[RFC 1/3] ipc/msg: split do_msgsnd into functions

[Usama Arif <usama.arif@bytedance.com>]

do_msgsnd is split into check_and_load_msgsnd and __do_msgsnd.
This does not introduce any change in the functions' operation.
Its only needed for async msgsnd in io_uring which will be added
in a later patch.

Functions used for msgsnd and msgrcv are also declared in the
header file for use in io_uring patches later.

Signed-off-by: Usama Arif <usama.arif@bytedance.com>
---
 include/linux/msg.h | 11 ++++++++++
 ipc/msg.c           | 52 ++++++++++++++++++++++++++++++++++-----------
 2 files changed, 51 insertions(+), 12 deletions(-)

diff --git a/include/linux/msg.h b/include/linux/msg.h
index 9a972a296b95..36e3116fed86 100644
--- a/include/linux/msg.h
+++ b/include/linux/msg.h
@@ -15,4 +15,15 @@ struct msg_msg {
 	/* the actual message follows immediately */
 };
 
+long check_and_load_msgsnd(int msqid, long mtype, void __user *mtext,
+			   struct msg_msg **msg, size_t msgsz);
+
+void free_msg(struct msg_msg *msg);
+
+long __do_msgsnd(int msqid, long mtype, struct msg_msg **msg,
+		 size_t msgsz, int msgflg);
+
+long ksys_msgrcv(int msqid, struct msgbuf __user *msgp, size_t msgsz,
+		 long msgtyp, int msgflg);
+
 #endif /* _LINUX_MSG_H */
diff --git a/ipc/msg.c b/ipc/msg.c
index a0d05775af2c..0682204a684e 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -839,14 +839,11 @@ static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg,
 	return 0;
 }
 
-static long do_msgsnd(int msqid, long mtype, void __user *mtext,
-		size_t msgsz, int msgflg)
+long check_and_load_msgsnd(int msqid, long mtype, void __user *mtext,
+			   struct msg_msg **msg, size_t msgsz)
 {
-	struct msg_queue *msq;
-	struct msg_msg *msg;
-	int err;
 	struct ipc_namespace *ns;
-	DEFINE_WAKE_Q(wake_q);
+	struct msg_msg *tmp;
 
 	ns = current->nsproxy->ipc_ns;
 
@@ -855,12 +852,45 @@ static long do_msgsnd(int msqid, long mtype, void __user *mtext,
 	if (mtype < 1)
 		return -EINVAL;
 
-	msg = load_msg(mtext, msgsz);
+	tmp = load_msg(mtext, msgsz);
 	if (IS_ERR(msg))
 		return PTR_ERR(msg);
 
-	msg->m_type = mtype;
-	msg->m_ts = msgsz;
+	tmp->m_type = mtype;
+	tmp->m_ts = msgsz;
+
+	*msg = tmp;
+	return 0;
+}
+
+static long do_msgsnd(int msqid, long mtype, void __user *mtext,
+		      size_t msgsz, int msgflg)
+{
+	struct msg_msg *msg;
+	int err;
+
+	err = check_and_load_msgsnd(msqid, mtype, mtext, &msg, msgsz);
+	if (err)
+		return err;
+
+	err = __do_msgsnd(msqid, mtype, &msg, msgsz, msgflg);
+	if (msg != NULL)
+		free_msg(msg);
+
+	return err;
+}
+
+long __do_msgsnd(int msqid, long mtype, struct msg_msg **_msg,
+		 size_t msgsz, int msgflg)
+{
+	struct msg_queue *msq;
+	struct msg_msg *msg;
+	int err;
+	struct ipc_namespace *ns;
+	DEFINE_WAKE_Q(wake_q);
+
+	msg = *_msg;
+	ns = current->nsproxy->ipc_ns;
 
 	rcu_read_lock();
 	msq = msq_obtain_object_check(ns, msqid);
@@ -940,15 +970,13 @@ static long do_msgsnd(int msqid, long mtype, void __user *mtext,
 	}
 
 	err = 0;
-	msg = NULL;
+	*_msg = NULL;
 
 out_unlock0:
 	ipc_unlock_object(&msq->q_perm);
 	wake_up_q(&wake_q);
 out_unlock1:
 	rcu_read_unlock();
-	if (msg != NULL)
-		free_msg(msg);
 	return err;
 }
 
-- 
2.25.1