The data->size field can be initialized to a lower value than bio->bi_vcnt,
if the bio is split. The bio_for_each_segment then iterates based on the original
indexes and the mismatch eventually causes a BUG_ON.
Fixes#714
Signed-off-by: Kozlowski Mateusz <mateusz.kozlowski@intel.com>
a45f0c854f