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diff --git a/src/common/deleter.h b/src/common/deleter.h
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+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2014 Cloudius Systems, Ltd.
+ */
+
+#ifndef CEPH_COMMON_DELETER_H
+#define CEPH_COMMON_DELETER_H
+
+#include <atomic>
+
+/// \addtogroup memory-module
+/// @{
+
+/// Provides a mechanism for managing the lifetime of a buffer.
+///
+/// A \c deleter is an object that is used to inform the consumer
+/// of some buffer (not referenced by the deleter itself) how to
+/// delete the buffer.  This can be by calling an arbitrary function
+/// or destroying an object carried by the deleter.  Examples of
+/// a deleter's encapsulated actions are:
+///
+///  - calling \c std::free(p) on some captured pointer, p
+///  - calling \c delete \c p on some captured pointer, p
+///  - decrementing a reference count somewhere
+///
+/// A deleter performs its action from its destructor.
+class deleter final {
+ public:
+  /// \cond internal
+  struct impl;
+  struct raw_object_tag {};
+  /// \endcond
+ private:
+  // if bit 0 set, point to object to be freed directly.
+  impl* _impl = nullptr;
+ public:
+  /// Constructs an empty deleter that does nothing in its destructor.
+  deleter() = default;
+  deleter(const deleter&) = delete;
+  /// Moves a deleter.
+  deleter(deleter&& x) noexcept : _impl(x._impl) { x._impl = nullptr; }
+  /// \cond internal
+  explicit deleter(impl* i) : _impl(i) {}
+  deleter(raw_object_tag tag, void* object)
+          : _impl(from_raw_object(object)) {}
+  /// \endcond
+  /// Destroys the deleter and carries out the encapsulated action.
+  ~deleter();
+  deleter& operator=(deleter&& x);
+  deleter& operator=(deleter&) = delete;
+  /// Performs a sharing operation.  The encapsulated action will only
+  /// be carried out after both the original deleter and the returned
+  /// deleter are both destroyed.
+  ///
+  /// \return a deleter with the same encapsulated action as this one.
+  deleter share();
+  /// Checks whether the deleter has an associated action.
+  explicit operator bool() const { return bool(_impl); }
+  /// \cond internal
+  void reset(impl* i) {
+    this->~deleter();
+    new (this) deleter(i);
+  }
+  /// \endcond
+  /// Appends another deleter to this deleter.  When this deleter is
+  /// destroyed, both encapsulated actions will be carried out.
+  void append(deleter d);
+ private:
+  static bool is_raw_object(impl* i) {
+    auto x = reinterpret_cast<uintptr_t>(i);
+    return x & 1;
+  }
+  bool is_raw_object() const {
+    return is_raw_object(_impl);
+  }
+  static void* to_raw_object(impl* i) {
+    auto x = reinterpret_cast<uintptr_t>(i);
+    return reinterpret_cast<void*>(x & ~uintptr_t(1));
+  }
+  void* to_raw_object() const {
+    return to_raw_object(_impl);
+  }
+  impl* from_raw_object(void* object) {
+    auto x = reinterpret_cast<uintptr_t>(object);
+    return reinterpret_cast<impl*>(x | 1);
+  }
+};
+
+/// \cond internal
+struct deleter::impl {
+  std::atomic_uint refs;
+  deleter next;
+  impl(deleter next) : refs(1), next(std::move(next)) {}
+  virtual ~impl() {}
+};
+/// \endcond
+
+inline deleter::~deleter() {
+  if (is_raw_object()) {
+    std::free(to_raw_object());
+    return;
+  }
+  if (_impl && --_impl->refs == 0) {
+    delete _impl;
+  }
+}
+
+inline deleter& deleter::operator=(deleter&& x) {
+  if (this != &x) {
+    this->~deleter();
+    new (this) deleter(std::move(x));
+  }
+  return *this;
+}
+
+/// \cond internal
+template <typename Deleter>
+struct lambda_deleter_impl final : deleter::impl {
+  Deleter del;
+  lambda_deleter_impl(deleter next, Deleter&& del)
+          : impl(std::move(next)), del(std::move(del)) {}
+  ~lambda_deleter_impl() override { del(); }
+};
+
+template <typename Object>
+struct object_deleter_impl final : deleter::impl {
+  Object obj;
+  object_deleter_impl(deleter next, Object&& obj)
+          : impl(std::move(next)), obj(std::move(obj)) {}
+};
+
+template <typename Object>
+inline
+object_deleter_impl<Object>* make_object_deleter_impl(deleter next, Object obj) {
+  return new object_deleter_impl<Object>(std::move(next), std::move(obj));
+}
+/// \endcond
+
+/// Makes a \ref deleter that encapsulates the action of
+/// destroying an object, as well as running another deleter.  The input
+/// object is moved to the deleter, and destroyed when the deleter is destroyed.
+///
+/// \param d deleter that will become part of the new deleter's encapsulated action
+/// \param o object whose destructor becomes part of the new deleter's encapsulated action
+/// \related deleter
+template <typename Object>
+deleter make_deleter(deleter next, Object o) {
+  return deleter(new lambda_deleter_impl<Object>(std::move(next), std::move(o)));
+}
+
+/// Makes a \ref deleter that encapsulates the action of destroying an object.  The input
+/// object is moved to the deleter, and destroyed when the deleter is destroyed.
+///
+/// \param o object whose destructor becomes the new deleter's encapsulated action
+/// \related deleter
+template <typename Object>
+deleter make_deleter(Object o) {
+  return make_deleter(deleter(), std::move(o));
+}
+
+/// \cond internal
+struct free_deleter_impl final : deleter::impl {
+  void* obj;
+  free_deleter_impl(void* obj) : impl(deleter()), obj(obj) {}
+  ~free_deleter_impl() override { std::free(obj); }
+};
+/// \endcond
+
+inline deleter deleter::share() {
+  if (!_impl) {
+    return deleter();
+  }
+  if (is_raw_object()) {
+    _impl = new free_deleter_impl(to_raw_object());
+  }
+  ++_impl->refs;
+  return deleter(_impl);
+}
+
+// Appends 'd' to the chain of deleters. Avoids allocation if possible. For
+// performance reasons the current chain should be shorter and 'd' should be
+// longer.
+inline void deleter::append(deleter d) {
+  if (!d._impl) {
+    return;
+  }
+  impl* next_impl = _impl;
+  deleter* next_d = this;
+  while (next_impl) {
+    if (next_impl == d._impl)
+      return ;
+    if (is_raw_object(next_impl)) {
+      next_d->_impl = next_impl = new free_deleter_impl(to_raw_object(next_impl));
+    }
+    if (next_impl->refs != 1) {
+      next_d->_impl = next_impl = make_object_deleter_impl(std::move(next_impl->next), deleter(next_impl));
+    }
+    next_d = &next_impl->next;
+    next_impl = next_d->_impl;
+  }
+  next_d->_impl = d._impl;
+  d._impl = nullptr;
+}
+
+/// Makes a deleter that calls \c std::free() when it is destroyed.
+///
+/// \param obj object to free.
+/// \related deleter
+inline deleter make_free_deleter(void* obj) {
+  if (!obj) {
+    return deleter();
+  }
+  return deleter(deleter::raw_object_tag(), obj);
+}
+
+/// Makes a deleter that calls \c std::free() when it is destroyed, as well
+/// as invoking the encapsulated action of another deleter.
+///
+/// \param d deleter to invoke.
+/// \param obj object to free.
+/// \related deleter
+inline deleter make_free_deleter(deleter next, void* obj) {
+  return make_deleter(std::move(next), [obj] () mutable { std::free(obj); });
+}
+
+/// \see make_deleter(Object)
+/// \related deleter
+template <typename T>
+inline deleter make_object_deleter(T&& obj) {
+  return deleter{make_object_deleter_impl(deleter(), std::move(obj))};
+}
+
+/// \see make_deleter(deleter, Object)
+/// \related deleter
+template <typename T>
+inline deleter make_object_deleter(deleter d, T&& obj) {
+  return deleter{make_object_deleter_impl(std::move(d), std::move(obj))};
+}
+
+/// @}
+
+#endif /* CEPH_COMMON_DELETER_H */