Commit ca21ed40 authored by Eric Biggers's avatar Eric Biggers Committed by Mikulas Patocka
Browse files

dm-verity-fec: compute target region directly 



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: default avatarEric Biggers <ebiggers@kernel.org>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
parent ca0da6cc

drivers/md/dm-verity-fec.c

+16 −21
Original line number Diff line number Diff line
@@ -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;