We only allow non critical writeback if the origin is idle. It is up
to the policy to decide what writeback work is critical.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
There is a race between a policy deciding to replace a cache entry,
the core target writing back any dirty data from this block, and other
IO threads doing IO to the same block.
This sort of problem is avoided most of the time by the core target
grabbing a bio prison cell before making the request to the policy.
But for a demotion the core target doesn't know which block will be
demoted, so can't do this in advance.
Fix this demotion race by introducing a callback to the policy interface
that allows the policy to grab the cell on behalf of the core target.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Separate dm cache policy version string into 3 unsigned numbers
corresponding to major, minor and patchlevel and store them at the end
of the on-disk metadata so we know which version of the policy generated
the hints in case a future version wants to use them differently.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
A simple cache policy that writes back all data to the origin.
This is used to decommission a dm cache by emptying it.
Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
