Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1754 insertions, 0 deletions

diff --git a/src/neorados/cls/fifo.h b/src/neorados/cls/fifo.h
new file mode 100644
index 000000000..05865dcca
--- /dev/null
+++ b/src/neorados/cls/fifo.h
@@ -0,0 +1,1754 @@
+// -*- 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) 2020 Red Hat <contact@redhat.com>
+ * Author: Adam C. Emerson
+ *
+ * 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.
+ *
+ */
+
+#ifndef CEPH_NEORADOS_CLS_FIFIO_H
+#define CEPH_NEORADOS_CLS_FIFIO_H
+
+#include <cstdint>
+#include <deque>
+#include <map>
+#include <memory>
+#include <mutex>
+#include <optional>
+#include <string_view>
+#include <vector>
+
+#include <boost/asio.hpp>
+#include <boost/system/error_code.hpp>
+
+#undef FMT_HEADER_ONLY
+#define FMT_HEADER_ONLY 1
+#include <fmt/format.h>
+
+#include "include/neorados/RADOS.hpp"
+#include "include/buffer.h"
+
+#include "common/allocate_unique.h"
+#include "common/async/bind_handler.h"
+#include "common/async/bind_like.h"
+#include "common/async/completion.h"
+#include "common/async/forward_handler.h"
+
+#include "common/dout.h"
+
+#include "cls/fifo/cls_fifo_types.h"
+#include "cls/fifo/cls_fifo_ops.h"
+
+namespace neorados::cls::fifo {
+namespace ba = boost::asio;
+namespace bs = boost::system;
+namespace ca = ceph::async;
+namespace cb = ceph::buffer;
+namespace fifo = rados::cls::fifo;
+
+inline constexpr auto dout_subsys = ceph_subsys_rados;
+inline constexpr std::uint64_t default_max_part_size = 4 * 1024 * 1024;
+inline constexpr std::uint64_t default_max_entry_size = 32 * 1024;
+inline constexpr auto MAX_RACE_RETRIES = 10;
+
+
+const boost::system::error_category& error_category() noexcept;
+
+enum class errc {
+  raced = 1,
+  inconsistency,
+  entry_too_large,
+  invalid_marker,
+  update_failed
+};
+}
+
+namespace boost::system {
+template<>
+struct is_error_code_enum<::neorados::cls::fifo::errc> {
+  static const bool value = true;
+};
+template<>
+struct is_error_condition_enum<::neorados::cls::fifo::errc> {
+  static const bool value = false;
+};
+}
+
+namespace neorados::cls::fifo {
+//  explicit conversion:
+inline bs::error_code make_error_code(errc e) noexcept {
+  return { static_cast<int>(e), error_category() };
+}
+
+inline bs::error_code make_error_category(errc e) noexcept {
+  return { static_cast<int>(e), error_category() };
+}
+
+void create_meta(WriteOp& op, std::string_view id,
+		 std::optional<fifo::objv> objv,
+		 std::optional<std::string_view> oid_prefix,
+		 bool exclusive = false,
+		 std::uint64_t max_part_size = default_max_part_size,
+		 std::uint64_t max_entry_size = default_max_entry_size);
+void get_meta(ReadOp& op, std::optional<fifo::objv> objv,
+	      bs::error_code* ec_out, fifo::info* info,
+	      std::uint32_t* part_header_size,
+	      std::uint32_t* part_entry_overhead);
+
+void update_meta(WriteOp& op, const fifo::objv& objv,
+		 const fifo::update& desc);
+
+void part_init(WriteOp& op, std::string_view tag,
+	       fifo::data_params params);
+
+void push_part(WriteOp& op, std::string_view tag,
+	       std::deque<cb::list> data_bufs,
+	       fu2::unique_function<void(bs::error_code, int)>);
+void trim_part(WriteOp& op, std::optional<std::string_view> tag,
+	       std::uint64_t ofs,
+	       bool exclusive);
+void list_part(ReadOp& op,
+	       std::optional<std::string_view> tag,
+	       std::uint64_t ofs,
+	       std::uint64_t max_entries,
+	       bs::error_code* ec_out,
+	       std::vector<fifo::part_list_entry>* entries,
+	       bool* more,
+	       bool* full_part,
+	       std::string* ptag);
+void get_part_info(ReadOp& op,
+		   bs::error_code* out_ec,
+		   fifo::part_header* header);
+
+struct marker {
+  std::int64_t num = 0;
+  std::uint64_t ofs = 0;
+
+  marker() = default;
+  marker(std::int64_t num, std::uint64_t ofs) : num(num), ofs(ofs) {}
+  static marker max() {
+    return { std::numeric_limits<decltype(num)>::max(),
+	     std::numeric_limits<decltype(ofs)>::max() };
+  }
+
+  std::string to_string() {
+    return fmt::format("{:0>20}:{:0>20}", num, ofs);
+  }
+};
+
+struct list_entry {
+  cb::list data;
+  std::string marker;
+  ceph::real_time mtime;
+};
+
+using part_info = fifo::part_header;
+
+namespace detail {
+template<typename Handler>
+class JournalProcessor;
+}
+
+/// Completions, Handlers, and CompletionTokens
+/// ===========================================
+///
+/// This class is based on Boost.Asio. For information, see
+/// https://www.boost.org/doc/libs/1_74_0/doc/html/boost_asio.html
+///
+/// As summary, Asio's design is that of functions taking completion
+/// handlers. Every handler has a signature, like
+/// (boost::system::error_code, std::string). The completion handler
+/// receives the result of the function, and the signature is the type
+/// of that result.
+///
+/// The completion handler is specified with a CompletionToken. The
+/// CompletionToken is any type that has a specialization of
+/// async_complete and async_result. See
+/// https://www.boost.org/doc/libs/1_74_0/doc/html/boost_asio/reference/async_completion.html
+/// and https://www.boost.org/doc/libs/1_74_0/doc/html/boost_asio/reference/async_result.html
+///
+/// The return type of a function taking a CompletionToken is
+/// async_result<CompletionToken, Signature>::return_type.
+///
+/// Functions
+/// ---------
+///
+/// The default implementations treat whatever value is described as a
+/// function, whose parameters correspond to the signature, and calls
+/// it upon completion.
+///
+/// EXAMPLE:
+/// Let f be an asynchronous function whose signature is (bs::error_code, int)
+/// Let g be an asynchronous function whose signature is
+/// (bs::error_code, int, std::string).
+///
+///
+///    f([](bs::error_code ec, int i) { ... });
+///    g([](bs::error_code ec, int i, std::string s) { ... });
+///
+/// Will schedule asynchronous tasks, and the provided lambdas will be
+/// called on completion. In this case, f and g return void.
+///
+/// There are other specializations. Commonly used ones are.
+///
+/// Futures
+/// -------
+///
+/// A CompletionToken of boost::asio::use_future will complete with a
+/// promise whose type matches (minus any initial error_code) the
+/// function's signature. The corresponding future is returned. If the
+/// error_code of the result is non-zero, the future is set with an
+/// exception of type boost::asio::system_error.
+///
+/// See https://www.boost.org/doc/libs/1_74_0/doc/html/boost_asio/reference/use_future_t.html
+///
+/// EXAMPLE:
+///
+/// std::future<int> = f(ba::use_future);
+/// std::future<std::tuple<int, std::string> = g(ba::use_future).
+///
+/// Coroutines
+/// ----------
+///
+/// A CompletionToken of type spawn::yield_context suspends execution
+/// of the current coroutine until completion of the operation. See
+/// src/spawn/README.md
+/// https://www.boost.org/doc/libs/1_74_0/doc/html/boost_asio/reference/spawn.html and
+/// https://www.boost.org/doc/libs/1_74_0/doc/html/boost_asio/reference/yield_context.html
+///
+/// Operations given this CompletionToken return their results, modulo
+/// any leading error_code. A non-zero error code will be thrown, by
+/// default, but may be bound to a variable instead with the overload
+/// of the array-subscript oeprator.
+///
+/// EXAMPLE:
+/// // Within a function with a yield_context parameter named y
+///
+/// try {
+///    int i = f(y);
+/// } catch (const bs::system_error& ec) { ... }
+///
+/// bs::error_code ec;
+/// auto [i, s] = g(y[ec]);
+///
+/// Blocking calls
+/// --------------
+///
+/// ceph::async::use_blocked, defined in src/common/async/blocked_completion.h
+/// Suspends the current thread of execution, returning the results of
+/// the operation on resumption. Its calling convention is analogous to
+/// that of yield_context.
+///
+/// EXAMPLE:
+/// try {
+///    int i = f(ca::use_blocked);
+/// } catch (const bs::system_error& e) { ... }
+///
+/// bs::error_code ec;
+/// auto [i, s] = g(ca::use_blocked[ec]);
+///
+/// librados Completions
+/// --------------------
+///
+/// If src/common/async/librados_completion.h is included in the
+/// current translation unit, then librados::AioCompletion* may be used
+/// as a CompletionToken. This is only permitted when the completion
+/// signature is either bs::system_error or void. The return type of
+/// functions provided a CompletionToken of AioCompletion* is void. If
+/// the signature includes an error code and the error code is set,
+/// then the error is translated to an int which is set as the result
+/// of the AioCompletion.
+///
+/// EXAMPLE:
+/// // Assume an asynchronous function h whose signature is bs::error_code.
+///
+/// AioCompletion* c = Rados::aio_create_completion();
+/// h(c);
+/// int r = c.get_return_value();
+///
+/// See also src/test/cls_fifo/bench_cls_fifo.cc for a full, simple
+/// example of a program using this class with coroutines.
+///
+///
+/// Markers
+/// =======
+///
+/// Markers represent a position within the FIFO. Internally, they are
+/// part/offset pairs. Externally, they are ordered but otherwise
+/// opaque strings. Markers that compare lower denote positions closer
+/// to the tail.
+///
+/// A marker is returned with every entry from a list() operation. They
+/// may be supplied to a list operation to resume from a given
+/// position, and must be supplied to trim give the position to which
+/// to trim.
+
+class FIFO {
+public:
+
+  FIFO(const FIFO&) = delete;
+  FIFO& operator =(const FIFO&) = delete;
+  FIFO(FIFO&&) = delete;
+  FIFO& operator =(FIFO&&) = delete;
+
+  /// Open an existing FIFO.
+  /// Signature: (bs::error_code ec, std::unique_ptr<FIFO> f)
+  template<typename CT>
+  static auto open(RADOS& r, //< RADOS handle
+		   const IOContext& ioc, //< Context for pool, namespace, etc.
+		   Object oid, //< OID for the 'main' object of the FIFO
+		   CT&& ct, //< CompletionToken
+		   /// Fail if is not this version
+		   std::optional<fifo::objv> objv = std::nullopt,
+		   /// Default executor. By default use the one
+		   /// associated with the RADOS handle.
+		   std::optional<ba::executor> executor = std::nullopt) {
+    ba::async_completion<CT, void(bs::error_code,
+				  std::unique_ptr<FIFO>)> init(ct);
+    auto e = ba::get_associated_executor(init.completion_handler,
+					 executor.value_or(r.get_executor()));
+    auto a = ba::get_associated_allocator(init.completion_handler);
+    _read_meta_(
+      &r, oid, ioc, objv,
+      ca::bind_ea(
+	e, a,
+	[&r, ioc, oid, executor, handler = std::move(init.completion_handler)]
+	(bs::error_code ec, fifo::info info,
+	 std::uint32_t size, std::uint32_t over) mutable {
+	  std::unique_ptr<FIFO> f(
+	    new FIFO(r, ioc, oid, executor.value_or(r.get_executor())));
+	  f->info = info;
+	  f->part_header_size = size;
+	  f->part_entry_overhead = over;
+	  // If there are journal entries, process them, in case
+	  // someone crashed mid-transaction.
+	  if (!ec && !info.journal.empty()) {
+	    auto e = ba::get_associated_executor(handler, f->get_executor());
+	    auto a = ba::get_associated_allocator(handler);
+	    auto g = f.get();
+	    g->_process_journal(
+	      ca::bind_ea(
+		e, a,
+		[f = std::move(f),
+		 handler = std::move(handler)](bs::error_code ec) mutable {
+		  std::move(handler)(ec, std::move(f));
+		}));
+	    return;
+	  }
+	  std::move(handler)(ec, std::move(f));
+	  return;
+	}));
+    return init.result.get();
+  }
+
+  /// Open an existing or create a new FIFO.
+  /// Signature: (bs::error_code ec, std::unique_ptr<FIFO> f)
+  template<typename CT>
+  static auto create(RADOS& r, /// RADOS handle
+		     const IOContext& ioc, /// Context for pool, namespace, etc.
+		     Object oid, /// OID for the 'main' object of the FIFO
+		     CT&& ct, /// CompletionToken
+		     /// Fail if FIFO exists and is not this version
+		     std::optional<fifo::objv> objv = std::nullopt,
+		     /// Custom prefix for parts
+		     std::optional<std::string_view> oid_prefix = std::nullopt,
+		     /// Fail if FIFO already exists
+		     bool exclusive = false,
+		     /// Size at which a part is considered full
+		     std::uint64_t max_part_size = default_max_part_size,
+		     /// Maximum size of any entry
+		     std::uint64_t max_entry_size = default_max_entry_size,
+		     /// Default executor. By default use the one
+		     /// associated with the RADOS handle.
+		     std::optional<ba::executor> executor = std::nullopt) {
+    ba::async_completion<CT, void(bs::error_code,
+				  std::unique_ptr<FIFO>)> init(ct);
+    WriteOp op;
+    create_meta(op, oid, objv, oid_prefix, exclusive, max_part_size,
+		max_entry_size);
+    auto e = ba::get_associated_executor(init.completion_handler,
+					 executor.value_or(r.get_executor()));
+    auto a = ba::get_associated_allocator(init.completion_handler);
+    r.execute(
+      oid, ioc, std::move(op),
+      ca::bind_ea(
+	e, a,
+	[objv, &r, ioc, oid, executor, handler = std::move(init.completion_handler)]
+	(bs::error_code ec) mutable {
+	  if (ec) {
+	    std::move(handler)(ec, nullptr);
+	    return;
+	  }
+	  auto e = ba::get_associated_executor(
+	    handler, executor.value_or(r.get_executor()));
+	  auto a = ba::get_associated_allocator(handler);
+	  FIFO::_read_meta_(
+	    &r, oid, ioc, objv,
+	    ca::bind_ea(
+	      e, a,
+	      [&r, ioc, executor, oid, handler = std::move(handler)]
+	      (bs::error_code ec, fifo::info info,
+	       std::uint32_t size, std::uint32_t over) mutable {
+		std::unique_ptr<FIFO> f(
+		  new FIFO(r, ioc, oid, executor.value_or(r.get_executor())));
+		f->info = info;
+		f->part_header_size = size;
+		f->part_entry_overhead = over;
+		if (!ec && !info.journal.empty()) {
+		  auto e = ba::get_associated_executor(handler,
+						       f->get_executor());
+		  auto a = ba::get_associated_allocator(handler);
+		  auto g = f.get();
+		  g->_process_journal(
+		    ca::bind_ea(
+		      e, a,
+		      [f = std::move(f), handler = std::move(handler)]
+		      (bs::error_code ec) mutable {
+			std::move(handler)(ec, std::move(f));
+		      }));
+		  return;
+		}
+		std::move(handler)(ec, std::move(f));
+	      }));
+	    }));
+    return init.result.get();
+  }
+
+  /// Force a re-read of FIFO metadata.
+  /// Signature: (bs::error_code ec)
+  template<typename CT>
+  auto read_meta(CT&& ct, //< CompletionToken
+		 /// Fail if FIFO not at this version
+		 std::optional<fifo::objv> objv = std::nullopt) {
+    std::unique_lock l(m);
+    auto version = info.version;
+    l.unlock();
+    ba::async_completion<CT, void(bs::error_code)> init(ct);
+    auto e = ba::get_associated_executor(init.completion_handler,
+					 get_executor());
+    auto a = ba::get_associated_allocator(init.completion_handler);
+    _read_meta_(
+      r, oid, ioc, objv,
+      ca::bind_ea(
+	e, a,
+	[this, version, handler = std::move(init.completion_handler)]
+	(bs::error_code ec, fifo::info newinfo,
+	 std::uint32_t size, std::uint32_t over) mutable {
+	  std::unique_lock l(m);
+	  if (version == info.version) {
+	    info = newinfo;
+	    part_header_size = size;
+	    part_entry_overhead = over;
+	  }
+	  l.unlock();
+	  return std::move(handler)(ec);
+	}));
+    return init.result.get();
+  }
+
+  /// Return a reference to currently known metadata
+  const fifo::info& meta() const {
+    return info;
+  }
+
+  /// Return header size and entry overhead of partitions.
+  std::pair<std::uint32_t, std::uint32_t> get_part_layout_info() {
+    return {part_header_size, part_entry_overhead};
+  }
+
+  /// Push a single entry to the FIFO.
+  /// Signature: (bs::error_code)
+  template<typename CT>
+  auto push(const cb::list& bl, //< Bufferlist holding entry to push
+	    CT&& ct //< CompletionToken
+    ) {
+    return push(std::vector{ bl }, std::forward<CT>(ct));
+  }
+
+  /// Push a many entries to the FIFO.
+  /// Signature: (bs::error_code)
+  template<typename CT>
+  auto push(const std::vector<cb::list>& data_bufs, //< Entries to push
+	    CT&& ct //< CompletionToken
+    ) {
+    ba::async_completion<CT, void(bs::error_code)> init(ct);
+    std::unique_lock l(m);
+    auto max_entry_size = info.params.max_entry_size;
+    auto need_new_head = info.need_new_head();
+    l.unlock();
+    auto e = ba::get_associated_executor(init.completion_handler,
+					 get_executor());
+    auto a = ba::get_associated_allocator(init.completion_handler);
+    if (data_bufs.empty() ) {
+      // Can't fail if you don't try.
+      e.post(ca::bind_handler(std::move(init.completion_handler),
+				  bs::error_code{}), a);
+      return init.result.get();
+    }
+
+    // Validate sizes
+    for (const auto& bl : data_bufs) {
+      if (bl.length() > max_entry_size) {
+	ldout(r->cct(), 10) << __func__ << "(): entry too large: "
+			    << bl.length() << " > "
+			    << info.params.max_entry_size << dendl;
+	e.post(ca::bind_handler(std::move(init.completion_handler),
+				    errc::entry_too_large), a);
+	return init.result.get();
+      }
+    }
+
+    auto p = ca::bind_ea(e, a,
+			 Pusher(this, {data_bufs.begin(), data_bufs.end()},
+				  {}, 0, std::move(init.completion_handler)));
+
+    if (need_new_head) {
+      _prepare_new_head(std::move(p));
+    } else {
+      e.dispatch(std::move(p), a);
+    }
+    return init.result.get();
+  }
+
+  /// List the entries in a FIFO
+  /// Signature(bs::error_code ec, bs::vector<list_entry> entries, bool more)
+  ///
+  /// More is true if entries beyond the last exist.
+  /// The list entries are of the form:
+  /// data - Contents of the entry
+  /// marker - String representing the position of this entry within the FIFO.
+  /// mtime - Time (on the OSD) at which the entry was pushed.
+  template<typename CT>
+  auto list(int max_entries, //< Maximum number of entries to fetch
+	    /// Optionally, a marker indicating the position after
+	    /// which to begin listing. If null, begin at the tail.
+	    std::optional<std::string_view> markstr,
+	    CT&& ct //< CompletionToken
+    ) {
+    ba::async_completion<CT, void(bs::error_code,
+				  std::vector<list_entry>, bool)> init(ct);
+    std::unique_lock l(m);
+    std::int64_t part_num = info.tail_part_num;
+    l.unlock();
+    std::uint64_t ofs = 0;
+    auto a = ba::get_associated_allocator(init.completion_handler);
+    auto e = ba::get_associated_executor(init.completion_handler);
+
+    if (markstr) {
+      auto marker = to_marker(*markstr);
+      if (!marker) {
+	ldout(r->cct(), 0) << __func__
+			   << "(): failed to parse marker (" << *markstr
+			   << ")" << dendl;
+	e.post(ca::bind_handler(std::move(init.completion_handler),
+				errc::invalid_marker,
+				std::vector<list_entry>{}, false), a);
+	return init.result.get();
+      }
+      part_num = marker->num;
+      ofs = marker->ofs;
+    }
+
+    using handler_type = decltype(init.completion_handler);
+    auto ls = ceph::allocate_unique<Lister<handler_type>>(
+      a, this, part_num, ofs, max_entries,
+      std::move(init.completion_handler));
+    ls.release()->list();
+    return init.result.get();
+  }
+
+  /// Trim entries from the tail to the given position
+  /// Signature: (bs::error_code)
+  template<typename CT>
+  auto trim(std::string_view markstr, //< Position to which to trim, inclusive
+	    bool exclusive, //< If true, trim markers up to but NOT INCLUDING
+	                    //< markstr, otherwise trim markstr as well.
+	    CT&& ct //< CompletionToken
+    ) {
+    auto m = to_marker(markstr);
+    ba::async_completion<CT, void(bs::error_code)> init(ct);
+    auto a = ba::get_associated_allocator(init.completion_handler);
+    auto e = ba::get_associated_executor(init.completion_handler);
+    if (!m) {
+      ldout(r->cct(), 0) << __func__ << "(): failed to parse marker: marker="
+			 << markstr << dendl;
+      e.post(ca::bind_handler(std::move(init.completion_handler),
+			      errc::invalid_marker), a);
+      return init.result.get();
+    } else {
+      using handler_type = decltype(init.completion_handler);
+      auto t = ceph::allocate_unique<Trimmer<handler_type>>(
+	a, this, m->num, m->ofs, exclusive, std::move(init.completion_handler));
+      t.release()->trim();
+    }
+    return init.result.get();
+  }
+
+  /// Get information about a specific partition
+  /// Signature: (bs::error_code, part_info)
+  ///
+  /// part_info has the following entries
+  /// tag - A random string identifying this partition. Used internally
+  ///       as a sanity check to make sure operations haven't been misdirected
+  /// params - Data parameters, identical for every partition within a
+  ///          FIFO and the same as what is returned from get_part_layout()
+  /// magic - A random magic number, used internally as a prefix to
+  ///         every entry stored on the OSD to ensure sync
+  /// min_ofs - Offset of the first entry
+  /// max_ofs - Offset of the highest entry
+  /// min_index - Minimum entry index
+  /// max_index - Maximum entry index
+  /// max_time - Time of the latest push
+  ///
+  /// The difference between ofs and index is that ofs is a byte
+  /// offset. Index is a count. Nothing really uses indices, but
+  /// they're tracked and sanity-checked as an invariant on the OSD.
+  ///
+  /// max_ofs and max_time are the two that have been used externally
+  /// so far.
+  template<typename CT>
+  auto get_part_info(int64_t part_num, // The number of the partition
+		     CT&& ct // CompletionToken
+    ) {
+
+    ba::async_completion<CT, void(bs::error_code, part_info)> init(ct);
+    fifo::op::get_part_info gpi;
+    cb::list in;
+    encode(gpi, in);
+    ReadOp op;
+    auto e = ba::get_associated_executor(init.completion_handler,
+					 get_executor());
+    auto a = ba::get_associated_allocator(init.completion_handler);
+    auto reply = ceph::allocate_unique<
+      ExecDecodeCB<fifo::op::get_part_info_reply>>(a);
+
+    op.exec(fifo::op::CLASS, fifo::op::GET_PART_INFO, in,
+	    std::ref(*reply));
+    std::unique_lock l(m);
+    auto part_oid = info.part_oid(part_num);
+    l.unlock();
+    r->execute(part_oid, ioc, std::move(op), nullptr,
+	       ca::bind_ea(e, a,
+			   PartInfoGetter(std::move(init.completion_handler),
+					  std::move(reply))));
+    return init.result.get();
+  }
+
+  using executor_type = ba::executor;
+
+  /// Return the default executor, as specified at creation.
+  ba::executor get_executor() const {
+    return executor;
+  }
+
+private:
+  template<typename Handler>
+  friend class detail::JournalProcessor;
+  RADOS* const r;
+  const IOContext ioc;
+  const Object oid;
+  std::mutex m;
+
+  fifo::info info;
+
+  std::uint32_t part_header_size = 0xdeadbeef;
+  std::uint32_t part_entry_overhead = 0xdeadbeef;
+
+  ba::executor executor;
+
+  std::optional<marker> to_marker(std::string_view s);
+
+  template<typename Handler, typename T>
+  static void assoc_delete(const Handler& handler, T* t) {
+    typename std::allocator_traits<typename ba::associated_allocator<Handler>::type>
+      ::template rebind_alloc<T> a(
+	ba::get_associated_allocator(handler));
+    a.destroy(t);
+    a.deallocate(t, 1);
+  }
+
+  FIFO(RADOS& r,
+       IOContext ioc,
+       Object oid,
+       ba::executor executor)
+    : r(&r), ioc(std::move(ioc)), oid(oid), executor(executor) {}
+
+  std::string generate_tag() const;
+
+  template <typename T>
+  struct ExecDecodeCB {
+    bs::error_code ec;
+    T result;
+    void operator()(bs::error_code e, const cb::list& r) {
+      if (e) {
+        ec = e;
+        return;
+      }
+      try {
+        auto p = r.begin();
+        using ceph::decode;
+        decode(result, p);
+      } catch (const cb::error& err) {
+        ec = err.code();
+      }
+    }
+  };
+
+  template<typename Handler>
+  class MetaReader {
+    Handler handler;
+    using allocator_type = boost::asio::associated_allocator_t<Handler>;
+    using decoder_type = ExecDecodeCB<fifo::op::get_meta_reply>;
+    using decoder_ptr = ceph::allocated_unique_ptr<decoder_type, allocator_type>;
+    decoder_ptr decoder;
+  public:
+    MetaReader(Handler&& handler, decoder_ptr&& decoder)
+      : handler(std::move(handler)), decoder(std::move(decoder)) {}
+
+    void operator ()(bs::error_code ec) {
+      if (!ec) {
+        ec = decoder->ec;
+      }
+      auto reply = std::move(decoder->result);
+      decoder.reset(); // free handler-allocated memory before dispatching
+
+      std::move(handler)(ec, std::move(reply.info),
+			 std::move(reply.part_header_size),
+			 std::move(reply.part_entry_overhead));
+    }
+  };
+
+  // Renamed to get around a compiler bug in Bionic that kept
+  // complaining we weren't capturing 'this' to make a static function call.
+  template<typename Handler>
+  static void _read_meta_(RADOS* r, const Object& oid, const IOContext& ioc,
+			  std::optional<fifo::objv> objv,
+			  Handler&& handler, /* error_code, info, uint64,
+						uint64 */
+			  std::optional<ba::executor> executor = std::nullopt){
+    fifo::op::get_meta gm;
+
+    gm.version = objv;
+
+    cb::list in;
+    encode(gm, in);
+    ReadOp op;
+
+    auto a = ba::get_associated_allocator(handler);
+    auto reply =
+      ceph::allocate_unique<ExecDecodeCB<fifo::op::get_meta_reply>>(a);
+
+    auto e = ba::get_associated_executor(handler);
+    op.exec(fifo::op::CLASS, fifo::op::GET_META, in, std::ref(*reply));
+    r->execute(oid, ioc, std::move(op), nullptr,
+	       ca::bind_ea(e, a, MetaReader(std::move(handler),
+					    std::move(reply))));
+  };
+
+  template<typename Handler>
+  void _read_meta(Handler&& handler /* error_code */) {
+    auto e = ba::get_associated_executor(handler, get_executor());
+    auto a = ba::get_associated_allocator(handler);
+    _read_meta_(r, oid, ioc,
+		nullopt,
+		ca::bind_ea(
+		  e, a,
+		  [this,
+		   handler = std::move(handler)](bs::error_code ec,
+						 fifo::info&& info,
+						 std::uint64_t phs,
+						 std::uint64_t peo) mutable {
+		    std::unique_lock l(m);
+		    if (ec) {
+		      l.unlock();
+		      std::move(handler)(ec);
+		      return;
+		    }
+		    // We have a newer version already!
+		    if (!info.version.same_or_later(this->info.version)) {
+		      l.unlock();
+		      std::move(handler)(bs::error_code{});
+		      return;
+		    }
+		    this->info = std::move(info);
+		    part_header_size = phs;
+		    part_entry_overhead = peo;
+		    l.unlock();
+		    std::move(handler)(bs::error_code{});
+		  }), get_executor());
+  }
+
+  bs::error_code apply_update(fifo::info* info,
+			      const fifo::objv& objv,
+			      const fifo::update& update);
+
+
+  template<typename Handler>
+  void _update_meta(const fifo::update& update,
+		    fifo::objv version,
+		    Handler&& handler /* error_code, bool */) {
+    WriteOp op;
+
+    cls::fifo::update_meta(op, info.version, update);
+
+    auto a = ba::get_associated_allocator(handler);
+    auto e = ba::get_associated_executor(handler, get_executor());
+
+    r->execute(
+      oid, ioc, std::move(op),
+      ca::bind_ea(
+	e, a,
+	[this, e, a, version, update,
+	 handler = std::move(handler)](bs::error_code ec) mutable {
+	  if (ec && ec != bs::errc::operation_canceled) {
+	    std::move(handler)(ec, bool{});
+	    return;
+	  }
+
+	  auto canceled = (ec == bs::errc::operation_canceled);
+
+	  if (!canceled) {
+	    ec = apply_update(&info,
+			      version,
+			      update);
+	    if (ec) {
+	      canceled = true;
+	    }
+	  }
+
+	  if (canceled) {
+	    _read_meta(
+	      ca::bind_ea(
+		e, a,
+		[handler = std::move(handler)](bs::error_code ec) mutable {
+		  std::move(handler)(ec, ec ? false : true);
+		}));
+	    return;
+	  }
+	  std::move(handler)(ec, false);
+	  return;
+	}));
+  }
+
+  template<typename Handler>
+  auto _process_journal(Handler&& handler /* error_code */) {
+    auto a = ba::get_associated_allocator(std::ref(handler));
+    auto j = ceph::allocate_unique<detail::JournalProcessor<Handler>>(
+      a, this, std::move(handler));
+    auto p = j.release();
+    p->process();
+  }
+
+  template<typename Handler>
+  class NewPartPreparer {
+    FIFO* f;
+    Handler handler;
+    std::vector<fifo::journal_entry> jentries;
+    int i;
+    std::int64_t new_head_part_num;
+
+  public:
+
+    void operator ()(bs::error_code ec, bool canceled) {
+      if (ec) {
+	std::move(handler)(ec);
+	return;
+      }
+
+      if (canceled) {
+	std::unique_lock l(f->m);
+	auto iter = f->info.journal.find(jentries.front().part_num);
+	auto max_push_part_num = f->info.max_push_part_num;
+	auto head_part_num = f->info.head_part_num;
+	auto version = f->info.version;
+	auto found = (iter != f->info.journal.end());
+	l.unlock();
+	if ((max_push_part_num >= jentries.front().part_num &&
+	    head_part_num >= new_head_part_num)) {
+	  /* raced, but new part was already written */
+	  std::move(handler)(bs::error_code{});
+	  return;
+	}
+	if (i >= MAX_RACE_RETRIES) {
+	  std::move(handler)(errc::raced);
+	  return;
+	}
+	if (!found) {
+	  auto e = ba::get_associated_executor(handler, f->get_executor());
+	  auto a = ba::get_associated_allocator(handler);
+	  f->_update_meta(fifo::update{}
+			  .journal_entries_add(jentries),
+                          version,
+			  ca::bind_ea(
+			    e, a,
+			    NewPartPreparer(f, std::move(handler),
+					    jentries,
+					    i + 1, new_head_part_num)));
+	  return;
+	}
+	// Fall through. We still need to process the journal.
+      }
+      f->_process_journal(std::move(handler));
+      return;
+    }
+
+    NewPartPreparer(FIFO* f,
+		    Handler&& handler,
+		    std::vector<fifo::journal_entry> jentries,
+		    int i, std::int64_t new_head_part_num)
+      : f(f), handler(std::move(handler)), jentries(std::move(jentries)),
+	i(i), new_head_part_num(new_head_part_num) {}
+  };
+
+  template<typename Handler>
+  void _prepare_new_part(bool is_head,
+			 Handler&& handler /* error_code */) {
+    std::unique_lock l(m);
+    std::vector jentries = { info.next_journal_entry(generate_tag()) };
+    std::int64_t new_head_part_num = info.head_part_num;
+    auto version = info.version;
+
+    if (is_head) {
+      auto new_head_jentry = jentries.front();
+      new_head_jentry.op = fifo::journal_entry::Op::set_head;
+      new_head_part_num = jentries.front().part_num;
+      jentries.push_back(std::move(new_head_jentry));
+    }
+    l.unlock();
+
+    auto e = ba::get_associated_executor(handler, get_executor());
+    auto a = ba::get_associated_allocator(handler);
+    _update_meta(fifo::update{}.journal_entries_add(jentries),
+		 version,
+		 ca::bind_ea(
+		   e, a,
+		   NewPartPreparer(this, std::move(handler),
+				   jentries, 0, new_head_part_num)));
+  }
+
+  template<typename Handler>
+  class NewHeadPreparer {
+    FIFO* f;
+    Handler handler;
+    int i;
+    std::int64_t new_head_num;
+
+  public:
+
+    void operator ()(bs::error_code ec, bool canceled) {
+      std::unique_lock l(f->m);
+      auto head_part_num = f->info.head_part_num;
+      auto version = f->info.version;
+      l.unlock();
+
+      if (ec) {
+	std::move(handler)(ec);
+	return;
+      }
+      if (canceled) {
+	if (i >= MAX_RACE_RETRIES) {
+	  std::move(handler)(errc::raced);
+	  return;
+	}
+
+	// Raced, but there's still work to do!
+	if (head_part_num < new_head_num) {
+	  auto e = ba::get_associated_executor(handler, f->get_executor());
+	  auto a = ba::get_associated_allocator(handler);
+	  f->_update_meta(fifo::update{}.head_part_num(new_head_num),
+			  version,
+			  ca::bind_ea(
+			    e, a,
+			    NewHeadPreparer(f, std::move(handler),
+					    i + 1,
+					    new_head_num)));
+	  return;
+	}
+      }
+      // Either we succeeded, or we were raced by someone who did it for us.
+      std::move(handler)(bs::error_code{});
+      return;
+    }
+
+    NewHeadPreparer(FIFO* f,
+		    Handler&& handler,
+		    int i, std::int64_t new_head_num)
+      : f(f), handler(std::move(handler)), i(i), new_head_num(new_head_num) {}
+  };
+
+  template<typename Handler>
+  void _prepare_new_head(Handler&& handler /* error_code */) {
+    std::unique_lock l(m);
+    int64_t new_head_num = info.head_part_num + 1;
+    auto max_push_part_num = info.max_push_part_num;
+    auto version = info.version;
+    l.unlock();
+
+    if (max_push_part_num < new_head_num) {
+      auto e = ba::get_associated_executor(handler, get_executor());
+      auto a = ba::get_associated_allocator(handler);
+      _prepare_new_part(
+	true,
+	ca::bind_ea(
+	  e, a,
+	  [this, new_head_num,
+	   handler = std::move(handler)](bs::error_code ec) mutable {
+	    if (ec) {
+	      handler(ec);
+	      return;
+	    }
+	    std::unique_lock l(m);
+	    if (info.max_push_part_num < new_head_num) {
+	      l.unlock();
+	      ldout(r->cct(), 0)
+		<< "ERROR: " << __func__
+		<< ": after new part creation: meta_info.max_push_part_num="
+		<< info.max_push_part_num << " new_head_num="
+		<< info.max_push_part_num << dendl;
+	      std::move(handler)(errc::inconsistency);
+	    } else {
+	      l.unlock();
+	      std::move(handler)(bs::error_code{});
+	    }
+	  }));
+      return;
+    }
+    auto e = ba::get_associated_executor(handler, get_executor());
+    auto a = ba::get_associated_allocator(handler);
+    _update_meta(fifo::update{}.head_part_num(new_head_num),
+		 version,
+		 ca::bind_ea(
+		   e, a,
+		   NewHeadPreparer(this, std::move(handler), 0,
+				   new_head_num)));
+  }
+
+  template<typename T>
+  struct ExecHandleCB {
+    bs::error_code ec;
+    T result;
+    void operator()(bs::error_code e, const T& t) {
+      if (e) {
+        ec = e;
+        return;
+      }
+      result = t;
+    }
+  };
+
+  template<typename Handler>
+  class EntryPusher {
+    Handler handler;
+    using allocator_type = boost::asio::associated_allocator_t<Handler>;
+    using decoder_type = ExecHandleCB<int>;
+    using decoder_ptr = ceph::allocated_unique_ptr<decoder_type, allocator_type>;
+    decoder_ptr decoder;
+
+  public:
+
+    EntryPusher(Handler&& handler, decoder_ptr&& decoder)
+      : handler(std::move(handler)), decoder(std::move(decoder)) {}
+
+    void operator ()(bs::error_code ec) {
+      if (!ec) {
+        ec = decoder->ec;
+      }
+      auto reply = std::move(decoder->result);
+      decoder.reset(); // free handler-allocated memory before dispatching
+
+      std::move(handler)(ec, std::move(reply));
+    }
+  };
+
+  template<typename Handler>
+  auto push_entries(const std::deque<cb::list>& data_bufs,
+		    Handler&& handler /* error_code, int */) {
+    WriteOp op;
+    std::unique_lock l(m);
+    auto head_part_num = info.head_part_num;
+    auto tag = info.head_tag;
+    auto oid = info.part_oid(head_part_num);
+    l.unlock();
+
+    auto a = ba::get_associated_allocator(handler);
+    auto reply = ceph::allocate_unique<ExecHandleCB<int>>(a);
+
+    auto e = ba::get_associated_executor(handler, get_executor());
+    push_part(op, tag, data_bufs, std::ref(*reply));
+    return r->execute(oid, ioc, std::move(op),
+		      ca::bind_ea(e, a, EntryPusher(std::move(handler),
+						    std::move(reply))));
+  }
+
+  template<typename CT>
+  auto trim_part(int64_t part_num,
+		 uint64_t ofs,
+		 std::optional<std::string_view> tag,
+		 bool exclusive,
+		 CT&& ct) {
+    WriteOp op;
+    cls::fifo::trim_part(op, tag, ofs, exclusive);
+    return r->execute(info.part_oid(part_num), ioc, std::move(op),
+		      std::forward<CT>(ct));
+  }
+
+
+  template<typename Handler>
+  class Pusher {
+    FIFO* f;
+    std::deque<cb::list> remaining;
+    std::deque<cb::list> batch;
+    int i;
+    Handler handler;
+
+    void prep_then_push(const unsigned successes) {
+      std::unique_lock l(f->m);
+      auto max_part_size = f->info.params.max_part_size;
+      auto part_entry_overhead = f->part_entry_overhead;
+      l.unlock();
+
+      uint64_t batch_len = 0;
+      if (successes > 0) {
+	if (successes == batch.size()) {
+	  batch.clear();
+	} else  {
+	  batch.erase(batch.begin(), batch.begin() + successes);
+	  for (const auto& b : batch) {
+	    batch_len +=  b.length() + part_entry_overhead;
+	  }
+	}
+      }
+
+      if (batch.empty() && remaining.empty()) {
+	std::move(handler)(bs::error_code{});
+	return;
+      }
+
+      while (!remaining.empty() &&
+	     (remaining.front().length() + batch_len <= max_part_size)) {
+
+	/* We can send entries with data_len up to max_entry_size,
+	   however, we want to also account the overhead when
+	   dealing with multiple entries. Previous check doesn't
+	   account for overhead on purpose. */
+	batch_len += remaining.front().length() + part_entry_overhead;
+	batch.push_back(std::move(remaining.front()));
+	remaining.pop_front();
+      }
+      push();
+    }
+
+    void push() {
+      auto e = ba::get_associated_executor(handler, f->get_executor());
+      auto a = ba::get_associated_allocator(handler);
+      f->push_entries(batch,
+		      ca::bind_ea(e, a,
+				  Pusher(f, std::move(remaining),
+					 batch, i,
+					 std::move(handler))));
+    }
+
+  public:
+
+    // Initial call!
+    void operator ()() {
+      prep_then_push(0);
+    }
+
+    // Called with response to push_entries
+    void operator ()(bs::error_code ec, int r) {
+      if (ec == bs::errc::result_out_of_range) {
+	auto e = ba::get_associated_executor(handler, f->get_executor());
+	auto a = ba::get_associated_allocator(handler);
+	f->_prepare_new_head(
+	  ca::bind_ea(e, a,
+		      Pusher(f, std::move(remaining),
+			     std::move(batch), i,
+			     std::move(handler))));
+	return;
+      }
+      if (ec) {
+	std::move(handler)(ec);
+	return;
+      }
+      i = 0; // We've made forward progress, so reset the race counter!
+      prep_then_push(r);
+    }
+
+    // Called with response to prepare_new_head
+    void operator ()(bs::error_code ec) {
+      if (ec == bs::errc::operation_canceled) {
+	if (i == MAX_RACE_RETRIES) {
+	  ldout(f->r->cct(), 0)
+	    << "ERROR: " << __func__
+	    << "(): race check failed too many times, likely a bug" << dendl;
+	  std::move(handler)(make_error_code(errc::raced));
+	  return;
+	}
+	++i;
+      } else if (ec) {
+	std::move(handler)(ec);
+	return;
+      }
+
+      if (batch.empty()) {
+	prep_then_push(0);
+	return;
+      } else {
+	push();
+	return;
+      }
+    }
+
+    Pusher(FIFO* f, std::deque<cb::list>&& remaining,
+	   std::deque<cb::list> batch, int i,
+	   Handler&& handler)
+      : f(f), remaining(std::move(remaining)),
+	batch(std::move(batch)), i(i),
+	handler(std::move(handler)) {}
+  };
+
+  template<typename Handler>
+  class Lister {
+    FIFO* f;
+    std::vector<list_entry> result;
+    bool more = false;
+    std::int64_t part_num;
+    std::uint64_t ofs;
+    int max_entries;
+    bs::error_code ec_out;
+    std::vector<fifo::part_list_entry> entries;
+    bool part_more = false;
+    bool part_full = false;
+    Handler handler;
+
+    void handle(bs::error_code ec) {
+      auto h = std::move(handler);
+      auto m = more;
+      auto r = std::move(result);
+
+      FIFO::assoc_delete(h, this);
+      std::move(h)(ec, std::move(r), m);
+    }
+
+  public:
+    Lister(FIFO* f, std::int64_t part_num, std::uint64_t ofs, int max_entries,
+	   Handler&& handler)
+      : f(f), part_num(part_num), ofs(ofs), max_entries(max_entries),
+	handler(std::move(handler)) {
+      result.reserve(max_entries);
+    }
+
+
+    Lister(const Lister&) = delete;
+    Lister& operator =(const Lister&) = delete;
+    Lister(Lister&&) = delete;
+    Lister& operator =(Lister&&) = delete;
+
+    void list() {
+      if (max_entries > 0) {
+	ReadOp op;
+	ec_out.clear();
+	part_more = false;
+	part_full = false;
+	entries.clear();
+
+	std::unique_lock l(f->m);
+	auto part_oid = f->info.part_oid(part_num);
+	l.unlock();
+
+	list_part(op,
+		  {},
+		  ofs,
+		  max_entries,
+		  &ec_out,
+		  &entries,
+		  &part_more,
+		  &part_full,
+		  nullptr);
+	auto e = ba::get_associated_executor(handler, f->get_executor());
+	auto a = ba::get_associated_allocator(handler);
+	f->r->execute(
+	  part_oid,
+	  f->ioc,
+	  std::move(op),
+	  nullptr,
+	  ca::bind_ea(
+	    e, a,
+	    [t = std::unique_ptr<Lister>(this), this,
+	     part_oid](bs::error_code ec) mutable {
+	      t.release();
+	      if (ec == bs::errc::no_such_file_or_directory) {
+		auto e = ba::get_associated_executor(handler,
+						     f->get_executor());
+		auto a = ba::get_associated_allocator(handler);
+		f->_read_meta(
+		  ca::bind_ea(
+		    e, a,
+		    [this](bs::error_code ec) mutable {
+		      if (ec) {
+			handle(ec);
+			return;
+		      }
+
+		      if (part_num < f->info.tail_part_num) {
+			/* raced with trim? restart */
+			max_entries += result.size();
+			result.clear();
+			part_num = f->info.tail_part_num;
+			ofs = 0;
+			list();
+		      }
+		      /* assuming part was not written yet, so end of data */
+		      more = false;
+		      handle({});
+		      return;
+		    }));
+		return;
+	      }
+	      if (ec) {
+		ldout(f->r->cct(), 0)
+		  << __func__
+		  << "(): list_part() on oid=" << part_oid
+		  << " returned ec=" << ec.message() << dendl;
+		handle(ec);
+		return;
+	      }
+	      if (ec_out) {
+		ldout(f->r->cct(), 0)
+		  << __func__
+		  << "(): list_part() on oid=" << f->info.part_oid(part_num)
+		  << " returned ec=" << ec_out.message() << dendl;
+		handle(ec_out);
+		return;
+	      }
+
+	      more = part_full || part_more;
+	      for (auto& entry : entries) {
+		list_entry e;
+		e.data = std::move(entry.data);
+		e.marker = marker{part_num, entry.ofs}.to_string();
+		e.mtime = entry.mtime;
+		result.push_back(std::move(e));
+	      }
+	      max_entries -= entries.size();
+	      entries.clear();
+	      if (max_entries > 0 &&
+		  part_more) {
+		list();
+		return;
+	      }
+
+	      if (!part_full) { /* head part is not full */
+		handle({});
+		return;
+	      }
+	      ++part_num;
+	      ofs = 0;
+	    list();
+	    }));
+      } else {
+	handle({});
+	return;
+      }
+    }
+  };
+
+  template<typename Handler>
+  class Trimmer {
+    FIFO* f;
+    std::int64_t part_num;
+    std::uint64_t ofs;
+    bool exclusive;
+    Handler handler;
+    std::int64_t pn;
+    int i = 0;
+
+    void handle(bs::error_code ec) {
+      auto h = std::move(handler);
+
+      FIFO::assoc_delete(h, this);
+      return std::move(h)(ec);
+    }
+
+    void update() {
+      std::unique_lock l(f->m);
+      auto objv = f->info.version;
+      l.unlock();
+      auto a = ba::get_associated_allocator(handler);
+      auto e = ba::get_associated_executor(handler, f->get_executor());
+      f->_update_meta(
+	fifo::update{}.tail_part_num(part_num),
+	objv,
+	ca::bind_ea(
+	  e, a,
+	  [this, t = std::unique_ptr<Trimmer>(this)](bs::error_code ec,
+						     bool canceled) mutable {
+	    t.release();
+	    if (canceled)
+	      if (i >= MAX_RACE_RETRIES) {
+		ldout(f->r->cct(), 0)
+		  << "ERROR: " << __func__
+		  << "(): race check failed too many times, likely a bug"
+		  << dendl;
+		handle(errc::raced);
+		return;
+	      }
+	    std::unique_lock l(f->m);
+	    auto tail_part_num = f->info.tail_part_num;
+	    l.unlock();
+	    if (tail_part_num < part_num) {
+	      ++i;
+	      update();
+	      return;
+	    }
+	    handle({});
+	    return;
+	  }));
+    }
+
+  public:
+    Trimmer(FIFO* f, std::int64_t part_num, std::uint64_t ofs,
+	    bool exclusive, Handler&& handler)
+      : f(f), part_num(part_num), ofs(ofs), exclusive(exclusive),
+	handler(std::move(handler)) {
+      std::unique_lock l(f->m);
+      pn = f->info.tail_part_num;
+    }
+
+    void trim() {
+      auto a = ba::get_associated_allocator(handler);
+      auto e = ba::get_associated_executor(handler, f->get_executor());
+      if (pn < part_num) {
+	std::unique_lock l(f->m);
+	auto max_part_size = f->info.params.max_part_size;
+	l.unlock();
+	f->trim_part(
+	  pn, max_part_size, std::nullopt,
+	  false,
+	  ca::bind_ea(
+	    e, a,
+	    [t = std::unique_ptr<Trimmer>(this),
+	     this](bs::error_code ec) mutable {
+	      t.release();
+	      if (ec && ec != bs::errc::no_such_file_or_directory) {
+		ldout(f->r->cct(), 0)
+		  << __func__ << "(): ERROR: trim_part() on part="
+		  << pn << " returned ec=" << ec.message() << dendl;
+		handle(ec);
+		return;
+	      }
+	      ++pn;
+	      trim();
+	    }));
+	return;
+      }
+      f->trim_part(
+	part_num, ofs, std::nullopt, exclusive,
+	ca::bind_ea(
+	  e, a,
+	  [t = std::unique_ptr<Trimmer>(this),
+	    this](bs::error_code ec) mutable {
+	    t.release();
+	    if (ec && ec != bs::errc::no_such_file_or_directory) {
+	      ldout(f->r->cct(), 0)
+		<< __func__ << "(): ERROR: trim_part() on part=" << part_num
+		<< " returned ec=" << ec.message() << dendl;
+	      handle(ec);
+	      return;
+	    }
+	    std::unique_lock l(f->m);
+	    auto tail_part_num = f->info.tail_part_num;
+	    l.unlock();
+	    if (part_num <= tail_part_num) {
+	      /* don't need to modify meta info */
+	      handle({});
+	      return;
+	    }
+	    update();
+	  }));
+    }
+  };
+
+  template<typename Handler>
+  class PartInfoGetter {
+    Handler handler;
+    using allocator_type = boost::asio::associated_allocator_t<Handler>;
+    using decoder_type = ExecDecodeCB<fifo::op::get_part_info_reply>;
+    using decoder_ptr = ceph::allocated_unique_ptr<decoder_type, allocator_type>;
+    decoder_ptr decoder;
+  public:
+    PartInfoGetter(Handler&& handler, decoder_ptr&& decoder)
+      : handler(std::move(handler)), decoder(std::move(decoder)) {}
+
+    void operator ()(bs::error_code ec) {
+      if (!ec) {
+        ec = decoder->ec;
+      }
+      auto reply = std::move(decoder->result);
+      decoder.reset(); // free handler-allocated memory before dispatching
+
+      auto p = ca::bind_handler(std::move(handler),
+				ec, std::move(reply.header));
+      std::move(p)();
+    }
+  };
+
+
+};
+
+namespace detail {
+template<typename Handler>
+class JournalProcessor {
+private:
+  FIFO* const fifo;
+  Handler handler;
+
+  std::vector<fifo::journal_entry> processed;
+  std::multimap<std::int64_t, fifo::journal_entry> journal;
+  std::multimap<std::int64_t, fifo::journal_entry>::iterator iter;
+  std::int64_t new_tail;
+  std::int64_t new_head;
+  std::int64_t new_max;
+  int race_retries = 0;
+
+  template<typename CT>
+  auto create_part(int64_t part_num, std::string_view tag, CT&& ct) {
+    WriteOp op;
+    op.create(false); /* We don't need exclusivity, part_init ensures
+			 we're creating from the  same journal entry. */
+    std::unique_lock l(fifo->m);
+    part_init(op, tag, fifo->info.params);
+    auto oid = fifo->info.part_oid(part_num);
+    l.unlock();
+    return fifo->r->execute(oid, fifo->ioc,
+			    std::move(op), std::forward<CT>(ct));
+  }
+
+  template<typename CT>
+  auto remove_part(int64_t part_num, std::string_view tag, CT&& ct) {
+    WriteOp op;
+    op.remove();
+    std::unique_lock l(fifo->m);
+    auto oid = fifo->info.part_oid(part_num);
+    l.unlock();
+    return fifo->r->execute(oid, fifo->ioc,
+			    std::move(op), std::forward<CT>(ct));
+  }
+
+  template<typename PP>
+  void process_journal_entry(const fifo::journal_entry& entry,
+			     PP&& pp) {
+    switch (entry.op) {
+    case fifo::journal_entry::Op::unknown:
+      std::move(pp)(errc::inconsistency);
+      return;
+      break;
+
+    case fifo::journal_entry::Op::create:
+      create_part(entry.part_num, entry.part_tag, std::move(pp));
+      return;
+      break;
+    case fifo::journal_entry::Op::set_head:
+      ba::post(ba::get_associated_executor(handler, fifo->get_executor()),
+		      [pp = std::move(pp)]() mutable {
+			std::move(pp)(bs::error_code{});
+		      });
+      return;
+      break;
+    case fifo::journal_entry::Op::remove:
+      remove_part(entry.part_num, entry.part_tag, std::move(pp));
+      return;
+      break;
+    }
+    std::move(pp)(errc::inconsistency);
+    return;
+  }
+
+  auto journal_entry_finisher(const fifo::journal_entry& entry) {
+    auto a = ba::get_associated_allocator(handler);
+    auto e = ba::get_associated_executor(handler, fifo->get_executor());
+    return
+      ca::bind_ea(
+	e, a,
+	[t = std::unique_ptr<JournalProcessor>(this), this,
+	 entry](bs::error_code ec) mutable {
+	  t.release();
+	  if (entry.op == fifo::journal_entry::Op::remove &&
+	      ec == bs::errc::no_such_file_or_directory)
+	    ec.clear();
+
+	  if (ec) {
+	    ldout(fifo->r->cct(), 0)
+	      << __func__
+	      << "(): ERROR: failed processing journal entry for part="
+	      << entry.part_num << " with error " << ec.message()
+	      << " Bug or inconsistency." << dendl;
+	    handle(errc::inconsistency);
+	    return;
+	  } else {
+	    switch (entry.op) {
+	    case fifo::journal_entry::Op::unknown:
+	      // Can't happen. Filtered out in process_journal_entry.
+	      abort();
+	      break;
+
+	    case fifo::journal_entry::Op::create:
+	      if (entry.part_num > new_max) {
+		new_max = entry.part_num;
+	      }
+	      break;
+	    case fifo::journal_entry::Op::set_head:
+	      if (entry.part_num > new_head) {
+		new_head = entry.part_num;
+	      }
+	      break;
+	    case fifo::journal_entry::Op::remove:
+	      if (entry.part_num >= new_tail) {
+		new_tail = entry.part_num + 1;
+	      }
+	      break;
+	    }
+	    processed.push_back(entry);
+	  }
+	  ++iter;
+	  process();
+	});
+  }
+
+  struct JournalPostprocessor {
+    std::unique_ptr<JournalProcessor> j_;
+    bool first;
+    void operator ()(bs::error_code ec, bool canceled) {
+      std::optional<int64_t> tail_part_num;
+      std::optional<int64_t> head_part_num;
+      std::optional<int64_t> max_part_num;
+
+      auto j = j_.release();
+
+      if (!first && !ec && !canceled) {
+	j->handle({});
+	return;
+      }
+
+      if (canceled) {
+	if (j->race_retries >= MAX_RACE_RETRIES) {
+	  ldout(j->fifo->r->cct(), 0) << "ERROR: " << __func__ <<
+	    "(): race check failed too many times, likely a bug" << dendl;
+	  j->handle(errc::raced);
+	  return;
+	}
+
+	++j->race_retries;
+
+	std::vector<fifo::journal_entry> new_processed;
+	std::unique_lock l(j->fifo->m);
+	for (auto& e : j->processed) {
+	  auto jiter = j->fifo->info.journal.find(e.part_num);
+	  /* journal entry was already processed */
+	  if (jiter == j->fifo->info.journal.end() ||
+	      !(jiter->second == e)) {
+	    continue;
+	  }
+	  new_processed.push_back(e);
+	}
+	j->processed = std::move(new_processed);
+      }
+
+      std::unique_lock l(j->fifo->m);
+      auto objv = j->fifo->info.version;
+      if (j->new_tail > j->fifo->info.tail_part_num) {
+	tail_part_num = j->new_tail;
+      }
+
+      if (j->new_head > j->fifo->info.head_part_num) {
+	head_part_num = j->new_head;
+      }
+
+      if (j->new_max > j->fifo->info.max_push_part_num) {
+	max_part_num = j->new_max;
+      }
+      l.unlock();
+
+      if (j->processed.empty() &&
+	  !tail_part_num &&
+	  !max_part_num) {
+	/* nothing to update anymore */
+	j->handle({});
+	return;
+      }
+      auto a = ba::get_associated_allocator(j->handler);
+      auto e = ba::get_associated_executor(j->handler, j->fifo->get_executor());
+      j->fifo->_update_meta(fifo::update{}
+			    .tail_part_num(tail_part_num)
+		            .head_part_num(head_part_num)
+		            .max_push_part_num(max_part_num)
+			    .journal_entries_rm(j->processed),
+                            objv,
+                            ca::bind_ea(
+			      e, a,
+			      JournalPostprocessor{j, false}));
+      return;
+    }
+
+    JournalPostprocessor(JournalProcessor* j, bool first)
+      : j_(j), first(first) {}
+  };
+
+  void postprocess() {
+    if (processed.empty()) {
+      handle({});
+      return;
+    }
+    JournalPostprocessor(this, true)({}, false);
+  }
+
+  void handle(bs::error_code ec) {
+    auto e = ba::get_associated_executor(handler, fifo->get_executor());
+    auto a = ba::get_associated_allocator(handler);
+    auto h = std::move(handler);
+    FIFO::assoc_delete(h, this);
+    e.dispatch(ca::bind_handler(std::move(h), ec), a);
+    return;
+  }
+
+public:
+
+  JournalProcessor(FIFO* fifo, Handler&& handler)
+    : fifo(fifo), handler(std::move(handler)) {
+    std::unique_lock l(fifo->m);
+    journal = fifo->info.journal;
+    iter = journal.begin();
+    new_tail = fifo->info.tail_part_num;
+    new_head = fifo->info.head_part_num;
+    new_max = fifo->info.max_push_part_num;
+  }
+
+  JournalProcessor(const JournalProcessor&) = delete;
+  JournalProcessor& operator =(const JournalProcessor&) = delete;
+  JournalProcessor(JournalProcessor&&) = delete;
+  JournalProcessor& operator =(JournalProcessor&&) = delete;
+
+  void process() {
+    if (iter != journal.end()) {
+      const auto entry = iter->second;
+      process_journal_entry(entry,
+			    journal_entry_finisher(entry));
+      return;
+    } else {
+      postprocess();
+      return;
+    }
+  }
+};
+}
+}
+
+#endif // CEPH_RADOS_CLS_FIFIO_H