[PATCH v5 08/10] IPC: message queue receive cleanup

[Stanislav Kinsbursky <skinsbursky@parallels.com>]

This patch moves all message related manipulation into one function msg_fill().
Actually, two functions because of the compat one.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
 include/linux/msg.h |    5 +++--
 ipc/compat.c        |   36 +++++++++++++++++++-----------------
 ipc/msg.c           |   44 +++++++++++++++++++++++---------------------
 3 files changed, 45 insertions(+), 40 deletions(-)

diff --git a/include/linux/msg.h b/include/linux/msg.h
index 6689e73..9411b76 100644
--- a/include/linux/msg.h
+++ b/include/linux/msg.h
@@ -105,8 +105,9 @@ struct msg_queue {
 /* Helper routines for sys_msgsnd and sys_msgrcv */
 extern long do_msgsnd(int msqid, long mtype, void __user *mtext,
 			size_t msgsz, int msgflg);
-extern long do_msgrcv(int msqid, long *pmtype, void __user *mtext,
-			size_t msgsz, long msgtyp, int msgflg);
+extern long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
+		      int msgflg,
+		      long (*msg_fill)(void __user *, struct msg_msg *, size_t ));
 
 #endif /* __KERNEL__ */
 
diff --git a/ipc/compat.c b/ipc/compat.c
index 84d8efd..b879d50 100644
--- a/ipc/compat.c
+++ b/ipc/compat.c
@@ -341,13 +341,23 @@ long compat_sys_msgsnd(int first, int second, int third, void __user *uptr)
 	return do_msgsnd(first, type, up->mtext, second, third);
 }
 
+long compat_do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
+{
+	struct compat_msgbuf __user *msgp = dest;
+	size_t msgsz;
+
+	if (put_user(msg->m_type, &msgp->mtype))
+		return -EFAULT;
+
+	msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
+	if (store_msg(msgp->mtext, msg, msgsz))
+		return -EFAULT;
+	return msgsz;
+}
+
 long compat_sys_msgrcv(int first, int second, int msgtyp, int third,
 			   int version, void __user *uptr)
 {
-	struct compat_msgbuf __user *up;
-	long type;
-	int err;
-
 	if (first < 0)
 		return -EINVAL;
 	if (second < 0)
@@ -355,23 +365,14 @@ long compat_sys_msgrcv(int first, int second, int msgtyp, int third,
 
 	if (!version) {
 		struct compat_ipc_kludge ipck;
-		err = -EINVAL;
 		if (!uptr)
-			goto out;
-		err = -EFAULT;
+			return -EINVAL;
 		if (copy_from_user (&ipck, uptr, sizeof(ipck)))
-			goto out;
+			return -EFAULT;
 		uptr = compat_ptr(ipck.msgp);
 		msgtyp = ipck.msgtyp;
 	}
-	up = uptr;
-	err = do_msgrcv(first, &type, up->mtext, second, msgtyp, third);
-	if (err < 0)
-		goto out;
-	if (put_user(type, &up->mtype))
-		err = -EFAULT;
-out:
-	return err;
+	return do_msgrcv(first, uptr, second, msgtyp, third, compat_do_msg_fill);
 }
 #else
 long compat_sys_semctl(int semid, int semnum, int cmd, int arg)
@@ -394,7 +395,8 @@ long compat_sys_msgrcv(int msqid, struct compat_msgbuf __user *msgp,
 {
 	long err, mtype;
 
-	err =  do_msgrcv(msqid, &mtype, msgp->mtext, (ssize_t)msgsz, msgtyp, msgflg);
+	err =  do_msgrcv(msqid, &mtype, msgp->mtext, (ssize_t)msgsz, msgtyp,
+			 msgflg, compat_do_msg_fill);
 	if (err < 0)
 		goto out;
 
diff --git a/ipc/msg.c b/ipc/msg.c
index ef4f118..d8168a7 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -763,15 +763,30 @@ static inline int convert_mode(long *msgtyp, int msgflg)
 	return SEARCH_EQUAL;
 }
 
-long do_msgrcv(int msqid, long *pmtype, void __user *mtext,
-		size_t msgsz, long msgtyp, int msgflg)
+static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
+{
+	struct msgbuf __user *msgp = dest;
+	size_t msgsz;
+
+	if (put_user(msg->m_type, &msgp->mtype))
+		return -EFAULT;
+
+	msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
+	if (store_msg(msgp->mtext, msg, msgsz))
+		return -EFAULT;
+	return msgsz;
+}
+
+long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
+	       int msgflg,
+	       long (*msg_handler)(void __user *, struct msg_msg *, size_t ))
 {
 	struct msg_queue *msq;
 	struct msg_msg *msg;
 	int mode;
 	struct ipc_namespace *ns;
 
-	if (msqid < 0 || (long) msgsz < 0)
+	if (msqid < 0 || (long) bufsz < 0)
 		return -EINVAL;
 	mode = convert_mode(&msgtyp, msgflg);
 	ns = current->nsproxy->ipc_ns;
@@ -814,7 +829,7 @@ long do_msgrcv(int msqid, long *pmtype, void __user *mtext,
 			 * Found a suitable message.
 			 * Unlink it from the queue.
 			 */
-			if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
+			if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 				msg = ERR_PTR(-E2BIG);
 				goto out_unlock;
 			}
@@ -841,7 +856,7 @@ long do_msgrcv(int msqid, long *pmtype, void __user *mtext,
 		if (msgflg & MSG_NOERROR)
 			msr_d.r_maxsize = INT_MAX;
 		else
-			msr_d.r_maxsize = msgsz;
+			msr_d.r_maxsize = bufsz;
 		msr_d.r_msg = ERR_PTR(-EAGAIN);
 		current->state = TASK_INTERRUPTIBLE;
 		msg_unlock(msq);
@@ -904,29 +919,16 @@ out_unlock:
 	if (IS_ERR(msg))
 		return PTR_ERR(msg);
 
-	msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz;
-	*pmtype = msg->m_type;
-	if (store_msg(mtext, msg, msgsz))
-		msgsz = -EFAULT;
-
+	bufsz = msg_handler(buf, msg, bufsz);
 	free_msg(msg);
 
-	return msgsz;
+	return bufsz;
 }
 
 SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 		long, msgtyp, int, msgflg)
 {
-	long err, mtype;
-
-	err =  do_msgrcv(msqid, &mtype, msgp->mtext, msgsz, msgtyp, msgflg);
-	if (err < 0)
-		goto out;
-
-	if (put_user(mtype, &msgp->mtype))
-		err = -EFAULT;
-out:
-	return err;
+	return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
 }
 
 #ifdef CONFIG_PROC_FS