+ struct llist_header head; // must be first field!
+ struct proc_mm* proc_vms;
+
+ // file mapped to this region
+ struct v_file* mfile;
+ // mapped file offset
+ off_t foff;
+ // mapped file length
+
+ ptr_t start;
+ ptr_t end;
+ u32_t attr;
+ size_t flen;
+
+ void** index; // fast reference, to accelerate access to this very region.
+
+ void* data;
+ // when a region is copied
+ void (*region_copied)(struct mm_region*);
+ // when a region is unmapped
+ void (*destruct_region)(struct mm_region*);