Do struct mm_struct have a unique id that could be used as ASID (Address Space ID) ?

[William Tambe <tambewilliam@xxxxxxxxx>]

Do struct mm_struct have a unique id that could be used as ASID
(Address Space ID) ?

For example struct task_struct have a unique id that is stored in its
field "pid", I was wondering whether struct mm_struct have a similar
unique id.