fec_read_bufs() just iterates over a sequence of message blocks with
step size region_blocks. At each step, 'ileaved' is just the offset (in
bytes) to one of these blocks. Compute it in the straightforward way,
eliminating fec_interleave().
In more detail, previously the code computed
'ileaved = (n / k) + (n % k) * (region_blocks * block_size)'
where n = rsb * k + i and 0 <= i < k. Substituting 'n' gives:
ileaved = ((rsb * k + i) / k) + ((rsb * k + i) % k) * region_blocks *
block_size
= rsb + (i * region_blocks * block_size)
The result is more efficient and easier to understand.
Signed-off-by: Eric Biggers <[email protected]>
---
drivers/md/dm-verity-fec.c | 13 +------------
1 file changed, 1 insertion(+), 12 deletions(-)
diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c
index 63eeef26a3999..3122017569718 100644
--- a/drivers/md/dm-verity-fec.c
+++ b/drivers/md/dm-verity-fec.c
@@ -21,21 +21,10 @@
static inline unsigned int fec_max_nbufs(struct dm_verity *v)
{
return 1 << (v->data_dev_block_bits - DM_VERITY_FEC_BUF_RS_BITS);
}
-/*
- * Return an interleaved offset for a byte in RS block.
- */
-static inline u64 fec_interleave(struct dm_verity *v, u64 offset)
-{
- u32 mod;
-
- mod = do_div(offset, v->fec->rs_k);
- return offset + mod * (v->fec->region_blocks << v->data_dev_block_bits);
-}
-
/* Loop over each allocated buffer. */
#define fec_for_each_buffer(io, __i) \
for (__i = 0; __i < (io)->nbufs; __i++)
/* Loop over each RS message in each allocated buffer. */
@@ -202,11 +191,11 @@ 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 = fec_interleave(v, rsb * 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
*/
--
2.52.0
