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[linux-2.6.9-moxart.git] / fs / vfat / namei.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 character and cleanup by
 *                              OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
 */

#include <linux/module.h>

#include <linux/jiffies.h>
#include <linux/msdos_fs.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/buffer_head.h>
#include <linux/namei.h>

static int vfat_hashi(struct dentry *parent, struct qstr *qstr);
static int vfat_hash(struct dentry *parent, struct qstr *qstr);
static int vfat_cmpi(struct dentry *dentry, struct qstr *a, struct qstr *b);
static int vfat_cmp(struct dentry *dentry, struct qstr *a, struct qstr *b);
static int vfat_revalidate(struct dentry *dentry, struct nameidata *nd);

static struct dentry_operations vfat_dentry_ops[4] = {
        {
                .d_hash         = vfat_hashi,
                .d_compare      = vfat_cmpi,
        },
        {
                .d_revalidate   = vfat_revalidate,
                .d_hash         = vfat_hashi,
                .d_compare      = vfat_cmpi,
        },
        {
                .d_hash         = vfat_hash,
                .d_compare      = vfat_cmp,
        },
        {
                .d_revalidate   = vfat_revalidate,
                .d_hash         = vfat_hash,
                .d_compare      = vfat_cmp,
        }
};

static int vfat_revalidate(struct dentry *dentry, struct nameidata *nd)
{
        int ret = 1;

        if (!dentry->d_inode &&
            nd && !(nd->flags & LOOKUP_CONTINUE) && (nd->flags & LOOKUP_CREATE))
                /*
                 * negative dentry is dropped, in order to make sure
                 * to use the name which a user desires if this is
                 * create path.
                 */
                ret = 0;
        else {
                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;
}

/* 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)
                        return 0;
        }
        return 1;
}

/*
 * Case sensitive compare of two vfat names.
 */
static int vfat_cmp(struct dentry *dentry, struct qstr *a, struct qstr *b)
{
        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 (strncmp(a->name, b->name, alen) == 0)
                        return 0;
        }
        return 1;
}

/* Characters that are undesirable in an MS-DOS file name */

static wchar_t bad_chars[] = {
        /*  `*'     `?'     `<'    `>'      `|'     `"'     `:'     `/' */
        0x002A, 0x003F, 0x003C, 0x003E, 0x007C, 0x0022, 0x003A, 0x002F,
        /*  `\' */
        0x005C, 0,
};
#define IS_BADCHAR(uni) (vfat_unistrchr(bad_chars, (uni)) != NULL)

static wchar_t replace_chars[] = {
        /*  `['     `]'    `;'     `,'     `+'      `=' */
        0x005B, 0x005D, 0x003B, 0x002C, 0x002B, 0x003D, 0,
};
#define IS_REPLACECHAR(uni)     (vfat_unistrchr(replace_chars, (uni)) != NULL)

static wchar_t skip_chars[] = {
        /*  `.'     ` ' */
        0x002E, 0x0020, 0,
};
#define IS_SKIPCHAR(uni) \
        ((wchar_t)(uni) == skip_chars[0] || (wchar_t)(uni) == skip_chars[1])

static inline wchar_t *vfat_unistrchr(const wchar_t *s, const wchar_t c)
{
        for(; *s != c; ++s)
                if (*s == 0)
                        return NULL;
        return (wchar_t *) s;
}

static inline int vfat_is_used_badchars(const wchar_t *s, int len)
{
        int i;
        
        for (i = 0; i < len; i++)
                if (s[i] < 0x0020 || IS_BADCHAR(s[i]))
                        return -EINVAL;
        return 0;
}

static int vfat_valid_longname(const unsigned char *name, unsigned int len)
{
        if (len && name[len-1] == ' ')
                return 0;
        if (len >= 256)
                return 0;

        /* MS-DOS "device special files" */
        if (len == 3 || (len > 3 && name[3] == '.')) {  /* basename == 3 */
                if (!strnicmp(name, "aux", 3) ||
                    !strnicmp(name, "con", 3) ||
                    !strnicmp(name, "nul", 3) ||
                    !strnicmp(name, "prn", 3))
                        return 0;
        }
        if (len == 4 || (len > 4 && name[4] == '.')) {  /* basename == 4 */
                /* "com1", "com2", ... */
                if ('1' <= name[3] && name[3] <= '9') {
                        if (!strnicmp(name, "com", 3) ||
                            !strnicmp(name, "lpt", 3))
                                return 0;
                }
        }

        return 1;
}

static int vfat_find_form(struct inode *dir, unsigned char *name)
{
        struct msdos_dir_entry *de;
        struct buffer_head *bh = NULL;
        loff_t i_pos;
        int res;

        res = fat_scan(dir, name, &bh, &de, &i_pos);
        brelse(bh);
        if (res < 0)
                return -ENOENT;
        return 0;
}

/* 
 * 1) Valid characters for the 8.3 format alias are any combination of
 * letters, uppercase alphabets, digits, any of the
 * following special characters:
 *     $ % ' ` - @ { } ~ ! # ( ) & _ ^
 * In this case Longfilename is not stored in disk.
 *
 * WinNT's Extension:
 * File name and extension name is contain uppercase/lowercase
 * only. And it is expressed by CASE_LOWER_BASE and CASE_LOWER_EXT.
 *     
 * 2) File name is 8.3 format, but it contain the uppercase and
 * lowercase char, muliti bytes char, etc. In this case numtail is not
 * added, but Longfilename is stored.
 * 
 * 3) When the one except for the above, or the following special
 * character are contained:
 *        .   [ ] ; , + =
 * numtail is added, and Longfilename must be stored in disk .
 */
struct shortname_info {
        unsigned char lower:1,
                      upper:1,
                      valid:1;
};
#define INIT_SHORTNAME_INFO(x)  do {            \
        (x)->lower = 1;                         \
        (x)->upper = 1;                         \
        (x)->valid = 1;                         \
} while (0)

static inline unsigned char
shortname_info_to_lcase(struct shortname_info *base,
                        struct shortname_info *ext)
{
        unsigned char lcase = 0;

        if (base->valid && ext->valid) {
                if (!base->upper && base->lower && (ext->lower || ext->upper))
                        lcase |= CASE_LOWER_BASE;
                if (!ext->upper && ext->lower && (base->lower || base->upper))
                        lcase |= CASE_LOWER_EXT;
        }

        return lcase;
}

static inline int to_shortname_char(struct nls_table *nls,
                                    unsigned char *buf, int buf_size, wchar_t *src,
                                    struct shortname_info *info)
{
        int len;

        if (IS_SKIPCHAR(*src)) {
                info->valid = 0;
                return 0;
        }
        if (IS_REPLACECHAR(*src)) {
                info->valid = 0;
                buf[0] = '_';
                return 1;
        }
        
        len = nls->uni2char(*src, buf, buf_size);
        if (len <= 0) {
                info->valid = 0;
                buf[0] = '_';
                len = 1;
        } else if (len == 1) {
                unsigned char prev = buf[0];

                if (buf[0] >= 0x7F) {
                        info->lower = 0;
                        info->upper = 0;
                }

                buf[0] = nls_toupper(nls, buf[0]);
                if (isalpha(buf[0])) {
                        if (buf[0] == prev)
                                info->lower = 0;
                        else
                                info->upper = 0;
                }
        } else {
                info->lower = 0;
                info->upper = 0;
        }
        
        return len;
}

/*
 * Given a valid longname, create a unique shortname.  Make sure the
 * shortname does not exist
 * Returns negative number on error, 0 for a normal
 * return, and 1 for valid shortname
 */
static int vfat_create_shortname(struct inode *dir, struct nls_table *nls,
                                 wchar_t *uname, int ulen,
                                 unsigned char *name_res, unsigned char *lcase)
{
        wchar_t *ip, *ext_start, *end, *name_start;
        unsigned char base[9], ext[4], buf[8], *p;
        unsigned char charbuf[NLS_MAX_CHARSET_SIZE];
        int chl, chi;
        int sz = 0, extlen, baselen, i, numtail_baselen, numtail2_baselen;
        int is_shortname;
        struct shortname_info base_info, ext_info;
        unsigned short opt_shortname = MSDOS_SB(dir->i_sb)->options.shortname;

        is_shortname = 1;
        INIT_SHORTNAME_INFO(&base_info);
        INIT_SHORTNAME_INFO(&ext_info);

        /* Now, we need to create a shortname from the long name */
        ext_start = end = &uname[ulen];
        while (--ext_start >= uname) {
                if (*ext_start == 0x002E) { /* is `.' */
                        if (ext_start == end - 1) {
                                sz = ulen;
                                ext_start = NULL;
                        }
                        break;
                }
        }

        if (ext_start == uname - 1) {
                sz = ulen;
                ext_start = NULL;
        } else if (ext_start) {
                /*
                 * Names which start with a dot could be just
                 * an extension eg. "...test".  In this case Win95
                 * uses the extension as the name and sets no extension.
                 */
                name_start = &uname[0];
                while (name_start < ext_start) {
                        if (!IS_SKIPCHAR(*name_start))
                                break;
                        name_start++;
                }
                if (name_start != ext_start) {
                        sz = ext_start - uname;
                        ext_start++;
                } else {
                        sz = ulen;
                        ext_start=NULL;
                }
        }

        numtail_baselen = 6;
        numtail2_baselen = 2;
        for (baselen = i = 0, p = base, ip = uname; i < sz; i++, ip++) {
                chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
                                        ip, &base_info);
                if (chl == 0)
                        continue;

                if (baselen < 2 && (baselen + chl) > 2)
                        numtail2_baselen = baselen;
                if (baselen < 6 && (baselen + chl) > 6)
                        numtail_baselen = baselen;
                for (chi = 0; chi < chl; chi++){
                        *p++ = charbuf[chi];
                        baselen++;
                        if (baselen >= 8)
                                break;
                }
                if (baselen >= 8) {
                        if ((chi < chl - 1) || (ip + 1) - uname < sz)
                                is_shortname = 0;
                        break;
                }
        }
        if (baselen == 0) {
                return -EINVAL;
        }

        extlen = 0;
        if (ext_start) {
                for (p = ext, ip = ext_start; extlen < 3 && ip < end; ip++) {
                        chl = to_shortname_char(nls, charbuf, sizeof(charbuf),
                                                ip, &ext_info);
                        if (chl == 0)
                                continue;

                        if ((extlen + chl) > 3) {
                                is_shortname = 0;
                                break;
                        }
                        for (chi = 0; chi < chl; chi++) {
                                *p++ = charbuf[chi];
                                extlen++;
                        }
                        if (extlen >= 3) {
                                if (ip + 1 != end)
                                        is_shortname = 0;
                                break;
                        }
                }
        }
        ext[extlen] = '\0';
        base[baselen] = '\0';

        /* Yes, it can happen. ".\xe5" would do it. */
        if (base[0] == DELETED_FLAG)
                base[0] = 0x05;

        /* OK, at this point we know that base is not longer than 8 symbols,
         * ext is not longer than 3, base is nonempty, both don't contain
         * any bad symbols (lowercase transformed to uppercase).
         */

        memset(name_res, ' ', MSDOS_NAME);
        memcpy(name_res, base, baselen);
        memcpy(name_res + 8, ext, extlen);
        *lcase = 0;
        if (is_shortname && base_info.valid && ext_info.valid) {
                if (vfat_find_form(dir, name_res) == 0)
                        return -EEXIST;

                if (opt_shortname & VFAT_SFN_CREATE_WIN95) {
                        return (base_info.upper && ext_info.upper);
                } else if (opt_shortname & VFAT_SFN_CREATE_WINNT) {
                        if ((base_info.upper || base_info.lower)
                            && (ext_info.upper || ext_info.lower)) {
                                *lcase = shortname_info_to_lcase(&base_info,
                                                                 &ext_info);
                                return 1;
                        }
                        return 0;
                } else {
                        BUG();
                }
        }
        
        if (MSDOS_SB(dir->i_sb)->options.numtail == 0)
                if (vfat_find_form(dir, name_res) < 0)
                        return 0;

        /*
         * Try to find a unique extension.  This used to
         * iterate through all possibilities sequentially,
         * but that gave extremely bad performance.  Windows
         * only tries a few cases before using random
         * values for part of the base.
         */

        if (baselen>6) {
                baselen = numtail_baselen;
                name_res[7] = ' ';
        }
        name_res[baselen] = '~';
        for (i = 1; i < 10; i++) {
                name_res[baselen+1] = i + '0';
                if (vfat_find_form(dir, name_res) < 0)
                        return 0;
        }

        i = jiffies & 0xffff;
        sz = (jiffies >> 16) & 0x7;
        if (baselen>2) {
                baselen = numtail2_baselen;
                name_res[7] = ' ';
        }
        name_res[baselen+4] = '~';
        name_res[baselen+5] = '1' + sz;
        while (1) {
                sprintf(buf, "%04X", i);
                memcpy(&name_res[baselen], buf, 4);
                if (vfat_find_form(dir, name_res) < 0)
                        break;
                i -= 11;
        }
        return 0;
}

/* Translate a string, including coded sequences into Unicode */
static int
xlate_to_uni(const unsigned char *name, int len, unsigned char *outname,
             int *longlen, int *outlen, int escape, int utf8,
             struct nls_table *nls)
{
        const unsigned char *ip;
        unsigned char nc;
        unsigned char *op;
        unsigned int ec;
        int i, k, fill;
        int charlen;

        if (utf8) {
                int name_len = strlen(name);

                *outlen = utf8_mbstowcs((wchar_t *)outname, name, PAGE_SIZE);

                /*
                 * We stripped '.'s before and set len appropriately,
                 * but utf8_mbstowcs doesn't care about len
                 */
                *outlen -= (name_len-len);

                op = &outname[*outlen * sizeof(wchar_t)];
        } else {
                if (nls) {
                        for (i = 0, ip = name, op = outname, *outlen = 0;
                             i < len && *outlen <= 260; *outlen += 1)
                        {
                                if (escape && (*ip == ':')) {
                                        if (i > len - 5)
                                                return -EINVAL;
                                        ec = 0;
                                        for (k = 1; k < 5; k++) {
                                                nc = ip[k];
                                                ec <<= 4;
                                                if (nc >= '0' && nc <= '9') {
                                                        ec |= nc - '0';
                                                        continue;
                                                }
                                                if (nc >= 'a' && nc <= 'f') {
                                                        ec |= nc - ('a' - 10);
                                                        continue;
                                                }
                                                if (nc >= 'A' && nc <= 'F') {
                                                        ec |= nc - ('A' - 10);
                                                        continue;
                                                }
                                                return -EINVAL;
                                        }
                                        *op++ = ec & 0xFF;
                                        *op++ = ec >> 8;
                                        ip += 5;
                                        i += 5;
                                } else {
                                        if ((charlen = nls->char2uni(ip, len-i, (wchar_t *)op)) < 0)
                                                return -EINVAL;
                                        ip += charlen;
                                        i += charlen;
                                        op += 2;
                                }
                        }
                } else {
                        for (i = 0, ip = name, op = outname, *outlen = 0;
                             i < len && *outlen <= 260; i++, *outlen += 1)
                        {
                                *op++ = *ip++;
                                *op++ = 0;
                        }
                }
        }
        if (*outlen > 260)
                return -ENAMETOOLONG;

        *longlen = *outlen;
        if (*outlen % 13) {
                *op++ = 0;
                *op++ = 0;
                *outlen += 1;
                if (*outlen % 13) {
                        fill = 13 - (*outlen % 13);
                        for (i = 0; i < fill; i++) {
                                *op++ = 0xff;
                                *op++ = 0xff;
                        }
                        *outlen += fill;
                }
        }

        return 0;
}

static int vfat_build_slots(struct inode *dir, const unsigned char *name,
                            int len, struct msdos_dir_slot *ds,
                            int *slots, int is_dir)
{
        struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
        struct fat_mount_options *opts = &sbi->options;
        struct msdos_dir_slot *ps;
        struct msdos_dir_entry *de;
        unsigned long page;
        unsigned char cksum, lcase;
        unsigned char msdos_name[MSDOS_NAME];
        wchar_t *uname;
        int res, slot, ulen, usize, i;
        loff_t offset;

        *slots = 0;
        if (!vfat_valid_longname(name, len))
                return -EINVAL;

        if(!(page = __get_free_page(GFP_KERNEL)))
                return -ENOMEM;

        uname = (wchar_t *)page;
        res = xlate_to_uni(name, len, (unsigned char *)uname, &ulen, &usize,
                           opts->unicode_xlate, opts->utf8, sbi->nls_io);
        if (res < 0)
                goto out_free;

        res = vfat_is_used_badchars(uname, ulen);
        if (res < 0)
                goto out_free;

        res = vfat_create_shortname(dir, sbi->nls_disk, uname, ulen,
                                    msdos_name, &lcase);
        if (res < 0)
                goto out_free;
        else if (res == 1) {
                de = (struct msdos_dir_entry *)ds;
                res = 0;
                goto shortname;
        }

        /* build the entry of long file name */
        *slots = usize / 13;
        for (cksum = i = 0; i < 11; i++) {
                cksum = (((cksum&1)<<7)|((cksum&0xfe)>>1)) + msdos_name[i];
        }

        for (ps = ds, slot = *slots; slot > 0; slot--, ps++) {
                ps->id = slot;
                ps->attr = ATTR_EXT;
                ps->reserved = 0;
                ps->alias_checksum = cksum;
                ps->start = 0;
                offset = (slot - 1) * 13;
                fatwchar_to16(ps->name0_4, uname + offset, 5);
                fatwchar_to16(ps->name5_10, uname + offset + 5, 6);
                fatwchar_to16(ps->name11_12, uname + offset + 11, 2);
        }
        ds[0].id |= 0x40;
        de = (struct msdos_dir_entry *) ps;

shortname:
        /* build the entry of 8.3 alias name */
        (*slots)++;
        memcpy(de->name, msdos_name, MSDOS_NAME);
        de->attr = is_dir ? ATTR_DIR : ATTR_ARCH;
        de->lcase = lcase;
        de->adate = de->cdate = de->date = 0;
        de->ctime = de->time = 0;
        de->ctime_ms = 0;
        de->start = 0;
        de->starthi = 0;
        de->size = 0;

out_free:
        free_page(page);
        return res;
}

static int vfat_add_entry(struct inode *dir,struct qstr* qname,
                          int is_dir, struct vfat_slot_info *sinfo_out,
                          struct buffer_head **bh, struct msdos_dir_entry **de)
{
        struct msdos_dir_slot *dir_slots;
        loff_t offset;
        int res, slots, slot;
        unsigned int len;
        struct msdos_dir_entry *dummy_de;
        struct buffer_head *dummy_bh;
        loff_t dummy_i_pos;

        len = vfat_striptail_len(qname);
        if (len == 0)
                return -ENOENT;

        dir_slots =
               kmalloc(sizeof(struct msdos_dir_slot) * MSDOS_SLOTS, GFP_KERNEL);
        if (dir_slots == NULL)
                return -ENOMEM;

        res = vfat_build_slots(dir, qname->name, len,
                               dir_slots, &slots, is_dir);
        if (res < 0)
                goto cleanup;

        /* build the empty directory entry of number of slots */
        offset = fat_add_entries(dir, slots, &dummy_bh, &dummy_de, &dummy_i_pos);
        if (offset < 0) {
                res = offset;
                goto cleanup;
        }
        brelse(dummy_bh);

        /* Now create the new entry */
        *bh = NULL;
        for (slot = 0; slot < slots; slot++) {
                if (fat_get_entry(dir, &offset, bh, de, &sinfo_out->i_pos) < 0) {
                        res = -EIO;
                        goto cleanup;
                }
                memcpy(*de, dir_slots + slot, sizeof(struct msdos_dir_slot));
                mark_buffer_dirty(*bh);
        }

        res = 0;
        /* update timestamp */
        dir->i_ctime = dir->i_mtime = dir->i_atime = CURRENT_TIME;
        mark_inode_dirty(dir);

        fat_date_unix2dos(dir->i_mtime.tv_sec, &(*de)->time, &(*de)->date);
        (*de)->ctime = (*de)->time;
        (*de)->adate = (*de)->cdate = (*de)->date;

        mark_buffer_dirty(*bh);

        /* slots can't be less than 1 */
        sinfo_out->long_slots = slots - 1;
        sinfo_out->longname_offset =
                offset - sizeof(struct msdos_dir_slot) * slots;

cleanup:
        kfree(dir_slots);
        return res;
}

static int vfat_find(struct inode *dir,struct qstr* qname,
        struct vfat_slot_info *sinfo, struct buffer_head **last_bh,
        struct msdos_dir_entry **last_de)
{
        struct super_block *sb = dir->i_sb;
        loff_t offset;
        unsigned int len;
        int res;

        len = vfat_striptail_len(qname);
        if (len == 0)
                return -ENOENT;

        res = fat_search_long(dir, qname->name, len,
                              (MSDOS_SB(sb)->options.name_check != 's'),
                              &offset, &sinfo->longname_offset);
        if (res>0) {
                sinfo->long_slots = res-1;
                if (fat_get_entry(dir,&offset,last_bh,last_de,&sinfo->i_pos)>=0)
                        return 0;
                res = -EIO;
        } 
        return res ? res : -ENOENT;
}

static struct dentry *vfat_lookup(struct inode *dir, struct dentry *dentry,
                struct nameidata *nd)
{
        int res;
        struct vfat_slot_info sinfo;
        struct inode *inode;
        struct dentry *alias;
        struct buffer_head *bh = NULL;
        struct msdos_dir_entry *de;
        int table;
        
        lock_kernel();
        table = (MSDOS_SB(dir->i_sb)->options.name_check == 's') ? 2 : 0;
        dentry->d_op = &vfat_dentry_ops[table];

        inode = NULL;
        res = vfat_find(dir,&dentry->d_name,&sinfo,&bh,&de);
        if (res < 0) {
                table++;
                goto error;
        }
        inode = fat_build_inode(dir->i_sb, de, sinfo.i_pos, &res);
        brelse(bh);
        if (res) {
                unlock_kernel();
                return ERR_PTR(res);
        }
        alias = d_find_alias(inode);
        if (alias) {
                if (d_invalidate(alias)==0)
                        dput(alias);
                else {
                        iput(inode);
                        unlock_kernel();
                        return alias;
                }
                
        }
error:
        unlock_kernel();
        dentry->d_op = &vfat_dentry_ops[table];
        dentry->d_time = dentry->d_parent->d_inode->i_version;
        dentry = d_splice_alias(inode, dentry);
        if (dentry) {
                dentry->d_op = &vfat_dentry_ops[table];
                dentry->d_time = dentry->d_parent->d_inode->i_version;
        }
        return dentry;
}

static int vfat_create(struct inode *dir, struct dentry* dentry, int mode,
                struct nameidata *nd)
{
        struct super_block *sb = dir->i_sb;
        struct inode *inode = NULL;
        struct buffer_head *bh = NULL;
        struct msdos_dir_entry *de;
        struct vfat_slot_info sinfo;
        int res;

        lock_kernel();
        res = vfat_add_entry(dir, &dentry->d_name, 0, &sinfo, &bh, &de);
        if (res < 0)
                goto out;
        inode = fat_build_inode(sb, de, sinfo.i_pos, &res);
        brelse(bh);
        if (!inode)
                goto out;
        res = 0;
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
        mark_inode_dirty(inode);
        inode->i_version++;
        dir->i_version++;
        dentry->d_time = dentry->d_parent->d_inode->i_version;
        d_instantiate(dentry,inode);
out:
        unlock_kernel();
        return res;
}

static void vfat_remove_entry(struct inode *dir,struct vfat_slot_info *sinfo,
     struct buffer_head *bh, struct msdos_dir_entry *de)
{
        loff_t offset, i_pos;
        int i;

        /* remove the shortname */
        dir->i_mtime = dir->i_atime = CURRENT_TIME;
        dir->i_version++;
        mark_inode_dirty(dir);
        de->name[0] = DELETED_FLAG;
        mark_buffer_dirty(bh);
        /* remove the longname */
        offset = sinfo->longname_offset; de = NULL;
        for (i = sinfo->long_slots; i > 0; --i) {
                if (fat_get_entry(dir, &offset, &bh, &de, &i_pos) < 0)
                        continue;
                de->name[0] = DELETED_FLAG;
                de->attr = ATTR_NONE;
                mark_buffer_dirty(bh);
        }
        brelse(bh);
}

static int vfat_rmdir(struct inode *dir, struct dentry* dentry)
{
        int res;
        struct vfat_slot_info sinfo;
        struct buffer_head *bh = NULL;
        struct msdos_dir_entry *de;

        lock_kernel();
        res = fat_dir_empty(dentry->d_inode);
        if (res)
                goto out;

        res = vfat_find(dir,&dentry->d_name,&sinfo, &bh, &de);
        if (res < 0)
                goto out;
        res = 0;
        dentry->d_inode->i_nlink = 0;
        dentry->d_inode->i_mtime = dentry->d_inode->i_atime = CURRENT_TIME;
        fat_detach(dentry->d_inode);
        mark_inode_dirty(dentry->d_inode);
        /* releases bh */
        vfat_remove_entry(dir,&sinfo,bh,de);
        dir->i_nlink--;
out:
        unlock_kernel();
        return res;
}

static int vfat_unlink(struct inode *dir, struct dentry *dentry)
{
        int res;
        struct vfat_slot_info sinfo;
        struct buffer_head *bh = NULL;
        struct msdos_dir_entry *de;

        lock_kernel();
        res = vfat_find(dir,&dentry->d_name,&sinfo,&bh,&de);
        if (res < 0)
                goto out;
        dentry->d_inode->i_nlink = 0;
        dentry->d_inode->i_mtime = dentry->d_inode->i_atime = CURRENT_TIME;
        fat_detach(dentry->d_inode);
        mark_inode_dirty(dentry->d_inode);
        /* releases bh */
        vfat_remove_entry(dir,&sinfo,bh,de);
out:
        unlock_kernel();

        return res;
}

static int vfat_mkdir(struct inode *dir,struct dentry* dentry,int mode)
{
        struct super_block *sb = dir->i_sb;
        struct inode *inode = NULL;
        struct vfat_slot_info sinfo;
        struct buffer_head *bh = NULL;
        struct msdos_dir_entry *de;
        int res;

        lock_kernel();
        res = vfat_add_entry(dir, &dentry->d_name, 1, &sinfo, &bh, &de);
        if (res < 0)
                goto out;
        inode = fat_build_inode(sb, de, sinfo.i_pos, &res);
        if (!inode)
                goto out_brelse;
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
        mark_inode_dirty(inode);
        inode->i_version++;
        dir->i_version++;
        dir->i_nlink++;
        inode->i_nlink = 2; /* no need to mark them dirty */
        res = fat_new_dir(inode, dir, 1);
        if (res < 0)
                goto mkdir_failed;
        dentry->d_time = dentry->d_parent->d_inode->i_version;
        d_instantiate(dentry,inode);
out_brelse:
        brelse(bh);
out:
        unlock_kernel();
        return res;

mkdir_failed:
        inode->i_nlink = 0;
        inode->i_mtime = inode->i_atime = CURRENT_TIME;
        fat_detach(inode);
        mark_inode_dirty(inode);
        /* releases bh */
        vfat_remove_entry(dir,&sinfo,bh,de);
        iput(inode);
        dir->i_nlink--;
        goto out;
}
 
static int vfat_rename(struct inode *old_dir, struct dentry *old_dentry,
                struct inode *new_dir, struct dentry *new_dentry)
{
        struct buffer_head *old_bh,*new_bh,*dotdot_bh;
        struct msdos_dir_entry *old_de,*new_de,*dotdot_de;
        loff_t dotdot_i_pos;
        struct inode *old_inode, *new_inode;
        int res, is_dir;
        struct vfat_slot_info old_sinfo,sinfo;

        old_bh = new_bh = dotdot_bh = NULL;
        old_inode = old_dentry->d_inode;
        new_inode = new_dentry->d_inode;
        lock_kernel();
        res = vfat_find(old_dir,&old_dentry->d_name,&old_sinfo,&old_bh,&old_de);
        if (res < 0)
                goto rename_done;

        is_dir = S_ISDIR(old_inode->i_mode);

        if (is_dir) {
                if (fat_scan(old_inode, MSDOS_DOTDOT, &dotdot_bh,
                             &dotdot_de, &dotdot_i_pos) < 0) {
                        res = -EIO;
                        goto rename_done;
                }
        }

        if (new_dentry->d_inode) {
                res = vfat_find(new_dir,&new_dentry->d_name,&sinfo,&new_bh,
                                &new_de);
                if (res < 0 || MSDOS_I(new_inode)->i_pos != sinfo.i_pos) {
                        /* WTF??? Cry and fail. */
                        printk(KERN_WARNING "vfat_rename: fs corrupted\n");
                        goto rename_done;
                }

                if (is_dir) {
                        res = fat_dir_empty(new_inode);
                        if (res)
                                goto rename_done;
                }
                fat_detach(new_inode);
        } else {
                res = vfat_add_entry(new_dir,&new_dentry->d_name,is_dir,&sinfo,
                                        &new_bh,&new_de);
                if (res < 0) goto rename_done;
        }

        new_dir->i_version++;

        /* releases old_bh */
        vfat_remove_entry(old_dir,&old_sinfo,old_bh,old_de);
        old_bh=NULL;
        fat_detach(old_inode);
        fat_attach(old_inode, sinfo.i_pos);
        mark_inode_dirty(old_inode);

        old_dir->i_version++;
        old_dir->i_ctime = old_dir->i_mtime = CURRENT_TIME;
        mark_inode_dirty(old_dir);
        if (new_inode) {
                new_inode->i_nlink--;
                new_inode->i_ctime=CURRENT_TIME;
        }

        if (is_dir) {
                int start = MSDOS_I(new_dir)->i_logstart;
                dotdot_de->start = cpu_to_le16(start);
                dotdot_de->starthi = cpu_to_le16(start>>16);
                mark_buffer_dirty(dotdot_bh);
                old_dir->i_nlink--;
                if (new_inode) {
                        new_inode->i_nlink--;
                } else {
                        new_dir->i_nlink++;
                        mark_inode_dirty(new_dir);
                }
        }

rename_done:
        brelse(dotdot_bh);
        brelse(old_bh);
        brelse(new_bh);
        unlock_kernel();
        return res;

}

static struct inode_operations vfat_dir_inode_operations = {
        .create         = vfat_create,
        .lookup         = vfat_lookup,
        .unlink         = vfat_unlink,
        .mkdir          = vfat_mkdir,
        .rmdir          = vfat_rmdir,
        .rename         = vfat_rename,
        .setattr        = fat_notify_change,
};

static int vfat_fill_super(struct super_block *sb, void *data, int silent)
{
        int res;

        res = fat_fill_super(sb, data, silent, &vfat_dir_inode_operations, 1);
        if (res)
                return res;

        if (MSDOS_SB(sb)->options.name_check != 's')
                sb->s_root->d_op = &vfat_dentry_ops[0];
        else
                sb->s_root->d_op = &vfat_dentry_ops[2];

        return 0;
}

static struct super_block *vfat_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data)
{
        return get_sb_bdev(fs_type, flags, dev_name, data, vfat_fill_super);
}

static struct file_system_type vfat_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "vfat",
        .get_sb         = vfat_get_sb,
        .kill_sb        = kill_block_super,
        .fs_flags       = FS_REQUIRES_DEV,
};

static int __init init_vfat_fs(void)
{
        return register_filesystem(&vfat_fs_type);
}

static void __exit exit_vfat_fs(void)
{
        unregister_filesystem(&vfat_fs_type);
}

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("VFAT filesystem support");
MODULE_AUTHOR("Gordon Chaffee");

module_init(init_vfat_fs)
module_exit(exit_vfat_fs)