tree 8baed3606be67900df9f02e42fcdb091b78c5def
parent 7d76345da6ed3927c9cbf5d3f7a7021e8bba7374
author Andi Kleen <ak@suse.de> 1231211109 +0000
committer Alasdair G Kergon <agk@redhat.com> 1231211109 +0000

dm: support barriers on simple devices

Implement barrier support for single device DM devices

This patch implements barrier support in DM for the common case of dm linear
just remapping a single underlying device. In this case we can safely
pass the barrier through because there can be no reordering between
devices.

 NB. Any DM device might cease to support barriers if it gets
     reconfigured so code must continue to allow for a possible
     -EOPNOTSUPP on every barrier bio submitted.  - agk

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>