From 41208f3707e97976f3b1b7c36c4c094e05e5cf1d Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Thu, 5 Feb 2026 20:59:31 -0800 Subject: [PATCH] dm-verity-fec: rename rounds to region_blocks It's hard to reconcile the value stored in dm_verity_fec::rounds with its name and documentation. Most likely "rounds" is being used as an alias for what is more commonly called the interleaving degree or "number of ways". But the interleaving is done at the byte level, whereas the units of "rounds" are blocks. So it's not really that. In practice, the reason the code needs this value is that it expresses the number of blocks in each "region" of the message data, where each region contains the bytes from a particular index in the RS codewords. Rename it to region_blocks to make the code a bit more understandable. Signed-off-by: Eric Biggers Signed-off-by: Mikulas Patocka --- drivers/md/dm-verity-fec.c | 16 ++++++++-------- drivers/md/dm-verity-fec.h | 2 +- 2 files changed, 9 insertions(+), 9 deletions(-) diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c index 1251d45f6f85..d132fd5dc7b4 100644 --- a/drivers/md/dm-verity-fec.c +++ b/drivers/md/dm-verity-fec.c @@ -31,7 +31,7 @@ static inline u64 fec_interleave(struct dm_verity *v, u64 offset) u32 mod; mod = do_div(offset, v->fec->rs_k); - return offset + mod * (v->fec->rounds << v->data_dev_block_bits); + return offset + mod * (v->fec->region_blocks << v->data_dev_block_bits); } /* Loop over each allocated buffer. */ @@ -405,13 +405,13 @@ int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io, */ offset = block << v->data_dev_block_bits; - res = div64_u64(offset, v->fec->rounds << v->data_dev_block_bits); + res = div64_u64(offset, v->fec->region_blocks << v->data_dev_block_bits); /* * The base RS block we can feed to the interleaver to find out all * blocks required for decoding. */ - rsb = offset - res * (v->fec->rounds << v->data_dev_block_bits); + rsb = offset - res * (v->fec->region_blocks << v->data_dev_block_bits); /* * Locating erasures is slow, so attempt to recover the block without @@ -659,15 +659,15 @@ int verity_fec_ctr(struct dm_verity *v) return -EINVAL; } - f->rounds = f->blocks; - if (sector_div(f->rounds, f->rs_k)) - f->rounds++; + f->region_blocks = f->blocks; + if (sector_div(f->region_blocks, f->rs_k)) + f->region_blocks++; /* * Due to optional metadata, f->blocks can be larger than * data_blocks and hash_blocks combined. */ - if (f->blocks < v->data_blocks + hash_blocks || !f->rounds) { + if (f->blocks < v->data_blocks + hash_blocks || !f->region_blocks) { ti->error = "Invalid " DM_VERITY_OPT_FEC_BLOCKS; return -EINVAL; } @@ -693,7 +693,7 @@ int verity_fec_ctr(struct dm_verity *v) dm_bufio_set_sector_offset(f->bufio, f->start << (v->data_dev_block_bits - SECTOR_SHIFT)); - if (dm_bufio_get_device_size(f->bufio) < f->rounds * f->roots) { + if (dm_bufio_get_device_size(f->bufio) < f->region_blocks * f->roots) { ti->error = "FEC device is too small"; return -E2BIG; } diff --git a/drivers/md/dm-verity-fec.h b/drivers/md/dm-verity-fec.h index 49d43894ea74..50b5e187d5cc 100644 --- a/drivers/md/dm-verity-fec.h +++ b/drivers/md/dm-verity-fec.h @@ -32,7 +32,7 @@ struct dm_verity_fec { size_t block_size; /* size of data, hash, and parity blocks in bytes */ sector_t start; /* parity data start in blocks */ sector_t blocks; /* number of blocks covered */ - sector_t rounds; /* number of interleaving rounds */ + sector_t region_blocks; /* blocks per region: ceil(blocks / rs_k) */ sector_t hash_blocks; /* blocks covered after v->hash_start */ unsigned char roots; /* parity bytes per RS codeword, n-k of RS(n, k) */ unsigned char rs_k; /* message bytes per RS codeword, k of RS(n, k) */