uvm_unmap() vs. uvm_deallocate()

Hello,

what is the difference between uvm_unmap() and uvm_deallocate()?

It does not become clear to me from what is written in uvm_map(9):


uvm_unmap() removes a valid mapping, from start to end, in map map, which
     must be unlocked.

uvm_deallocate() deallocates kernel memory in map map from address start
     to start + size.


uvm_deallocate() is used e.g. in sysv_shm.c, in which case I would
have expected uvm_unmap().


Thanks,

Stephan