[S390] s390: use simple_read_from_buffer()

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/hypfs/inode.c

@@ -150,33 +150,24 @@ static ssize_t hypfs_aio_read(struct kiocb *iocb, const struct iovec *iov,
 			      unsigned long nr_segs, loff_t offset)
 {
 	char *data;
-	size_t len;
+	ssize_t ret;
 	struct file *filp = iocb->ki_filp;
 	/* XXX: temporary */
 	char __user *buf = iov[0].iov_base;
 	size_t count = iov[0].iov_len;
 
-	if (nr_segs != 1) {
-		count = -EINVAL;
-		goto out;
-	}
+	if (nr_segs != 1)
+		return -EINVAL;
 
 	data = filp->private_data;
-	len = strlen(data);
-	if (offset > len) {
-		count = 0;
-		goto out;
-	}
-	if (count > len - offset)
-		count = len - offset;
-	if (copy_to_user(buf, data + offset, count)) {
-		count = -EFAULT;
-		goto out;
-	}
-	iocb->ki_pos += count;
+	ret = simple_read_from_buffer(buf, count, &offset, data, strlen(data));
+	if (ret <= 0)
+		return ret;
+
+	iocb->ki_pos += ret;
 	file_accessed(filp);
-out:
-	return count;
+
+	return ret;
 }
 static ssize_t hypfs_aio_write(struct kiocb *iocb, const struct iovec *iov,
 			      unsigned long nr_segs, loff_t offset)