Instead do the actual left and right shift work in the callers, and just
keep a helper to update the bmap and rmap btrees as well as the in-core
extent list.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>