Commit 8ef45923 authored by Eric Biggers's avatar Eric Biggers Committed by Mikulas Patocka
Browse files

dm-verity-fec: simplify computation of rsb 



To compute 'rsb', verity_fec_decode() divides 'offset' by
'v->fec->region_blocks << v->data_dev_block_bits', then subtracts the
quotient times that divisor.  That's simply the long way to do a modulo
operation, i.e. a - b * floor(a / b) instead of just a % b.  Use
div64_u64_rem() to get the remainder more concisely.

Signed-off-by: default avatarEric Biggers <ebiggers@kernel.org>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
parent 41208f37

drivers/md/dm-verity-fec.c

+3 −3
Original line number Diff line number Diff line
@@ -377,7 +377,7 @@ int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io, 
{

	int r;

	struct dm_verity_fec_io *fio;

	u64 offset, res, rsb;

	u64 offset, rsb;



	if (!verity_fec_is_enabled(v))

		return -EOPNOTSUPP;
@@ -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->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->region_blocks << v->data_dev_block_bits);

	div64_u64_rem(offset, v->fec->region_blocks << v->data_dev_block_bits,

		      &rsb);



	/*

	 * Locating erasures is slow, so attempt to recover the block without