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dm-verity-fec: replace {MAX,MIN}_RSN with {MIN,MAX}_ROOTS

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Every time DM_VERITY_FEC_{MAX,MIN}_RSN are used, they are subtracted
from DM_VERITY_FEC_RSM to get the bounds on the number of roots.
Therefore, replace these with {MIN,MAX}_ROOTS constants which are more
directly useful.  (Note the inversion, where MAX_RSN maps to MIN_ROOTS
and MIN_RSN maps to MAX_ROOTS.)  No functional change.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This commit is contained in:
Eric Biggers
2026-03-09 15:11:59 +01:00
committed by Mikulas Patocka
parent 05777b2800
commit 82fbd6a3e2
2 changed files with 6 additions and 7 deletions
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drivers/md/dm-verity-fec.c
+3 -3
View File
@@ -73,7 +73,7 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
int r, corrected = 0, res;
struct dm_buffer *buf;
unsigned int n, i, j, parity_pos, to_copy;
uint16_t par_buf[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN];
uint16_t par_buf[DM_VERITY_FEC_MAX_ROOTS];
u8 *par, *block;
u64 parity_block;
struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
@@ -572,8 +572,8 @@ int verity_fec_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
} else if (!strcasecmp(arg_name, DM_VERITY_OPT_FEC_ROOTS)) {
if (sscanf(arg_value, "%hhu%c", &num_c, &dummy) != 1 || !num_c ||
num_c < (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MAX_RSN) ||
num_c > (DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN)) {
num_c < DM_VERITY_FEC_MIN_ROOTS ||
num_c > DM_VERITY_FEC_MAX_ROOTS) {
ti->error = "Invalid " DM_VERITY_OPT_FEC_ROOTS;
return -EINVAL;
}
drivers/md/dm-verity-fec.h
+3 -4
View File
@@ -13,8 +13,8 @@
/* Reed-Solomon(M, N) parameters */
#define DM_VERITY_FEC_RSM 255
#define DM_VERITY_FEC_MAX_RSN 253
#define DM_VERITY_FEC_MIN_RSN 231 /* ~10% space overhead */
#define DM_VERITY_FEC_MIN_ROOTS 2 /* RS(255, 253): ~0.8% space overhead */
#define DM_VERITY_FEC_MAX_ROOTS 24 /* RS(255, 231): ~10% space overhead */
/* buffers for deinterleaving and decoding */
#define DM_VERITY_FEC_BUF_RS_BITS 4 /* 1 << RS blocks per buffer */
@@ -47,8 +47,7 @@ struct dm_verity_fec {
/* per-bio data */
struct dm_verity_fec_io {
struct rs_control *rs; /* Reed-Solomon state */
/* erasures for decode_rs8 */
int erasures[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN + 1];
int erasures[DM_VERITY_FEC_MAX_ROOTS + 1]; /* erasures for decode_rs8 */
u8 *output; /* buffer for corrected output */
unsigned int level; /* recursion level */
unsigned int nbufs; /* number of buffers allocated */