ext4: test partial blocksize defrag integrity issue

ext4: test partial blocksize defrag integrity issue

Calling EXT4_IOC_MOVE_EXTENT on file not aligned with block size and
block size is smaller than page size would cause integrity issue on the
partial-blocksize part when copying data between orign file and donor
file.

This ext4 kernel patch would fix it, titled
"ext4: don't read blocks from disk after extents being swapped in
move_extent_per_page())"

Though this bug only happens in the blocksize smaller than pagesize
case, there's no harm to test on various block size fs, so no block size
is specified in the test, it depends on the test configurations.

Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>