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dm-verity-fec: compute target region directly

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Instead of determining the target block's region by checking which block
of the k blocks being iterated over in fec_read_bufs() is equal to the
target block, instead just directly use the quotient of the division of
target_block by region_blocks.

This is the same value, just derived in a more straightforward way.

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 20:59:37 -08:00 committed by Mikulas Patocka
parent ca0da6cc09
commit ca21ed4089
1 changed files with 16 additions and 21 deletions
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37
drivers/md/dm-verity-fec.c
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@ -49,8 +49,8 @@ static inline u8 *fec_buffer_rs_message(struct dm_verity *v,
* the corrected bytes into fio->output starting from out_pos.
*/
static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
struct dm_verity_fec_io *fio, u64 rsb, int byte_index,
unsigned int out_pos, int neras)
struct dm_verity_fec_io *fio, u64 rsb,
int target_region, unsigned int out_pos, int neras)
{
int r, corrected = 0, res;
struct dm_buffer *buf;
@ -120,7 +120,7 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
}
corrected += res;
fio->output[out_pos++] = msg_buf[byte_index];
fio->output[out_pos++] = msg_buf[target_region];
if (out_pos >= v->fec->block_size)
goto done;
@ -158,10 +158,10 @@ static int fec_is_erasure(struct dm_verity *v, struct dm_verity_io *io,
* fits into buffers. Check for erasure locations if @neras is non-NULL.
*/
static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
u64 rsb, u64 target, unsigned int out_pos, int *neras)
u64 rsb, unsigned int out_pos, int *neras)
{
bool is_zero;
int i, j, target_index = -1;
int i, j;
struct dm_buffer *buf;
struct dm_bufio_client *bufio;
struct dm_verity_fec_io *fio = io->fec_io;
@ -183,14 +183,6 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
*/
for (i = 0; i < v->fec->rs_k; i++) {
ileaved = rsb + i * (v->fec->region_blocks << v->data_dev_block_bits);
/*
* target is the data block we want to correct, target_index is
* the index of this block within the rs_k RS blocks
*/
if (ileaved == target)
target_index = i;
block = ileaved >> v->data_dev_block_bits;
bufio = v->fec->data_bufio;
@ -252,8 +244,7 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
done:
dm_bufio_release(buf);
}
return target_index;
return 0;
}
/*
@ -320,22 +311,26 @@ static int fec_decode(struct dm_verity *v, struct dm_verity_io *io,
const u8 *want_digest, bool use_erasures)
{
int r, neras = 0;
unsigned int out_pos;
u64 offset = target_block << v->data_dev_block_bits;
unsigned int target_region, out_pos;
u64 rsb;
div64_u64_rem(offset, v->fec->region_blocks << v->data_dev_block_bits,
&rsb);
target_region = div64_u64_rem(
target_block << v->data_dev_block_bits,
v->fec->region_blocks << v->data_dev_block_bits, &rsb);
if (WARN_ON_ONCE(target_region >= v->fec->rs_k))
/* target_block is out-of-bounds. Should never happen. */
return -EIO;
for (out_pos = 0; out_pos < v->fec->block_size;) {
fec_init_bufs(v, fio);
r = fec_read_bufs(v, io, rsb, offset, out_pos,
r = fec_read_bufs(v, io, rsb, out_pos,
use_erasures ? &neras : NULL);
if (unlikely(r < 0))
return r;
r = fec_decode_bufs(v, io, fio, rsb, r, out_pos, neras);
r = fec_decode_bufs(v, io, fio, rsb, target_region,
out_pos, neras);
if (r < 0)
return r;