/*
 *  linux/fs/bad_inode.c
 *
 *  Copyright (C) 1997, Stephen Tweedie
 *
 *  Provide stub functions for unreadable inodes
 */

#include <linux/fs.h>
#include <linux/stat.h>
#include <linux/sched.h>

/*
 * The follow_link operation is special: it must behave as a no-op
 * so that a bad root inode can at least be unmounted. To do this
 * we must dput() the base and return the dentry with a dget().
 */
static struct dentry * bad_follow_link(struct dentry *dent, struct dentry *base, unsigned int follow)
{
	dput(base);
	return dget(dent);
}

static int return_EIO(void)
{
	return -EIO;
}

#define EIO_ERROR ((void *) (return_EIO))

static struct file_operations bad_file_ops =
{
	llseek:		EIO_ERROR,
	read:		EIO_ERROR,
	write:		EIO_ERROR,
	readdir:	EIO_ERROR,
	poll:		EIO_ERROR,
	ioctl:		EIO_ERROR,
	mmap:		EIO_ERROR,
	open:		EIO_ERROR,
	flush:		EIO_ERROR,
	release:	EIO_ERROR,
	fsync:		EIO_ERROR,
	fasync:		EIO_ERROR,
	lock:		EIO_ERROR,
};

struct inode_operations bad_inode_ops =
{
	&bad_file_ops,		/* default file operations */
	EIO_ERROR,		/* create */
	EIO_ERROR,		/* lookup */
	EIO_ERROR,		/* link */
	EIO_ERROR,		/* unlink */
	EIO_ERROR,		/* symlink */
	EIO_ERROR,		/* mkdir */
	EIO_ERROR,		/* rmdir */
	EIO_ERROR,		/* mknod */
	EIO_ERROR,		/* rename */
	EIO_ERROR,		/* readlink */
	bad_follow_link,	/* follow_link */
	EIO_ERROR,		/* truncate */
	EIO_ERROR,		/* permission */
	EIO_ERROR		/* revalidate */
};


/* 
 * When a filesystem is unable to read an inode due to an I/O error in
 * its read_inode() function, it can call make_bad_inode() to return a
 * set of stubs which will return EIO errors as required. 
 *
 * We only need to do limited initialisation: all other fields are
 * preinitialised to zero automatically.
 */
void make_bad_inode(struct inode * inode) 
{
	inode->i_mode = S_IFREG;
	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
	inode->i_op = &bad_inode_ops;	
}

/*
 * This tests whether an inode has been flagged as bad. The test uses
 * &bad_inode_ops to cover the case of invalidated inodes as well as
 * those created by make_bad_inode() above.
 */
int is_bad_inode(struct inode * inode) 
{
	return (inode->i_op == &bad_inode_ops);	
}
