Factor a helper to calculate the extent-size aligned block out of the
iomap code, so that it can be reused by the upcoming reflink dio code.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>