rbd: simplify rbd_merge_bvec()

			  struct bio_vec *bvec)

{

	struct rbd_device *rbd_dev = q->queuedata;

	unsigned int chunk_sectors;

	sector_t sector;

	unsigned int bio_sectors;

	int max;

	chunk_sectors = 1 << (rbd_dev->header.obj_order - SECTOR_SHIFT);

	sector = bmd->bi_sector + get_start_sect(bmd->bi_bdev);

	bio_sectors = bmd->bi_size >> SECTOR_SHIFT;

	max =  (chunk_sectors - ((sector & (chunk_sectors - 1))

				 + bio_sectors)) << SECTOR_SHIFT;

	if (max < 0)

		max = 0; /* bio_add cannot handle a negative return */

	if (max <= bvec->bv_len && bio_sectors == 0)

		return bvec->bv_len;

	return max;

	sector_t sector_offset;

	sector_t sectors_per_obj;

	sector_t obj_sector_offset;

	int ret;

	/*

	 * Find how far into its rbd object the partition-relative

	 * bio start sector is to offset relative to the enclosing

	 * device.

	 */

	sector_offset = get_start_sect(bmd->bi_bdev) + bmd->bi_sector;

	sectors_per_obj = 1 << (rbd_dev->header.obj_order - SECTOR_SHIFT);

	obj_sector_offset = sector_offset & (sectors_per_obj - 1);

	/*

	 * Compute the number of bytes from that offset to the end

	 * of the object.  Account for what's already used by the bio.

	 */

	ret = (int) (sectors_per_obj - obj_sector_offset) << SECTOR_SHIFT;

	if (ret > bmd->bi_size)

		ret -= bmd->bi_size;

	else

		ret = 0;

	/*

	 * Don't send back more than was asked for.  And if the bio

	 * was empty, let the whole thing through because:  "Note

	 * that a block device *must* allow a single page to be

	 * added to an empty bio."

	 */

	rbd_assert(bvec->bv_len <= PAGE_SIZE);

	if (ret > (int) bvec->bv_len || !bmd->bi_size)

		ret = (int) bvec->bv_len;

	return ret;

}

static void rbd_free_disk(struct rbd_device *rbd_dev)