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 */
 16bool 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 */
 25static 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 */
 34static 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 * Read error-correcting codes for the requested RS block. Returns a pointer
 44 * to the data block. Caller is responsible for releasing buf.
 45 */
 46static u8 *fec_read_parity(struct dm_verity *v, u64 rsb, int index,
 47			   unsigned int *offset, unsigned int par_buf_offset,
 48			   struct dm_buffer **buf, unsigned short ioprio)
 49{
 50	u64 position, block, rem;
 51	u8 *res;
 52
 53	/* We have already part of parity bytes read, skip to the next block */
 54	if (par_buf_offset)
 55		index++;
 56
 57	position = (index + rsb) * v->fec->roots;
 58	block = div64_u64_rem(position, v->fec->io_size, &rem);
 59	*offset = par_buf_offset ? 0 : (unsigned int)rem;
 60
 61	res = dm_bufio_read_with_ioprio(v->fec->bufio, block, buf, ioprio);
 62	if (IS_ERR(res)) {
 63		DMERR("%s: FEC %llu: parity read failed (block %llu): %ld",
 64		      v->data_dev->name, (unsigned long long)rsb,
 65		      (unsigned long long)block, PTR_ERR(res));
 66		*buf = NULL;
 67	}
 68
 69	return res;
 70}
 71
 72/* Loop over each preallocated buffer slot. */
 73#define fec_for_each_prealloc_buffer(__i) \
 74	for (__i = 0; __i < DM_VERITY_FEC_BUF_PREALLOC; __i++)
 75
 76/* Loop over each extra buffer slot. */
 77#define fec_for_each_extra_buffer(io, __i) \
 78	for (__i = DM_VERITY_FEC_BUF_PREALLOC; __i < DM_VERITY_FEC_BUF_MAX; __i++)
 79
 80/* Loop over each allocated buffer. */
 81#define fec_for_each_buffer(io, __i) \
 82	for (__i = 0; __i < (io)->nbufs; __i++)
 83
 84/* Loop over each RS block in each allocated buffer. */
 85#define fec_for_each_buffer_rs_block(io, __i, __j) \
 86	fec_for_each_buffer(io, __i) \
 87		for (__j = 0; __j < 1 << DM_VERITY_FEC_BUF_RS_BITS; __j++)
 88
 89/*
 90 * Return a pointer to the current RS block when called inside
 91 * fec_for_each_buffer_rs_block.
 92 */
 93static inline u8 *fec_buffer_rs_block(struct dm_verity *v,
 94				      struct dm_verity_fec_io *fio,
 95				      unsigned int i, unsigned int j)
 96{
 97	return &fio->bufs[i][j * v->fec->rsn];
 98}
 99
100/*
101 * Return an index to the current RS block when called inside
102 * fec_for_each_buffer_rs_block.
103 */
104static inline unsigned int fec_buffer_rs_index(unsigned int i, unsigned int j)
105{
106	return (i << DM_VERITY_FEC_BUF_RS_BITS) + j;
107}
108
109/*
110 * Decode all RS blocks from buffers and copy corrected bytes into fio->output
111 * starting from block_offset.
112 */
113static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
114			   struct dm_verity_fec_io *fio, u64 rsb, int byte_index,
115			   unsigned int block_offset, int neras)
116{
117	int r, corrected = 0, res;
118	struct dm_buffer *buf;
119	unsigned int n, i, j, offset, par_buf_offset = 0;
120	uint16_t par_buf[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN];
121	u8 *par, *block;
122	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
123
124	par = fec_read_parity(v, rsb, block_offset, &offset,
125			      par_buf_offset, &buf, bio->bi_ioprio);
126	if (IS_ERR(par))
127		return PTR_ERR(par);
128
129	/*
130	 * Decode the RS blocks we have in bufs. Each RS block results in
131	 * one corrected target byte and consumes fec->roots parity bytes.
132	 */
133	fec_for_each_buffer_rs_block(fio, n, i) {
134		block = fec_buffer_rs_block(v, fio, n, i);
135		for (j = 0; j < v->fec->roots - par_buf_offset; j++)
136			par_buf[par_buf_offset + j] = par[offset + j];
137		/* Decode an RS block using Reed-Solomon */
138		res = decode_rs8(fio->rs, block, par_buf, v->fec->rsn,
139				 NULL, neras, fio->erasures, 0, NULL);
140		if (res < 0) {
141			r = res;
142			goto error;
143		}
144
145		corrected += res;
146		fio->output[block_offset] = block[byte_index];
147
148		block_offset++;
149		if (block_offset >= 1 << v->data_dev_block_bits)
150			goto done;
151
152		/* Read the next block when we run out of parity bytes */
153		offset += (v->fec->roots - par_buf_offset);
154		/* Check if parity bytes are split between blocks */
155		if (offset < v->fec->io_size && (offset + v->fec->roots) > v->fec->io_size) {
156			par_buf_offset = v->fec->io_size - offset;
157			for (j = 0; j < par_buf_offset; j++)
158				par_buf[j] = par[offset + j];
159			offset += par_buf_offset;
160		} else
161			par_buf_offset = 0;
162
163		if (offset >= v->fec->io_size) {
164			dm_bufio_release(buf);
165
166			par = fec_read_parity(v, rsb, block_offset, &offset,
167					      par_buf_offset, &buf, bio->bi_ioprio);
168			if (IS_ERR(par))
169				return PTR_ERR(par);
170		}
171	}
172done:
173	r = corrected;
174error:
175	dm_bufio_release(buf);
176
177	if (r < 0 && neras)
178		DMERR_LIMIT("%s: FEC %llu: failed to correct: %d",
179			    v->data_dev->name, (unsigned long long)rsb, r);
180	else if (r > 0) {
181		DMWARN_LIMIT("%s: FEC %llu: corrected %d errors",
182			     v->data_dev->name, (unsigned long long)rsb, r);
183		atomic64_inc(&v->fec->corrected);
184	}
185
186	return r;
187}
188
189/*
190 * Locate data block erasures using verity hashes.
191 */
192static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io,
193			  const u8 *want_digest, const u8 *data)
194{
195	if (unlikely(verity_hash(v, io, data, 1 << v->data_dev_block_bits,
196				 io->tmp_digest)))
197		return 0;
198
199	return memcmp(io->tmp_digest, want_digest, v->digest_size) != 0;
200}
201
202/*
203 * Read data blocks that are part of the RS block and deinterleave as much as
204 * fits into buffers. Check for erasure locations if @neras is non-NULL.
205 */
206static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
207			 u64 rsb, u64 target, unsigned int block_offset,
208			 int *neras)
209{
210	bool is_zero;
211	int i, j, target_index = -1;
212	struct dm_buffer *buf;
213	struct dm_bufio_client *bufio;
214	struct dm_verity_fec_io *fio = fec_io(io);
215	u64 block, ileaved;
216	u8 *bbuf, *rs_block;
217	u8 want_digest[HASH_MAX_DIGESTSIZE];
218	unsigned int n, k;
219	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
220
221	if (neras)
222		*neras = 0;
223
224	if (WARN_ON(v->digest_size > sizeof(want_digest)))
225		return -EINVAL;
226
227	/*
228	 * read each of the rsn data blocks that are part of the RS block, and
229	 * interleave contents to available bufs
230	 */
231	for (i = 0; i < v->fec->rsn; i++) {
232		ileaved = fec_interleave(v, rsb * v->fec->rsn + i);
233
234		/*
235		 * target is the data block we want to correct, target_index is
236		 * the index of this block within the rsn RS blocks
237		 */
238		if (ileaved == target)
239			target_index = i;
240
241		block = ileaved >> v->data_dev_block_bits;
242		bufio = v->fec->data_bufio;
243
244		if (block >= v->data_blocks) {
245			block -= v->data_blocks;
246
247			/*
248			 * blocks outside the area were assumed to contain
249			 * zeros when encoding data was generated
250			 */
251			if (unlikely(block >= v->fec->hash_blocks))
252				continue;
253
254			block += v->hash_start;
255			bufio = v->bufio;
256		}
257
258		bbuf = dm_bufio_read_with_ioprio(bufio, block, &buf, bio->bi_ioprio);
259		if (IS_ERR(bbuf)) {
260			DMWARN_LIMIT("%s: FEC %llu: read failed (%llu): %ld",
261				     v->data_dev->name,
262				     (unsigned long long)rsb,
263				     (unsigned long long)block, PTR_ERR(bbuf));
264
265			/* assume the block is corrupted */
266			if (neras && *neras <= v->fec->roots)
267				fio->erasures[(*neras)++] = i;
268
269			continue;
270		}
271
272		/* locate erasures if the block is on the data device */
273		if (bufio == v->fec->data_bufio &&
274		    verity_hash_for_block(v, io, block, want_digest,
275					  &is_zero) == 0) {
276			/* skip known zero blocks entirely */
277			if (is_zero)
278				goto done;
279
280			/*
281			 * skip if we have already found the theoretical
282			 * maximum number (i.e. fec->roots) of erasures
283			 */
284			if (neras && *neras <= v->fec->roots &&
285			    fec_is_erasure(v, io, want_digest, bbuf))
286				fio->erasures[(*neras)++] = i;
287		}
288
289		/*
290		 * deinterleave and copy the bytes that fit into bufs,
291		 * starting from block_offset
292		 */
293		fec_for_each_buffer_rs_block(fio, n, j) {
294			k = fec_buffer_rs_index(n, j) + block_offset;
295
296			if (k >= 1 << v->data_dev_block_bits)
297				goto done;
298
299			rs_block = fec_buffer_rs_block(v, fio, n, j);
300			rs_block[i] = bbuf[k];
301		}
302done:
303		dm_bufio_release(buf);
304	}
305
306	return target_index;
307}
308
309/*
310 * Allocate RS control structure and FEC buffers from preallocated mempools,
311 * and attempt to allocate as many extra buffers as available.
312 */
313static int fec_alloc_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
314{
315	unsigned int n;
316
317	if (!fio->rs)
318		fio->rs = mempool_alloc(&v->fec->rs_pool, GFP_NOIO);
319
320	fec_for_each_prealloc_buffer(n) {
321		if (fio->bufs[n])
322			continue;
323
324		fio->bufs[n] = mempool_alloc(&v->fec->prealloc_pool, GFP_NOIO);
325	}
326
327	/* try to allocate the maximum number of buffers */
328	fec_for_each_extra_buffer(fio, n) {
329		if (fio->bufs[n])
330			continue;
331
332		fio->bufs[n] = kmem_cache_alloc(v->fec->cache, GFP_NOWAIT);
333		/* we can manage with even one buffer if necessary */
334		if (unlikely(!fio->bufs[n]))
335			break;
336	}
337	fio->nbufs = n;
338
339	if (!fio->output)
340		fio->output = mempool_alloc(&v->fec->output_pool, GFP_NOIO);
341
342	return 0;
343}
344
345/*
346 * Initialize buffers and clear erasures. fec_read_bufs() assumes buffers are
347 * zeroed before deinterleaving.
348 */
349static void fec_init_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
350{
351	unsigned int n;
352
353	fec_for_each_buffer(fio, n)
354		memset(fio->bufs[n], 0, v->fec->rsn << DM_VERITY_FEC_BUF_RS_BITS);
355
356	memset(fio->erasures, 0, sizeof(fio->erasures));
357}
358
359/*
360 * Decode all RS blocks in a single data block and return the target block
361 * (indicated by @offset) in fio->output. If @use_erasures is non-zero, uses
362 * hashes to locate erasures.
363 */
364static int fec_decode_rsb(struct dm_verity *v, struct dm_verity_io *io,
365			  struct dm_verity_fec_io *fio, u64 rsb, u64 offset,
366			  const u8 *want_digest, bool use_erasures)
367{
368	int r, neras = 0;
369	unsigned int pos;
370
371	r = fec_alloc_bufs(v, fio);
372	if (unlikely(r < 0))
373		return r;
374
375	for (pos = 0; pos < 1 << v->data_dev_block_bits; ) {
376		fec_init_bufs(v, fio);
377
378		r = fec_read_bufs(v, io, rsb, offset, pos,
379				  use_erasures ? &neras : NULL);
380		if (unlikely(r < 0))
381			return r;
382
383		r = fec_decode_bufs(v, io, fio, rsb, r, pos, neras);
384		if (r < 0)
385			return r;
386
387		pos += fio->nbufs << DM_VERITY_FEC_BUF_RS_BITS;
388	}
389
390	/* Always re-validate the corrected block against the expected hash */
391	r = verity_hash(v, io, fio->output, 1 << v->data_dev_block_bits,
392			io->tmp_digest);
393	if (unlikely(r < 0))
394		return r;
395
396	if (memcmp(io->tmp_digest, want_digest, 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. */
406int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
407		      enum verity_block_type type, const u8 *want_digest,
408		      sector_t block, u8 *dest)
409{
410	int r;
411	struct dm_verity_fec_io *fio = fec_io(io);
412	u64 offset, res, rsb;
413
414	if (!verity_fec_is_enabled(v))
415		return -EOPNOTSUPP;
416
417	if (fio->level)
418		return -EIO;
419
420	fio->level++;
421
422	if (type == DM_VERITY_BLOCK_TYPE_METADATA)
423		block = block - v->hash_start + v->data_blocks;
424
425	/*
426	 * For RS(M, N), the continuous FEC data is divided into blocks of N
427	 * bytes. Since block size may not be divisible by N, the last block
428	 * is zero padded when decoding.
429	 *
430	 * Each byte of the block is covered by a different RS(M, N) code,
431	 * and each code is interleaved over N blocks to make it less likely
432	 * that bursty corruption will leave us in unrecoverable state.
433	 */
434
435	offset = block << v->data_dev_block_bits;
436	res = div64_u64(offset, v->fec->rounds << v->data_dev_block_bits);
437
438	/*
439	 * The base RS block we can feed to the interleaver to find out all
440	 * blocks required for decoding.
441	 */
442	rsb = offset - res * (v->fec->rounds << v->data_dev_block_bits);
443
444	/*
445	 * Locating erasures is slow, so attempt to recover the block without
446	 * them first. Do a second attempt with erasures if the corruption is
447	 * bad enough.
448	 */
449	r = fec_decode_rsb(v, io, fio, rsb, offset, want_digest, false);
450	if (r < 0) {
451		r = fec_decode_rsb(v, io, fio, rsb, offset, want_digest, true);
452		if (r < 0)
453			goto done;
454	}
455
456	memcpy(dest, fio->output, 1 << v->data_dev_block_bits);
457
458done:
459	fio->level--;
460	return r;
461}
462
463/*
464 * Clean up per-bio data.
465 */
466void verity_fec_finish_io(struct dm_verity_io *io)
467{
468	unsigned int n;
469	struct dm_verity_fec *f = io->v->fec;
470	struct dm_verity_fec_io *fio = fec_io(io);
471
472	if (!verity_fec_is_enabled(io->v))
473		return;
474
475	mempool_free(fio->rs, &f->rs_pool);
476
477	fec_for_each_prealloc_buffer(n)
478		mempool_free(fio->bufs[n], &f->prealloc_pool);
479
480	fec_for_each_extra_buffer(fio, n)
481		if (fio->bufs[n])
482			kmem_cache_free(f->cache, fio->bufs[n]);
483
484	mempool_free(fio->output, &f->output_pool);
485}
486
487/*
488 * Initialize per-bio data.
489 */
490void 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 */
507unsigned 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
525void 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->output_pool);
535	kmem_cache_destroy(f->cache);
536
537	if (!IS_ERR_OR_NULL(f->data_bufio))
538		dm_bufio_client_destroy(f->data_bufio);
539	if (!IS_ERR_OR_NULL(f->bufio))
540		dm_bufio_client_destroy(f->bufio);
541
542	if (f->dev)
543		dm_put_device(v->ti, f->dev);
544out:
545	kfree(f);
546	v->fec = NULL;
547}
548
549static void *fec_rs_alloc(gfp_t gfp_mask, void *pool_data)
550{
551	struct dm_verity *v = pool_data;
552
553	return init_rs_gfp(8, 0x11d, 0, 1, v->fec->roots, gfp_mask);
554}
555
556static void fec_rs_free(void *element, void *pool_data)
557{
558	struct rs_control *rs = element;
559
560	if (rs)
561		free_rs(rs);
562}
563
564bool verity_is_fec_opt_arg(const char *arg_name)
565{
566	return (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV) ||
567		!strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS) ||
568		!strcasecmp(arg_name, DM_VERITY_OPT_FEC_START) ||
569		!strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS));
570}
571
572int verity_fec_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
573			      unsigned int *argc, const char *arg_name)
574{
575	int r;
576	struct dm_target *ti = v->ti;
577	const char *arg_value;
578	unsigned long long num_ll;
579	unsigned char num_c;
580	char dummy;
581
582	if (!*argc) {
583		ti->error = "FEC feature arguments require a value";
584		return -EINVAL;
585	}
586
587	arg_value = dm_shift_arg(as);
588	(*argc)--;
589
590	if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_DEV)) {
591		if (v->fec->dev) {
592			ti->error = "FEC device already specified";
593			return -EINVAL;
594		}
595		r = dm_get_device(ti, arg_value, BLK_OPEN_READ, &v->fec->dev);
596		if (r) {
597			ti->error = "FEC device lookup failed";
598			return r;
599		}
600
601	} else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_BLOCKS)) {
602		if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
603		    ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
604		     >> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
605			ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
606			return -EINVAL;
607		}
608		v->fec->blocks = num_ll;
609
610	} else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_START)) {
611		if (sscanf(arg_value, "%llu%c", &num_ll, &dummy) != 1 ||
612		    ((sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) >>
613		     (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll)) {
614			ti->error = "Invalid " DM_VERITY_OPT_FEC_START;
615			return -EINVAL;
616		}
617		v->fec->start = num_ll;
618
619	} else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS)) {
620		if (sscanf(arg_value, "%hhu%c", &num_c, &dummy) != 1 || !num_c ||
621		    num_c < (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MAX_RSN) ||
622		    num_c > (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN)) {
623			ti->error = "Invalid " DM_VERITY_OPT_FEC_ROOTS;
624			return -EINVAL;
625		}
626		v->fec->roots = num_c;
627
628	} else {
629		ti->error = "Unrecognized verity FEC feature request";
630		return -EINVAL;
631	}
632
633	return 0;
634}
635
636/*
637 * Allocate dm_verity_fec for v->fec. Must be called before verity_fec_ctr.
638 */
639int verity_fec_ctr_alloc(struct dm_verity *v)
640{
641	struct dm_verity_fec *f;
642
643	f = kzalloc(sizeof(struct dm_verity_fec), GFP_KERNEL);
644	if (!f) {
645		v->ti->error = "Cannot allocate FEC structure";
646		return -ENOMEM;
647	}
648	v->fec = f;
649
650	return 0;
651}
652
653/*
654 * Validate arguments and preallocate memory. Must be called after arguments
655 * have been parsed using verity_fec_parse_opt_args.
656 */
657int verity_fec_ctr(struct dm_verity *v)
658{
659	struct dm_verity_fec *f = v->fec;
660	struct dm_target *ti = v->ti;
661	u64 hash_blocks, fec_blocks;
662	int ret;
663
664	if (!verity_fec_is_enabled(v)) {
665		verity_fec_dtr(v);
666		return 0;
667	}
668
669	/*
670	 * FEC is computed over data blocks, possible metadata, and
671	 * hash blocks. In other words, FEC covers total of fec_blocks
672	 * blocks consisting of the following:
673	 *
674	 *  data blocks | hash blocks | metadata (optional)
675	 *
676	 * We allow metadata after hash blocks to support a use case
677	 * where all data is stored on the same device and FEC covers
678	 * the entire area.
679	 *
680	 * If metadata is included, we require it to be available on the
681	 * hash device after the hash blocks.
682	 */
683
684	hash_blocks = v->hash_blocks - v->hash_start;
685
686	/*
687	 * Require matching block sizes for data and hash devices for
688	 * simplicity.
689	 */
690	if (v->data_dev_block_bits != v->hash_dev_block_bits) {
691		ti->error = "Block sizes must match to use FEC";
692		return -EINVAL;
693	}
694
695	if (!f->roots) {
696		ti->error = "Missing " DM_VERITY_OPT_FEC_ROOTS;
697		return -EINVAL;
698	}
699	f->rsn = DM_VERITY_FEC_RSM - f->roots;
700
701	if (!f->blocks) {
702		ti->error = "Missing " DM_VERITY_OPT_FEC_BLOCKS;
703		return -EINVAL;
704	}
705
706	f->rounds = f->blocks;
707	if (sector_div(f->rounds, f->rsn))
708		f->rounds++;
709
710	/*
711	 * Due to optional metadata, f->blocks can be larger than
712	 * data_blocks and hash_blocks combined.
713	 */
714	if (f->blocks < v->data_blocks + hash_blocks || !f->rounds) {
715		ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS;
716		return -EINVAL;
717	}
718
719	/*
720	 * Metadata is accessed through the hash device, so we require
721	 * it to be large enough.
722	 */
723	f->hash_blocks = f->blocks - v->data_blocks;
724	if (dm_bufio_get_device_size(v->bufio) < f->hash_blocks) {
725		ti->error = "Hash device is too small for "
726			DM_VERITY_OPT_FEC_BLOCKS;
727		return -E2BIG;
728	}
729
730	f->io_size = 1 << v->data_dev_block_bits;
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	/* Preallocate an output buffer for each thread */
787	ret = mempool_init_kmalloc_pool(&f->output_pool, num_online_cpus(),
788					1 << v->data_dev_block_bits);
789	if (ret) {
790		ti->error = "Cannot allocate FEC output pool";
791		return ret;
792	}
793
794	/* Reserve space for our per-bio data */
795	ti->per_io_data_size += sizeof(struct dm_verity_fec_io);
796
797	return 0;
798}