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| author | Sami Tolvanen <samitolvanen@google.com> | 2015-12-03 14:26:30 +0000 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2015-12-10 10:39:03 -0500 |
| commit | a739ff3f543afbb4a041c16cd0182c8e8d366e70 (patch) | |
| tree | 2613a382283548a1b88e6f2ba589252312d05fff /drivers/md/dm-verity.h | |
| parent | bb4d73ac5e4f0a6c4853f35824f6cb2d396a2f9c (diff) | |
| download | op-kernel-dev-a739ff3f543afbb4a041c16cd0182c8e8d366e70.zip op-kernel-dev-a739ff3f543afbb4a041c16cd0182c8e8d366e70.tar.gz | |
dm verity: add support for forward error correction
Add support for correcting corrupted blocks using Reed-Solomon.
This code uses RS(255, N) interleaved across data and hash
blocks. Each error-correcting block covers N bytes evenly
distributed across the combined total data, so that each byte is a
maximum distance away from the others. This makes it possible to
recover from several consecutive corrupted blocks with relatively
small space overhead.
In addition, using verity hashes to locate erasures nearly doubles
the effectiveness of error correction. Being able to detect
corrupted blocks also improves performance, because only corrupted
blocks need to corrected.
For a 2 GiB partition, RS(255, 253) (two parity bytes for each
253-byte block) can correct up to 16 MiB of consecutive corrupted
blocks if erasures can be located, and 8 MiB if they cannot, with
16 MiB space overhead.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm-verity.h')
| -rw-r--r-- | drivers/md/dm-verity.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h index f5af52d..8e85372 100644 --- a/drivers/md/dm-verity.h +++ b/drivers/md/dm-verity.h @@ -29,6 +29,8 @@ enum verity_block_type { DM_VERITY_BLOCK_TYPE_METADATA }; +struct dm_verity_fec; + struct dm_verity { struct dm_dev *data_dev; struct dm_dev *hash_dev; @@ -58,6 +60,8 @@ struct dm_verity { /* starting blocks for each tree level. 0 is the lowest level. */ sector_t hash_level_block[DM_VERITY_MAX_LEVELS]; + + struct dm_verity_fec *fec; /* forward error correction */ }; struct dm_verity_io { @@ -103,6 +107,12 @@ static inline u8 *verity_io_want_digest(struct dm_verity *v, return (u8 *)(io + 1) + v->shash_descsize + v->digest_size; } +static inline u8 *verity_io_digest_end(struct dm_verity *v, + struct dm_verity_io *io) +{ + return verity_io_want_digest(v, io) + v->digest_size; +} + extern int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io, struct bvec_iter *iter, int (*process)(struct dm_verity *v, |
