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diff --git a/src/tools/rbd_mirror/image_map/Policy.h b/src/tools/rbd_mirror/image_map/Policy.h
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+++ b/src/tools/rbd_mirror/image_map/Policy.h
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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#ifndef CEPH_RBD_MIRROR_IMAGE_MAP_POLICY_H
+#define CEPH_RBD_MIRROR_IMAGE_MAP_POLICY_H
+
+#include <map>
+#include <tuple>
+#include <boost/optional.hpp>
+
+#include "common/RWLock.h"
+#include "cls/rbd/cls_rbd_types.h"
+#include "include/rados/librados.hpp"
+#include "tools/rbd_mirror/image_map/StateTransition.h"
+#include "tools/rbd_mirror/image_map/Types.h"
+
+class Context;
+
+namespace rbd {
+namespace mirror {
+namespace image_map {
+
+class Policy {
+public:
+  Policy(librados::IoCtx &ioctx);
+
+  virtual ~Policy() {
+  }
+
+  // init -- called during initialization
+  void init(
+      const std::map<std::string, cls::rbd::MirrorImageMap> &image_mapping);
+
+  // lookup an image from the map
+  LookupInfo lookup(const std::string &global_image_id);
+
+  // add, remove
+  bool add_image(const std::string &global_image_id);
+  bool remove_image(const std::string &global_image_id);
+
+  // shuffle images when instances are added/removed
+  void add_instances(const InstanceIds &instance_ids,
+                     GlobalImageIds* global_image_ids);
+  void remove_instances(const InstanceIds &instance_ids,
+                        GlobalImageIds* global_image_ids);
+
+  ActionType start_action(const std::string &global_image_id);
+  bool finish_action(const std::string &global_image_id, int r);
+
+protected:
+  typedef std::map<std::string, std::set<std::string> > InstanceToImageMap;
+
+  bool is_dead_instance(const std::string instance_id) {
+    ceph_assert(ceph_mutex_is_locked(m_map_lock));
+    return m_dead_instances.find(instance_id) != m_dead_instances.end();
+  }
+
+  bool is_image_shuffling(const std::string &global_image_id);
+  bool can_shuffle_image(const std::string &global_image_id);
+
+  // map an image (global image id) to an instance
+  virtual std::string do_map(const InstanceToImageMap& map,
+                             const std::string &global_image_id) = 0;
+
+  // shuffle images when instances are added/removed
+  virtual void do_shuffle_add_instances(
+      const InstanceToImageMap& map, size_t image_count,
+      std::set<std::string> *remap_global_image_ids) = 0;
+
+private:
+  struct ImageState {
+    std::string instance_id = UNMAPPED_INSTANCE_ID;
+    utime_t mapped_time;
+
+    ImageState() {}
+    ImageState(const std::string& instance_id, const utime_t& mapped_time)
+      : instance_id(instance_id), mapped_time(mapped_time) {
+    }
+
+    // active state and action
+    StateTransition::State state = StateTransition::STATE_UNASSOCIATED;
+    StateTransition::Transition transition;
+
+    // next scheduled state
+    boost::optional<StateTransition::State> next_state = boost::none;
+  };
+
+  typedef std::map<std::string, ImageState> ImageStates;
+
+  librados::IoCtx &m_ioctx;
+
+  ceph::shared_mutex m_map_lock;        // protects m_map
+  InstanceToImageMap m_map; // instance_id -> global_id map
+
+  ImageStates m_image_states;
+  std::set<std::string> m_dead_instances;
+
+  bool m_initial_update = true;
+
+  void remove_instances(const ceph::shared_mutex& lock,
+			const InstanceIds &instance_ids,
+                        GlobalImageIds* global_image_ids);
+
+  bool set_state(ImageState* image_state, StateTransition::State state,
+                 bool ignore_current_state);
+
+  void execute_policy_action(const std::string& global_image_id,
+                             ImageState* image_state,
+                             StateTransition::PolicyAction policy_action);
+
+  void map(const std::string& global_image_id, ImageState* image_state);
+  void unmap(const std::string &global_image_id, ImageState* image_state);
+
+  bool is_state_scheduled(const ImageState& image_state,
+                          StateTransition::State state) const;
+
+};
+
+} // namespace image_map
+} // namespace mirror
+} // namespace rbd
+
+#endif // CEPH_RBD_MIRROR_IMAGE_MAP_POLICY_H