Introduce an alternate mode of operation where dm-integrity uses a
bitmap instead of a journal. If a bit in the bitmap is 1, the
corresponding region's data and integrity tags are not synchronized - if
the machine crashes, the unsynchronized regions will be recalculated.
The bitmap mode is faster than the journal mode, because we don't have
to write the data twice, but it is also less reliable, because if data
corruption happens when the machine crashes, it may not be detected.
Benchmark results for an SSD connected to a SATA300 port, when doing
large linear writes with dd:
buffered I/O:
raw device throughput - 245MB/s
dm-integrity with journaling - 120MB/s
dm-integrity with bitmap - 238MB/s
direct I/O with 1MB block size:
raw device throughput - 248MB/s
dm-integrity with journaling - 123MB/s
dm-integrity with bitmap - 223MB/s
For more info see dm-integrity in Documentation/device-mapper/
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Update documentation with the "meta_device" parameter and flags.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
When using external metadata device and internal hash, recalculate the
checksums when the device is created - so that dm-integrity doesn't
have to overwrite the device. The superblock stores the last position
when the recalculation ended, so that it is properly restarted.
Integrity tags that haven't been recalculated yet are ignored.
Also bump the target version.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The DM integrity block size can now be 512, 1k, 2k or 4k. Using larger
blocks reduces metadata handling overhead. The block size can be
configured at table load time using the "block_size:<value>" option;
where <value> is expressed in bytes (defult is still 512 bytes).
It is safe to use larger block sizes with DM integrity, because the
DM integrity journal makes sure that the whole block is updated
atomically even if the underlying device doesn't support atomic writes
of that size (e.g. 4k block ontop of a 512b device).
Depends-on: 2859323e ("block: fix blk_integrity_register to use template's interval_exp if not 0")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Some coding style changes.
Fix a bug that the array test_tag has insufficient size if the digest
size of internal has is bigger than the tag size.
The function __fls is undefined for zero argument, this patch fixes
undefined behavior if the user sets zero interleave_sectors.
Fix the limit of optional arguments to 8.
Don't allocate crypt_data on the stack to avoid a BUG with debug kernel.
Rename all optional argument names to have underscores rather than
dashes.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
In recovery mode, we don't:
- replay the journal
- check checksums
- allow writes to the device
This mode can be used as a last resort for data recovery. The
motivation for recovery mode is that when there is a single error in the
journal, the user should not lose access to the whole device.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
The dm-integrity target emulates a block device that has additional
per-sector tags that can be used for storing integrity information.
A general problem with storing integrity tags with every sector is that
writing the sector and the integrity tag must be atomic - i.e. in case of
crash, either both sector and integrity tag or none of them is written.
To guarantee write atomicity the dm-integrity target uses a journal. It
writes sector data and integrity tags into a journal, commits the journal
and then copies the data and integrity tags to their respective location.
The dm-integrity target can be used with the dm-crypt target - in this
situation the dm-crypt target creates the integrity data and passes them
to the dm-integrity target via bio_integrity_payload attached to the bio.
In this mode, the dm-crypt and dm-integrity targets provide authenticated
disk encryption - if the attacker modifies the encrypted device, an I/O
error is returned instead of random data.
The dm-integrity target can also be used as a standalone target, in this
mode it calculates and verifies the integrity tag internally. In this
mode, the dm-integrity target can be used to detect silent data
corruption on the disk or in the I/O path.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
