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dm-verity-fec: simplify computation of rsb

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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: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This commit is contained in:
Eric Biggers 2026-02-05 20:59:32 -08:00 committed by Mikulas Patocka
parent 41208f3707
commit 8ef45923fd
1 changed files with 3 additions and 3 deletions
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6
drivers/md/dm-verity-fec.c
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@ -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