exit: add kernel_waitid_prepare() helper

Move the setup logic out of kernel_waitid(), and into a separate helper.

No functional changes intended in this patch.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

kernel/exit.c

@@ -1662,14 +1662,13 @@ static long do_wait(struct wait_opts *wo)
 	return retval;
 }
 
-static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
-			  int options, struct rusage *ru)
+static int kernel_waitid_prepare(struct wait_opts *wo, int which, pid_t upid,
+				 struct waitid_info *infop, int options,
+				 struct rusage *ru)
 {
-	struct wait_opts wo;
+	unsigned int f_flags = 0;
 	struct pid *pid = NULL;
 	enum pid_type type;
-	long ret;
-	unsigned int f_flags = 0;
 
 	if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED|
 			__WNOTHREAD|__WCLONE|__WALL))
@@ -1712,19 +1711,32 @@ static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
 		return -EINVAL;
 	}
 
-	wo.wo_type	= type;
-	wo.wo_pid	= pid;
-	wo.wo_flags	= options;
-	wo.wo_info	= infop;
-	wo.wo_rusage	= ru;
+	wo->wo_type	= type;
+	wo->wo_pid	= pid;
+	wo->wo_flags	= options;
+	wo->wo_info	= infop;
+	wo->wo_rusage	= ru;
 	if (f_flags & O_NONBLOCK)
-		wo.wo_flags |= WNOHANG;
+		wo->wo_flags |= WNOHANG;
+
+	return 0;
+}
+
+static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
+			  int options, struct rusage *ru)
+{
+	struct wait_opts wo;
+	long ret;
+
+	ret = kernel_waitid_prepare(&wo, which, upid, infop, options, ru);
+	if (ret)
+		return ret;
 
 	ret = do_wait(&wo);
-	if (!ret && !(options & WNOHANG) && (f_flags & O_NONBLOCK))
+	if (!ret && !(options & WNOHANG) && (wo.wo_flags & WNOHANG))
 		ret = -EAGAIN;
 
-	put_pid(pid);
+	put_pid(wo.wo_pid);
 	return ret;
 }