int do_lo_send_write (struct loop_device * lo, struct bio_vec * bvec, int bsize, loff_t pos, struct page * page);
This is the slow, transforming version for filesystems which do not implement the address space operations prepare_write and commit_write. It uses the write file operation which should be present on all writeable filesystems.
Using fops->write is slower than using aops->{prepare,commit}_write in the transforming case because we need to double buffer the data as we cannot do the transformations in place as we do not have direct access to the destination pages of the backing file.