From 3d200242a6c968af321913b635fc4014b238cba4 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 5 May 2022 21:47:55 -0600
Subject: [PATCH] io_uring: add buffer selection support to IORING_OP_NOP
Git-commit: 3d200242a6c968af321913b635fc4014b238cba4
Patch-mainline: v5.19-rc1
References: bsc#1205205

Obviously not really useful since it's not transferring data, but it
is helpful in benchmarking overhead of provided buffers.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
---
 fs/io_uring.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1053,6 +1053,7 @@ struct io_op_def {
 static const struct io_op_def io_op_defs[] = {
 	[IORING_OP_NOP] = {
 		.iopoll			= 1,
+		.buffer_select		= 1,
 	},
 	[IORING_OP_READV] = {
 		.needs_file		= 1,
@@ -4514,7 +4515,17 @@ done:
  */
 static int io_nop(struct io_kiocb *req, unsigned int issue_flags)
 {
-	__io_req_complete(req, issue_flags, 0, 0);
+	void __user *buf;
+
+	if (req->flags & REQ_F_BUFFER_SELECT) {
+		size_t len = 1;
+
+		buf = io_buffer_select(req, &len, issue_flags);
+		if (IS_ERR(buf))
+			return PTR_ERR(buf);
+	}
+
+	__io_req_complete(req, issue_flags, 0, io_put_kbuf(req, issue_flags));
 	return 0;
 }