path: root/fs/fat/namei_vfat.c

/*
 *  linux/fs/vfat/namei.c
 *
 *  Written 1992,1993 by Werner Almesberger
 *
 *  Windows95/Windows NT compatible extended MSDOS filesystem
 *    by Gordon Chaffee Copyright (C) 1995.  Send bug reports for the
 *    VFAT filesystem to <chaffee@cs.berkeley.edu>.  Specify
 *    what file operation caused you trouble and if you can duplicate
 *    the problem, send a script that demonstrates it.
 *
 *  Short name translation 1999, 2001 by Wolfram Pienkoss <wp@bszh.de>
 *
 *  Support Multibyte characters and cleanup by
 *				OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
 */

#include <linux/module.h>
#include <linux/jiffies.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>
#include <linux/namei.h>
#include "fat.h"

/*
 * If new entry was created in the parent, it could create the 8.3
 * alias (the shortname of logname).  So, the parent may have the
 * negative-dentry which matches the created 8.3 alias.
 *
 * If it happened, the negative dentry isn't actually negative
 * anymore.  So, drop it.
 */
static int vfat_revalidate_shortname(struct dentry *dentry)
{
	int ret = 1;
	spin_lock(&dentry->d_lock);
	if (dentry->d_time != dentry->d_parent->d_inode->i_version)
		ret = 0;
	spin_unlock(&dentry->d_lock);
	return ret;
}

static int vfat_revalidate(struct dentry *dentry, struct nameidata *nd)
{
	/* This is not negative dentry. Always valid. */
	if (dentry->d_inode)
		return 1;
	return vfat_revalidate_shortname(dentry);
}

static int vfat_revalidate_ci(struct dentry *dentry, struct nameidata *nd)
{
	/*
	 * This is not negative dentry. Always valid.
	 *
	 * Note, rename() to existing directory entry will have ->d_inode,
	 * and will use existing name which isn't specified name by user.
	 *
	 * We may be able to drop this positive dentry here. But dropping
	 * positive dentry isn't good idea. So it's unsupported like
	 * rename("filename", "FILENAME") for now.
	 */
	if (dentry->d_inode)
		return 1;

	/*
	 * This may be nfsd (or something), anyway, we can't see the
	 * intent of this. So, since this can be for creation, drop it.
	 */
	if (!nd)
		return 0;

	/*
	 * Drop the negative dentry, in order to make sure to use the
	 * case sensitive name which is specified by user if this is
	 * for creation.
	 */
	if (!(nd->flags & (LOOKUP_CONTINUE | LOOKUP_PARENT))) {
		if (nd->flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET))
			return 0;
	}

	return vfat_revalidate_shortname(dentry);
}

/* returns the length of a struct qstr, ignoring trailing dots */
static unsigned int vfat_striptail_len(struct qstr *qstr)
{
	unsigned int len = qstr->len;

	while (len && qstr->name[len - 1] == '.')
		len--;
	return len;
}

/*
 * Compute the hash for the vfat name corresponding to the dentry.
 * Note: if the name is invalid, we leave the hash code unchanged so
 * that the existing dentry can be used. The vfat fs routines will
 * return ENOENT or EINVAL as appropriate.
 */
static int vfat_hash(struct dentry *dentry, struct qstr *qstr)
{
	qstr->hash = full_name_hash(qstr->name, vfat_striptail_len(qstr));
	return 0;
}

/*
 * Compute the hash for the vfat name corresponding to the dentry.
 * Note: if the name is invalid, we leave the hash code unchanged so
 * that the existing dentry can be used. The vfat fs routines will
 * return ENOENT or EINVAL as appropriate.
 */
static int vfat_hashi(struct dentry *dentry, struct qstr *qstr)
{
	struct nls_table *t = MSDOS_SB(dentry->d_inode->i_sb)->nls_io;
	const unsigned char *name;
	unsigned int len;
	unsigned long hash;

	name = qstr->name;
	len = vfat_striptail_len(qstr);

	hash = init_name_hash();
	while (len--)
		hash = partial_name_hash(nls_tolower(t, *name++), hash);
	qstr->hash = end_name_hash(hash);

	return 0;
}

/*
 * Case insensitive compare of two vfat names.
 */
static int vfat_cmpi(struct dentry *dentry, struct qstr *a, struct qstr *b)
{
	struct nls_table *t = MSDOS_SB(dentry->d_inode->i_sb)->nls_io;
	unsigned int alen, blen;

	/* A filename cannot end in '.' or we treat it like it has none */
	alen = vfat_striptail_len(a);
	blen = vfat_striptail_len(b);
	if (alen == blen) {
		if (nls_strnicmp(t, a->name, b->name, alen) == 0)