When src and dst is the same file, and the latter part of source region overlaps with the former part of destination region, current implement will overwrite data which hasn't been moved yet and truncate data in overlapped region. This patch return -EINVAL when such cases occur and return 0 when source region and destination region is actually the same part of the same file. Signed-off-by: Fan li <fanofcode.li@samsung.com> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>