[PATCH 1/3] io_uring: add buffer selection support to IORING_OP_NOP

[Jens Axboe <axboe@kernel.dk>]

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>
---
 fs/io_uring.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 64450af959ff..7a458a7b3280 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1058,6 +1058,7 @@ static const struct io_op_def io_op_defs[] = {
 	[IORING_OP_NOP] = {
 		.audit_skip		= 1,
 		.iopoll			= 1,
+		.buffer_select		= 1,
 	},
 	[IORING_OP_READV] = {
 		.needs_file		= 1,
@@ -4538,7 +4539,17 @@ static int io_splice(struct io_kiocb *req, unsigned int issue_flags)
  */
 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;
 }
 
-- 
2.35.1