From cd8a069ab394ae6f2ad76a999fa1b2fd23a542b1 Mon Sep 17 00:00:00 2001
From: Samuel Just <sjust@redhat.com>
Date: Wed, 24 Aug 2022 15:42:33 -0700
Subject: [PATCH] crimson/common: introduce smp_helpers.h, crimson::submit_to

Introduce crimson::submit_to wrapper to transparently deal with
vanilla and errorated futures, adds helpers to errorator.h.

Signed-off-by: Samuel Just <sjust@redhat.com>
---
 src/crimson/common/errorator.h   | 18 +++++++
 src/crimson/common/smp_helpers.h | 80 ++++++++++++++++++++++++++++++++
 2 files changed, 98 insertions(+)
 create mode 100644 src/crimson/common/smp_helpers.h

diff --git a/src/crimson/common/errorator.h b/src/crimson/common/errorator.h
index c6c1a8b476d..aee05f66915 100644
--- a/src/crimson/common/errorator.h
+++ b/src/crimson/common/errorator.h
@@ -475,6 +475,10 @@ private:
       : base_t(std::move(base)) {
     }
 
+    base_t to_base() && {
+      return std::move(*this);
+    }
+
     template <class... A>
     [[gnu::always_inline]]
     _future(ready_future_marker, A&&... a)
@@ -1199,6 +1203,20 @@ using stateful_errc = stateful_error_t<std::errc>;
 using stateful_errint = stateful_error_t<int>;
 using stateful_ec = stateful_error_t<std::error_code>;
 
+template <typename F>
+struct is_errorated_future {
+  static constexpr bool value = false;
+};
+template <template <class...> class ErroratedFutureT,
+	  class ValueT>
+struct is_errorated_future<
+  ErroratedFutureT<::crimson::errorated_future_marker<ValueT>>
+  > {
+  static constexpr bool value = true;
+};
+template <typename T>
+constexpr bool is_errorated_future_v = is_errorated_future<T>::value;
+
 } // namespace crimson
 
 
diff --git a/src/crimson/common/smp_helpers.h b/src/crimson/common/smp_helpers.h
new file mode 100644
index 00000000000..165f110b6e8
--- /dev/null
+++ b/src/crimson/common/smp_helpers.h
@@ -0,0 +1,80 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#pragma once
+
+#include <limits>
+
+#include <seastar/core/smp.hh>
+
+#include "crimson/common/errorator.h"
+#include "crimson/common/utility.h"
+
+namespace crimson {
+
+using core_id_t = seastar::shard_id;
+static constexpr core_id_t NULL_CORE = std::numeric_limits<core_id_t>::max();
+
+auto submit_to(core_id_t core, auto &&f) {
+  using ret_type = decltype(f());
+  if constexpr (is_errorated_future_v<ret_type>) {
+    auto ret = seastar::smp::submit_to(
+      core,
+      [f=std::move(f)]() mutable {
+	return f().to_base();
+      });
+    return ret_type(std::move(ret));
+  } else {
+    return seastar::smp::submit_to(core, std::move(f));
+  }
+}
+
+template <typename Obj, typename Method, typename... Args>
+auto proxy_method_on_core(
+  core_id_t core, Obj &obj, Method method, Args&&... args) {
+  return crimson::submit_to(
+    core,
+    [&obj, method,
+     arg_tuple=std::make_tuple(std::forward<Args>(args)...)]() mutable {
+      return apply_method_to_tuple(obj, method, std::move(arg_tuple));
+    });
+}
+
+/**
+ * sharded_map_seq
+ *
+ * Invokes f on each shard of t sequentially.  Caller may assume that
+ * f will not be invoked concurrently on multiple cores.
+ */
+template <typename T, typename F>
+auto sharded_map_seq(T &t, F &&f) {
+  using ret_type = decltype(f(t.local()));
+  // seastar::smp::submit_to because sharded::invoke_on doesn't have
+  // a const overload.
+  if constexpr (is_errorated_future_v<ret_type>) {
+    auto ret = crimson::do_for_each(
+      seastar::smp::all_cpus().begin(),
+      seastar::smp::all_cpus().end(),
+      [&t, f=std::move(f)](auto core) mutable {
+	return seastar::smp::submit_to(
+	  core,
+	  [&t, &f] {
+	    return std::invoke(f, t.local());
+	  });
+      });
+    return ret_type(ret);
+  } else {
+    return seastar::do_for_each(
+      seastar::smp::all_cpus().begin(),
+      seastar::smp::all_cpus().end(),
+      [&t, f=std::move(f)](auto core) mutable {
+	return seastar::smp::submit_to(
+	  core,
+	  [&t, &f] {
+	    return std::invoke(f, t.local());
+	  });
+      });
+  }
+}
+
+}
-- 
2.39.5