Update the comments in and above fec_read_bufs() to more clearly describe what it does.
Signed-off-by: Eric Biggers <[email protected]> --- drivers/md/dm-verity-fec.c | 30 ++++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-) diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c index fbe01f809aca3..70aa4a20891bc 100644 --- a/drivers/md/dm-verity-fec.c +++ b/drivers/md/dm-verity-fec.c @@ -152,12 +152,25 @@ static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io, return memcmp(io->tmp_digest, want_digest, v->digest_size) != 0; } /* - * Read data blocks that are part of the RS block and deinterleave as much as - * fits into buffers. Check for erasure locations if @neras is non-NULL. + * Read the message block at index @index_in_region within each of the + * @v->fec->rs_k regions and deinterleave their contents into @io->fec_io->bufs. + * + * @target_block gives the index of specific block within this sequence that is + * being corrected, relative to the start of all the FEC message blocks. + * + * @out_pos gives the current output position, i.e. the position in (each) block + * from which to start the deinterleaving. Deinterleaving continues until + * either end-of-block is reached or there's no more buffer space. + * + * If @neras is non-NULL, then also use verity hashes and the presence/absence + * of I/O errors to determine which of the message blocks in the sequence are + * likely to be incorrect. Write the number of such blocks to *@neras and the + * indices of the corresponding RS message bytes in [0, k - 1] to + * @io->fec_io->erasures, up to a limit of @v->fec->roots + 1 such blocks. */ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io, u64 target_block, u64 index_in_region, unsigned int out_pos, int *neras) { @@ -176,15 +189,15 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io, *neras = 0; if (WARN_ON(v->digest_size > sizeof(want_digest))) return -EINVAL; - /* - * read each of the rs_k data blocks that are part of the RS block, and - * interleave contents to available bufs - */ for (i = 0; i < v->fec->rs_k; i++) { + /* + * Read the block from region i. It contains the i'th message + * byte of the target block's RS codewords. + */ block = i * v->fec->region_blocks + index_in_region; bufio = v->fec->data_bufio; if (block >= v->data_blocks) { block -= v->data_blocks; @@ -229,12 +242,13 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io, fec_is_erasure(v, io, want_digest, bbuf)) fio->erasures[(*neras)++] = i; } /* - * deinterleave and copy the bytes that fit into bufs, - * starting from out_pos + * Deinterleave the bytes of the block, starting from 'out_pos', + * into the i'th byte of the RS message buffers. Stop when + * end-of-block is reached or there are no more buffers. */ src_pos = out_pos; fec_for_each_buffer_rs_message(fio, n, j) { if (src_pos >= v->fec->block_size) goto done; -- 2.52.0
