ipc: convert prepare_copy() from macro to function

This code works if CONFIG_CHECKPOINT_RESTORE is disabled.

[akpm@linux-foundation.org: remove __maybe_unused]
Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ipc/msg.c

@@ -803,8 +803,15 @@ static inline void free_copy(struct msg_msg *copy)
 		free_msg(copy);
 }
 #else
-#define prepare_copy(buf, sz, msgflg, msgtyp, copy_nr)	ERR_PTR(-ENOSYS)
 #define fill_copy(copy_nr, msg_nr, msg, copy)		NULL
+
+static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz,
+					   int msgflg, long *msgtyp,
+					   unsigned long *copy_number)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
 static inline void free_copy(struct msg_msg *copy)
 {
 }
@@ -819,7 +826,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
 	int mode;
 	struct ipc_namespace *ns;
 	struct msg_msg *copy = NULL;
-	unsigned long __maybe_unused copy_number;
+	unsigned long copy_number = 0;
 
 	if (msqid < 0 || (long) bufsz < 0)
 		return -EINVAL;