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diff --git a/src/rgw/rgw_aio_throttle.h b/src/rgw/rgw_aio_throttle.h
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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2018 Red Hat, Inc.
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation. See file COPYING.
+ *
+ */
+
+#pragma once
+
+#include "include/rados/librados_fwd.hpp"
+#include <memory>
+#include "common/ceph_mutex.h"
+#include "services/svc_rados.h"
+#include "rgw_aio.h"
+
+namespace rgw {
+
+// a throttle for aio operations that enforces a maximum window on outstanding
+// bytes. only supports a single waiter, so all public functions must be called
+// from the same thread
+class AioThrottle : public Aio {
+ protected:
+  const uint64_t window;
+  uint64_t pending_size = 0;
+
+  bool is_available() const { return pending_size <= window; }
+  bool has_completion() const { return !completed.empty(); }
+  bool is_drained() const { return pending.empty(); }
+
+  struct Pending : AioResultEntry {
+    AioThrottle *parent = nullptr;
+    uint64_t cost = 0;
+    librados::AioCompletion *completion = nullptr;
+  };
+  OwningList<Pending> pending;
+  AioResultList completed;
+
+  enum class Wait { None, Available, Completion, Drained };
+  Wait waiter = Wait::None;
+
+  bool waiter_ready() const;
+
+  ceph::mutex mutex = ceph::make_mutex("AioThrottle");
+  ceph::condition_variable cond;
+
+  void get(Pending& p);
+  void put(Pending& p);
+
+  static void aio_cb(void *cb, void *arg);
+
+ public:
+  AioThrottle(uint64_t window) : window(window) {}
+
+  virtual ~AioThrottle() {
+    // must drain before destructing
+    ceph_assert(pending.empty());
+    ceph_assert(completed.empty());
+  }
+
+  AioResultList submit(RGWSI_RADOS::Obj& obj,
+                       librados::ObjectReadOperation *op,
+                       uint64_t cost, uint64_t id) override;
+
+  AioResultList submit(RGWSI_RADOS::Obj& obj,
+                       librados::ObjectWriteOperation *op,
+                       uint64_t cost, uint64_t id) override;
+
+  AioResultList poll() override;
+
+  AioResultList wait() override;
+
+  AioResultList drain() override;
+};
+
+} // namespace rgw