NFSD: Use simple_read_from_buffer for coping data to userspace

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/fault_inject.c

@@ -97,25 +97,14 @@ static ssize_t fault_inject_read(struct file *file, char __user *buf,
 {
 	static u64 val;
 	char read_buf[25];
-	size_t size, ret;
+	size_t size;
 	loff_t pos = *ppos;
 
 	if (!pos)
 		nfsd_inject_get(file_inode(file)->i_private, &val);
 	size = scnprintf(read_buf, sizeof(read_buf), "%llu\n", val);
 
-	if (pos < 0)
-		return -EINVAL;
-	if (pos >= size || !len)
-		return 0;
-	if (len > size - pos)
-		len = size - pos;
-	ret = copy_to_user(buf, read_buf + pos, len);
-	if (ret == len)
-		return -EFAULT;
-	len -= ret;
-	*ppos = pos + len;
-	return len;
+	return simple_read_from_buffer(buf, len, ppos, read_buf, size);
 }
 
 static ssize_t fault_inject_write(struct file *file, const char __user *buf,