io_uring: keep sendrecv flags in ioprio

We waste a u64 SQE field for flags even though we don't need as many
bits and it can be used for something more useful later. Store io_uring
specific send/recv flags in sqe->ioprio instead of ->addr2.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Fixes: 0455d4cc ("io_uring: add POLL_FIRST support for send/sendmsg and recv/recvmsg")
[axboe: change comment in io_uring.h as well]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -1183,6 +1183,7 @@ static const struct io_op_def io_op_defs[] = {
 		.unbound_nonreg_file	= 1,
 		.pollout		= 1,
 		.needs_async_setup	= 1,
+		.ioprio			= 1,
 		.async_size		= sizeof(struct io_async_msghdr),
 	},
 	[IORING_OP_RECVMSG] = {
@@ -1191,6 +1192,7 @@ static const struct io_op_def io_op_defs[] = {
 		.pollin			= 1,
 		.buffer_select		= 1,
 		.needs_async_setup	= 1,
+		.ioprio			= 1,
 		.async_size		= sizeof(struct io_async_msghdr),
 	},
 	[IORING_OP_TIMEOUT] = {
@@ -1266,6 +1268,7 @@ static const struct io_op_def io_op_defs[] = {
 		.unbound_nonreg_file	= 1,
 		.pollout		= 1,
 		.audit_skip		= 1,
+		.ioprio			= 1,
 	},
 	[IORING_OP_RECV] = {
 		.needs_file		= 1,
@@ -1273,6 +1276,7 @@ static const struct io_op_def io_op_defs[] = {
 		.pollin			= 1,
 		.buffer_select		= 1,
 		.audit_skip		= 1,
+		.ioprio			= 1,
 	},
 	[IORING_OP_OPENAT2] = {
 	},
@@ -6075,12 +6079,12 @@ static int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_sr_msg *sr = &req->sr_msg;
 
-	if (unlikely(sqe->file_index))
+	if (unlikely(sqe->file_index || sqe->addr2))
 		return -EINVAL;
 
 	sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
 	sr->len = READ_ONCE(sqe->len);
-	sr->flags = READ_ONCE(sqe->addr2);
+	sr->flags = READ_ONCE(sqe->ioprio);
 	if (sr->flags & ~IORING_RECVSEND_POLL_FIRST)
 		return -EINVAL;
 	sr->msg_flags = READ_ONCE(sqe->msg_flags) | MSG_NOSIGNAL;
@@ -6311,12 +6315,12 @@ static int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_sr_msg *sr = &req->sr_msg;
 
-	if (unlikely(sqe->file_index))
+	if (unlikely(sqe->file_index || sqe->addr2))
 		return -EINVAL;
 
 	sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
 	sr->len = READ_ONCE(sqe->len);
-	sr->flags = READ_ONCE(sqe->addr2);
+	sr->flags = READ_ONCE(sqe->ioprio);
 	if (sr->flags & ~IORING_RECVSEND_POLL_FIRST)
 		return -EINVAL;
 	sr->msg_flags = READ_ONCE(sqe->msg_flags) | MSG_NOSIGNAL;

include/uapi/linux/io_uring.h

@@ -244,7 +244,7 @@ enum io_uring_op {
 #define IORING_ASYNC_CANCEL_ANY	(1U << 2)
 
 /*
- * send/sendmsg and recv/recvmsg flags (sqe->addr2)
+ * send/sendmsg and recv/recvmsg flags (sqe->ioprio)
  *
  * IORING_RECVSEND_POLL_FIRST	If set, instead of first attempting to send
  *				or receive and arm poll if that yields an