dm_rh_region_to_sector
from.sector = m->offset + dm_rh_region_to_sector(ms->rh, key);
dest->sector = m->offset + dm_rh_region_to_sector(ms->rh, key);
EXPORT_SYMBOL_GPL(dm_rh_region_to_sector);
sector_t dm_rh_region_to_sector(struct dm_region_hash *rh, region_t region);