tag	line	file	source code
readdir	29	fs/read_write.c	if (file->f_op && file->f_op->readdir) {
readdir	32	fs/read_write.c	error = file->f_op->readdir(inode,file,dirent,count);
readdir	264	include/linux/fs.h	int (*readdir) (struct inode *, struct file *, struct dirent *, int);