namei_vfat.c

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/*
 *  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 <[email protected]>.  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 <[email protected]>
 *
 *  Support Multibyte characters and cleanup by
 *              OGAWA Hirofumi <[email protected]>
 */

#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, unsigned int flags)
{
    if (flags & LOOKUP_RCU)
        return -ECHILD;

    /* 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, unsigned int flags)
{
    if (flags & LOOKUP_RCU)
        return -ECHILD;

    /*
     * 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 (!flags)
        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 (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(unsigned int len, const char *name)
{
    while (len && name[len - 1] == '.')
        len--;
    return len;
}

static unsigned int vfat_striptail_len(const struct qstr *qstr)
{
    return __vfat_striptail_len(qstr->len, qstr->name);
}

/*
 * 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(const struct dentry *dentry, const struct inode *inode,
        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(const struct dentry *dentry, const struct inode *inode,
        struct qstr *qstr)
{
    struct nls_table *t = MSDOS_SB(dentry->d_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(const struct dentry *parent, const struct inode *pinode,
        const struct dentry *dentry, const struct inode *inode,
        unsigned int len, const char *str, const struct qstr *name)
{
    struct nls_table *t = MSDOS_SB(parent->d_sb)->nls_io;
    unsigned int alen, blen;

    /* A filename cannot end in '.' or we treat it like it has none */
    alen = vfat_striptail_len(name);
    blen = __vfat_striptail_len(len, str);
    if (alen == blen) {
        if (nls_strnicmp(t, name->name, str, alen) == 0)
            return 0;
    }
    return 1;
}

/*
 * Case sensitive compare of two vfat names.
 */
static int vfat_cmp(const struct dentry *parent, const struct inode *pinode,
        const struct dentry *dentry, const struct inode *inode,
        unsigned int len, const char *str, const struct qstr *name)
{
    unsigned int alen, blen;

    /* A filename cannot end in '.' or we treat it like it has none */
    alen = vfat_striptail_len(name);
    blen = __vfat_striptail_len(len, str);
    if (alen == blen) {
        if (strncmp(name->name, str, alen) == 0)
            return 0;
    }
    return 1;
}

static const struct dentry_operations vfat_ci_dentry_ops = {
    .d_revalidate   = vfat_revalidate_ci,
    .d_hash     = vfat_hashi,
    .d_compare  = vfat_cmpi,
};

static const struct dentry_operations vfat_dentry_ops = {
    .d_revalidate   = vfat_revalidate,
    .d_hash     = vfat_hash,
    .d_compare  = vfat_cmp,
};

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

static inline wchar_t vfat_bad_char(wchar_t w)
{
    return (w < 0x0020)
        || (w == '*') || (w == '?') || (w == '<') || (w == '>')
        || (w == '|') || (w == '"') || (w == ':') || (w == '/')
        || (w == '\\');
}

static inline wchar_t vfat_replace_char(wchar_t w)
{
    return (w == '[') || (w == ']') || (w == ';') || (w == ',')
        || (w == '+') || (w == '=');
}

static wchar_t vfat_skip_char(wchar_t w)
{
    return (w == '.') || (w == ' ');
}

static inline int vfat_is_used_badchars(const wchar_t *s, int len)
{
    int i;

    for (i = 0; i < len; i++)
        if (vfat_bad_char(s[i]))
            return -EINVAL;

    if (s[i - 1] == ' ') /* last character cannot be space */
        return -EINVAL;

    return 0;
}

static int vfat_find_form(struct inode *dir, unsigned char *name)
{
    struct fat_slot_info sinfo;
    int err = fat_scan(dir, name, &sinfo);
    if (err)
        return -ENOENT;
    brelse(sinfo.bh);
    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 int to_shortname_char(struct nls_table *nls,
                    unsigned char *buf, int buf_size,
                    wchar_t *src, struct shortname_info *info)
{
    int len;

    if (vfat_skip_char(*src)) {
        info->valid = 0;
        return 0;
    }
    if (vfat_replace_char(*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)
{
    struct fat_mount_options *opts = &MSDOS_SB(dir->i_sb)->options;
    wchar_t *ip, *ext_start, *end, *name_start;
    unsigned char base[9], ext[4], buf[5], *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;

    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 (!vfat_skip_char(*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 (opts->shortname & VFAT_SFN_CREATE_WIN95) {
            return (base_info.upper && ext_info.upper);
        } else if (opts->shortname & VFAT_SFN_CREATE_WINNT) {
            if ((base_info.upper || base_info.lower) &&
                (ext_info.upper || ext_info.lower)) {
                if (!base_info.upper && base_info.lower)
                    *lcase |= CASE_LOWER_BASE;
                if (!ext_info.upper && ext_info.lower)
                    *lcase |= CASE_LOWER_EXT;
                return 1;
            }
            return 0;
        } else {
            BUG();
        }
    }

    if (opts->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;
    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) {
        snprintf(buf, sizeof(buf), "%04X", i & 0xffff);
        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) {
        *outlen = utf8s_to_utf16s(name, len, UTF16_HOST_ENDIAN,
                (wchar_t *) outname, FAT_LFN_LEN + 2);
        if (*outlen < 0)
            return *outlen;
        else if (*outlen > FAT_LFN_LEN)
            return -ENAMETOOLONG;

        op = &outname[*outlen * sizeof(wchar_t)];
    } else {
        for (i = 0, ip = name, op = outname, *outlen = 0;
             i < len && *outlen < FAT_LFN_LEN;
             *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 {
                charlen = nls->char2uni(ip, len - i,
                                    (wchar_t *)op);
                if (charlen < 0)
                    return -EINVAL;
                ip += charlen;
                i += charlen;
                op += 2;
            }
        }
        if (i < len)
            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, int is_dir, int cluster,
                struct timespec *ts,
                struct msdos_dir_slot *slots, int *nr_slots)
{
    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 char cksum, lcase;
    unsigned char msdos_name[MSDOS_NAME];
    wchar_t *uname;
    __le16 time, date;
    u8 time_cs;
    int err, ulen, usize, i;
    loff_t offset;

    *nr_slots = 0;

    uname = __getname();
    if (!uname)
        return -ENOMEM;

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

    err = vfat_is_used_badchars(uname, ulen);
    if (err)
        goto out_free;

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

    /* build the entry of long file name */
    cksum = fat_checksum(msdos_name);

    *nr_slots = usize / 13;
    for (ps = slots, i = *nr_slots; i > 0; i--, ps++) {
        ps->id = i;
        ps->attr = ATTR_EXT;
        ps->reserved = 0;
        ps->alias_checksum = cksum;
        ps->start = 0;
        offset = (i - 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);
    }
    slots[0].id |= 0x40;
    de = (struct msdos_dir_entry *)ps;

shortname:
    /* build the entry of 8.3 alias name */
    (*nr_slots)++;
    memcpy(de->name, msdos_name, MSDOS_NAME);
    de->attr = is_dir ? ATTR_DIR : ATTR_ARCH;
    de->lcase = lcase;
    fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);
    de->time = de->ctime = time;
    de->date = de->cdate = de->adate = date;
    de->ctime_cs = time_cs;
    fat_set_start(de, cluster);
    de->size = 0;
out_free:
    __putname(uname);
    return err;
}

static int vfat_add_entry(struct inode *dir, struct qstr *qname, int is_dir,
              int cluster, struct timespec *ts,
              struct fat_slot_info *sinfo)
{
    struct msdos_dir_slot *slots;
    unsigned int len;
    int err, nr_slots;

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

    slots = kmalloc(sizeof(*slots) * MSDOS_SLOTS, GFP_NOFS);
    if (slots == NULL)
        return -ENOMEM;

    err = vfat_build_slots(dir, qname->name, len, is_dir, cluster, ts,
                   slots, &nr_slots);
    if (err)
        goto cleanup;

    err = fat_add_entries(dir, slots, nr_slots, sinfo);
    if (err)
        goto cleanup;

    /* update timestamp */
    dir->i_ctime = dir->i_mtime = dir->i_atime = *ts;
    if (IS_DIRSYNC(dir))
        (void)fat_sync_inode(dir);
    else
        mark_inode_dirty(dir);
cleanup:
    kfree(slots);
    return err;
}

static int vfat_find(struct inode *dir, struct qstr *qname,
             struct fat_slot_info *sinfo)
{
    unsigned int len = vfat_striptail_len(qname);
    if (len == 0)
        return -ENOENT;
    return fat_search_long(dir, qname->name, len, sinfo);
}

/*
 * (nfsd's) anonymous disconnected dentry?
 * NOTE: !IS_ROOT() is not anonymous (I.e. d_splice_alias() did the job).
 */
static int vfat_d_anon_disconn(struct dentry *dentry)
{
    return IS_ROOT(dentry) && (dentry->d_flags & DCACHE_DISCONNECTED);
}

static struct dentry *vfat_lookup(struct inode *dir, struct dentry *dentry,
                  unsigned int flags)
{
    struct super_block *sb = dir->i_sb;
    struct fat_slot_info sinfo;
    struct inode *inode;
    struct dentry *alias;
    int err;

    mutex_lock(&MSDOS_SB(sb)->s_lock);

    err = vfat_find(dir, &dentry->d_name, &sinfo);
    if (err) {
        if (err == -ENOENT) {
            inode = NULL;
            goto out;
        }
        goto error;
    }

    inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
    brelse(sinfo.bh);
    if (IS_ERR(inode)) {
        err = PTR_ERR(inode);
        goto error;
    }

    alias = d_find_alias(inode);
    if (alias && !vfat_d_anon_disconn(alias)) {
        /*
         * This inode has non anonymous-DCACHE_DISCONNECTED
         * dentry. This means, the user did ->lookup() by an
         * another name (longname vs 8.3 alias of it) in past.
         *
         * Switch to new one for reason of locality if possible.
         */
        BUG_ON(d_unhashed(alias));
        if (!S_ISDIR(inode->i_mode))
            d_move(alias, dentry);
        iput(inode);
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
        return alias;
    } else
        dput(alias);

out:
    mutex_unlock(&MSDOS_SB(sb)->s_lock);
    dentry->d_time = dentry->d_parent->d_inode->i_version;
    dentry = d_splice_alias(inode, dentry);
    if (dentry)
        dentry->d_time = dentry->d_parent->d_inode->i_version;
    return dentry;

error:
    mutex_unlock(&MSDOS_SB(sb)->s_lock);
    return ERR_PTR(err);
}

static int vfat_create(struct inode *dir, struct dentry *dentry, umode_t mode,
               bool excl)
{
    struct super_block *sb = dir->i_sb;
    struct inode *inode;
    struct fat_slot_info sinfo;
    struct timespec ts;
    int err;

    mutex_lock(&MSDOS_SB(sb)->s_lock);

    ts = CURRENT_TIME_SEC;
    err = vfat_add_entry(dir, &dentry->d_name, 0, 0, &ts, &sinfo);
    if (err)
        goto out;
    dir->i_version++;

    inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
    brelse(sinfo.bh);
    if (IS_ERR(inode)) {
        err = PTR_ERR(inode);
        goto out;
    }
    inode->i_version++;
    inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
    /* timestamp is already written, so mark_inode_dirty() is unneeded. */

    dentry->d_time = dentry->d_parent->d_inode->i_version;
    d_instantiate(dentry, inode);
out:
    mutex_unlock(&MSDOS_SB(sb)->s_lock);
    return err;
}

static int vfat_rmdir(struct inode *dir, struct dentry *dentry)
{
    struct inode *inode = dentry->d_inode;
    struct super_block *sb = dir->i_sb;
    struct fat_slot_info sinfo;
    int err;

    mutex_lock(&MSDOS_SB(sb)->s_lock);

    err = fat_dir_empty(inode);
    if (err)
        goto out;
    err = vfat_find(dir, &dentry->d_name, &sinfo);
    if (err)
        goto out;

    err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
    if (err)
        goto out;
    drop_nlink(dir);

    clear_nlink(inode);
    inode->i_mtime = inode->i_atime = CURRENT_TIME_SEC;
    fat_detach(inode);
out:
    mutex_unlock(&MSDOS_SB(sb)->s_lock);

    return err;
}

static int vfat_unlink(struct inode *dir, struct dentry *dentry)
{
    struct inode *inode = dentry->d_inode;
    struct super_block *sb = dir->i_sb;
    struct fat_slot_info sinfo;
    int err;

    mutex_lock(&MSDOS_SB(sb)->s_lock);

    err = vfat_find(dir, &dentry->d_name, &sinfo);
    if (err)
        goto out;

    err = fat_remove_entries(dir, &sinfo);  /* and releases bh */
    if (err)
        goto out;
    clear_nlink(inode);
    inode->i_mtime = inode->i_atime = CURRENT_TIME_SEC;
    fat_detach(inode);
out:
    mutex_unlock(&MSDOS_SB(sb)->s_lock);

    return err;
}

static int vfat_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
    struct super_block *sb = dir->i_sb;
    struct inode *inode;
    struct fat_slot_info sinfo;
    struct timespec ts;
    int err, cluster;

    mutex_lock(&MSDOS_SB(sb)->s_lock);

    ts = CURRENT_TIME_SEC;
    cluster = fat_alloc_new_dir(dir, &ts);
    if (cluster < 0) {
        err = cluster;
        goto out;
    }
    err = vfat_add_entry(dir, &dentry->d_name, 1, cluster, &ts, &sinfo);
    if (err)
        goto out_free;
    dir->i_version++;
    inc_nlink(dir);

    inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
    brelse(sinfo.bh);
    if (IS_ERR(inode)) {
        err = PTR_ERR(inode);
        /* the directory was completed, just return a error */
        goto out;
    }
    inode->i_version++;
    set_nlink(inode, 2);
    inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
    /* timestamp is already written, so mark_inode_dirty() is unneeded. */

    dentry->d_time = dentry->d_parent->d_inode->i_version;
    d_instantiate(dentry, inode);

    mutex_unlock(&MSDOS_SB(sb)->s_lock);
    return 0;

out_free:
    fat_free_clusters(dir, cluster);
out:
    mutex_unlock(&MSDOS_SB(sb)->s_lock);
    return err;
}

static int vfat_rename(struct inode *old_dir, struct dentry *old_dentry,
               struct inode *new_dir, struct dentry *new_dentry)
{
    struct buffer_head *dotdot_bh;
    struct msdos_dir_entry *dotdot_de;
    struct inode *old_inode, *new_inode;
    struct fat_slot_info old_sinfo, sinfo;
    struct timespec ts;
    loff_t new_i_pos;
    int err, is_dir, update_dotdot, corrupt = 0;
    struct super_block *sb = old_dir->i_sb;

    old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
    old_inode = old_dentry->d_inode;
    new_inode = new_dentry->d_inode;
    mutex_lock(&MSDOS_SB(sb)->s_lock);
    err = vfat_find(old_dir, &old_dentry->d_name, &old_sinfo);
    if (err)
        goto out;

    is_dir = S_ISDIR(old_inode->i_mode);
    update_dotdot = (is_dir && old_dir != new_dir);
    if (update_dotdot) {
        if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
            err = -EIO;
            goto out;
        }
    }

    ts = CURRENT_TIME_SEC;
    if (new_inode) {
        if (is_dir) {
            err = fat_dir_empty(new_inode);
            if (err)
                goto out;
        }
        new_i_pos = MSDOS_I(new_inode)->i_pos;
        fat_detach(new_inode);
    } else {
        err = vfat_add_entry(new_dir, &new_dentry->d_name, is_dir, 0,
                     &ts, &sinfo);
        if (err)
            goto out;
        new_i_pos = sinfo.i_pos;
    }
    new_dir->i_version++;

    fat_detach(old_inode);
    fat_attach(old_inode, new_i_pos);
    if (IS_DIRSYNC(new_dir)) {
        err = fat_sync_inode(old_inode);
        if (err)
            goto error_inode;
    } else
        mark_inode_dirty(old_inode);

    if (update_dotdot) {
        fat_set_start(dotdot_de, MSDOS_I(new_dir)->i_logstart);
        mark_buffer_dirty_inode(dotdot_bh, old_inode);
        if (IS_DIRSYNC(new_dir)) {
            err = sync_dirty_buffer(dotdot_bh);
            if (err)
                goto error_dotdot;
        }
        drop_nlink(old_dir);
        if (!new_inode)
            inc_nlink(new_dir);
    }

    err = fat_remove_entries(old_dir, &old_sinfo);  /* and releases bh */
    old_sinfo.bh = NULL;
    if (err)
        goto error_dotdot;
    old_dir->i_version++;
    old_dir->i_ctime = old_dir->i_mtime = ts;
    if (IS_DIRSYNC(old_dir))
        (void)fat_sync_inode(old_dir);
    else
        mark_inode_dirty(old_dir);

    if (new_inode) {
        drop_nlink(new_inode);
        if (is_dir)
            drop_nlink(new_inode);
        new_inode->i_ctime = ts;
    }
out:
    brelse(sinfo.bh);
    brelse(dotdot_bh);
    brelse(old_sinfo.bh);
    mutex_unlock(&MSDOS_SB(sb)->s_lock);

    return err;

error_dotdot:
    /* data cluster is shared, serious corruption */
    corrupt = 1;

    if (update_dotdot) {
        fat_set_start(dotdot_de, MSDOS_I(old_dir)->i_logstart);
        mark_buffer_dirty_inode(dotdot_bh, old_inode);
        corrupt |= sync_dirty_buffer(dotdot_bh);
    }
error_inode:
    fat_detach(old_inode);
    fat_attach(old_inode, old_sinfo.i_pos);
    if (new_inode) {
        fat_attach(new_inode, new_i_pos);
        if (corrupt)
            corrupt |= fat_sync_inode(new_inode);
    } else {
        /*
         * If new entry was not sharing the data cluster, it
         * shouldn't be serious corruption.
         */
        int err2 = fat_remove_entries(new_dir, &sinfo);
        if (corrupt)
            corrupt |= err2;
        sinfo.bh = NULL;
    }
    if (corrupt < 0) {
        fat_fs_error(new_dir->i_sb,
                 "%s: Filesystem corrupted (i_pos %lld)",
                 __func__, sinfo.i_pos);
    }
    goto out;
}

static const 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_setattr,
    .getattr    = fat_getattr,
};

static void setup(struct super_block *sb)
{
    MSDOS_SB(sb)->dir_ops = &vfat_dir_inode_operations;
    if (MSDOS_SB(sb)->options.name_check != 's')
        sb->s_d_op = &vfat_ci_dentry_ops;
    else
        sb->s_d_op = &vfat_dentry_ops;
}

static int vfat_fill_super(struct super_block *sb, void *data, int silent)
{
    return fat_fill_super(sb, data, silent, 1, setup);
}

static struct dentry *vfat_mount(struct file_system_type *fs_type,
               int flags, const char *dev_name,
               void *data)
{
    return mount_bdev(fs_type, flags, dev_name, data, vfat_fill_super);
}

static struct file_system_type vfat_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "vfat",
    .mount      = vfat_mount,
    .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)