mem_charge
u64 mem_charge; /* Copy of mem charged to owner. Protected by "lock" */
local_storage->mem_charge -= uncharge;
local_storage->mem_charge += smap->elem_size;
err = mem_charge(smap, owner, sizeof(*storage));
storage->mem_charge = sizeof(*storage);
if (mem_charge(smap, owner, smap->elem_size))
return local_storage->mem_charge;