/*
 *  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/time.h>
#include <linux/smp_lock.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 int bad_follow_link(struct dentry *dent, struct nameidata *nd)
{
	return vfs_follow_link(nd, ERR_PTR(-EIO));
}

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 =
{
	.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	= EIO_ERROR,
	.follow_link	= bad_follow_link,
	.truncate	= EIO_ERROR,
	.permission	= EIO_ERROR,
	.getattr	= EIO_ERROR,
};


/*
 * 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.
 */
 
/**
 *	make_bad_inode - mark an inode bad due to an I/O error
 *	@inode: Inode to mark bad
 *
 *	When an inode cannot be read due to a media or remote network
 *	failure this function makes the inode "bad" and causes I/O operations
 *	on it to fail from this point on.
 */
 
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;	
	inode->i_fop = &bad_file_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.
 */
 
/**
 *	is_bad_inode - is an inode errored
 *	@inode: inode to test
 *
 *	Returns true if the inode in question has been marked as bad.
 */
 
int is_bad_inode(struct inode * inode) 
{
	return (inode->i_op == &bad_inode_ops);	
}