Add a device-mapper target called dm-switch to provide a multipath
framework for storage arrays that dynamically reconfigure their
preferred paths for different device regions.

Fix a bug in the verity target that prevented its use with some
specific sizes of devices.

Improve some locking mechanisms in the device-mapper core and bufio.

Add Mike Snitzer as a device-mapper maintainer.

A few more clean-ups and fixes.
dm: add switch target

dm-switch is a new target that maps IO to underlying block devices
efficiently when there is a large number of fixed-sized address regions
but there is no simple pattern to allow for a compact mapping
representation such as dm-stripe.

Though we have developed this target for a specific storage device, Dell
EqualLogic, we have made an effort to keep it as general purpose as
possible in the hope that others may benefit.

Originally developed by Jim Ramsay. Simplified by Mikulas Patocka.

Signed-off-by: Jim Ramsay <>
Signed-off-by: Mikulas Patocka <>
Signed-off-by: Alasdair G Kergon <>
4 files changed