From effc34c86fcf2740b3f64b1cd27b0b6c7b8f3574 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Sun, 17 Mar 2019 18:41:45 -0700
Subject: [PATCH] ircd::fs::aio: Add struct aio_ring from the kernel ABI.

---
 ircd/fs_aio.cc |  8 ++++++++
 ircd/fs_aio.h  | 16 ++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/ircd/fs_aio.cc b/ircd/fs_aio.cc
index 4acd2249e..ab869bcf6 100644
--- a/ircd/fs_aio.cc
+++ b/ircd/fs_aio.cc
@@ -412,6 +412,14 @@ try
 }
 {
 	syscall<SYS_io_setup>(this->max_events(), &idp);
+
+	const aio_ring *const ring
+	{
+		reinterpret_cast<const aio_ring *>(idp)
+	};
+
+	assert(ring->magic == aio_ring::MAGIC);
+
 	log::debug
 	{
 		"Established AIO(%p) context (fd:%d max_events:%zu max_submit:%zu)",
diff --git a/ircd/fs_aio.h b/ircd/fs_aio.h
index 0c3b13fc8..17465260d 100644
--- a/ircd/fs_aio.h
+++ b/ircd/fs_aio.h
@@ -23,6 +23,22 @@ namespace ircd::fs::aio
 	void fsync(const fd &, const sync_opts &);
 }
 
+struct aio_ring
+{
+	static constexpr uint MAGIC {0xa10a10a1};
+
+	uint id; // kernel internal index number
+	uint nr; // number of io_events
+	uint head;
+	uint tail;
+	uint magic;
+	uint compat_features;
+	uint incompat_features;
+	uint header_length;  // size of aio_ring
+	struct io_event io_events[0];
+};
+// 128 bytes + ring size
+
 /// AIO context instance from the system. Right now this is a singleton with
 /// an extern instance pointer at fs::aio::context maintained by fs::aio::init.
 struct ircd::fs::aio::system