vm: controller: implement asynchronous DETACH page requests

include/kernel/vm-controller.h

@@ -13,13 +13,11 @@ enum page_request_status {
 	PAGE_REQUEST_PENDING = 0,
 	PAGE_REQUEST_IN_PROGRESS,
 	PAGE_REQUEST_COMPLETE,
+	PAGE_REQUEST_ASYNC,
 };
 
 struct vm_controller {
 	struct object vc_base;
-	/* tree of struct vm_objects bound to this controller, keyed with the
-	 * equeue_key_t specified when the object(s) were created. */
-	struct btree vc_objects;
 	/* tree of pending page requests */
 	struct btree vc_requests;
 	/* the equeue to send async page requests to */
@@ -36,7 +34,7 @@ struct page_request {
 	enum page_request_status req_status;
 	kern_status_t req_result;
 	spin_lock_t req_lock;
-	struct vm_object *req_object;
+	equeue_key_t req_object;
 	struct thread *req_sender;
 	struct btree_node req_node;
 	off_t req_offset;