diff --git a/src/virtual_memory.rs b/src/virtual_memory.rs
index af87e20..97bd74c 100644
--- a/src/virtual_memory.rs
+++ b/src/virtual_memory.rs
@@ -1,18 +1,24 @@
-use std::ptr::{NonNull, null};
-
 pub unsafe trait VirtualMemoryApi: Sized + Drop {
-    type Reservation: Reservation;
+    type Reservation<'s>: Reservation + 's
+    where
+        Self: 's;
 
     fn getPageSize(&self) -> usize;
 
-    fn reserveMemory(
-        &mut self,
-        extend: Option<&Self::Reservation>,
+    fn reserveMemory<'s>(
+        &'s self,
+        extend: ReservationToExtend<&Self::Reservation<'s>>,
         pagesCount: usize,
-    ) -> Self::Reservation;
+    ) -> Option<Self::Reservation<'s>>;
+}
+
+pub enum ReservationToExtend<T> {
+    ReserveAnywhere,
+    TryExtend(T),
 }
 
 pub unsafe trait Reservation: Sized + Ord + Drop {
-    fn commitPages(&mut self, indexOfFirst: usize, count: usize) -> *mut [u8];
-    fn decommitPages(&mut self, indexOfFirst: usize, count: usize);
+    unsafe fn commitPages(&mut self, indexOfFirst: usize, count: usize) -> *mut [u8];
+    unsafe fn decommitPages(&mut self, indexOfFirst: usize, count: usize);
+    unsafe fn release(self);
 }