io/uring/Close: wrapper for io_uring_prep_close()

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

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

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: [