Save space by removing entries from the space map ref_count tree if
they're no longer needed.
Ref counts are stored in two places: a bitmap if the ref_count is
below 3, or a btree of uint32_t if 3 or above.
When a ref_count that was above 3 drops below we can remove it from
the tree and save some metadata space. This removal was commented out
before because I was unsure why this was causing under-populated btree
nodes. Earlier patches have fixed this issue.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
The persistent-data library offers a re-usable framework for the storage
and management of on-disk metadata in device-mapper targets.
It's used by the thin-provisioning target in the next patch and in an
upcoming hierarchical storage target.
For further information, please read
Documentation/device-mapper/persistent-data.txt
Signed-off-by: Joe Thornber <thornber@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Joe Thornber
Joe Thornber