Add some helpers to assemble a list of fs block extents. Generally,
repair functions will iterate the rmapbt to make a list (1) of all
extents owned by the nominal owner of the metadata structure; then they
will iterate all other structures with the same rmap owner to make a
list (2) of active blocks; and finally we have a subtraction function to
subtract all the blocks in (2) from (1), with the result that (1) is now
a list of blocks that were owned by the old btree and must be disposed.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
64a39d876e