From 7c9a460786dad77c7bf3643e21da1193542467b3 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max.kellermann@ionos.com>
Date: Mon, 27 Jan 2025 12:49:25 +0100
Subject: [PATCH] io/uring/Ring: add method SetMaxWorkers()

---
 src/io/uring/Queue.hxx |  8 ++++++++
 src/io/uring/Ring.cxx  |  8 ++++++++
 src/io/uring/Ring.hxx  | 17 +++++++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/src/io/uring/Queue.hxx b/src/io/uring/Queue.hxx
index 2264b9e49..6f88ee516 100644
--- a/src/io/uring/Queue.hxx
+++ b/src/io/uring/Queue.hxx
@@ -30,6 +30,14 @@ public:
 		return ring.GetFileDescriptor();
 	}
 
+	void SetMaxWorkers(unsigned values[2]) {
+		ring.SetMaxWorkers(values);
+	}
+
+	void SetMaxWorkers(unsigned bounded, unsigned unbounded) {
+		ring.SetMaxWorkers(bounded, unbounded);
+	}
+
 	struct io_uring_sqe *GetSubmitEntry() noexcept {
 		return ring.GetSubmitEntry();
 	}
diff --git a/src/io/uring/Ring.cxx b/src/io/uring/Ring.cxx
index 7b171dfb8..222b24363 100644
--- a/src/io/uring/Ring.cxx
+++ b/src/io/uring/Ring.cxx
@@ -21,6 +21,14 @@ Ring::Ring(unsigned entries, struct io_uring_params &params)
 		throw MakeErrno(-error, "io_uring_queue_init_params() failed");
 }
 
+void
+Ring::SetMaxWorkers(unsigned values[2])
+{
+	if (int error = io_uring_register_iowq_max_workers(&ring, values);
+	    error < 0)
+		throw MakeErrno(-error, "io_uring_register_iowq_max_workers() failed");
+}
+
 void
 Ring::Submit()
 {
diff --git a/src/io/uring/Ring.hxx b/src/io/uring/Ring.hxx
index aac105fc3..8c1128995 100644
--- a/src/io/uring/Ring.hxx
+++ b/src/io/uring/Ring.hxx
@@ -50,6 +50,23 @@ public:
 		return FileDescriptor(ring.ring_fd);
 	}
 
+	/**
+	 * Wrapper for io_uring_register_iowq_max_workers().
+	 *
+	 * Throws on error.
+	 */
+	void SetMaxWorkers(unsigned values[2]);
+
+	/**
+	 * This overload constructs an array for
+	 * io_uring_register_iowq_max_workers() and discards the
+	 * output values.
+	 */
+	void SetMaxWorkers(unsigned bounded, unsigned unbounded) {
+		unsigned values[2] = {bounded, unbounded};
+		SetMaxWorkers(values);
+	}
+
 	/**
 	 * Returns a submit queue entry or nullptr if the submit queue
 	 * is full.