rgw: add rgw::putobj::Aio interface

the Aio operations return a ResultList of previous completions that can
be inspected for the error code and object name (the latter is needed to
track created objects that need to be removed on cancelation)

returning results in a list avoids the extra locking that may be
required to poll/wait for a single completion at a time

Signed-off-by: Casey Bodley <cbodley@redhat.com>

diff --git a/src/rgw/rgw_putobj_aio.h b/src/rgw/rgw_putobj_aio.h
new file mode 100644 (file)
index 0000000..00526bd
--- /dev/null
+++ b/src/rgw/rgw_putobj_aio.h
@@ -0,0 +1,81 @@
+// -*- 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 <boost/intrusive/list.hpp>
+#include "rgw_common.h"
+
+namespace librados {
+class ObjectReadOperation;
+class ObjectWriteOperation;
+}
+struct rgw_rados_ref;
+
+namespace rgw::putobj {
+
+struct Result {
+  rgw_raw_obj obj;
+  int result = 0;
+};
+struct ResultEntry : Result, boost::intrusive::list_base_hook<> {
+  virtual ~ResultEntry() {}
+};
+// a list of polymorphic entries that frees them on destruction
+template <typename T, typename ...Args>
+struct OwningList : boost::intrusive::list<T, Args...> {
+  OwningList() = default;
+  ~OwningList() { this->clear_and_dispose(std::default_delete<T>{}); }
+  OwningList(OwningList&&) = default;
+  OwningList& operator=(OwningList&&) = default;
+  OwningList(const OwningList&) = delete;
+  OwningList& operator=(const OwningList&) = delete;
+};
+using ResultList = OwningList<ResultEntry>;
+
+// returns the first error code or 0 if all succeeded
+inline int check_for_errors(const ResultList& results) {
+  for (auto& e : results) {
+    if (e.result < 0) {
+      return e.result;
+    }
+  }
+  return 0;
+}
+
+// interface to submit async librados operations and wait on their completions.
+// each call returns a list of results from prior completions
+class Aio {
+ public:
+  virtual ~Aio() {}
+
+  virtual ResultList submit(rgw_rados_ref& ref, const rgw_raw_obj& obj,
+                            librados::ObjectReadOperation *op,
+                            bufferlist *data, uint64_t cost) = 0;
+
+  virtual ResultList submit(rgw_rados_ref& ref, const rgw_raw_obj& obj,
+                            librados::ObjectWriteOperation *op,
+                            uint64_t cost) = 0;
+
+  // poll for any ready completions without waiting
+  virtual ResultList poll() = 0;
+
+  // return any ready completions. if there are none, wait for the next
+  virtual ResultList wait() = 0;
+
+  // wait for all outstanding completions and return their results
+  virtual ResultList drain() = 0;
+};
+
+} // namespace rgw::putobj