Commit 548c6edb authored by Milan Broz's avatar Milan Broz Committed by Mikulas Patocka
Browse files

dm-verity FEC: Avoid copying RS parity bytes twice. 



Caching RS parity bytes is already done in fec_decode_bufs() now,
no need to use yet another buffer for conversion to uint16_t.

This patch removes that double copy of RS parity bytes.

Signed-off-by: default avatarMilan Broz <gmazyland@gmail.com>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
parent 6df90c02

drivers/md/dm-verity-fec.c

+10 −21
Original line number Diff line number Diff line
@@ -39,22 +39,6 @@ static inline u64 fec_interleave(struct dm_verity *v, u64 offset) 
	return offset + mod * (v->fec->rounds << v->data_dev_block_bits);

}



/*

 * Decode an RS block using Reed-Solomon.

 */

static int fec_decode_rs8(struct dm_verity *v, struct dm_verity_fec_io *fio,

			  u8 *data, u8 *fec, int neras)

{

	int i;

	uint16_t par[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN];



	for (i = 0; i < v->fec->roots; i++)

		par[i] = fec[i];



	return decode_rs8(fio->rs, data, par, v->fec->rsn, NULL, neras,

			  fio->erasures, 0, NULL);

}



/*

 * Read error-correcting codes for the requested RS block. Returns a pointer

 * to the data block. Caller is responsible for releasing buf.
@@ -132,8 +116,9 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io, 
{

	int r, corrected = 0, res;

	struct dm_buffer *buf;

	unsigned int n, i, offset, par_buf_offset = 0;

	u8 *par, *block, par_buf[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN];

	unsigned int n, i, j, offset, par_buf_offset = 0;

	uint16_t par_buf[DM_VERITY_FEC_RSM - DM_VERITY_FEC_MIN_RSN];

	u8 *par, *block;

	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);



	par = fec_read_parity(v, rsb, block_offset, &offset,
@@ -147,8 +132,11 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io, 
	 */

	fec_for_each_buffer_rs_block(fio, n, i) {

		block = fec_buffer_rs_block(v, fio, n, i);

		memcpy(&par_buf[par_buf_offset], &par[offset], v->fec->roots - par_buf_offset);

		res = fec_decode_rs8(v, fio, block, par_buf, neras);

		for (j = 0; j < v->fec->roots - par_buf_offset; j++)

			par_buf[par_buf_offset + j] = par[offset + j];

		/* Decode an RS block using Reed-Solomon */

		res = decode_rs8(fio->rs, block, par_buf, v->fec->rsn,

				 NULL, neras, fio->erasures, 0, NULL);

		if (res < 0) {

			r = res;

			goto error;
@@ -166,7 +154,8 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_io *io, 
		/* Check if parity bytes are split between blocks */

		if (offset < v->fec->io_size && (offset + v->fec->roots) > v->fec->io_size) {

			par_buf_offset = v->fec->io_size - offset;

			memcpy(par_buf, &par[offset], par_buf_offset);

			for (j = 0; j < par_buf_offset; j++)

				par_buf[j] = par[offset + j];

			offset += par_buf_offset;

		} else

			par_buf_offset = 0;