From d9b1f6223ef54e59e02f64e2f2d3e17c1e669c36 Mon Sep 17 00:00:00 2001
From: Max Kellermann <mk@cm4all.com>
Date: Thu, 23 Mar 2023 06:09:20 +0100
Subject: [PATCH] io/uring/Close: wrapper for io_uring_prep_close()

---
 src/io/uring/Close.cxx   | 25 +++++++++++++++++++++++++
 src/io/uring/Close.hxx   | 21 +++++++++++++++++++++
 src/io/uring/meson.build |  1 +
 3 files changed, 47 insertions(+)
 create mode 100644 src/io/uring/Close.cxx
 create mode 100644 src/io/uring/Close.hxx

diff --git a/src/io/uring/Close.cxx b/src/io/uring/Close.cxx
new file mode 100644
index 000000000..b8d2e5fba
--- /dev/null
+++ b/src/io/uring/Close.cxx
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright CM4all GmbH
+// author: Max Kellermann <mk@cm4all.com>
+
+#include "Close.hxx"
+#include "Queue.hxx"
+#include "io/FileDescriptor.hxx"
+
+namespace Uring {
+
+void
+Close(Queue *queue, FileDescriptor fd) noexcept
+{
+	if (auto *s = queue != nullptr ? queue->GetSubmitEntry() : nullptr) {
+		io_uring_prep_close(s, fd.Get());
+		io_uring_sqe_set_data(s, nullptr);
+		queue->Submit();
+	} else {
+		/* io_uring not available or queue full: fall back to
+		   the classic close() system call */
+		fd.Close();
+	}
+}
+
+} // namespace Uring
diff --git a/src/io/uring/Close.hxx b/src/io/uring/Close.hxx
new file mode 100644
index 000000000..9685fbb3e
--- /dev/null
+++ b/src/io/uring/Close.hxx
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright CM4all GmbH
+// author: Max Kellermann <mk@cm4all.com>
+
+#pragma once
+
+class FileDescriptor;
+
+namespace Uring {
+
+class Queue;
+
+/**
+ * Schedule a close() on the given file descriptor.  If no
+ * #io_uring_sqe is available, this function falls back to close().
+ * No callback will be invoked.
+ */
+void
+Close(Queue *queue, FileDescriptor fd) noexcept;
+
+} // namespace Uring
diff --git a/src/io/uring/meson.build b/src/io/uring/meson.build
index 9bfe24654..ed958f646 100644
--- a/src/io/uring/meson.build
+++ b/src/io/uring/meson.build
@@ -21,6 +21,7 @@ uring = static_library(
   'Ring.cxx',
   'Queue.cxx',
   'Operation.cxx',
+  'Close.cxx',
   'ReadOperation.cxx',
   include_directories: inc,
   dependencies: [