io_uring: move all prep state for IORING_OP_{SEND,RECV}_MGS to prep handler

Add struct io_sr_msg in our io_kiocb per-command union, and ensure that
the send/recvmsg prep handlers have grabbed what they need from the SQE
by the time prep is done.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -345,6 +345,12 @@ struct io_connect {
 	int				addr_len;
 };
 
+struct io_sr_msg {
+	struct file			*file;
+	struct user_msghdr __user	*msg;
+	int				msg_flags;
+};
+
 struct io_async_connect {
 	struct sockaddr_storage		address;
 };
@@ -389,6 +395,7 @@ struct io_kiocb {
 		struct io_cancel	cancel;
 		struct io_timeout	timeout;
 		struct io_connect	connect;
+		struct io_sr_msg	sr_msg;
 	};
 
 	const struct io_uring_sqe	*sqe;
@@ -2164,15 +2171,15 @@ static int io_sendmsg_prep(struct io_kiocb *req, struct io_async_ctx *io)
 {
 #if defined(CONFIG_NET)
 	const struct io_uring_sqe *sqe = req->sqe;
-	struct user_msghdr __user *msg;
-	unsigned flags;
+	struct io_sr_msg *sr = &req->sr_msg;
 
-	flags = READ_ONCE(sqe->msg_flags);
-	msg = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	sr->msg_flags = READ_ONCE(sqe->msg_flags);
+	sr->msg = u64_to_user_ptr(READ_ONCE(sqe->addr));
 	io->msg.iov = io->msg.fast_iov;
-	return sendmsg_copy_msghdr(&io->msg.msg, msg, flags, &io->msg.iov);
+	return sendmsg_copy_msghdr(&io->msg.msg, sr->msg, sr->msg_flags,
+					&io->msg.iov);
 #else
-	return 0;
+	return -EOPNOTSUPP;
 #endif
 }
 
@@ -2180,7 +2187,6 @@ static int io_sendmsg(struct io_kiocb *req, struct io_kiocb **nxt,
 		      bool force_nonblock)
 {
 #if defined(CONFIG_NET)
-	const struct io_uring_sqe *sqe = req->sqe;
 	struct io_async_msghdr *kmsg = NULL;
 	struct socket *sock;
 	int ret;
@@ -2194,12 +2200,6 @@ static int io_sendmsg(struct io_kiocb *req, struct io_kiocb **nxt,
 		struct sockaddr_storage addr;
 		unsigned flags;
 
-		flags = READ_ONCE(sqe->msg_flags);
-		if (flags & MSG_DONTWAIT)
-			req->flags |= REQ_F_NOWAIT;
-		else if (force_nonblock)
-			flags |= MSG_DONTWAIT;
-
 		if (req->io) {
 			kmsg = &req->io->msg;
 			kmsg->msg.msg_name = &addr;
@@ -2215,6 +2215,12 @@ static int io_sendmsg(struct io_kiocb *req, struct io_kiocb **nxt,
 				goto out;
 		}
 
+		flags = req->sr_msg.msg_flags;
+		if (flags & MSG_DONTWAIT)
+			req->flags |= REQ_F_NOWAIT;
+		else if (force_nonblock)
+			flags |= MSG_DONTWAIT;
+
 		ret = __sys_sendmsg_sock(sock, &kmsg->msg, flags);
 		if (force_nonblock && ret == -EAGAIN) {
 			if (req->io)
@@ -2245,17 +2251,15 @@ static int io_sendmsg(struct io_kiocb *req, struct io_kiocb **nxt,
 static int io_recvmsg_prep(struct io_kiocb *req, struct io_async_ctx *io)
 {
 #if defined(CONFIG_NET)
-	const struct io_uring_sqe *sqe = req->sqe;
-	struct user_msghdr __user *msg;
-	unsigned flags;
+	struct io_sr_msg *sr = &req->sr_msg;
 
-	flags = READ_ONCE(sqe->msg_flags);
-	msg = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	sr->msg_flags = READ_ONCE(req->sqe->msg_flags);
+	sr->msg = u64_to_user_ptr(READ_ONCE(req->sqe->addr));
 	io->msg.iov = io->msg.fast_iov;
-	return recvmsg_copy_msghdr(&io->msg.msg, msg, flags, &io->msg.uaddr,
-					&io->msg.iov);
+	return recvmsg_copy_msghdr(&io->msg.msg, sr->msg, sr->msg_flags,
+					&io->msg.uaddr, &io->msg.iov);
 #else
-	return 0;
+	return -EOPNOTSUPP;
 #endif
 }
 
@@ -2263,7 +2267,6 @@ static int io_recvmsg(struct io_kiocb *req, struct io_kiocb **nxt,
 		      bool force_nonblock)
 {
 #if defined(CONFIG_NET)
-	const struct io_uring_sqe *sqe = req->sqe;
 	struct io_async_msghdr *kmsg = NULL;
 	struct socket *sock;
 	int ret;
@@ -2273,18 +2276,10 @@ static int io_recvmsg(struct io_kiocb *req, struct io_kiocb **nxt,
 
 	sock = sock_from_file(req->file, &ret);
 	if (sock) {
-		struct user_msghdr __user *msg;
 		struct io_async_ctx io;
 		struct sockaddr_storage addr;
 		unsigned flags;
 
-		flags = READ_ONCE(sqe->msg_flags);
-		if (flags & MSG_DONTWAIT)
-			req->flags |= REQ_F_NOWAIT;
-		else if (force_nonblock)
-			flags |= MSG_DONTWAIT;
-
-		msg = u64_to_user_ptr(READ_ONCE(sqe->addr));
 		if (req->io) {
 			kmsg = &req->io->msg;
 			kmsg->msg.msg_name = &addr;
@@ -2300,7 +2295,14 @@ static int io_recvmsg(struct io_kiocb *req, struct io_kiocb **nxt,
 				goto out;
 		}
 
-		ret = __sys_recvmsg_sock(sock, &kmsg->msg, msg, kmsg->uaddr, flags);
+		flags = req->sr_msg.msg_flags;
+		if (flags & MSG_DONTWAIT)
+			req->flags |= REQ_F_NOWAIT;
+		else if (force_nonblock)
+			flags |= MSG_DONTWAIT;
+
+		ret = __sys_recvmsg_sock(sock, &kmsg->msg, req->sr_msg.msg,
+						kmsg->uaddr, flags);
 		if (force_nonblock && ret == -EAGAIN) {
 			if (req->io)
 				return -EAGAIN;