Commit 4f6d6fb3 authored by Eric Biggers's avatar Eric Biggers Committed by Mikulas Patocka
Browse files

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



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

Signed-off-by: default avatarEric Biggers <ebiggers@kernel.org>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
parent d0829329

drivers/md/dm-verity-fec.c

+22 −8
Original line number Diff line number Diff line
@@ -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;



	for (i = 0; i < v->fec->rs_k; i++) {

		/*

	 * read each of the rs_k data blocks that are part of the RS block, and

	 * interleave contents to available bufs

		 * Read the block from region i.  It contains the i'th message

		 * byte of the target block's RS codewords.

		 */

	for (i = 0; i < v->fec->rs_k; i++) {

		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) {