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Message-ID: <20260206045942.52965-20-ebiggers@kernel.org>
Date: Thu, 5 Feb 2026 20:59:38 -0800
From: Eric Biggers <ebiggers@...nel.org>
To: dm-devel@...ts.linux.dev,
Alasdair Kergon <agk@...hat.com>,
Mike Snitzer <snitzer@...nel.org>,
Mikulas Patocka <mpatocka@...hat.com>,
Benjamin Marzinski <bmarzins@...hat.com>
Cc: Sami Tolvanen <samitolvanen@...gle.com>,
linux-kernel@...r.kernel.org,
Eric Biggers <ebiggers@...nel.org>
Subject: [PATCH 19/22] dm-verity-fec: pass down index_in_region instead of rsb
Replace 'rsb', which is a byte index, with 'index_in_region' which is a
block index. The block index is slightly easier to compute, it matches
what fec_read_bufs() wants, and it avoids the mismatch between the name
and the units of the variable. ('rsb' stood for "Reed-Solomon block",
but its units were bytes, not blocks.)
fec_decode_bufs() does want it as a byte index when computing
parity_block, but that's easily handled locally.
As long as the parameters to the log messages are being adjusted, also
eliminate the unnecessary casts to 'unsigned long long'. %llu is the
correct way to print a u64 in the Linux kernel, as documented in
printk-formats.rst. There's no PRIu64 macro like there is in userspace.
Signed-off-by: Eric Biggers <ebiggers@...nel.org>
---
drivers/md/dm-verity-fec.c | 47 +++++++++++++++++++++-----------------
1 file changed, 26 insertions(+), 21 deletions(-)
diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c
index 1b5052ba4f5a5..37c4eb6a11dee 100644
--- a/drivers/md/dm-verity-fec.c
+++ b/drivers/md/dm-verity-fec.c
@@ -47,11 +47,11 @@ static inline u8 *fec_buffer_rs_message(struct dm_verity *v,
/*
* Decode all RS codewords whose message bytes were loaded into fio->bufs. Copy
* 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,
+ struct dm_verity_fec_io *fio, u64 index_in_region,
int target_region, unsigned int out_pos, int neras)
{
int r, corrected = 0, res;
struct dm_buffer *buf;
unsigned int n, i, j, parity_pos, to_copy;
@@ -65,18 +65,20 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
* the starting position in that block. Then read that block.
*
* block_size is always a power of 2, but roots might not be. Note that
* when it's not, a codeword's parity bytes can span a block boundary.
*/
- parity_block = (rsb + out_pos) * v->fec->roots;
+ parity_block = ((index_in_region << v->data_dev_block_bits) + out_pos) *
+ v->fec->roots;
parity_pos = parity_block & (v->fec->block_size - 1);
parity_block >>= v->data_dev_block_bits;
par = dm_bufio_read_with_ioprio(v->fec->bufio, parity_block, &buf,
bio->bi_ioprio);
if (IS_ERR(par)) {
DMERR("%s: FEC %llu: parity read failed (block %llu): %ld",
- v->data_dev->name, rsb, parity_block, PTR_ERR(par));
+ v->data_dev->name, index_in_region, parity_block,
+ PTR_ERR(par));
return PTR_ERR(par);
}
/*
* Decode the RS codewords whose message bytes are in bufs. Each RS
@@ -101,12 +103,12 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
par = dm_bufio_read_with_ioprio(v->fec->bufio,
parity_block, &buf,
bio->bi_ioprio);
if (IS_ERR(par)) {
DMERR("%s: FEC %llu: parity read failed (block %llu): %ld",
- v->data_dev->name, rsb, parity_block,
- PTR_ERR(par));
+ v->data_dev->name, index_in_region,
+ parity_block, PTR_ERR(par));
return PTR_ERR(par);
}
for (; j < v->fec->roots; j++)
par_buf[j] = par[parity_pos++];
}
@@ -130,14 +132,14 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io,
error:
dm_bufio_release(buf);
if (r < 0 && neras)
DMERR_LIMIT("%s: FEC %llu: failed to correct: %d",
- v->data_dev->name, (unsigned long long)rsb, r);
+ v->data_dev->name, index_in_region, r);
else if (r > 0)
DMWARN_LIMIT("%s: FEC %llu: corrected %d errors",
- v->data_dev->name, (unsigned long long)rsb, r);
+ v->data_dev->name, index_in_region, r);
return r;
}
/*
@@ -156,18 +158,18 @@ 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.
*/
static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
- u64 rsb, unsigned int out_pos, int *neras)
+ u64 index_in_region, unsigned int out_pos, int *neras)
{
bool is_zero;
int i, j;
struct dm_buffer *buf;
struct dm_bufio_client *bufio;
struct dm_verity_fec_io *fio = io->fec_io;
- u64 block, ileaved;
+ u64 block;
u8 *bbuf;
u8 want_digest[HASH_MAX_DIGESTSIZE];
unsigned int n, src_pos;
struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
@@ -180,12 +182,11 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
/*
* 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++) {
- ileaved = rsb + i * (v->fec->region_blocks << v->data_dev_block_bits);
- block = ileaved >> v->data_dev_block_bits;
+ block = i * v->fec->region_blocks + index_in_region;
bufio = v->fec->data_bufio;
if (block >= v->data_blocks) {
block -= v->data_blocks;
@@ -201,13 +202,12 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
}
bbuf = dm_bufio_read_with_ioprio(bufio, block, &buf, bio->bi_ioprio);
if (IS_ERR(bbuf)) {
DMWARN_LIMIT("%s: FEC %llu: read failed (%llu): %ld",
- v->data_dev->name,
- (unsigned long long)rsb,
- (unsigned long long)block, PTR_ERR(bbuf));
+ v->data_dev->name, index_in_region, block,
+ PTR_ERR(bbuf));
/* assume the block is corrupted */
if (neras && *neras <= v->fec->roots)
fio->erasures[(*neras)++] = i;
@@ -310,28 +310,33 @@ static int fec_decode(struct dm_verity *v, struct dm_verity_io *io,
struct dm_verity_fec_io *fio, u64 target_block,
const u8 *want_digest, bool use_erasures)
{
int r, neras = 0;
unsigned int target_region, out_pos;
- u64 rsb;
+ u64 index_in_region;
- target_region = div64_u64_rem(
- target_block << v->data_dev_block_bits,
- v->fec->region_blocks << v->data_dev_block_bits, &rsb);
+ /*
+ * Compute 'target_region', the index of the region the target block is
+ * in; and 'index_in_region', the index of the target block within its
+ * region. The latter value is also the index within its region of each
+ * message block that shares its RS codewords with the target block.
+ */
+ target_region = div64_u64_rem(target_block, v->fec->region_blocks,
+ &index_in_region);
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, out_pos,
+ r = fec_read_bufs(v, io, index_in_region, out_pos,
use_erasures ? &neras : NULL);
if (unlikely(r < 0))
return r;
- r = fec_decode_bufs(v, io, fio, rsb, target_region,
+ r = fec_decode_bufs(v, io, fio, index_in_region, target_region,
out_pos, neras);
if (r < 0)
return r;
out_pos += fio->nbufs << DM_VERITY_FEC_BUF_RS_BITS;
@@ -342,11 +347,11 @@ static int fec_decode(struct dm_verity *v, struct dm_verity_io *io,
if (unlikely(r < 0))
return r;
if (memcmp(io->tmp_digest, want_digest, v->digest_size)) {
DMERR_LIMIT("%s: FEC %llu: failed to correct (%d erasures)",
- v->data_dev->name, (unsigned long long)rsb, neras);
+ v->data_dev->name, index_in_region, neras);
return -EILSEQ;
}
return 0;
}
--
2.52.0
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