/*
 *  linux/fs/fat/dir.c
 *
 *  directory handling functions for fat-based filesystems
 *
 *  Written 1992,1993 by Werner Almesberger
 *
 *  Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
 *
 *  VFAT extensions by Gordon Chaffee <chaffee@plateau.cs.berkeley.edu>
 *  Merged with msdos fs by Henrik Storner <storner@osiris.ping.dk>
 *  Rewritten for constant inumbers. Plugged buffer overrun in readdir(). AV
 *  Short name translation 1999, 2001 by Wolfram Pienkoss <wp@bszh.de>
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/msdos_fs.h>
#include <linux/dirent.h>
#include <linux/smp_lock.h>
#include <linux/buffer_head.h>
#include <linux/compat.h>
#include <asm/uaccess.h>

static inline loff_t fat_make_i_pos(struct super_block *sb,
                                    struct buffer_head *bh,
                                    struct msdos_dir_entry *de)
{
        return ((loff_t)bh->b_blocknr << MSDOS_SB(sb)->dir_per_block_bits)
                | (de - (struct msdos_dir_entry *)bh->b_data);
}

static inline void fat_dir_readahead(struct inode *dir, sector_t iblock,
                                     sector_t phys)
{
        struct super_block *sb = dir->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bh;
        int sec;

        /* This is not a first sector of cluster, or sec_per_clus == 1 */
        if ((iblock & (sbi->sec_per_clus - 1)) || sbi->sec_per_clus == 1)
                return;
        /* root dir of FAT12/FAT16 */
        if ((sbi->fat_bits != 32) && (dir->i_ino == MSDOS_ROOT_INO))
                return;

        bh = sb_find_get_block(sb, phys);
        if (bh == NULL || !buffer_uptodate(bh)) {
                for (sec = 0; sec < sbi->sec_per_clus; sec++)
                        sb_breadahead(sb, phys + sec);
        }
        brelse(bh);
}

/* Returns the inode number of the directory entry at offset pos. If bh is
   non-NULL, it is brelse'd before. Pos is incremented. The buffer header is
   returned in bh.
   AV. Most often we do it item-by-item. Makes sense to optimize.
   AV. OK, there we go: if both bh and de are non-NULL we assume that we just
   AV. want the next entry (took one explicit de=NULL in vfat/namei.c).
   AV. It's done in fat_get_entry() (inlined), here the slow case lives.
   AV. Additionally, when we return -1 (i.e. reached the end of directory)
   AV. we make bh NULL.
 */
static int fat__get_entry(struct inode *dir, loff_t *pos,
                          struct buffer_head **bh, struct msdos_dir_entry **de)
{
        struct super_block *sb = dir->i_sb;
        sector_t phys, iblock;
        unsigned long mapped_blocks;
        int err, offset;

next:
        if (*bh)
                brelse(*bh);

        *bh = NULL;
        iblock = *pos >> sb->s_blocksize_bits;
        err = fat_bmap(dir, iblock, &phys, &mapped_blocks);
        if (err || !phys)
                return -1;      /* beyond EOF or error */

        fat_dir_readahead(dir, iblock, phys);

        *bh = sb_bread(sb, phys);
        if (*bh == NULL) {
                printk(KERN_ERR "FAT: Directory bread(block %llu) failed\n",
                       (unsigned long long)phys);
                /* skip this block */
                *pos = (iblock + 1) << sb->s_blocksize_bits;
                goto next;
        }

        offset = *pos & (sb->s_blocksize - 1);
        *pos += sizeof(struct msdos_dir_entry);
        *de = (struct msdos_dir_entry *)((*bh)->b_data + offset);

        return 0;
}

static inline int fat_get_entry(struct inode *dir, loff_t *pos,
                                struct buffer_head **bh,
                                struct msdos_dir_entry **de)
{
        /* Fast stuff first */
        if (*bh && *de &&
            (*de - (struct msdos_dir_entry *)(*bh)->b_data) < MSDOS_SB(dir->i_sb)->dir_per_block - 1) {
                *pos += sizeof(struct msdos_dir_entry);
                (*de)++;
                return 0;
        }
        return fat__get_entry(dir, pos, bh, de);
}

/*
 * Convert Unicode 16 to UTF-8, translated Unicode, or ASCII.
 * If uni_xlate is enabled and we can't get a 1:1 conversion, use a
 * colon as an escape character since it is normally invalid on the vfat
 * filesystem. The following four characters are the hexadecimal digits
 * of Unicode value. This lets us do a full dump and restore of Unicode
 * filenames. We could get into some trouble with long Unicode names,
 * but ignore that right now.
 * Ahem... Stack smashing in ring 0 isn't fun. Fixed.
 */
static int uni16_to_x8(unsigned char *ascii, wchar_t *uni, int uni_xlate,
                       struct nls_table *nls)
{
        wchar_t *ip, ec;
        unsigned char *op, nc;
        int charlen;
        int k;

        ip = uni;
        op = ascii;

        while (*ip) {
                ec = *ip++;
                if ( (charlen = nls->uni2char(ec, op, NLS_MAX_CHARSET_SIZE)) > 0) {
                        op += charlen;
                } else {
                        if (uni_xlate == 1) {
                                *op = ':';
                                for (k = 4; k > 0; k--) {
                                        nc = ec & 0xF;
                                        op[k] = nc > 9  ? nc + ('a' - 10)
                                                        : nc + '0';
                                        ec >>= 4;
                                }
                                op += 5;
                        } else {
                                *op++ = '?';
                        }
                }
                /* We have some slack there, so it's OK */
                if (op>ascii+256) {
                        op = ascii + 256;
                        break;
                }
        }
        *op = 0;
        return (op - ascii);
}

static inline int
fat_short2uni(struct nls_table *t, unsigned char *c, int clen, wchar_t *uni)
{
        int charlen;

        charlen = t->char2uni(c, clen, uni);
        if (charlen < 0) {
                *uni = 0x003f;  /* a question mark */
                charlen = 1;
        }
        return charlen;
}

static inline int
fat_short2lower_uni(struct nls_table *t, unsigned char *c, int clen, wchar_t *uni)
{
        int charlen;
        wchar_t wc;

        charlen = t->char2uni(c, clen, &wc);
        if (charlen < 0) {
                *uni = 0x003f;  /* a question mark */
                charlen = 1;
        } else if (charlen <= 1) {
                unsigned char nc = t->charset2lower[*c];

                if (!nc)
                        nc = *c;

                if ( (charlen = t->char2uni(&nc, 1, uni)) < 0) {
                        *uni = 0x003f;  /* a question mark */
                        charlen = 1;
                }
        } else
                *uni = wc;

        return charlen;
}

static inline int
fat_shortname2uni(struct nls_table *nls, unsigned char *buf, int buf_size,
                  wchar_t *uni_buf, unsigned short opt, int lower)
{
        int len = 0;

        if (opt & VFAT_SFN_DISPLAY_LOWER)
                len =  fat_short2lower_uni(nls, buf, buf_size, uni_buf);
        else if (opt & VFAT_SFN_DISPLAY_WIN95)
                len = fat_short2uni(nls, buf, buf_size, uni_buf);
        else if (opt & VFAT_SFN_DISPLAY_WINNT) {
                if (lower)
                        len = fat_short2lower_uni(nls, buf, buf_size, uni_buf);
                else
                        len = fat_short2uni(nls, buf, buf_size, uni_buf);
        } else
                len = fat_short2uni(nls, buf, buf_size, uni_buf);

        return len;
}

enum { PARSE_INVALID = 1, PARSE_NOT_LONGNAME, PARSE_EOF, };

/**
 * fat_parse_long - Parse extended directory entry.
 *
 * This function returns zero on success, negative value on error, or one of
 * the following:
 *
 * %PARSE_INVALID - Directory entry is invalid.
 * %PARSE_NOT_LONGNAME - Directory entry does not contain longname.
 * %PARSE_EOF - Directory has no more entries.
 */
static int fat_parse_long(struct inode *dir, loff_t *pos,
                          struct buffer_head **bh, struct msdos_dir_entry **de,
                          wchar_t **unicode, unsigned char *nr_slots)
{
        struct msdos_dir_slot *ds;
        unsigned char id, slot, slots, alias_checksum;

        if (!*unicode) {
                *unicode = (wchar_t *)__get_free_page(GFP_KERNEL);
                if (!*unicode) {
                        brelse(*bh);
                        return -ENOMEM;
                }
        }
parse_long:
        slots = 0;
        ds = (struct msdos_dir_slot *)*de;
        id = ds->id;
        if (!(id & 0x40))
                return PARSE_INVALID;
        slots = id & ~0x40;
        if (slots > 20 || !slots)       /* ceil(256 * 2 / 26) */
                return PARSE_INVALID;
        *nr_slots = slots;
        alias_checksum = ds->alias_checksum;

        slot = slots;
        while (1) {
                int offset;

                slot--;
                offset = slot * 13;
                fat16_towchar(*unicode + offset, ds->name0_4, 5);
                fat16_towchar(*unicode + offset + 5, ds->name5_10, 6);
                fat16_towchar(*unicode + offset + 11, ds->name11_12, 2);

                if (ds->id & 0x40)
                        (*unicode)[offset + 13] = 0;
                if (fat_get_entry(dir, pos, bh, de) < 0)
                        return PARSE_EOF;
                if (slot == 0)
                        break;
                ds = (struct msdos_dir_slot *)*de;
                if (ds->attr != ATTR_EXT)
                        return PARSE_NOT_LONGNAME;
                if ((ds->id & ~0x40) != slot)
                        goto parse_long;
                if (ds->alias_checksum != alias_checksum)
                        goto parse_long;
        }
        if ((*de)->name[0] == DELETED_FLAG)
                return PARSE_INVALID;
        if ((*de)->attr == ATTR_EXT)
                goto parse_long;
        if (IS_FREE((*de)->name) || ((*de)->attr & ATTR_VOLUME))
                return PARSE_INVALID;
        if (fat_checksum((*de)->name) != alias_checksum)
                *nr_slots = 0;

        return 0;
}

/*
 * Return values: negative -> error, 0 -> not found, positive -> found,
 * value is the total amount of slots, including the shortname entry.
 */
int fat_search_long(struct inode *inode, const unsigned char *name,
                    int name_len, struct fat_slot_info *sinfo)
{
        struct super_block *sb = inode->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bh = NULL;
        struct msdos_dir_entry *de;
        struct nls_table *nls_io = sbi->nls_io;
        struct nls_table *nls_disk = sbi->nls_disk;
        wchar_t bufuname[14];
        unsigned char xlate_len, nr_slots;
        wchar_t *unicode = NULL;
        unsigned char work[MSDOS_NAME], bufname[260];   /* 256 + 4 */
        int uni_xlate = sbi->options.unicode_xlate;
        int utf8 = sbi->options.utf8;
        int anycase = (sbi->options.name_check != 's');
        unsigned short opt_shortname = sbi->options.shortname;
        loff_t cpos = 0;
        int chl, i, j, last_u, err;

        err = -ENOENT;
        while(1) {
                if (fat_get_entry(inode, &cpos, &bh, &de) == -1)
                        goto EODir;
parse_record:
                nr_slots = 0;
                if (de->name[0] == DELETED_FLAG)
                        continue;
                if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
                        continue;
                if (de->attr != ATTR_EXT && IS_FREE(de->name))
                        continue;
                if (de->attr == ATTR_EXT) {
                        int status = fat_parse_long(inode, &cpos, &bh, &de,
                                                    &unicode, &nr_slots);
                        if (status < 0)
                                return status;
                        else if (status == PARSE_INVALID)
                                continue;
                        else if (status == PARSE_NOT_LONGNAME)
                                goto parse_record;
                        else if (status == PARSE_EOF)
                                goto EODir;
                }

                memcpy(work, de->name, sizeof(de->name));
                /* see namei.c, msdos_format_name */
                if (work[0] == 0x05)
                        work[0] = 0xE5;
                for (i = 0, j = 0, last_u = 0; i < 8;) {
                        if (!work[i])
                                break;
                        chl = fat_shortname2uni(nls_disk, &work[i], 8 - i,
                                                &bufuname[j++], opt_shortname,
                                                de->lcase & CASE_LOWER_BASE);
                        if (chl <= 1) {
                                if (work[i] != ' ')
                                        last_u = j;
                        } else {
                                last_u = j;
                        }
                        i += chl;
                }
                j = last_u;
                fat_short2uni(nls_disk, ".", 1, &bufuname[j++]);
                for (i = 8; i < MSDOS_NAME;) {
                        if (!work[i])
                                break;
                        chl = fat_shortname2uni(nls_disk, &work[i],
                                                MSDOS_NAME - i,
                                                &bufuname[j++], opt_shortname,
                                                de->lcase & CASE_LOWER_EXT);
                        if (chl <= 1) {
                                if (work[i] != ' ')
                                        last_u = j;
                        } else {
                                last_u = j;
                        }
                        i += chl;
                }
                if (!last_u)
                        continue;

                bufuname[last_u] = 0x0000;
                xlate_len = utf8
                        ?utf8_wcstombs(bufname, bufuname, sizeof(bufname))
                        :uni16_to_x8(bufname, bufuname, uni_xlate, nls_io);
                if (xlate_len == name_len)
                        if ((!anycase && !memcmp(name, bufname, xlate_len)) ||
                            (anycase && !nls_strnicmp(nls_io, name, bufname,
                                                                xlate_len)))
                                goto Found;

                if (nr_slots) {
                        xlate_len = utf8
                                ?utf8_wcstombs(bufname, unicode, sizeof(bufname))
                                :uni16_to_x8(bufname, unicode, uni_xlate, nls_io);
                        if (xlate_len != name_len)
                                continue;
                        if ((!anycase && !memcmp(name, bufname, xlate_len)) ||
                            (anycase && !nls_strnicmp(nls_io, name, bufname,
                                                                xlate_len)))
                                goto Found;
                }
        }

Found:
        nr_slots++;     /* include the de */
        sinfo->slot_off = cpos - nr_slots * sizeof(*de);
        sinfo->nr_slots = nr_slots;
        sinfo->de = de;
        sinfo->bh = bh;
        sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
        err = 0;
EODir:
        if (unicode)
                free_page((unsigned long)unicode);

        return err;
}

EXPORT_SYMBOL_GPL(fat_search_long);

struct fat_ioctl_filldir_callback {
        void __user *dirent;
        int result;
        /* for dir ioctl */
        const char *longname;
        int long_len;
        const char *shortname;
        int short_len;
};

static int __fat_readdir(struct inode *inode, struct file *filp, void *dirent,
                         filldir_t filldir, int short_only, int both)
{
        struct super_block *sb = inode->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bh;
        struct msdos_dir_entry *de;
        struct nls_table *nls_io = sbi->nls_io;
        struct nls_table *nls_disk = sbi->nls_disk;
        unsigned char long_slots;
        const char *fill_name;
        int fill_len;
        wchar_t bufuname[14];
        wchar_t *unicode = NULL;
        unsigned char c, work[MSDOS_NAME], bufname[56], *ptname = bufname;
        unsigned long lpos, dummy, *furrfu = &lpos;
        int uni_xlate = sbi->options.unicode_xlate;
        int isvfat = sbi->options.isvfat;
        int utf8 = sbi->options.utf8;
        int nocase = sbi->options.nocase;
        unsigned short opt_shortname = sbi->options.shortname;
        unsigned long inum;
        int chi, chl, i, i2, j, last, last_u, dotoffset = 0;
        loff_t cpos;
        int ret = 0;

        lock_kernel();

        cpos = filp->f_pos;
        /* Fake . and .. for the root directory. */
        if (inode->i_ino == MSDOS_ROOT_INO) {
                while (cpos < 2) {
                        if (filldir(dirent, "..", cpos+1, cpos, MSDOS_ROOT_INO, DT_DIR) < 0)
                                goto out;
                        cpos++;
                        filp->f_pos++;
                }
                if (cpos == 2) {
                        dummy = 2;
                        furrfu = &dummy;
                        cpos = 0;
                }
        }
        if (cpos & (sizeof(struct msdos_dir_entry)-1)) {
                ret = -ENOENT;
                goto out;
        }

        bh = NULL;
GetNew:
        if (fat_get_entry(inode, &cpos, &bh, &de) == -1)
                goto EODir;
parse_record:
        long_slots = 0;
        /* Check for long filename entry */
        if (isvfat) {
                if (de->name[0] == DELETED_FLAG)
                        goto RecEnd;
                if (de->attr != ATTR_EXT && (de->attr & ATTR_VOLUME))
                        goto RecEnd;
                if (de->attr != ATTR_EXT && IS_FREE(de->name))
                        goto RecEnd;
        } else {
                if ((de->attr & ATTR_VOLUME) || IS_FREE(de->name))
                        goto RecEnd;
        }

        if (isvfat && de->attr == ATTR_EXT) {
                int status = fat_parse_long(inode, &cpos, &bh, &de,
                                            &unicode, &long_slots);
                if (status < 0) {
                        filp->f_pos = cpos;
                        ret = status;
                        goto out;
                } else if (status == PARSE_INVALID)
                        goto RecEnd;
                else if (status == PARSE_NOT_LONGNAME)
                        goto parse_record;
                else if (status == PARSE_EOF)
                        goto EODir;
        }

        if (sbi->options.dotsOK) {
                ptname = bufname;
                dotoffset = 0;
                if (de->attr & ATTR_HIDDEN) {
                        *ptname++ = '.';
                        dotoffset = 1;
                }
        }

        memcpy(work, de->name, sizeof(de->name));
        /* see namei.c, msdos_format_name */
        if (work[0] == 0x05)
                work[0] = 0xE5;
        for (i = 0, j = 0, last = 0, last_u = 0; i < 8;) {
                if (!(c = work[i]))
                        break;
                chl = fat_shortname2uni(nls_disk, &work[i], 8 - i,
                                        &bufuname[j++], opt_shortname,
                                        de->lcase & CASE_LOWER_BASE);
                if (chl <= 1) {
                        ptname[i++] = (!nocase && c>='A' && c<='Z') ? c+32 : c;
                        if (c != ' ') {
                                last = i;
                                last_u = j;
                        }
                } else {
                        last_u = j;
                        for (chi = 0; chi < chl && i < 8; chi++) {
                                ptname[i] = work[i];
                                i++; last = i;
                        }
                }
        }
        i = last;
        j = last_u;
        fat_short2uni(nls_disk, ".", 1, &bufuname[j++]);
        ptname[i++] = '.';
        for (i2 = 8; i2 < MSDOS_NAME;) {
                if (!(c = work[i2]))
                        break;
                chl = fat_shortname2uni(nls_disk, &work[i2], MSDOS_NAME - i2,
                                        &bufuname[j++], opt_shortname,
                                        de->lcase & CASE_LOWER_EXT);
                if (chl <= 1) {
                        i2++;
                        ptname[i++] = (!nocase && c>='A' && c<='Z') ? c+32 : c;
                        if (c != ' ') {
                                last = i;
                                last_u = j;
                        }
                } else {
                        last_u = j;
                        for (chi = 0; chi < chl && i2 < MSDOS_NAME; chi++) {
                                ptname[i++] = work[i2++];
                                last = i;
                        }
                }
        }
        if (!last)
                goto RecEnd;

        i = last + dotoffset;
        j = last_u;

        lpos = cpos - (long_slots+1)*sizeof(struct msdos_dir_entry);
        if (!memcmp(de->name, MSDOS_DOT, MSDOS_NAME))
                inum = inode->i_ino;
        else if (!memcmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) {
                inum = parent_ino(filp->f_path.dentry);
        } else {
                loff_t i_pos = fat_make_i_pos(sb, bh, de);
                struct inode *tmp = fat_iget(sb, i_pos);
                if (tmp) {
                        inum = tmp->i_ino;
                        iput(tmp);
                } else
                        inum = iunique(sb, MSDOS_ROOT_INO);
        }

        if (isvfat) {
                bufuname[j] = 0x0000;
                i = utf8 ? utf8_wcstombs(bufname, bufuname, sizeof(bufname))
                         : uni16_to_x8(bufname, bufuname, uni_xlate, nls_io);
        }

        fill_name = bufname;
        fill_len = i;
        if (!short_only && long_slots) {
                /* convert the unicode long name. 261 is maximum size
                 * of unicode buffer. (13 * slots + nul) */
                void *longname = unicode + 261;
                int buf_size = PAGE_SIZE - (261 * sizeof(unicode[0]));
                int long_len = utf8
                        ? utf8_wcstombs(longname, unicode, buf_size)
                        : uni16_to_x8(longname, unicode, uni_xlate, nls_io);

                if (!both) {
                        fill_name = longname;
                        fill_len = long_len;
                } else {
                        /* hack for fat_ioctl_filldir() */
                        struct fat_ioctl_filldir_callback *p = dirent;

                        p->longname = longname;
                        p->long_len = long_len;
                        p->shortname = bufname;
                        p->short_len = i;
                        fill_name = NULL;
                        fill_len = 0;
                }
        }
        if (filldir(dirent, fill_name, fill_len, *furrfu, inum,
                    (de->attr & ATTR_DIR) ? DT_DIR : DT_REG) < 0)
                goto FillFailed;

RecEnd:
        furrfu = &lpos;
        filp->f_pos = cpos;
        goto GetNew;
EODir:
        filp->f_pos = cpos;
FillFailed:
        brelse(bh);
        if (unicode)
                free_page((unsigned long)unicode);
out:
        unlock_kernel();
        return ret;
}

static int fat_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
        struct inode *inode = filp->f_path.dentry->d_inode;
        return __fat_readdir(inode, filp, dirent, filldir, 0, 0);
}

#define FAT_IOCTL_FILLDIR_FUNC(func, dirent_type)                          \
static int func(void *__buf, const char *name, int name_len,               \
                             loff_t offset, u64 ino, unsigned int d_type)  \
{                                                                          \
        struct fat_ioctl_filldir_callback *buf = __buf;                    \
        struct dirent_type __user *d1 = buf->dirent;                       \
        struct dirent_type __user *d2 = d1 + 1;                            \
                                                                           \
        if (buf->result)                                                   \
                return -EINVAL;                                            \
        buf->result++;                                                     \
                                                                           \
        if (name != NULL) {                                                \
                /* dirent has only short name */                           \
                if (name_len >= sizeof(d1->d_name))                        \
                        name_len = sizeof(d1->d_name) - 1;                 \
                                                                           \
                if (put_user(0, d2->d_name)                     ||         \
                    put_user(0, &d2->d_reclen)                  ||         \
                    copy_to_user(d1->d_name, name, name_len)    ||         \
                    put_user(0, d1->d_name + name_len)          ||         \
                    put_user(name_len, &d1->d_reclen))                     \
                        goto efault;                                       \
        } else {                                                           \
                /* dirent has short and long name */                       \
                const char *longname = buf->longname;                      \
                int long_len = buf->long_len;                              \
                const char *shortname = buf->shortname;                    \
                int short_len = buf->short_len;                            \
                                                                           \
                if (long_len >= sizeof(d1->d_name))                        \
                        long_len = sizeof(d1->d_name) - 1;                 \
                if (short_len >= sizeof(d1->d_name))                       \
                        short_len = sizeof(d1->d_name) - 1;                \
                                                                           \
                if (copy_to_user(d2->d_name, longname, long_len)        || \
                    put_user(0, d2->d_name + long_len)                  || \
                    put_user(long_len, &d2->d_reclen)                   || \
                    put_user(ino, &d2->d_ino)                           || \
                    put_user(offset, &d2->d_off)                        || \
                    copy_to_user(d1->d_name, shortname, short_len)      || \
                    put_user(0, d1->d_name + short_len)                 || \
                    put_user(short_len, &d1->d_reclen))                    \
                        goto efault;                                       \
        }                                                                  \
        return 0;                                                          \
efault:                                                                    \
        buf->result = -EFAULT;                                             \
        return -EFAULT;                                                    \
}

FAT_IOCTL_FILLDIR_FUNC(fat_ioctl_filldir, dirent)

static int fat_ioctl_readdir(struct inode *inode, struct file *filp,
                             void __user *dirent, filldir_t filldir,
                             int short_only, int both)
{
        struct fat_ioctl_filldir_callback buf;
        int ret;

        buf.dirent = dirent;
        buf.result = 0;
        mutex_lock(&inode->i_mutex);
        ret = -ENOENT;
        if (!IS_DEADDIR(inode)) {
                ret = __fat_readdir(inode, filp, &buf, filldir,
                                    short_only, both);
        }
        mutex_unlock(&inode->i_mutex);
        if (ret >= 0)
                ret = buf.result;
        return ret;
}

static int fat_dir_ioctl(struct inode *inode, struct file *filp,
                         unsigned int cmd, unsigned long arg)
{
        struct dirent __user *d1 = (struct dirent __user *)arg;
        int short_only, both;

        switch (cmd) {
        case VFAT_IOCTL_READDIR_SHORT:
                short_only = 1;
                both = 0;
                break;
        case VFAT_IOCTL_READDIR_BOTH:
                short_only = 0;
                both = 1;
                break;
        default:
                return fat_generic_ioctl(inode, filp, cmd, arg);
        }

        if (!access_ok(VERIFY_WRITE, d1, sizeof(struct dirent[2])))
                return -EFAULT;
        /*
         * Yes, we don't need this put_user() absolutely. However old
         * code didn't return the right value. So, app use this value,
         * in order to check whether it is EOF.
         */
        if (put_user(0, &d1->d_reclen))
                return -EFAULT;

        return fat_ioctl_readdir(inode, filp, d1, fat_ioctl_filldir,
                                 short_only, both);
}

#ifdef CONFIG_COMPAT
#define VFAT_IOCTL_READDIR_BOTH32       _IOR('r', 1, struct compat_dirent[2])
#define VFAT_IOCTL_READDIR_SHORT32      _IOR('r', 2, struct compat_dirent[2])

FAT_IOCTL_FILLDIR_FUNC(fat_compat_ioctl_filldir, compat_dirent)

static long fat_compat_dir_ioctl(struct file *filp, unsigned cmd,
                                 unsigned long arg)
{
        struct inode *inode = filp->f_path.dentry->d_inode;
        struct compat_dirent __user *d1 = compat_ptr(arg);
        int short_only, both;

        switch (cmd) {
        case VFAT_IOCTL_READDIR_SHORT32:
                short_only = 1;
                both = 0;
                break;
        case VFAT_IOCTL_READDIR_BOTH32:
                short_only = 0;
                both = 1;
                break;
        default:
                return -ENOIOCTLCMD;
        }

        if (!access_ok(VERIFY_WRITE, d1, sizeof(struct compat_dirent[2])))
                return -EFAULT;
        /*
         * Yes, we don't need this put_user() absolutely. However old
         * code didn't return the right value. So, app use this value,
         * in order to check whether it is EOF.
         */
        if (put_user(0, &d1->d_reclen))
                return -EFAULT;

        return fat_ioctl_readdir(inode, filp, d1, fat_compat_ioctl_filldir,
                                 short_only, both);
}
#endif /* CONFIG_COMPAT */

const struct file_operations fat_dir_operations = {
        .read           = generic_read_dir,
        .readdir        = fat_readdir,
        .ioctl          = fat_dir_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = fat_compat_dir_ioctl,
#endif
        .fsync          = file_fsync,
};

static int fat_get_short_entry(struct inode *dir, loff_t *pos,
                               struct buffer_head **bh,
                               struct msdos_dir_entry **de)
{
        while (fat_get_entry(dir, pos, bh, de) >= 0) {
                /* free entry or long name entry or volume label */
                if (!IS_FREE((*de)->name) && !((*de)->attr & ATTR_VOLUME))
                        return 0;
        }
        return -ENOENT;
}

/*
 * The ".." entry can not provide the "struct fat_slot_info" informations
 * for inode. So, this function provide the some informations only.
 */
int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
                         struct msdos_dir_entry **de, loff_t *i_pos)
{
        loff_t offset;

        offset = 0;
        *bh = NULL;
        while (fat_get_short_entry(dir, &offset, bh, de) >= 0) {
                if (!strncmp((*de)->name, MSDOS_DOTDOT, MSDOS_NAME)) {
                        *i_pos = fat_make_i_pos(dir->i_sb, *bh, *de);
                        return 0;
                }
        }
        return -ENOENT;
}

EXPORT_SYMBOL_GPL(fat_get_dotdot_entry);

/* See if directory is empty */
int fat_dir_empty(struct inode *dir)
{
        struct buffer_head *bh;
        struct msdos_dir_entry *de;
        loff_t cpos;
        int result = 0;

        bh = NULL;
        cpos = 0;
        while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) {
                if (strncmp(de->name, MSDOS_DOT   , MSDOS_NAME) &&
                    strncmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) {
                        result = -ENOTEMPTY;
                        break;
                }
        }
        brelse(bh);
        return result;
}

EXPORT_SYMBOL_GPL(fat_dir_empty);

/*
 * fat_subdirs counts the number of sub-directories of dir. It can be run
 * on directories being created.
 */
int fat_subdirs(struct inode *dir)
{
        struct buffer_head *bh;
        struct msdos_dir_entry *de;
        loff_t cpos;
        int count = 0;

        bh = NULL;
        cpos = 0;
        while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) {
                if (de->attr & ATTR_DIR)
                        count++;
        }
        brelse(bh);
        return count;
}

/*
 * Scans a directory for a given file (name points to its formatted name).
 * Returns an error code or zero.
 */
int fat_scan(struct inode *dir, const unsigned char *name,
             struct fat_slot_info *sinfo)
{
        struct super_block *sb = dir->i_sb;

        sinfo->slot_off = 0;
        sinfo->bh = NULL;
        while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh,
                                   &sinfo->de) >= 0) {
                if (!strncmp(sinfo->de->name, name, MSDOS_NAME)) {
                        sinfo->slot_off -= sizeof(*sinfo->de);
                        sinfo->nr_slots = 1;
                        sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
                        return 0;
                }
        }
        return -ENOENT;
}

EXPORT_SYMBOL_GPL(fat_scan);

static int __fat_remove_entries(struct inode *dir, loff_t pos, int nr_slots)
{
        struct super_block *sb = dir->i_sb;
        struct buffer_head *bh;
        struct msdos_dir_entry *de, *endp;
        int err = 0, orig_slots;

        while (nr_slots) {
                bh = NULL;
                if (fat_get_entry(dir, &pos, &bh, &de) < 0) {
                        err = -EIO;
                        break;
                }

                orig_slots = nr_slots;
                endp = (struct msdos_dir_entry *)(bh->b_data + sb->s_blocksize);
                while (nr_slots && de < endp) {
                        de->name[0] = DELETED_FLAG;
                        de++;
                        nr_slots--;
                }
                mark_buffer_dirty(bh);
                if (IS_DIRSYNC(dir))
                        err = sync_dirty_buffer(bh);
                brelse(bh);
                if (err)
                        break;

                /* pos is *next* de's position, so this does `- sizeof(de)' */
                pos += ((orig_slots - nr_slots) * sizeof(*de)) - sizeof(*de);
        }

        return err;
}

int fat_remove_entries(struct inode *dir, struct fat_slot_info *sinfo)
{
        struct msdos_dir_entry *de;
        struct buffer_head *bh;
        int err = 0, nr_slots;

        /*
         * First stage: Remove the shortname. By this, the directory
         * entry is removed.
         */
        nr_slots = sinfo->nr_slots;
        de = sinfo->de;
        sinfo->de = NULL;
        bh = sinfo->bh;
        sinfo->bh = NULL;
        while (nr_slots && de >= (struct msdos_dir_entry *)bh->b_data) {
                de->name[0] = DELETED_FLAG;
                de--;
                nr_slots--;
        }
        mark_buffer_dirty(bh);
        if (IS_DIRSYNC(dir))
                err = sync_dirty_buffer(bh);
        brelse(bh);
        if (err)
                return err;
        dir->i_version++;

        if (nr_slots) {
                /*
                 * Second stage: remove the remaining longname slots.
                 * (This directory entry is already removed, and so return
                 * the success)
                 */
                err = __fat_remove_entries(dir, sinfo->slot_off, nr_slots);
                if (err) {
                        printk(KERN_WARNING
                               "FAT: Couldn't remove the long name slots\n");
                }
        }

        dir->i_mtime = dir->i_atime = CURRENT_TIME_SEC;
        if (IS_DIRSYNC(dir))
                (void)fat_sync_inode(dir);
        else
                mark_inode_dirty(dir);

        return 0;
}

EXPORT_SYMBOL_GPL(fat_remove_entries);

static int fat_zeroed_cluster(struct inode *dir, sector_t blknr, int nr_used,
                              struct buffer_head **bhs, int nr_bhs)
{
        struct super_block *sb = dir->i_sb;
        sector_t last_blknr = blknr + MSDOS_SB(sb)->sec_per_clus;
        int err, i, n;

        /* Zeroing the unused blocks on this cluster */
        blknr += nr_used;
        n = nr_used;
        while (blknr < last_blknr) {
                bhs[n] = sb_getblk(sb, blknr);
                if (!bhs[n]) {
                        err = -ENOMEM;
                        goto error;
                }
                memset(bhs[n]->b_data, 0, sb->s_blocksize);
                set_buffer_uptodate(bhs[n]);
                mark_buffer_dirty(bhs[n]);

                n++;
                blknr++;
                if (n == nr_bhs) {
                        if (IS_DIRSYNC(dir)) {
                                err = fat_sync_bhs(bhs, n);
                                if (err)
                                        goto error;
                        }
                        for (i = 0; i < n; i++)
                                brelse(bhs[i]);
                        n = 0;
                }
        }
        if (IS_DIRSYNC(dir)) {
                err = fat_sync_bhs(bhs, n);
                if (err)
                        goto error;
        }
        for (i = 0; i < n; i++)
                brelse(bhs[i]);

        return 0;

error:
        for (i = 0; i < n; i++)
                bforget(bhs[i]);
        return err;
}

int fat_alloc_new_dir(struct inode *dir, struct timespec *ts)
{
        struct super_block *sb = dir->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bhs[MAX_BUF_PER_PAGE];
        struct msdos_dir_entry *de;
        sector_t blknr;
        __le16 date, time;
        int err, cluster;

        err = fat_alloc_clusters(dir, &cluster, 1);
        if (err)
                goto error;

        blknr = fat_clus_to_blknr(sbi, cluster);
        bhs[0] = sb_getblk(sb, blknr);
        if (!bhs[0]) {
                err = -ENOMEM;
                goto error_free;
        }

        fat_date_unix2dos(ts->tv_sec, &time, &date);

        de = (struct msdos_dir_entry *)bhs[0]->b_data;
        /* filling the new directory slots ("." and ".." entries) */
        memcpy(de[0].name, MSDOS_DOT, MSDOS_NAME);
        memcpy(de[1].name, MSDOS_DOTDOT, MSDOS_NAME);
        de->attr = de[1].attr = ATTR_DIR;
        de[0].lcase = de[1].lcase = 0;
        de[0].time = de[1].time = time;
        de[0].date = de[1].date = date;
        de[0].ctime_cs = de[1].ctime_cs = 0;
        if (sbi->options.isvfat) {
                /* extra timestamps */
                de[0].ctime = de[1].ctime = time;
                de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = date;
        } else {
                de[0].ctime = de[1].ctime = 0;
                de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = 0;
        }
        de[0].start = cpu_to_le16(cluster);
        de[0].starthi = cpu_to_le16(cluster >> 16);
        de[1].start = cpu_to_le16(MSDOS_I(dir)->i_logstart);
        de[1].starthi = cpu_to_le16(MSDOS_I(dir)->i_logstart >> 16);
        de[0].size = de[1].size = 0;
        memset(de + 2, 0, sb->s_blocksize - 2 * sizeof(*de));
        set_buffer_uptodate(bhs[0]);
        mark_buffer_dirty(bhs[0]);

        err = fat_zeroed_cluster(dir, blknr, 1, bhs, MAX_BUF_PER_PAGE);
        if (err)
                goto error_free;

        return cluster;

error_free:
        fat_free_clusters(dir, cluster);
error:
        return err;
}

EXPORT_SYMBOL_GPL(fat_alloc_new_dir);

static int fat_add_new_entries(struct inode *dir, void *slots, int nr_slots,
                               int *nr_cluster, struct msdos_dir_entry **de,
                               struct buffer_head **bh, loff_t *i_pos)
{
        struct super_block *sb = dir->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bhs[MAX_BUF_PER_PAGE];
        sector_t blknr, start_blknr, last_blknr;
        unsigned long size, copy;
        int err, i, n, offset, cluster[2];

        /*
         * The minimum cluster size is 512bytes, and maximum entry
         * size is 32*slots (672bytes).  So, iff the cluster size is
         * 512bytes, we may need two clusters.
         */
        size = nr_slots * sizeof(struct msdos_dir_entry);
        *nr_cluster = (size + (sbi->cluster_size - 1)) >> sbi->cluster_bits;
        BUG_ON(*nr_cluster > 2);

        err = fat_alloc_clusters(dir, cluster, *nr_cluster);
        if (err)
                goto error;

        /*
         * First stage: Fill the directory entry.  NOTE: This cluster
         * is not referenced from any inode yet, so updates order is
         * not important.
         */
        i = n = copy = 0;
        do {
                start_blknr = blknr = fat_clus_to_blknr(sbi, cluster[i]);
                last_blknr = start_blknr + sbi->sec_per_clus;
                while (blknr < last_blknr) {
                        bhs[n] = sb_getblk(sb, blknr);
                        if (!bhs[n]) {
                                err = -ENOMEM;
                                goto error_nomem;
                        }

                        /* fill the directory entry */
                        copy = min(size, sb->s_blocksize);
                        memcpy(bhs[n]->b_data, slots, copy);
                        slots += copy;
                        size -= copy;
                        set_buffer_uptodate(bhs[n]);
                        mark_buffer_dirty(bhs[n]);
                        if (!size)
                                break;
                        n++;
                        blknr++;
                }
        } while (++i < *nr_cluster);

        memset(bhs[n]->b_data + copy, 0, sb->s_blocksize - copy);
        offset = copy - sizeof(struct msdos_dir_entry);
        get_bh(bhs[n]);
        *bh = bhs[n];
        *de = (struct msdos_dir_entry *)((*bh)->b_data + offset);
        *i_pos = fat_make_i_pos(sb, *bh, *de);

        /* Second stage: clear the rest of cluster, and write outs */
        err = fat_zeroed_cluster(dir, start_blknr, ++n, bhs, MAX_BUF_PER_PAGE);
        if (err)
                goto error_free;

        return cluster[0];

error_free:
        brelse(*bh);
        *bh = NULL;
        n = 0;
error_nomem:
        for (i = 0; i < n; i++)
                bforget(bhs[i]);
        fat_free_clusters(dir, cluster[0]);
error:
        return err;
}

int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
                    struct fat_slot_info *sinfo)
{
        struct super_block *sb = dir->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
        struct buffer_head *bh, *prev, *bhs[3]; /* 32*slots (672bytes) */
        struct msdos_dir_entry *de;
        int err, free_slots, i, nr_bhs;
        loff_t pos, i_pos;

        sinfo->nr_slots = nr_slots;

        /* First stage: search free direcotry entries */
        free_slots = nr_bhs = 0;
        bh = prev = NULL;
        pos = 0;
        err = -ENOSPC;
        while (fat_get_entry(dir, &pos, &bh, &de) > -1) {
                /* check the maximum size of directory */
                if (pos >= FAT_MAX_DIR_SIZE)
                        goto error;

                if (IS_FREE(de->name)) {
                        if (prev != bh) {
                                get_bh(bh);
                                bhs[nr_bhs] = prev = bh;
                                nr_bhs++;
                        }
                        free_slots++;
                        if (free_slots == nr_slots)
                                goto found;
                } else {
                        for (i = 0; i < nr_bhs; i++)
                                brelse(bhs[i]);
                        prev = NULL;
                        free_slots = nr_bhs = 0;
                }
        }
        if (dir->i_ino == MSDOS_ROOT_INO) {
                if (sbi->fat_bits != 32)
                        goto error;
        } else if (MSDOS_I(dir)->i_start == 0) {
                printk(KERN_ERR "FAT: Corrupted directory (i_pos %lld)\n",
                       MSDOS_I(dir)->i_pos);
                err = -EIO;
                goto error;
        }

found:
        err = 0;
        pos -= free_slots * sizeof(*de);
        nr_slots -= free_slots;
        if (free_slots) {
                /*
                 * Second stage: filling the free entries with new entries.
                 * NOTE: If this slots has shortname, first, we write
                 * the long name slots, then write the short name.
                 */
                int size = free_slots * sizeof(*de);
                int offset = pos & (sb->s_blocksize - 1);
                int long_bhs = nr_bhs - (nr_slots == 0);

                /* Fill the long name slots. */
                for (i = 0; i < long_bhs; i++) {
                        int copy = min_t(int, sb->s_blocksize - offset, size);
                        memcpy(bhs[i]->b_data + offset, slots, copy);
                        mark_buffer_dirty(bhs[i]);
                        offset = 0;
                        slots += copy;
                        size -= copy;
                }
                if (long_bhs && IS_DIRSYNC(dir))
                        err = fat_sync_bhs(bhs, long_bhs);
                if (!err && i < nr_bhs) {
                        /* Fill the short name slot. */
                        int copy = min_t(int, sb->s_blocksize - offset, size);
                        memcpy(bhs[i]->b_data + offset, slots, copy);
                        mark_buffer_dirty(bhs[i]);
                        if (IS_DIRSYNC(dir))
                                err = sync_dirty_buffer(bhs[i]);
                }
                for (i = 0; i < nr_bhs; i++)
                        brelse(bhs[i]);
                if (err)
                        goto error_remove;
        }

        if (nr_slots) {
                int cluster, nr_cluster;

                /*
                 * Third stage: allocate the cluster for new entries.
                 * And initialize the cluster with new entries, then
                 * add the cluster to dir.
                 */
                cluster = fat_add_new_entries(dir, slots, nr_slots, &nr_cluster,
                                              &de, &bh, &i_pos);
                if (cluster < 0) {
                        err = cluster;
                        goto error_remove;
                }
                err = fat_chain_add(dir, cluster, nr_cluster);
                if (err) {
                        fat_free_clusters(dir, cluster);
                        goto error_remove;
                }
                if (dir->i_size & (sbi->cluster_size - 1)) {
                        fat_fs_panic(sb, "Odd directory size");
                        dir->i_size = (dir->i_size + sbi->cluster_size - 1)
                                & ~((loff_t)sbi->cluster_size - 1);
                }
                dir->i_size += nr_cluster << sbi->cluster_bits;
                MSDOS_I(dir)->mmu_private += nr_cluster << sbi->cluster_bits;
        }
        sinfo->slot_off = pos;
        sinfo->de = de;
        sinfo->bh = bh;
        sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);

        return 0;

error:
        brelse(bh);
        for (i = 0; i < nr_bhs; i++)
                brelse(bhs[i]);
        return err;

error_remove:
        brelse(bh);
        if (free_slots)
                __fat_remove_entries(dir, pos, free_slots);
        return err;
}

EXPORT_SYMBOL_GPL(fat_add_entries);