449 450 /* And check the crc32 again */ 451 crc = crc32_le(~0, data, blocksize); 452 if (crc == bc_crc32e) { 453 ocfs2_blockcheck_inc_recover(stats); 454 goto out; 455 } 456 457 mlog(ML_ERROR, "Fixed CRC32 failed: stored: 0x%x, computed 0x%x\n", 458 (unsigned int)bc_crc32e, (unsigned int)crc); 459 460 rc = -EIO; 461 462 out: 463 bc->bc_crc32e = cpu_to_le32(bc_crc32e); 464 bc->bc_ecc = cpu_to_le16(bc_ecc); 465 466 return rc; 467 } 468 469 /* 470 * This function generates check information for a list of buffer_heads. 471 * bhs is the blocks to be checked. bc is a pointer to the 472 * ocfs2_block_check structure describing the crc32 and the ecc. 473 * 474 * bc should be a pointer inside data, as the function will 475 * take care of zeroing it before calculating the check information. If 476 * bc does not point inside data, the caller must make sure any inline 477 * ocfs2_block_check structures are zeroed. 478 * 479 * The data buffer must be in on-disk endian (little endian for ocfs2). 480 * bc will be filled with little-endian values and will be ready to go to 481 * disk. 482 */ 483 void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr, 484 struct ocfs2_block_check *bc) 485 { 486 int i; 487 u32 crc, ecc; 488 489 BUG_ON(nr < 0); 490 491 if (!nr) 492 return; 493 494 memset(bc, 0, sizeof(struct ocfs2_block_check)); 495 496 for (i = 0, crc = ~0, ecc = 0; i < nr; i++) { 497 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size); 498 /* 499 * The number of bits in a buffer is obviously b_size*8. 500 * The offset of this buffer is b_size*i, so the bit offset 501 * of this buffer is b_size*8*i. 502 */ 503 ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data, 504 bhs[i]->b_size * 8, 505 bhs[i]->b_size * 8 * i); 506 } 507 508 /* 509 * No ecc'd ocfs2 structure is larger than 4K, so ecc will be no 510 * larger than 16 bits. 511 */ 512 BUG_ON(ecc > USHRT_MAX); 513 514 bc->bc_crc32e = cpu_to_le32(crc); 515 bc->bc_ecc = cpu_to_le16((u16)ecc); 516 } 517 518 /* 519 * This function validates existing check information on a list of 520 * buffer_heads. Like _compute_bhs, the function will take care of 521 * zeroing bc before calculating check codes. If bc is not a pointer 522 * inside data, the caller must have zeroed any inline 523 * ocfs2_block_check structures. 524 * 525 * Again, the data passed in should be the on-disk endian. 526 */ 527 int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr, 528 struct ocfs2_block_check *bc, 529 struct ocfs2_blockcheck_stats *stats) 530 { 531 int i, rc = 0; 532 u32 bc_crc32e; 533 u16 bc_ecc; 534 u32 crc, ecc, fix; 535 536 BUG_ON(nr < 0); 537 538 if (!nr) 539 return 0; 540 541 ocfs2_blockcheck_inc_check(stats); 542 543 bc_crc32e = le32_to_cpu(bc->bc_crc32e); 544 bc_ecc = le16_to_cpu(bc->bc_ecc); 545 546 memset(bc, 0, sizeof(struct ocfs2_block_check)); 547 548 /* Fast path - if the crc32 validates, we're good to go */ 549 for (i = 0, crc = ~0; i < nr; i++) 550 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size); 551 if (crc == bc_crc32e) 552 goto out; 553 554 ocfs2_blockcheck_inc_failure(stats); 555 mlog(ML_ERROR, 556 "CRC32 failed: stored: %u, computed %u. Applying ECC.\n", 557 (unsigned int)bc_crc32e, (unsigned int)crc); 558 559 /* Ok, try ECC fixups */ 560 for (i = 0, ecc = 0; i < nr; i++) { 561 /* 562 * The number of bits in a buffer is obviously b_size*8. 563 * The offset of this buffer is b_size*i, so the bit offset 564 * of this buffer is b_size*8*i. 565 */ 566 ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data, 567 bhs[i]->b_size * 8, 568 bhs[i]->b_size * 8 * i); 569 } 570 fix = ecc ^ bc_ecc; 571 for (i = 0; i < nr; i++) { 572 /* 573 * Try the fix against each buffer. It will only affect 574 * one of them. 575 */ 576 ocfs2_hamming_fix(bhs[i]->b_data, bhs[i]->b_size * 8, 577 bhs[i]->b_size * 8 * i, fix); 578 } 579 580 /* And check the crc32 again */ 581 for (i = 0, crc = ~0; i < nr; i++) 582 crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size); 583 if (crc == bc_crc32e) { 584 ocfs2_blockcheck_inc_recover(stats); 585 goto out; 586 } 587 588 mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n", 589 (unsigned int)bc_crc32e, (unsigned int)crc); 590 591 rc = -EIO; 592 593 out: 594 bc->bc_crc32e = cpu_to_le32(bc_crc32e); 595 bc->bc_ecc = cpu_to_le16(bc_ecc); 596 597 return rc; 598 } 599 600 /* 601 * These are the main API. They check the superblock flag before 602 * calling the underlying operations. 603 * 604 * They expect the buffer(s) to be in disk format. 605 */ 606 void ocfs2_compute_meta_ecc(struct super_block *sb, void *data, 607 struct ocfs2_block_check *bc) 608 { 609 if (ocfs2_meta_ecc(OCFS2_SB(sb))) 610 ocfs2_block_check_compute(data, sb->s_blocksize, bc); 611 } 612 613 int ocfs2_validate_meta_ecc(struct super_block *sb, void *data, 614 struct ocfs2_block_check *bc) 615 { 616 int rc = 0; 617 struct ocfs2_super *osb = OCFS2_SB(sb); 618 619 if (ocfs2_meta_ecc(osb)) 620 rc = ocfs2_block_check_validate(data, sb->s_blocksize, bc, 621 &osb->osb_ecc_stats); 622 623 return rc; 624 } 625 626 void ocfs2_compute_meta_ecc_bhs(struct super_block *sb, 627 struct buffer_head **bhs, int nr, 628 struct ocfs2_block_check *bc) 629 { 630 if (ocfs2_meta_ecc(OCFS2_SB(sb))) 631 ocfs2_block_check_compute_bhs(bhs, nr, bc); 632 } 633 634 int ocfs2_validate_meta_ecc_bhs(struct super_block *sb, 635 struct buffer_head **bhs, int nr, 636 struct ocfs2_block_check *bc) 637 { 638 int rc = 0; 639 struct ocfs2_super *osb = OCFS2_SB(sb); 640 641 if (ocfs2_meta_ecc(osb)) 642 rc = ocfs2_block_check_validate_bhs(bhs, nr, bc, 643 &osb->osb_ecc_stats); 644 645 return rc; 646 } 647 648