talos-op-linux/Documentation/device-mapper, branch v3.5

dm: verity fix documentation

2012-07-03T11:55:41+00:00

Veritysetup is now part of cryptsetup package. Remove on-disk header description (which is not parsed in kernel) and point users to cryptsetup where it the format is documented. Mention units for block size paramaters. Fix target line specification and dmsetup parameters. Signed-off-by: Milan Broz Cc: stable@kernel.org Signed-off-by: Alasdair G Kergon

dm thin: provide userspace access to pool metadata

2012-06-02T23:30:01+00:00

This patch implements two new messages that can be sent to the thin pool target allowing it to take a snapshot of the _metadata_. This, read-only snapshot can be accessed by userland, concurrently with the live target. Only one metadata snapshot can be held at a time. The pool's status line will give the block location for the current msnap. Since version 0.1.5 of the userland thin provisioning tools, the thin_dump program displays the msnap as follows: thin_dump -m Available here: https://github.com/jthornber/thin-provisioning-tools Now that userland can access the metadata we can do various things that have traditionally been kernel side tasks: i) Incremental backups. By using metadata snapshots we can work out what blocks have changed over time. Combined with data snapshots we can ensure the data doesn't change while we back it up. A short proof of concept script can be found here: https://github.com/jthornber/thinp-test-suite/blob/master/incremental_backup_example.rb ii) Migration of thin devices from one pool to another. iii) Merging snapshots back into an external origin. iv) Asyncronous replication. Signed-off-by: Joe Thornber Signed-off-by: Alasdair G Kergon

dm: add verity target

2012-03-28T17:43:38+00:00

This device-mapper target creates a read-only device that transparently validates the data on one underlying device against a pre-generated tree of cryptographic checksums stored on a second device. Two checksum device formats are supported: version 0 which is already shipping in Chromium OS and version 1 which incorporates some improvements. Signed-off-by: Mikulas Patocka Signed-off-by: Mandeep Singh Baines Signed-off-by: Will Drewry Signed-off-by: Elly Jones Cc: Milan Broz Cc: Olof Johansson Cc: Steffen Klassert Cc: Andrew Morton Signed-off-by: Alasdair G Kergon

dm thin: add pool target flags to control discard

2012-03-28T17:41:29+00:00

Add dm thin target arguments to control discard support. ignore_discard: Disables discard support no_discard_passdown: Don't pass discards down to the underlying data device, but just remove the mapping within the thin provisioning target. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon

dm thin: support read only external snapshot origins

2012-03-28T17:41:28+00:00

Support the use of an external _read only_ device as an origin for a thin device. Any read to an unprovisioned area of the thin device will be passed through to the origin. Writes trigger allocation of new blocks as usual. One possible use case for this would be VM hosts that want to run guests on thinly-provisioned volumes but have the base image on another device (possibly shared between many VMs). Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon

dm thin: relax hard limit on the maximum size of a metadata device

2012-03-28T17:41:28+00:00

The thin metadata format can only make use of a device that is <= THIN_METADATA_MAX_SECTORS (currently 15.9375 GB). Therefore, there is no practical benefit to using a larger device. However, it may be that other factors impose a certain granularity for the space that is allocated to a device (E.g. lvm2 can impose a coarse granularity through the use of large, >= 1 GB, physical extents). Rather than reject a larger metadata device, during thin-pool device construction, switch to allowing it but issue a warning if a device larger than THIN_METADATA_MAX_SECTORS_WARNING (16 GB) is provided. Any space over 15.9375 GB will not be used. Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon

dm thin: correct comments

2012-03-28T17:41:24+00:00

Remove documentation for unimplemented 'trim' message. I'd planned a 'trim' target message for shrinking thin devices, but this is better handled via the discard ioctl. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon

Documentation: Fix multiple typo in Documentation

2012-03-07T15:08:24+00:00

Signed-off-by: Masanari Iida Acked-by: Randy Dunlap Signed-off-by: Jiri Kosina

Documentation: Fix typo in thin-provisioning.txt

2012-02-21T10:40:37+00:00

Correct spelling "descibes" to "describes" in Documentation/device-mapper/thin-provisioning.txt Signed-off-by: Masanari Iida Signed-off-by: Jiri Kosina

dm log userspace: fix comment hyphens

2011-10-31T20:21:22+00:00

Fix comments: clustered-disk needs a hyphen not an underscore. Signed-off-by: Jonathan Brassow Signed-off-by: Alasdair G Kergon