drivers/md/dm-verity-fec.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * Copyright (C) 2015 Google, Inc.
0004  *
0005  * Author: Sami Tolvanen <samitolvanen@google.com>
0006  */
0007
0008 #include "dm-verity-fec.h"
0009 #include <linux/math64.h>
0010
0011 #define DM_MSG_PREFIX   "verity-fec"
0012
0013 /*
0014  * If error correction has been configured, returns true.
0015  */
0016 bool verity_fec_is_enabled(struct dm_verity *v)
0017 {
0018     return v->fec && v->fec->dev;
0019 }
0020
0021 /*
0022  * Return a pointer to dm_verity_fec_io after dm_verity_io and its variable
0023  * length fields.
0024  */
0025 static inline struct dm_verity_fec_io *fec_io(struct dm_verity_io *io)
0026 {
0027     return (struct dm_verity_fec_io *) verity_io_digest_end(io->v, io);
0028 }
0029
0030 /*
0031  * Return an interleaved offset for a byte in RS block.
0032  */
0033 static inline u64 fec_interleave(struct dm_verity *v, u64 offset)
0034 {
0035     u32 mod;
0036
0037     mod = do_div(offset, v->fec->rsn);
0038     return offset + mod * (v->fec->rounds << v->data_dev_block_bits);
0039 }
0040
0041 /*
0042  * Decode an RS block using Reed-Solomon.
0043  */
0044 static int fec_decode_rs8(struct dm_verity *v, struct dm_verity_fec_io *fio,
0045               u8 *data, u8 *fec, int neras)
0046 {
0047     int i;
0048     uint16_t par[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN];
0049
0050     for (i = 0; i < v->fec->roots; i++)
0051         par[i] = fec[i];
0052
0053     return decode_rs8(fio->rs, data, par, v->fec->rsn, NULL, neras,
0054               fio->erasures, 0, NULL);
0055 }
0056
0057 /*
0058  * Read error-correcting codes for the requested RS block. Returns a pointer
0059  * to the data block. Caller is responsible for releasing buf.
0060  */
0061 static u8 *fec_read_parity(struct dm_verity *v, u64 rsb, int index,
0062                unsigned *offset, struct dm_buffer **buf)
0063 {
0064     u64 position, block, rem;
0065     u8 *res;
0066
0067     position = (index + rsb) * v->fec->roots;
0068     block = div64_u64_rem(position, v->fec->io_size, &rem);
0069     *offset = (unsigned)rem;
0070
0071     res = dm_bufio_read(v->fec->bufio, block, buf);
0072     if (IS_ERR(res)) {
0073         DMERR("%s: FEC %llu: parity read failed (block %llu): %ld",
0074               v->data_dev->name, (unsigned long long)rsb,
0075               (unsigned long long)block, PTR_ERR(res));
0076         *buf = NULL;
0077     }
0078
0079     return res;
0080 }
0081
0082 /* Loop over each preallocated buffer slot. */
0083 #define fec_for_each_prealloc_buffer(__i) \
0084     for (__i = 0; __i < DM_VERITY_FEC_BUF_PREALLOC; __i++)
0085
0086 /* Loop over each extra buffer slot. */
0087 #define fec_for_each_extra_buffer(io, __i) \
0088     for (__i = DM_VERITY_FEC_BUF_PREALLOC; __i < DM_VERITY_FEC_BUF_MAX; __i++)
0089
0090 /* Loop over each allocated buffer. */
0091 #define fec_for_each_buffer(io, __i) \
0092     for (__i = 0; __i < (io)->nbufs; __i++)
0093
0094 /* Loop over each RS block in each allocated buffer. */
0095 #define fec_for_each_buffer_rs_block(io, __i, __j) \
0096     fec_for_each_buffer(io, __i) \
0097         for (__j = 0; __j < 1 << DM_VERITY_FEC_BUF_RS_BITS; __j++)
0098
0099 /*
0100  * Return a pointer to the current RS block when called inside
0101  * fec_for_each_buffer_rs_block.
0102  */
0103 static inline u8 *fec_buffer_rs_block(struct dm_verity *v,
0104                       struct dm_verity_fec_io *fio,
0105                       unsigned i, unsigned j)
0106 {
0107     return &fio->bufs[i][j * v->fec->rsn];
0108 }
0109
0110 /*
0111  * Return an index to the current RS block when called inside
0112  * fec_for_each_buffer_rs_block.
0113  */
0114 static inline unsigned fec_buffer_rs_index(unsigned i, unsigned j)
0115 {
0116     return (i << DM_VERITY_FEC_BUF_RS_BITS) + j;
0117 }
0118
0119 /*
0120  * Decode all RS blocks from buffers and copy corrected bytes into fio->output
0121  * starting from block_offset.
0122  */
0123 static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio,
0124                u64 rsb, int byte_index, unsigned block_offset,
0125                int neras)
0126 {
0127     int r, corrected = 0, res;
0128     struct dm_buffer *buf;
0129     unsigned n, i, offset;
0130     u8 *par, *block;
0131
0132     par = fec_read_parity(v, rsb, block_offset, &offset, &buf);
0133     if (IS_ERR(par))
0134         return PTR_ERR(par);
0135
0136     /*
0137      * Decode the RS blocks we have in bufs. Each RS block results in
0138      * one corrected target byte and consumes fec->roots parity bytes.
0139      */
0140     fec_for_each_buffer_rs_block(fio, n, i) {
0141         block = fec_buffer_rs_block(v, fio, n, i);
0142         res = fec_decode_rs8(v, fio, block, &par[offset], neras);
0143         if (res < 0) {
0144             r = res;
0145             goto error;
0146         }
0147
0148         corrected += res;
0149         fio->output[block_offset] = block[byte_index];
0150
0151         block_offset++;
0152         if (block_offset >= 1 << v->data_dev_block_bits)
0153             goto done;
0154
0155         /* read the next block when we run out of parity bytes */
0156         offset += v->fec->roots;
0157         if (offset >= v->fec->io_size) {
0158             dm_bufio_release(buf);
0159
0160             par = fec_read_parity(v, rsb, block_offset, &offset, &buf);
0161             if (IS_ERR(par))
0162                 return PTR_ERR(par);
0163         }
0164     }
0165 done:
0166     r = corrected;
0167 error:
0168     dm_bufio_release(buf);
0169
0170     if (r < 0 && neras)
0171         DMERR_LIMIT("%s: FEC %llu: failed to correct: %d",
0172                 v->data_dev->name, (unsigned long long)rsb, r);
0173     else if (r > 0)
0174         DMWARN_LIMIT("%s: FEC %llu: corrected %d errors",
0175                  v->data_dev->name, (unsigned long long)rsb, r);
0176
0177     return r;
0178 }
0179
0180 /*
0181  * Locate data block erasures using verity hashes.
0182  */
0183 static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io,
0184               u8 *want_digest, u8 *data)
0185 {
0186     if (unlikely(verity_hash(v, verity_io_hash_req(v, io),
0187                  data, 1 << v->data_dev_block_bits,
0188                  verity_io_real_digest(v, io))))
0189         return 0;
0190
0191     return memcmp(verity_io_real_digest(v, io), want_digest,
0192               v->digest_size) != 0;
0193 }
0194
0195 /*
0196  * Read data blocks that are part of the RS block and deinterleave as much as
0197  * fits into buffers. Check for erasure locations if @neras is non-NULL.
0198  */
0199 static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
0200              u64 rsb, u64 target, unsigned block_offset,
0201              int *neras)
0202 {
0203     bool is_zero;
0204     int i, j, target_index = -1;
0205     struct dm_buffer *buf;
0206     struct dm_bufio_client *bufio;
0207     struct dm_verity_fec_io *fio = fec_io(io);
0208     u64 block, ileaved;
0209     u8 *bbuf, *rs_block;
0210     u8 want_digest[HASH_MAX_DIGESTSIZE];
0211     unsigned n, k;
0212
0213     if (neras)
0214         *neras = 0;
0215
0216     if (WARN_ON(v->digest_size > sizeof(want_digest)))
0217         return -EINVAL;
0218
0219     /*
0220      * read each of the rsn data blocks that are part of the RS block, and
0221      * interleave contents to available bufs
0222      */
0223     for (i = 0; i < v->fec->rsn; i++) {
0224         ileaved = fec_interleave(v, rsb * v->fec->rsn + i);
0225
0226         /*
0227          * target is the data block we want to correct, target_index is
0228          * the index of this block within the rsn RS blocks
0229          */
0230         if (ileaved == target)
0231             target_index = i;
0232
0233         block = ileaved >> v->data_dev_block_bits;
0234         bufio = v->fec->data_bufio;
0235
0236         if (block >= v->data_blocks) {
0237             block -= v->data_blocks;
0238
0239             /*
0240              * blocks outside the area were assumed to contain
0241              * zeros when encoding data was generated
0242              */
0243             if (unlikely(block >= v->fec->hash_blocks))
0244                 continue;
0245
0246             block += v->hash_start;
0247             bufio = v->bufio;
0248         }
0249
0250         bbuf = dm_bufio_read(bufio, block, &buf);
0251         if (IS_ERR(bbuf)) {
0252             DMWARN_LIMIT("%s: FEC %llu: read failed (%llu): %ld",
0253                      v->data_dev->name,
0254                      (unsigned long long)rsb,
0255                      (unsigned long long)block, PTR_ERR(bbuf));
0256
0257             /* assume the block is corrupted */
0258             if (neras && *neras <= v->fec->roots)
0259                 fio->erasures[(*neras)++] = i;
0260
0261             continue;
0262         }
0263
0264         /* locate erasures if the block is on the data device */
0265         if (bufio == v->fec->data_bufio &&
0266             verity_hash_for_block(v, io, block, want_digest,
0267                       &is_zero) == 0) {
0268             /* skip known zero blocks entirely */
0269             if (is_zero)
0270                 goto done;
0271
0272             /*
0273              * skip if we have already found the theoretical
0274              * maximum number (i.e. fec->roots) of erasures
0275              */
0276             if (neras && *neras <= v->fec->roots &&
0277                 fec_is_erasure(v, io, want_digest, bbuf))
0278                 fio->erasures[(*neras)++] = i;
0279         }
0280
0281         /*
0282          * deinterleave and copy the bytes that fit into bufs,
0283          * starting from block_offset
0284          */
0285         fec_for_each_buffer_rs_block(fio, n, j) {
0286             k = fec_buffer_rs_index(n, j) + block_offset;
0287
0288             if (k >= 1 << v->data_dev_block_bits)
0289                 goto done;
0290
0291             rs_block = fec_buffer_rs_block(v, fio, n, j);
0292             rs_block[i] = bbuf[k];
0293         }
0294 done:
0295         dm_bufio_release(buf);
0296     }
0297
0298     return target_index;
0299 }
0300
0301 /*
0302  * Allocate RS control structure and FEC buffers from preallocated mempools,
0303  * and attempt to allocate as many extra buffers as available.
0304  */
0305 static int fec_alloc_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
0306 {
0307     unsigned n;
0308
0309     if (!fio->rs)
0310         fio->rs = mempool_alloc(&v->fec->rs_pool, GFP_NOIO);
0311
0312     fec_for_each_prealloc_buffer(n) {
0313         if (fio->bufs[n])
0314             continue;
0315
0316         fio->bufs[n] = mempool_alloc(&v->fec->prealloc_pool, GFP_NOWAIT);
0317         if (unlikely(!fio->bufs[n])) {
0318             DMERR("failed to allocate FEC buffer");
0319             return -ENOMEM;
0320         }
0321     }
0322
0323     /* try to allocate the maximum number of buffers */
0324     fec_for_each_extra_buffer(fio, n) {
0325         if (fio->bufs[n])
0326             continue;
0327
0328         fio->bufs[n] = mempool_alloc(&v->fec->extra_pool, GFP_NOWAIT);
0329         /* we can manage with even one buffer if necessary */
0330         if (unlikely(!fio->bufs[n]))
0331             break;
0332     }
0333     fio->nbufs = n;
0334
0335     if (!fio->output)
0336         fio->output = mempool_alloc(&v->fec->output_pool, GFP_NOIO);
0337
0338     return 0;
0339 }
0340
0341 /*
0342  * Initialize buffers and clear erasures. fec_read_bufs() assumes buffers are
0343  * zeroed before deinterleaving.
0344  */
0345 static void fec_init_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
0346 {
0347     unsigned n;
0348
0349     fec_for_each_buffer(fio, n)
0350         memset(fio->bufs[n], 0, v->fec->rsn << DM_VERITY_FEC_BUF_RS_BITS);
0351
0352     memset(fio->erasures, 0, sizeof(fio->erasures));
0353 }
0354
0355 /*
0356  * Decode all RS blocks in a single data block and return the target block
0357  * (indicated by @offset) in fio->output. If @use_erasures is non-zero, uses
0358  * hashes to locate erasures.
0359  */
0360 static int fec_decode_rsb(struct dm_verity *v, struct dm_verity_io *io,
0361               struct dm_verity_fec_io *fio, u64 rsb, u64 offset,
0362               bool use_erasures)
0363 {
0364     int r, neras = 0;
0365     unsigned pos;
0366
0367     r = fec_alloc_bufs(v, fio);
0368     if (unlikely(r < 0))
0369         return r;
0370
0371     for (pos = 0; pos < 1 << v->data_dev_block_bits; ) {
0372         fec_init_bufs(v, fio);
0373
0374         r = fec_read_bufs(v, io, rsb, offset, pos,
0375                   use_erasures ? &neras : NULL);
0376         if (unlikely(r < 0))
0377             return r;
0378
0379         r = fec_decode_bufs(v, fio, rsb, r, pos, neras);
0380         if (r < 0)
0381             return r;
0382
0383         pos += fio->nbufs << DM_VERITY_FEC_BUF_RS_BITS;
0384     }
0385
0386     /* Always re-validate the corrected block against the expected hash */
0387     r = verity_hash(v, verity_io_hash_req(v, io), fio->output,
0388             1 << v->data_dev_block_bits,
0389             verity_io_real_digest(v, io));
0390     if (unlikely(r < 0))
0391         return r;
0392
0393     if (memcmp(verity_io_real_digest(v, io), verity_io_want_digest(v, io),
0394            v->digest_size)) {
0395         DMERR_LIMIT("%s: FEC %llu: failed to correct (%d erasures)",
0396                 v->data_dev->name, (unsigned long long)rsb, neras);
0397         return -EILSEQ;
0398     }
0399
0400     return 0;
0401 }
0402
0403 static int fec_bv_copy(struct dm_verity *v, struct dm_verity_io *io, u8 *data,
0404                size_t len)
0405 {
0406     struct dm_verity_fec_io *fio = fec_io(io);
0407
0408     memcpy(data, &fio->output[fio->output_pos], len);
0409     fio->output_pos += len;
0410
0411     return 0;
0412 }
0413
0414 /*
0415  * Correct errors in a block. Copies corrected block to dest if non-NULL,
0416  * otherwise to a bio_vec starting from iter.
0417  */
0418 int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
0419               enum verity_block_type type, sector_t block, u8 *dest,
0420               struct bvec_iter *iter)
0421 {
0422     int r;
0423     struct dm_verity_fec_io *fio = fec_io(io);
0424     u64 offset, res, rsb;
0425
0426     if (!verity_fec_is_enabled(v))
0427         return -EOPNOTSUPP;
0428
0429     if (fio->level >= DM_VERITY_FEC_MAX_RECURSION) {
0430         DMWARN_LIMIT("%s: FEC: recursion too deep", v->data_dev->name);
0431         return -EIO;
0432     }
0433
0434     fio->level++;
0435
0436     if (type == DM_VERITY_BLOCK_TYPE_METADATA)
0437         block = block - v->hash_start + v->data_blocks;
0438
0439     /*
0440      * For RS(M, N), the continuous FEC data is divided into blocks of N
0441      * bytes. Since block size may not be divisible by N, the last block
0442      * is zero padded when decoding.
0443      *
0444      * Each byte of the block is covered by a different RS(M, N) code,
0445      * and each code is interleaved over N blocks to make it less likely
0446      * that bursty corruption will leave us in unrecoverable state.
0447      */
0448
0449     offset = block << v->data_dev_block_bits;
0450     res = div64_u64(offset, v->fec->rounds << v->data_dev_block_bits);
0451
0452     /*
0453      * The base RS block we can feed to the interleaver to find out all
0454      * blocks required for decoding.
0455      */
0456     rsb = offset - res * (v->fec->rounds << v->data_dev_block_bits);
0457
0458     /*
0459      * Locating erasures is slow, so attempt to recover the block without
0460      * them first. Do a second attempt with erasures if the corruption is
0461      * bad enough.
0462      */
0463     r = fec_decode_rsb(v, io, fio, rsb, offset, false);
0464     if (r < 0) {
0465         r = fec_decode_rsb(v, io, fio, rsb, offset, true);
0466         if (r < 0)
0467             goto done;
0468     }
0469
0470     if (dest)
0471         memcpy(dest, fio->output, 1 << v->data_dev_block_bits);
0472     else if (iter) {
0473         fio->output_pos = 0;
0474         r = verity_for_bv_block(v, io, iter, fec_bv_copy);
0475     }
0476
0477 done:
0478     fio->level--;
0479     return r;
0480 }
0481
0482 /*
0483  * Clean up per-bio data.
0484  */
0485 void verity_fec_finish_io(struct dm_verity_io *io)
0486 {
0487     unsigned n;
0488     struct dm_verity_fec *f = io->v->fec;
0489     struct dm_verity_fec_io *fio = fec_io(io);
0490
0491     if (!verity_fec_is_enabled(io->v))
0492         return;
0493
0494     mempool_free(fio->rs, &f->rs_pool);
0495
0496     fec_for_each_prealloc_buffer(n)
0497         mempool_free(fio->bufs[n], &f->prealloc_pool);
0498
0499     fec_for_each_extra_buffer(fio, n)
0500         mempool_free(fio->bufs[n], &f->extra_pool);
0501
0502     mempool_free(fio->output, &f->output_pool);
0503 }
0504
0505 /*
0506  * Initialize per-bio data.
0507  */
0508 void verity_fec_init_io(struct dm_verity_io *io)
0509 {
0510     struct dm_verity_fec_io *fio = fec_io(io);
0511
0512     if (!verity_fec_is_enabled(io->v))
0513         return;
0514
0515     fio->rs = NULL;
0516     memset(fio->bufs, 0, sizeof(fio->bufs));
0517     fio->nbufs = 0;
0518     fio->output = NULL;
0519     fio->level = 0;
0520 }
0521
0522 /*
0523  * Append feature arguments and values to the status table.
0524  */
0525 unsigned verity_fec_status_table(struct dm_verity *v, unsigned sz,
0526                  char *result, unsigned maxlen)
0527 {
0528     if (!verity_fec_is_enabled(v))
0529         return sz;
0530
0531     DMEMIT(" " DM_VERITY_OPT_FEC_DEV " %s "
0532            DM_VERITY_OPT_FEC_BLOCKS " %llu "
0533            DM_VERITY_OPT_FEC_START " %llu "
0534            DM_VERITY_OPT_FEC_ROOTS " %d",
0535            v->fec->dev->name,
0536            (unsigned long long)v->fec->blocks,
0537            (unsigned long long)v->fec->start,
0538            v->fec->roots);
0539
0540     return sz;
0541 }
0542
0543 void verity_fec_dtr(struct dm_verity *v)
0544 {
0545     struct dm_verity_fec *f = v->fec;
0546
0547     if (!verity_fec_is_enabled(v))
0548         goto out;
0549
0550     mempool_exit(&f->rs_pool);
0551     mempool_exit(&f->prealloc_pool);
0552     mempool_exit(&f->extra_pool);
0553     mempool_exit(&f->output_pool);
0554     kmem_cache_destroy(f->cache);
0555
0556     if (f->data_bufio)
0557         dm_bufio_client_destroy(f->data_bufio);
0558     if (f->bufio)
0559         dm_bufio_client_destroy(f->bufio);
0560
0561     if (f->dev)
0562         dm_put_device(v->ti, f->dev);
0563 out:
0564     kfree(f);
0565     v->fec = NULL;
0566 }
0567
0568 static void *fec_rs_alloc(gfp_t gfp_mask, void *pool_data)
0569 {
0570     struct dm_verity *v = (struct dm_verity *)pool_data;
0571
0572     return init_rs_gfp(8, 0x11d, 0, 1, v->fec->roots, gfp_mask);
0573 }
0574
0575 static void fec_rs_free(void *element, void *pool_data)
0576 {
0577     struct rs_control *rs = (struct rs_control *)element;
0578
0579     if (rs)
0580         free_rs(rs);
0581 }
0582
0583 bool verity_is_fec_opt_arg(const char *arg_name)
0584 {
0585     return (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV) ||
0586         !strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS) ||
0587         !strcasecmp(arg_name, DM_VERITY_OPT_FEC_START) ||
0588         !strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS));
0589 }
0590
0591 int verity_fec_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
0592                   unsigned *argc, const char *arg_name)
0593 {
0594     int r;
0595     struct dm_target *ti = v->ti;
0596     const char *arg_value;
0597     unsigned long long num_ll;
0598     unsigned char num_c;
0599     char dummy;
0600
0601     if (!*argc) {
0602         ti->error = "FEC feature arguments require a value";
0603         return -EINVAL;
0604     }
0605
0606     arg_value = dm_shift_arg(as);
0607     (*argc)--;
0608
0609     if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV)) {
0610         r = dm_get_device(ti, arg_value, FMODE_READ, &v->fec->dev);
0611         if (r) {
0612             ti->error = "FEC device lookup failed";
0613             return r;
0614         }
0615
0616     } else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS)) {
0617         if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
0618             ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
0619              >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
0620             ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
0621             return -EINVAL;
0622         }
0623         v->fec->blocks = num_ll;
0624
0625     } else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_START)) {
0626         if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
0627             ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) >>
0628              (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
0629             ti->error = "Invalid " DM_VERITY_OPT_FEC_START;
0630             return -EINVAL;
0631         }
0632         v->fec->start = num_ll;
0633
0634     } else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS)) {
0635         if (sscanf(arg_value, "%hhu%c", &num_c, &dummy) != 1 || !num_c ||
0636             num_c < (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MAX_RSN) ||
0637             num_c > (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN)) {
0638             ti->error = "Invalid " DM_VERITY_OPT_FEC_ROOTS;
0639             return -EINVAL;
0640         }
0641         v->fec->roots = num_c;
0642
0643     } else {
0644         ti->error = "Unrecognized verity FEC feature request";
0645         return -EINVAL;
0646     }
0647
0648     return 0;
0649 }
0650
0651 /*
0652  * Allocate dm_verity_fec for v->fec. Must be called before verity_fec_ctr.
0653  */
0654 int verity_fec_ctr_alloc(struct dm_verity *v)
0655 {
0656     struct dm_verity_fec *f;
0657
0658     f = kzalloc(sizeof(struct dm_verity_fec), GFP_KERNEL);
0659     if (!f) {
0660         v->ti->error = "Cannot allocate FEC structure";
0661         return -ENOMEM;
0662     }
0663     v->fec = f;
0664
0665     return 0;
0666 }
0667
0668 /*
0669  * Validate arguments and preallocate memory. Must be called after arguments
0670  * have been parsed using verity_fec_parse_opt_args.
0671  */
0672 int verity_fec_ctr(struct dm_verity *v)
0673 {
0674     struct dm_verity_fec *f = v->fec;
0675     struct dm_target *ti = v->ti;
0676     u64 hash_blocks, fec_blocks;
0677     int ret;
0678
0679     if (!verity_fec_is_enabled(v)) {
0680         verity_fec_dtr(v);
0681         return 0;
0682     }
0683
0684     /*
0685      * FEC is computed over data blocks, possible metadata, and
0686      * hash blocks. In other words, FEC covers total of fec_blocks
0687      * blocks consisting of the following:
0688      *
0689      *  data blocks | hash blocks | metadata (optional)
0690      *
0691      * We allow metadata after hash blocks to support a use case
0692      * where all data is stored on the same device and FEC covers
0693      * the entire area.
0694      *
0695      * If metadata is included, we require it to be available on the
0696      * hash device after the hash blocks.
0697      */
0698
0699     hash_blocks = v->hash_blocks - v->hash_start;
0700
0701     /*
0702      * Require matching block sizes for data and hash devices for
0703      * simplicity.
0704      */
0705     if (v->data_dev_block_bits != v->hash_dev_block_bits) {
0706         ti->error = "Block sizes must match to use FEC";
0707         return -EINVAL;
0708     }
0709
0710     if (!f->roots) {
0711         ti->error = "Missing " DM_VERITY_OPT_FEC_ROOTS;
0712         return -EINVAL;
0713     }
0714     f->rsn = DM_VERITY_FEC_RSM - f->roots;
0715
0716     if (!f->blocks) {
0717         ti->error = "Missing " DM_VERITY_OPT_FEC_BLOCKS;
0718         return -EINVAL;
0719     }
0720
0721     f->rounds = f->blocks;
0722     if (sector_div(f->rounds, f->rsn))
0723         f->rounds++;
0724
0725     /*
0726      * Due to optional metadata, f->blocks can be larger than
0727      * data_blocks and hash_blocks combined.
0728      */
0729     if (f->blocks < v->data_blocks + hash_blocks || !f->rounds) {
0730         ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
0731         return -EINVAL;
0732     }
0733
0734     /*
0735      * Metadata is accessed through the hash device, so we require
0736      * it to be large enough.
0737      */
0738     f->hash_blocks = f->blocks - v->data_blocks;
0739     if (dm_bufio_get_device_size(v->bufio) < f->hash_blocks) {
0740         ti->error = "Hash device is too small for "
0741             DM_VERITY_OPT_FEC_BLOCKS;
0742         return -E2BIG;
0743     }
0744
0745     if ((f->roots << SECTOR_SHIFT) & ((1 << v->data_dev_block_bits) - 1))
0746         f->io_size = 1 << v->data_dev_block_bits;
0747     else
0748         f->io_size = v->fec->roots << SECTOR_SHIFT;
0749
0750     f->bufio = dm_bufio_client_create(f->dev->bdev,
0751                       f->io_size,
0752                       1, 0, NULL, NULL, 0);
0753     if (IS_ERR(f->bufio)) {
0754         ti->error = "Cannot initialize FEC bufio client";
0755         return PTR_ERR(f->bufio);
0756     }
0757
0758     dm_bufio_set_sector_offset(f->bufio, f->start << (v->data_dev_block_bits - SECTOR_SHIFT));
0759
0760     fec_blocks = div64_u64(f->rounds * f->roots, v->fec->roots << SECTOR_SHIFT);
0761     if (dm_bufio_get_device_size(f->bufio) < fec_blocks) {
0762         ti->error = "FEC device is too small";
0763         return -E2BIG;
0764     }
0765
0766     f->data_bufio = dm_bufio_client_create(v->data_dev->bdev,
0767                            1 << v->data_dev_block_bits,
0768                            1, 0, NULL, NULL, 0);
0769     if (IS_ERR(f->data_bufio)) {
0770         ti->error = "Cannot initialize FEC data bufio client";
0771         return PTR_ERR(f->data_bufio);
0772     }
0773
0774     if (dm_bufio_get_device_size(f->data_bufio) < v->data_blocks) {
0775         ti->error = "Data device is too small";
0776         return -E2BIG;
0777     }
0778
0779     /* Preallocate an rs_control structure for each worker thread */
0780     ret = mempool_init(&f->rs_pool, num_online_cpus(), fec_rs_alloc,
0781                fec_rs_free, (void *) v);
0782     if (ret) {
0783         ti->error = "Cannot allocate RS pool";
0784         return ret;
0785     }
0786
0787     f->cache = kmem_cache_create("dm_verity_fec_buffers",
0788                      f->rsn << DM_VERITY_FEC_BUF_RS_BITS,
0789                      0, 0, NULL);
0790     if (!f->cache) {
0791         ti->error = "Cannot create FEC buffer cache";
0792         return -ENOMEM;
0793     }
0794
0795     /* Preallocate DM_VERITY_FEC_BUF_PREALLOC buffers for each thread */
0796     ret = mempool_init_slab_pool(&f->prealloc_pool, num_online_cpus() *
0797                      DM_VERITY_FEC_BUF_PREALLOC,
0798                      f->cache);
0799     if (ret) {
0800         ti->error = "Cannot allocate FEC buffer prealloc pool";
0801         return ret;
0802     }
0803
0804     ret = mempool_init_slab_pool(&f->extra_pool, 0, f->cache);
0805     if (ret) {
0806         ti->error = "Cannot allocate FEC buffer extra pool";
0807         return ret;
0808     }
0809
0810     /* Preallocate an output buffer for each thread */
0811     ret = mempool_init_kmalloc_pool(&f->output_pool, num_online_cpus(),
0812                     1 << v->data_dev_block_bits);
0813     if (ret) {
0814         ti->error = "Cannot allocate FEC output pool";
0815         return ret;
0816     }
0817
0818     /* Reserve space for our per-bio data */
0819     ti->per_io_data_size += sizeof(struct dm_verity_fec_io);
0820
0821     return 0;
0822 }