drivers/md/dm-verity-fec.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2015 Google, Inc.
   4  *
   5  * Author: Sami Tolvanen <samitolvanen@google.com>
   6  */
   7
   8 #include "dm-verity-fec.h"
   9 #include <linux/math64.h>
  10
  11 #define DM_MSG_PREFIX   "verity-fec"
  12
  13 /*
  14  * If error correction has been configured, returns true.
  15  */
  16 bool verity_fec_is_enabled(struct dm_verity *v)
  17 {
  18         return v->fec && v->fec->dev;
  19 }
  20
  21 /*
  22  * Return a pointer to dm_verity_fec_io after dm_verity_io and its variable
  23  * length fields.
  24  */
  25 static inline struct dm_verity_fec_io *fec_io(struct dm_verity_io *io)
  26 {
  27         return (struct dm_verity_fec_io *)
  28                 ((char *)io + io->v->ti->per_io_data_size - sizeof(struct dm_verity_fec_io));
  29 }
  30
  31 /*
  32  * Return an interleaved offset for a byte in RS block.
  33  */
  34 static inline u64 fec_interleave(struct dm_verity *v, u64 offset)
  35 {
  36         u32 mod;
  37
  38         mod = do_div(offset, v->fec->rsn);
  39         return offset + mod * (v->fec->rounds << v->data_dev_block_bits);
  40 }
  41
  42 /*
  43  * Decode an RS block using Reed-Solomon.
  44  */
  45 static int fec_decode_rs8(struct dm_verity *v, struct dm_verity_fec_io *fio,
  46                           u8 *data, u8 *fec, int neras)
  47 {
  48         int i;
  49         uint16_t par[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN];
  50
  51         for (i = 0; i < v->fec->roots; i++)
  52                 par[i] = fec[i];
  53
  54         return decode_rs8(fio->rs, data, par, v->fec->rsn, NULL, neras,
  55                           fio->erasures, 0, NULL);
  56 }
  57
  58 /*
  59  * Read error-correcting codes for the requested RS block. Returns a pointer
  60  * to the data block. Caller is responsible for releasing buf.
  61  */
  62 static u8 *fec_read_parity(struct dm_verity *v, u64 rsb, int index,
  63                            unsigned int *offset, struct dm_buffer **buf,
  64                            unsigned short ioprio)
  65 {
  66         u64 position, block, rem;
  67         u8 *res;
  68
  69         position = (index + rsb) * v->fec->roots;
  70         block = div64_u64_rem(position, v->fec->io_size, &rem);
  71         *offset = (unsigned int)rem;
  72
  73         res = dm_bufio_read_with_ioprio(v->fec->bufio, block, buf, ioprio);
  74         if (IS_ERR(res)) {
  75                 DMERR("%s: FEC %llu: parity read failed (block %llu): %ld",
  76                       v->data_dev->name, (unsigned long long)rsb,
  77                       (unsigned long long)block, PTR_ERR(res));
  78                 *buf = NULL;
  79         }
  80
  81         return res;
  82 }
  83
  84 /* Loop over each preallocated buffer slot. */
  85 #define fec_for_each_prealloc_buffer(__i) \
  86         for (__i = 0; __i < DM_VERITY_FEC_BUF_PREALLOC; __i++)
  87
  88 /* Loop over each extra buffer slot. */
  89 #define fec_for_each_extra_buffer(io, __i) \
  90         for (__i = DM_VERITY_FEC_BUF_PREALLOC; __i < DM_VERITY_FEC_BUF_MAX; __i++)
  91
  92 /* Loop over each allocated buffer. */
  93 #define fec_for_each_buffer(io, __i) \
  94         for (__i = 0; __i < (io)->nbufs; __i++)
  95
  96 /* Loop over each RS block in each allocated buffer. */
  97 #define fec_for_each_buffer_rs_block(io, __i, __j) \
  98         fec_for_each_buffer(io, __i) \
  99                 for (__j = 0; __j < 1 << DM_VERITY_FEC_BUF_RS_BITS; __j++)
 100
 101 /*
 102  * Return a pointer to the current RS block when called inside
 103  * fec_for_each_buffer_rs_block.
 104  */
 105 static inline u8 *fec_buffer_rs_block(struct dm_verity *v,
 106                                       struct dm_verity_fec_io *fio,
 107                                       unsigned int i, unsigned int j)
 108 {
 109         return &fio->bufs[i][j * v->fec->rsn];
 110 }
 111
 112 /*
 113  * Return an index to the current RS block when called inside
 114  * fec_for_each_buffer_rs_block.
 115  */
 116 static inline unsigned int fec_buffer_rs_index(unsigned int i, unsigned int j)
 117 {
 118         return (i << DM_VERITY_FEC_BUF_RS_BITS) + j;
 119 }
 120
 121 /*
 122  * Decode all RS blocks from buffers and copy corrected bytes into fio->output
 123  * starting from block_offset.
 124  */
 125 static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
 126                            struct dm_verity_fec_io *fio, u64 rsb, int byte_index,
 127                            unsigned int block_offset, int neras)
 128 {
 129         int r, corrected = 0, res;
 130         struct dm_buffer *buf;
 131         unsigned int n, i, offset;
 132         u8 *par, *block;
 133         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 134
 135         par = fec_read_parity(v, rsb, block_offset, &offset, &buf, bio_prio(bio));
 136         if (IS_ERR(par))
 137                 return PTR_ERR(par);
 138
 139         /*
 140          * Decode the RS blocks we have in bufs. Each RS block results in
 141          * one corrected target byte and consumes fec->roots parity bytes.
 142          */
 143         fec_for_each_buffer_rs_block(fio, n, i) {
 144                 block = fec_buffer_rs_block(v, fio, n, i);
 145                 res = fec_decode_rs8(v, fio, block, &par[offset], neras);
 146                 if (res < 0) {
 147                         r = res;
 148                         goto error;
 149                 }
 150
 151                 corrected += res;
 152                 fio->output[block_offset] = block[byte_index];
 153
 154                 block_offset++;
 155                 if (block_offset >= 1 << v->data_dev_block_bits)
 156                         goto done;
 157
 158                 /* read the next block when we run out of parity bytes */
 159                 offset += v->fec->roots;
 160                 if (offset >= v->fec->io_size) {
 161                         dm_bufio_release(buf);
 162
 163                         par = fec_read_parity(v, rsb, block_offset, &offset, &buf, bio_prio(bio));
 164                         if (IS_ERR(par))
 165                                 return PTR_ERR(par);
 166                 }
 167         }
 168 done:
 169         r = corrected;
 170 error:
 171         dm_bufio_release(buf);
 172
 173         if (r < 0 && neras)
 174                 DMERR_LIMIT("%s: FEC %llu: failed to correct: %d",
 175                             v->data_dev->name, (unsigned long long)rsb, r);
 176         else if (r > 0)
 177                 DMWARN_LIMIT("%s: FEC %llu: corrected %d errors",
 178                              v->data_dev->name, (unsigned long long)rsb, r);
 179
 180         return r;
 181 }
 182
 183 /*
 184  * Locate data block erasures using verity hashes.
 185  */
 186 static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io,
 187                           u8 *want_digest, u8 *data)
 188 {
 189         if (unlikely(verity_hash(v, io, data, 1 << v->data_dev_block_bits,
 190                                  verity_io_real_digest(v, io), true)))
 191                 return 0;
 192
 193         return memcmp(verity_io_real_digest(v, io), want_digest,
 194                       v->digest_size) != 0;
 195 }
 196
 197 /*
 198  * Read data blocks that are part of the RS block and deinterleave as much as
 199  * fits into buffers. Check for erasure locations if @neras is non-NULL.
 200  */
 201 static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
 202                          u64 rsb, u64 target, unsigned int block_offset,
 203                          int *neras)
 204 {
 205         bool is_zero;
 206         int i, j, target_index = -1;
 207         struct dm_buffer *buf;
 208         struct dm_bufio_client *bufio;
 209         struct dm_verity_fec_io *fio = fec_io(io);
 210         u64 block, ileaved;
 211         u8 *bbuf, *rs_block;
 212         u8 want_digest[HASH_MAX_DIGESTSIZE];
 213         unsigned int n, k;
 214         struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
 215
 216         if (neras)
 217                 *neras = 0;
 218
 219         if (WARN_ON(v->digest_size > sizeof(want_digest)))
 220                 return -EINVAL;
 221
 222         /*
 223          * read each of the rsn data blocks that are part of the RS block, and
 224          * interleave contents to available bufs
 225          */
 226         for (i = 0; i < v->fec->rsn; i++) {
 227                 ileaved = fec_interleave(v, rsb * v->fec->rsn + i);
 228
 229                 /*
 230                  * target is the data block we want to correct, target_index is
 231                  * the index of this block within the rsn RS blocks
 232                  */
 233                 if (ileaved == target)
 234                         target_index = i;
 235
 236                 block = ileaved >> v->data_dev_block_bits;
 237                 bufio = v->fec->data_bufio;
 238
 239                 if (block >= v->data_blocks) {
 240                         block -= v->data_blocks;
 241
 242                         /*
 243                          * blocks outside the area were assumed to contain
 244                          * zeros when encoding data was generated
 245                          */
 246                         if (unlikely(block >= v->fec->hash_blocks))
 247                                 continue;
 248
 249                         block += v->hash_start;
 250                         bufio = v->bufio;
 251                 }
 252
 253                 bbuf = dm_bufio_read_with_ioprio(bufio, block, &buf, bio_prio(bio));
 254                 if (IS_ERR(bbuf)) {
 255                         DMWARN_LIMIT("%s: FEC %llu: read failed (%llu): %ld",
 256                                      v->data_dev->name,
 257                                      (unsigned long long)rsb,
 258                                      (unsigned long long)block, PTR_ERR(bbuf));
 259
 260                         /* assume the block is corrupted */
 261                         if (neras && *neras <= v->fec->roots)
 262                                 fio->erasures[(*neras)++] = i;
 263
 264                         continue;
 265                 }
 266
 267                 /* locate erasures if the block is on the data device */
 268                 if (bufio == v->fec->data_bufio &&
 269                     verity_hash_for_block(v, io, block, want_digest,
 270                                           &is_zero) == 0) {
 271                         /* skip known zero blocks entirely */
 272                         if (is_zero)
 273                                 goto done;
 274
 275                         /*
 276                          * skip if we have already found the theoretical
 277                          * maximum number (i.e. fec->roots) of erasures
 278                          */
 279                         if (neras && *neras <= v->fec->roots &&
 280                             fec_is_erasure(v, io, want_digest, bbuf))
 281                                 fio->erasures[(*neras)++] = i;
 282                 }
 283
 284                 /*
 285                  * deinterleave and copy the bytes that fit into bufs,
 286                  * starting from block_offset
 287                  */
 288                 fec_for_each_buffer_rs_block(fio, n, j) {
 289                         k = fec_buffer_rs_index(n, j) + block_offset;
 290
 291                         if (k >= 1 << v->data_dev_block_bits)
 292                                 goto done;
 293
 294                         rs_block = fec_buffer_rs_block(v, fio, n, j);
 295                         rs_block[i] = bbuf[k];
 296                 }
 297 done:
 298                 dm_bufio_release(buf);
 299         }
 300
 301         return target_index;
 302 }
 303
 304 /*
 305  * Allocate RS control structure and FEC buffers from preallocated mempools,
 306  * and attempt to allocate as many extra buffers as available.
 307  */
 308 static int fec_alloc_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
 309 {
 310         unsigned int n;
 311
 312         if (!fio->rs)
 313                 fio->rs = mempool_alloc(&v->fec->rs_pool, GFP_NOIO);
 314
 315         fec_for_each_prealloc_buffer(n) {
 316                 if (fio->bufs[n])
 317                         continue;
 318
 319                 fio->bufs[n] = mempool_alloc(&v->fec->prealloc_pool, GFP_NOWAIT);
 320                 if (unlikely(!fio->bufs[n])) {
 321                         DMERR("failed to allocate FEC buffer");
 322                         return -ENOMEM;
 323                 }
 324         }
 325
 326         /* try to allocate the maximum number of buffers */
 327         fec_for_each_extra_buffer(fio, n) {
 328                 if (fio->bufs[n])
 329                         continue;
 330
 331                 fio->bufs[n] = mempool_alloc(&v->fec->extra_pool, GFP_NOWAIT);
 332                 /* we can manage with even one buffer if necessary */
 333                 if (unlikely(!fio->bufs[n]))
 334                         break;
 335         }
 336         fio->nbufs = n;
 337
 338         if (!fio->output)
 339                 fio->output = mempool_alloc(&v->fec->output_pool, GFP_NOIO);
 340
 341         return 0;
 342 }
 343
 344 /*
 345  * Initialize buffers and clear erasures. fec_read_bufs() assumes buffers are
 346  * zeroed before deinterleaving.
 347  */
 348 static void fec_init_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
 349 {
 350         unsigned int n;
 351
 352         fec_for_each_buffer(fio, n)
 353                 memset(fio->bufs[n], 0, v->fec->rsn << DM_VERITY_FEC_BUF_RS_BITS);
 354
 355         memset(fio->erasures, 0, sizeof(fio->erasures));
 356 }
 357
 358 /*
 359  * Decode all RS blocks in a single data block and return the target block
 360  * (indicated by @offset) in fio->output. If @use_erasures is non-zero, uses
 361  * hashes to locate erasures.
 362  */
 363 static int fec_decode_rsb(struct dm_verity *v, struct dm_verity_io *io,
 364                           struct dm_verity_fec_io *fio, u64 rsb, u64 offset,
 365                           bool use_erasures)
 366 {
 367         int r, neras = 0;
 368         unsigned int pos;
 369
 370         r = fec_alloc_bufs(v, fio);
 371         if (unlikely(r < 0))
 372                 return r;
 373
 374         for (pos = 0; pos < 1 << v->data_dev_block_bits; ) {
 375                 fec_init_bufs(v, fio);
 376
 377                 r = fec_read_bufs(v, io, rsb, offset, pos,
 378                                   use_erasures ? &neras : NULL);
 379                 if (unlikely(r < 0))
 380                         return r;
 381
 382                 r = fec_decode_bufs(v, io, fio, rsb, r, pos, neras);
 383                 if (r < 0)
 384                         return r;
 385
 386                 pos += fio->nbufs << DM_VERITY_FEC_BUF_RS_BITS;
 387         }
 388
 389         /* Always re-validate the corrected block against the expected hash */
 390         r = verity_hash(v, io, fio->output, 1 << v->data_dev_block_bits,
 391                         verity_io_real_digest(v, io), true);
 392         if (unlikely(r < 0))
 393                 return r;
 394
 395         if (memcmp(verity_io_real_digest(v, io), verity_io_want_digest(v, io),
 396                    v->digest_size)) {
 397                 DMERR_LIMIT("%s: FEC %llu: failed to correct (%d erasures)",
 398                             v->data_dev->name, (unsigned long long)rsb, neras);
 399                 return -EILSEQ;
 400         }
 401
 402         return 0;
 403 }
 404
 405 /* Correct errors in a block. Copies corrected block to dest. */
 406 int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
 407                       enum verity_block_type type, sector_t block, u8 *dest)
 408 {
 409         int r;
 410         struct dm_verity_fec_io *fio = fec_io(io);
 411         u64 offset, res, rsb;
 412
 413         if (!verity_fec_is_enabled(v))
 414                 return -EOPNOTSUPP;
 415
 416         if (fio->level >= DM_VERITY_FEC_MAX_RECURSION) {
 417                 DMWARN_LIMIT("%s: FEC: recursion too deep", v->data_dev->name);
 418                 return -EIO;
 419         }
 420
 421         fio->level++;
 422
 423         if (type == DM_VERITY_BLOCK_TYPE_METADATA)
 424                 block = block - v->hash_start + v->data_blocks;
 425
 426         /*
 427          * For RS(M, N), the continuous FEC data is divided into blocks of N
 428          * bytes. Since block size may not be divisible by N, the last block
 429          * is zero padded when decoding.
 430          *
 431          * Each byte of the block is covered by a different RS(M, N) code,
 432          * and each code is interleaved over N blocks to make it less likely
 433          * that bursty corruption will leave us in unrecoverable state.
 434          */
 435
 436         offset = block << v->data_dev_block_bits;
 437         res = div64_u64(offset, v->fec->rounds << v->data_dev_block_bits);
 438
 439         /*
 440          * The base RS block we can feed to the interleaver to find out all
 441          * blocks required for decoding.
 442          */
 443         rsb = offset - res * (v->fec->rounds << v->data_dev_block_bits);
 444
 445         /*
 446          * Locating erasures is slow, so attempt to recover the block without
 447          * them first. Do a second attempt with erasures if the corruption is
 448          * bad enough.
 449          */
 450         r = fec_decode_rsb(v, io, fio, rsb, offset, false);
 451         if (r < 0) {
 452                 r = fec_decode_rsb(v, io, fio, rsb, offset, true);
 453                 if (r < 0)
 454                         goto done;
 455         }
 456
 457         memcpy(dest, fio->output, 1 << v->data_dev_block_bits);
 458
 459 done:
 460         fio->level--;
 461         return r;
 462 }
 463
 464 /*
 465  * Clean up per-bio data.
 466  */
 467 void verity_fec_finish_io(struct dm_verity_io *io)
 468 {
 469         unsigned int n;
 470         struct dm_verity_fec *f = io->v->fec;
 471         struct dm_verity_fec_io *fio = fec_io(io);
 472
 473         if (!verity_fec_is_enabled(io->v))
 474                 return;
 475
 476         mempool_free(fio->rs, &f->rs_pool);
 477
 478         fec_for_each_prealloc_buffer(n)
 479                 mempool_free(fio->bufs[n], &f->prealloc_pool);
 480
 481         fec_for_each_extra_buffer(fio, n)
 482                 mempool_free(fio->bufs[n], &f->extra_pool);
 483
 484         mempool_free(fio->output, &f->output_pool);
 485 }
 486
 487 /*
 488  * Initialize per-bio data.
 489  */
 490 void verity_fec_init_io(struct dm_verity_io *io)
 491 {
 492         struct dm_verity_fec_io *fio = fec_io(io);
 493
 494         if (!verity_fec_is_enabled(io->v))
 495                 return;
 496
 497         fio->rs = NULL;
 498         memset(fio->bufs, 0, sizeof(fio->bufs));
 499         fio->nbufs = 0;
 500         fio->output = NULL;
 501         fio->level = 0;
 502 }
 503
 504 /*
 505  * Append feature arguments and values to the status table.
 506  */
 507 unsigned int verity_fec_status_table(struct dm_verity *v, unsigned int sz,
 508                                  char *result, unsigned int maxlen)
 509 {
 510         if (!verity_fec_is_enabled(v))
 511                 return sz;
 512
 513         DMEMIT(" " DM_VERITY_OPT_FEC_DEV " %s "
 514                DM_VERITY_OPT_FEC_BLOCKS " %llu "
 515                DM_VERITY_OPT_FEC_START " %llu "
 516                DM_VERITY_OPT_FEC_ROOTS " %d",
 517                v->fec->dev->name,
 518                (unsigned long long)v->fec->blocks,
 519                (unsigned long long)v->fec->start,
 520                v->fec->roots);
 521
 522         return sz;
 523 }
 524
 525 void verity_fec_dtr(struct dm_verity *v)
 526 {
 527         struct dm_verity_fec *f = v->fec;
 528
 529         if (!verity_fec_is_enabled(v))
 530                 goto out;
 531
 532         mempool_exit(&f->rs_pool);
 533         mempool_exit(&f->prealloc_pool);
 534         mempool_exit(&f->extra_pool);
 535         mempool_exit(&f->output_pool);
 536         kmem_cache_destroy(f->cache);
 537
 538         if (f->data_bufio)
 539                 dm_bufio_client_destroy(f->data_bufio);
 540         if (f->bufio)
 541                 dm_bufio_client_destroy(f->bufio);
 542
 543         if (f->dev)
 544                 dm_put_device(v->ti, f->dev);
 545 out:
 546         kfree(f);
 547         v->fec = NULL;
 548 }
 549
 550 static void *fec_rs_alloc(gfp_t gfp_mask, void *pool_data)
 551 {
 552         struct dm_verity *v = pool_data;
 553
 554         return init_rs_gfp(8, 0x11d, 0, 1, v->fec->roots, gfp_mask);
 555 }
 556
 557 static void fec_rs_free(void *element, void *pool_data)
 558 {
 559         struct rs_control *rs = element;
 560
 561         if (rs)
 562                 free_rs(rs);
 563 }
 564
 565 bool verity_is_fec_opt_arg(const char *arg_name)
 566 {
 567         return (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV) ||
 568                 !strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS) ||
 569                 !strcasecmp(arg_name, DM_VERITY_OPT_FEC_START) ||
 570                 !strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS));
 571 }
 572
 573 int verity_fec_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
 574                               unsigned int *argc, const char *arg_name)
 575 {
 576         int r;
 577         struct dm_target *ti = v->ti;
 578         const char *arg_value;
 579         unsigned long long num_ll;
 580         unsigned char num_c;
 581         char dummy;
 582
 583         if (!*argc) {
 584                 ti->error = "FEC feature arguments require a value";
 585                 return -EINVAL;
 586         }
 587
 588         arg_value = dm_shift_arg(as);
 589         (*argc)--;
 590
 591         if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV)) {
 592                 r = dm_get_device(ti, arg_value, BLK_OPEN_READ, &v->fec->dev);
 593                 if (r) {
 594                         ti->error = "FEC device lookup failed";
 595                         return r;
 596                 }
 597
 598         } else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS)) {
 599                 if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
 600                     ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
 601                      >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
 602                         ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
 603                         return -EINVAL;
 604                 }
 605                 v->fec->blocks = num_ll;
 606
 607         } else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_START)) {
 608                 if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
 609                     ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) >>
 610                      (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
 611                         ti->error = "Invalid " DM_VERITY_OPT_FEC_START;
 612                         return -EINVAL;
 613                 }
 614                 v->fec->start = num_ll;
 615
 616         } else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS)) {
 617                 if (sscanf(arg_value, "%hhu%c", &num_c, &dummy) != 1 || !num_c ||
 618                     num_c < (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MAX_RSN) ||
 619                     num_c > (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN)) {
 620                         ti->error = "Invalid " DM_VERITY_OPT_FEC_ROOTS;
 621                         return -EINVAL;
 622                 }
 623                 v->fec->roots = num_c;
 624
 625         } else {
 626                 ti->error = "Unrecognized verity FEC feature request";
 627                 return -EINVAL;
 628         }
 629
 630         return 0;
 631 }
 632
 633 /*
 634  * Allocate dm_verity_fec for v->fec. Must be called before verity_fec_ctr.
 635  */
 636 int verity_fec_ctr_alloc(struct dm_verity *v)
 637 {
 638         struct dm_verity_fec *f;
 639
 640         f = kzalloc(sizeof(struct dm_verity_fec), GFP_KERNEL);
 641         if (!f) {
 642                 v->ti->error = "Cannot allocate FEC structure";
 643                 return -ENOMEM;
 644         }
 645         v->fec = f;
 646
 647         return 0;
 648 }
 649
 650 /*
 651  * Validate arguments and preallocate memory. Must be called after arguments
 652  * have been parsed using verity_fec_parse_opt_args.
 653  */
 654 int verity_fec_ctr(struct dm_verity *v)
 655 {
 656         struct dm_verity_fec *f = v->fec;
 657         struct dm_target *ti = v->ti;
 658         u64 hash_blocks, fec_blocks;
 659         int ret;
 660
 661         if (!verity_fec_is_enabled(v)) {
 662                 verity_fec_dtr(v);
 663                 return 0;
 664         }
 665
 666         /*
 667          * FEC is computed over data blocks, possible metadata, and
 668          * hash blocks. In other words, FEC covers total of fec_blocks
 669          * blocks consisting of the following:
 670          *
 671          *  data blocks | hash blocks | metadata (optional)
 672          *
 673          * We allow metadata after hash blocks to support a use case
 674          * where all data is stored on the same device and FEC covers
 675          * the entire area.
 676          *
 677          * If metadata is included, we require it to be available on the
 678          * hash device after the hash blocks.
 679          */
 680
 681         hash_blocks = v->hash_blocks - v->hash_start;
 682
 683         /*
 684          * Require matching block sizes for data and hash devices for
 685          * simplicity.
 686          */
 687         if (v->data_dev_block_bits != v->hash_dev_block_bits) {
 688                 ti->error = "Block sizes must match to use FEC";
 689                 return -EINVAL;
 690         }
 691
 692         if (!f->roots) {
 693                 ti->error = "Missing " DM_VERITY_OPT_FEC_ROOTS;
 694                 return -EINVAL;
 695         }
 696         f->rsn = DM_VERITY_FEC_RSM - f->roots;
 697
 698         if (!f->blocks) {
 699                 ti->error = "Missing " DM_VERITY_OPT_FEC_BLOCKS;
 700                 return -EINVAL;
 701         }
 702
 703         f->rounds = f->blocks;
 704         if (sector_div(f->rounds, f->rsn))
 705                 f->rounds++;
 706
 707         /*
 708          * Due to optional metadata, f->blocks can be larger than
 709          * data_blocks and hash_blocks combined.
 710          */
 711         if (f->blocks < v->data_blocks + hash_blocks || !f->rounds) {
 712                 ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
 713                 return -EINVAL;
 714         }
 715
 716         /*
 717          * Metadata is accessed through the hash device, so we require
 718          * it to be large enough.
 719          */
 720         f->hash_blocks = f->blocks - v->data_blocks;
 721         if (dm_bufio_get_device_size(v->bufio) < f->hash_blocks) {
 722                 ti->error = "Hash device is too small for "
 723                         DM_VERITY_OPT_FEC_BLOCKS;
 724                 return -E2BIG;
 725         }
 726
 727         if ((f->roots << SECTOR_SHIFT) & ((1 << v->data_dev_block_bits) - 1))
 728                 f->io_size = 1 << v->data_dev_block_bits;
 729         else
 730                 f->io_size = v->fec->roots << SECTOR_SHIFT;
 731
 732         f->bufio = dm_bufio_client_create(f->dev->bdev,
 733                                           f->io_size,
 734                                           1, 0, NULL, NULL, 0);
 735         if (IS_ERR(f->bufio)) {
 736                 ti->error = "Cannot initialize FEC bufio client";
 737                 return PTR_ERR(f->bufio);
 738         }
 739
 740         dm_bufio_set_sector_offset(f->bufio, f->start << (v->data_dev_block_bits - SECTOR_SHIFT));
 741
 742         fec_blocks = div64_u64(f->rounds * f->roots, v->fec->roots << SECTOR_SHIFT);
 743         if (dm_bufio_get_device_size(f->bufio) < fec_blocks) {
 744                 ti->error = "FEC device is too small";
 745                 return -E2BIG;
 746         }
 747
 748         f->data_bufio = dm_bufio_client_create(v->data_dev->bdev,
 749                                                1 << v->data_dev_block_bits,
 750                                                1, 0, NULL, NULL, 0);
 751         if (IS_ERR(f->data_bufio)) {
 752                 ti->error = "Cannot initialize FEC data bufio client";
 753                 return PTR_ERR(f->data_bufio);
 754         }
 755
 756         if (dm_bufio_get_device_size(f->data_bufio) < v->data_blocks) {
 757                 ti->error = "Data device is too small";
 758                 return -E2BIG;
 759         }
 760
 761         /* Preallocate an rs_control structure for each worker thread */
 762         ret = mempool_init(&f->rs_pool, num_online_cpus(), fec_rs_alloc,
 763                            fec_rs_free, (void *) v);
 764         if (ret) {
 765                 ti->error = "Cannot allocate RS pool";
 766                 return ret;
 767         }
 768
 769         f->cache = kmem_cache_create("dm_verity_fec_buffers",
 770                                      f->rsn << DM_VERITY_FEC_BUF_RS_BITS,
 771                                      0, 0, NULL);
 772         if (!f->cache) {
 773                 ti->error = "Cannot create FEC buffer cache";
 774                 return -ENOMEM;
 775         }
 776
 777         /* Preallocate DM_VERITY_FEC_BUF_PREALLOC buffers for each thread */
 778         ret = mempool_init_slab_pool(&f->prealloc_pool, num_online_cpus() *
 779                                      DM_VERITY_FEC_BUF_PREALLOC,
 780                                      f->cache);
 781         if (ret) {
 782                 ti->error = "Cannot allocate FEC buffer prealloc pool";
 783                 return ret;
 784         }
 785
 786         ret = mempool_init_slab_pool(&f->extra_pool, 0, f->cache);
 787         if (ret) {
 788                 ti->error = "Cannot allocate FEC buffer extra pool";
 789                 return ret;
 790         }
 791
 792         /* Preallocate an output buffer for each thread */
 793         ret = mempool_init_kmalloc_pool(&f->output_pool, num_online_cpus(),
 794                                         1 << v->data_dev_block_bits);
 795         if (ret) {
 796                 ti->error = "Cannot allocate FEC output pool";
 797                 return ret;
 798         }
 799
 800         /* Reserve space for our per-bio data */
 801         ti->per_io_data_size += sizeof(struct dm_verity_fec_io);
 802
 803         return 0;
 804 }