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dm-verity-fec: improve comments for fec_read_bufs()

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Update the comments in and above fec_read_bufs() to more clearly
describe what it does.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This commit is contained in:
Eric Biggers 2026-02-05 20:59:41 -08:00 committed by Mikulas Patocka
parent d0829329de
commit 4f6d6fb3a6
1 changed files with 22 additions and 8 deletions
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30
drivers/md/dm-verity-fec.c
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@ -154,8 +154,21 @@ static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io,
}
/*
* 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,
@ -178,11 +191,11 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
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;
@ -231,8 +244,9 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
}
/*
* 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) {