/*
   *  linux/fs/vfat/namei.c
   *
   *  Written 1992,1993 by Werner Almesberger
   *
   *  Windows95/Windows NT compatible extended MSDOS filesystem
   *    by Gordon Chaffee Copyright (C) 1995.  Send bug reports for the
   *    VFAT filesystem to <chaffee@cs.berkeley.edu>.  Specify
   *    what file operation caused you trouble and if you can duplicate
   *    the problem, send a script that demonstrates it.
   *
   *  Short name translation 1999, 2001 by Wolfram Pienkoss <wp@bszh.de>
   *
   *  Support Multibyte characters and cleanup by
   *				OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
   */
  
  #include <linux/module.h>
  #include <linux/jiffies.h>
  #include <linux/ctype.h>
  #include <linux/slab.h>
  #include <linux/buffer_head.h>
  #include <linux/namei.h>
  #include "fat.h"
  
  /*
   * If new entry was created in the parent, it could create the 8.3
   * alias (the shortname of logname).  So, the parent may have the
   * negative-dentry which matches the created 8.3 alias.
   *
   * If it happened, the negative dentry isn't actually negative
   * anymore.  So, drop it.
   */
  static int vfat_revalidate_shortname(struct dentry *dentry)
  {
  	int ret = 1;
  	spin_lock(&dentry->d_lock);
  	if (dentry->d_time != dentry->d_parent->d_inode->i_version)
  		ret = 0;
  	spin_unlock(&dentry->d_lock);
  	return ret;
  }
  
  static int vfat_revalidate(struct dentry *dentry, 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, 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, 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 dentry *dentry,
  		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 dentry *dentry,
  		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,
  };
  MODULE_ALIAS_FS("vfat");
  
  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)