Factor out helper with some checks on in/out file that are
common to clone_file_range and copy_file_range.
Suggested-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NAmir Goldstein <amir73il@gmail.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>