bio_list_size
zwp_bio_list_size = bio_list_size(&zwplug->bio_list);
ASSERT(bio_list_size(bio_list) == 0);
atomic_set(&rbio->stripes_pending, bio_list_size(bio_list));
atomic_set(&rbio->stripes_pending, bio_list_size(bio_list));
ASSERT(bio_list_size(&bio_list));