fs/fat/namei_msdos.c - third_party/linux - Git at Google

 /*
  *  linux/fs/msdos/namei.c
  *
  *  Written 1992,1993 by Werner Almesberger
  *  Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
  *  Rewritten for constant inumbers 1999 by Al Viro
  */

 #include <linux/module.h>
 #include <linux/iversion.h>
 #include "fat.h"

 /* Characters that are undesirable in an MS-DOS file name */
 static unsigned char bad_chars[] = "*?<>|\"";
 static unsigned char bad_if_strict[] = "+=,; ";

 /***** Formats an MS-DOS file name. Rejects invalid names. */
 static int msdos_format_name(const unsigned char *name, int len,
 			     unsigned char *res, struct fat_mount_options *opts)
 	/*
 	 * name is the proposed name, len is its length, res is
 	 * the resulting name, opts->name_check is either (r)elaxed,
 	 * (n)ormal or (s)trict, opts->dotsOK allows dots at the
 	 * beginning of name (for hidden files)
 	 */
 {
 	unsigned char *walk;
 	unsigned char c;
 	int space;

 	if (name[0] == '.') {	/* dotfile because . and .. already done */
 		if (opts->dotsOK) {
 			/* Get rid of dot - test for it elsewhere */
 			name++;
 			len--;
 		} else
 			return -EINVAL;
 	}
 	/*
 	 * disallow names that _really_ start with a dot
 	 */
 	space = 1;
 	c = 0;
 	for (walk = res; len && walk - res < 8; walk++) {
 		c = *name++;
 		len--;
 		if (opts->name_check != 'r' && strchr(bad_chars, c))
 			return -EINVAL;
 		if (opts->name_check == 's' && strchr(bad_if_strict, c))
 			return -EINVAL;
 		if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
 			return -EINVAL;
 		if (c < ' ' || c == ':' || c == '\\')
 			return -EINVAL;
 	/*
 	 * 0xE5 is legal as a first character, but we must substitute
 	 * 0x05 because 0xE5 marks deleted files.  Yes, DOS really
 	 * does this.
 	 * It seems that Microsoft hacked DOS to support non-US
 	 * characters after the 0xE5 character was already in use to
 	 * mark deleted files.
 	 */
 		if ((res == walk) && (c == 0xE5))
 			c = 0x05;
 		if (c == '.')
 			break;
 		space = (c == ' ');
 		*walk = (!opts->nocase && c >= 'a' && c <= 'z') ? c - 32 : c;
 	}
 	if (space)
 		return -EINVAL;
 	if (opts->name_check == 's' && len && c != '.') {
 		c = *name++;
 		len--;
 		if (c != '.')
 			return -EINVAL;
 	}
 	while (c != '.' && len--)
 		c = *name++;
 	if (c == '.') {
 		while (walk - res < 8)
 			*walk++ = ' ';
 		while (len > 0 && walk - res < MSDOS_NAME) {
 			c = *name++;
 			len--;
 			if (opts->name_check != 'r' && strchr(bad_chars, c))
 				return -EINVAL;
 			if (opts->name_check == 's' &&
 			    strchr(bad_if_strict, c))
 				return -EINVAL;
 			if (c < ' ' || c == ':' || c == '\\')
 				return -EINVAL;
 			if (c == '.') {
 				if (opts->name_check == 's')
 					return -EINVAL;
 				break;
 			}
 			if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
 				return -EINVAL;
 			space = c == ' ';
 			if (!opts->nocase && c >= 'a' && c <= 'z')
 				*walk++ = c - 32;
 			else
 				*walk++ = c;
 		}
 		if (space)
 			return -EINVAL;
 		if (opts->name_check == 's' && len)
 			return -EINVAL;
 	}
 	while (walk - res < MSDOS_NAME)
 		*walk++ = ' ';

 	return 0;
 }

 /***** Locates a directory entry.  Uses unformatted name. */
 static int msdos_find(struct inode *dir, const unsigned char *name, int len,
 		      struct fat_slot_info *sinfo)
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
 	unsigned char msdos_name[MSDOS_NAME];
 	int err;

 	err = msdos_format_name(name, len, msdos_name, &sbi->options);
 	if (err)
 		return -ENOENT;

 	err = fat_scan(dir, msdos_name, sinfo);
 	if (!err && sbi->options.dotsOK) {
 		if (name[0] == '.') {
 			if (!(sinfo->de->attr & ATTR_HIDDEN))
 				err = -ENOENT;
 		} else {
 			if (sinfo->de->attr & ATTR_HIDDEN)
 				err = -ENOENT;
 		}
 		if (err)
 			brelse(sinfo->bh);
 	}
 	return err;
 }

 /*
  * Compute the hash for the msdos 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 msdos fs routines will
  * return ENOENT or EINVAL as appropriate.
  */
 static int msdos_hash(const struct dentry *dentry, struct qstr *qstr)
 {
 	struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
 	unsigned char msdos_name[MSDOS_NAME];
 	int error;

 	error = msdos_format_name(qstr->name, qstr->len, msdos_name, options);
 	if (!error)
 		qstr->hash = full_name_hash(dentry, msdos_name, MSDOS_NAME);
 	return 0;
 }

 /*
  * Compare two msdos names. If either of the names are invalid,
  * we fall back to doing the standard name comparison.
  */
 static int msdos_cmp(const struct dentry *dentry,
 		unsigned int len, const char *str, const struct qstr *name)
 {
 	struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
 	unsigned char a_msdos_name[MSDOS_NAME], b_msdos_name[MSDOS_NAME];
 	int error;

 	error = msdos_format_name(name->name, name->len, a_msdos_name, options);
 	if (error)
 		goto old_compare;
 	error = msdos_format_name(str, len, b_msdos_name, options);
 	if (error)
 		goto old_compare;
 	error = memcmp(a_msdos_name, b_msdos_name, MSDOS_NAME);
 out:
 	return error;

 old_compare:
 	error = 1;
 	if (name->len == len)
 		error = memcmp(name->name, str, len);
 	goto out;
 }

 static const struct dentry_operations msdos_dentry_operations = {
 	.d_hash		= msdos_hash,
 	.d_compare	= msdos_cmp,
 };

 /*
  * AV. Wrappers for FAT sb operations. Is it wise?
  */

 /***** Get inode using directory and name */
 static struct dentry *msdos_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;
 	int err;

 	mutex_lock(&MSDOS_SB(sb)->s_lock);
 	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
 	switch (err) {
 	case -ENOENT:
 		inode = NULL;
 		break;
 	case 0:
 		inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
 		brelse(sinfo.bh);
 		break;
 	default:
 		inode = ERR_PTR(err);
 	}
 	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 	return d_splice_alias(inode, dentry);
 }

 /***** Creates a directory entry (name is already formatted). */
 static int msdos_add_entry(struct inode *dir, const unsigned char *name,
 			   int is_dir, int is_hid, int cluster,
 			   struct timespec *ts, struct fat_slot_info *sinfo)
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
 	struct msdos_dir_entry de;
 	__le16 time, date;
 	int err;

 	memcpy(de.name, name, MSDOS_NAME);
 	de.attr = is_dir ? ATTR_DIR : ATTR_ARCH;
 	if (is_hid)
 		de.attr |= ATTR_HIDDEN;
 	de.lcase = 0;
 	fat_time_unix2fat(sbi, ts, &time, &date, NULL);
 	de.cdate = de.adate = 0;
 	de.ctime = 0;
 	de.ctime_cs = 0;
 	de.time = time;
 	de.date = date;
 	fat_set_start(&de, cluster);
 	de.size = 0;

 	err = fat_add_entries(dir, &de, 1, sinfo);
 	if (err)
 		return err;

 	dir->i_ctime = dir->i_mtime = timespec_to_timespec64(*ts);
 	if (IS_DIRSYNC(dir))
 		(void)fat_sync_inode(dir);
 	else
 		mark_inode_dirty(dir);

 	return 0;
 }

 /***** Create a file */
 static int msdos_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 			bool excl)
 {
 	struct super_block *sb = dir->i_sb;
 	struct inode *inode = NULL;
 	struct fat_slot_info sinfo;
 	struct timespec64 ts;
 	struct timespec t;
 	unsigned char msdos_name[MSDOS_NAME];
 	int err, is_hid;

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

 	err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
 				msdos_name, &MSDOS_SB(sb)->options);
 	if (err)
 		goto out;
 	is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
 	/* Have to do it due to foo vs. .foo conflicts */
 	if (!fat_scan(dir, msdos_name, &sinfo)) {
 		brelse(sinfo.bh);
 		err = -EINVAL;
 		goto out;
 	}

 	ts = current_time(dir);
 	t = timespec64_to_timespec(ts);
 	err = msdos_add_entry(dir, msdos_name, 0, is_hid, 0, &t, &sinfo);
 	if (err)
 		goto out;
 	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_mtime = inode->i_atime = inode->i_ctime = ts;
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */

 	d_instantiate(dentry, inode);
 out:
 	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 	if (!err)
 		err = fat_flush_inodes(sb, dir, inode);
 	return err;
 }

 /***** Remove a directory */
 static int msdos_rmdir(struct inode *dir, struct dentry *dentry)
 {
 	struct super_block *sb = dir->i_sb;
 	struct inode *inode = d_inode(dentry);
 	struct fat_slot_info sinfo;
 	int err;

 	mutex_lock(&MSDOS_SB(sb)->s_lock);
 	err = fat_dir_empty(inode);
 	if (err)
 		goto out;
 	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &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_ctime = current_time(inode);
 	fat_detach(inode);
 out:
 	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 	if (!err)
 		err = fat_flush_inodes(sb, dir, inode);

 	return err;
 }

 /***** Make a directory */
 static int msdos_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 {
 	struct super_block *sb = dir->i_sb;
 	struct fat_slot_info sinfo;
 	struct inode *inode;
 	unsigned char msdos_name[MSDOS_NAME];
 	struct timespec64 ts;
 	struct timespec t;
 	int err, is_hid, cluster;

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

 	err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
 				msdos_name, &MSDOS_SB(sb)->options);
 	if (err)
 		goto out;
 	is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
 	/* foo vs .foo situation */
 	if (!fat_scan(dir, msdos_name, &sinfo)) {
 		brelse(sinfo.bh);
 		err = -EINVAL;
 		goto out;
 	}

 	ts = current_time(dir);
 	t = timespec64_to_timespec(ts);
 	cluster = fat_alloc_new_dir(dir, &t);
 	if (cluster < 0) {
 		err = cluster;
 		goto out;
 	}
 	err = msdos_add_entry(dir, msdos_name, 1, is_hid, cluster, &t, &sinfo);
 	if (err)
 		goto out_free;
 	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;
 	}
 	set_nlink(inode, 2);
 	inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */

 	d_instantiate(dentry, inode);

 	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 	fat_flush_inodes(sb, dir, inode);
 	return 0;

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

 /***** Unlink a file */
 static int msdos_unlink(struct inode *dir, struct dentry *dentry)
 {
 	struct inode *inode = d_inode(dentry);
 	struct super_block *sb = inode->i_sb;
 	struct fat_slot_info sinfo;
 	int err;

 	mutex_lock(&MSDOS_SB(sb)->s_lock);
 	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
 	if (err)
 		goto out;

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

 	return err;
 }

 static int do_msdos_rename(struct inode *old_dir, unsigned char *old_name,
 			   struct dentry *old_dentry,
 			   struct inode *new_dir, unsigned char *new_name,
 			   struct dentry *new_dentry, int is_hid)
 {
 	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 timespec64 ts;
 	loff_t new_i_pos;
 	int err, old_attrs, is_dir, update_dotdot, corrupt = 0;

 	old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
 	old_inode = d_inode(old_dentry);
 	new_inode = d_inode(new_dentry);

 	err = fat_scan(old_dir, old_name, &old_sinfo);
 	if (err) {
 		err = -EIO;
 		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;
 		}
 	}

 	old_attrs = MSDOS_I(old_inode)->i_attrs;
 	err = fat_scan(new_dir, new_name, &sinfo);
 	if (!err) {
 		if (!new_inode) {
 			/* "foo" -> ".foo" case. just change the ATTR_HIDDEN */
 			if (sinfo.de != old_sinfo.de) {
 				err = -EINVAL;
 				goto out;
 			}
 			if (is_hid)
 				MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
 			else
 				MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
 			if (IS_DIRSYNC(old_dir)) {
 				err = fat_sync_inode(old_inode);
 				if (err) {
 					MSDOS_I(old_inode)->i_attrs = old_attrs;
 					goto out;
 				}
 			} else
 				mark_inode_dirty(old_inode);

 			inode_inc_iversion(old_dir);
 			old_dir->i_ctime = old_dir->i_mtime = current_time(old_dir);
 			if (IS_DIRSYNC(old_dir))
 				(void)fat_sync_inode(old_dir);
 			else
 				mark_inode_dirty(old_dir);
 			goto out;
 		}
 	}

 	ts = current_time(old_inode);
 	if (new_inode) {
 		if (err)
 			goto out;
 		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 {
 		struct timespec t = timespec64_to_timespec(ts);
 		err = msdos_add_entry(new_dir, new_name, is_dir, is_hid, 0,
 				      &t, &sinfo);
 		if (err)
 			goto out;
 		new_i_pos = sinfo.i_pos;
 	}
 	inode_inc_iversion(new_dir);

 	fat_detach(old_inode);
 	fat_attach(old_inode, new_i_pos);
 	if (is_hid)
 		MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
 	else
 		MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
 	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;
 	inode_inc_iversion(old_dir);
 	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);
 	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);
 	MSDOS_I(old_inode)->i_attrs = old_attrs;
 	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;
 }

 /***** Rename, a wrapper for rename_same_dir & rename_diff_dir */
 static int msdos_rename(struct inode *old_dir, struct dentry *old_dentry,
 			struct inode *new_dir, struct dentry *new_dentry,
 			unsigned int flags)
 {
 	struct super_block *sb = old_dir->i_sb;
 	unsigned char old_msdos_name[MSDOS_NAME], new_msdos_name[MSDOS_NAME];
 	int err, is_hid;

 	if (flags & ~RENAME_NOREPLACE)
 		return -EINVAL;

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

 	err = msdos_format_name(old_dentry->d_name.name,
 				old_dentry->d_name.len, old_msdos_name,
 				&MSDOS_SB(old_dir->i_sb)->options);
 	if (err)
 		goto out;
 	err = msdos_format_name(new_dentry->d_name.name,
 				new_dentry->d_name.len, new_msdos_name,
 				&MSDOS_SB(new_dir->i_sb)->options);
 	if (err)
 		goto out;

 	is_hid =
 	     (new_dentry->d_name.name[0] == '.') && (new_msdos_name[0] != '.');

 	err = do_msdos_rename(old_dir, old_msdos_name, old_dentry,
 			      new_dir, new_msdos_name, new_dentry, is_hid);
 out:
 	mutex_unlock(&MSDOS_SB(sb)->s_lock);
 	if (!err)
 		err = fat_flush_inodes(sb, old_dir, new_dir);
 	return err;
 }

 static const struct inode_operations msdos_dir_inode_operations = {
 	.create		= msdos_create,
 	.lookup		= msdos_lookup,
 	.unlink		= msdos_unlink,
 	.mkdir		= msdos_mkdir,
 	.rmdir		= msdos_rmdir,
 	.rename		= msdos_rename,
 	.setattr	= fat_setattr,
 	.getattr	= fat_getattr,
 };

 static void setup(struct super_block *sb)
 {
 	MSDOS_SB(sb)->dir_ops = &msdos_dir_inode_operations;
 	sb->s_d_op = &msdos_dentry_operations;
 	sb->s_flags |= SB_NOATIME;
 }

 static int msdos_fill_super(struct super_block *sb, void *data, int silent)
 {
 	return fat_fill_super(sb, data, silent, 0, setup);
 }

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

 static struct file_system_type msdos_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "msdos",
 	.mount		= msdos_mount,
 	.kill_sb	= kill_block_super,
 	.fs_flags	= FS_REQUIRES_DEV,
 };
 MODULE_ALIAS_FS("msdos");

 static int __init init_msdos_fs(void)
 {
 	return register_filesystem(&msdos_fs_type);
 }

 static void __exit exit_msdos_fs(void)
 {
 	unregister_filesystem(&msdos_fs_type);
 }

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Werner Almesberger");
 MODULE_DESCRIPTION("MS-DOS filesystem support");

 module_init(init_msdos_fs)
 module_exit(exit_msdos_fs)
	/*
	* linux/fs/msdos/namei.c
	*
	* Written 1992,1993 by Werner Almesberger
	* Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
	* Rewritten for constant inumbers 1999 by Al Viro
	*/

	#include <linux/module.h>
	#include <linux/iversion.h>
	#include "fat.h"

	/* Characters that are undesirable in an MS-DOS file name */
	static unsigned char bad_chars[] = "*?<>\|\"";
	static unsigned char bad_if_strict[] = "+=,; ";

	/***** Formats an MS-DOS file name. Rejects invalid names. */
	static int msdos_format_name(const unsigned char *name, int len,
	unsigned char res, struct fat_mount_options opts)
	/*
	* name is the proposed name, len is its length, res is
	* the resulting name, opts->name_check is either (r)elaxed,
	* (n)ormal or (s)trict, opts->dotsOK allows dots at the
	* beginning of name (for hidden files)
	*/
	{
	unsigned char *walk;
	unsigned char c;
	int space;

	if (name[0] == '.') { /* dotfile because . and .. already done */
	if (opts->dotsOK) {
	/* Get rid of dot - test for it elsewhere */
	name++;
	len--;
	} else
	return -EINVAL;
	}
	/*
	* disallow names that _really_ start with a dot
	*/
	space = 1;
	c = 0;
	for (walk = res; len && walk - res < 8; walk++) {
	c = *name++;
	len--;
	if (opts->name_check != 'r' && strchr(bad_chars, c))
	return -EINVAL;
	if (opts->name_check == 's' && strchr(bad_if_strict, c))
	return -EINVAL;
	if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
	return -EINVAL;
	if (c < ' ' \|\| c == ':' \|\| c == '\\')
	return -EINVAL;
	/*
	* 0xE5 is legal as a first character, but we must substitute
	* 0x05 because 0xE5 marks deleted files. Yes, DOS really
	* does this.
	* It seems that Microsoft hacked DOS to support non-US
	* characters after the 0xE5 character was already in use to
	* mark deleted files.
	*/
	if ((res == walk) && (c == 0xE5))
	c = 0x05;
	if (c == '.')
	break;
	space = (c == ' ');
	*walk = (!opts->nocase && c >= 'a' && c <= 'z') ? c - 32 : c;
	}
	if (space)
	return -EINVAL;
	if (opts->name_check == 's' && len && c != '.') {
	c = *name++;
	len--;
	if (c != '.')
	return -EINVAL;
	}
	while (c != '.' && len--)
	c = *name++;
	if (c == '.') {
	while (walk - res < 8)
	*walk++ = ' ';
	while (len > 0 && walk - res < MSDOS_NAME) {
	c = *name++;
	len--;
	if (opts->name_check != 'r' && strchr(bad_chars, c))
	return -EINVAL;
	if (opts->name_check == 's' &&
	strchr(bad_if_strict, c))
	return -EINVAL;
	if (c < ' ' \|\| c == ':' \|\| c == '\\')
	return -EINVAL;
	if (c == '.') {
	if (opts->name_check == 's')
	return -EINVAL;
	break;
	}
	if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
	return -EINVAL;
	space = c == ' ';
	if (!opts->nocase && c >= 'a' && c <= 'z')
	*walk++ = c - 32;
	else
	*walk++ = c;
	}
	if (space)
	return -EINVAL;
	if (opts->name_check == 's' && len)
	return -EINVAL;
	}
	while (walk - res < MSDOS_NAME)
	*walk++ = ' ';

	return 0;
	}

	/***** Locates a directory entry. Uses unformatted name. */
	static int msdos_find(struct inode dir, const unsigned char name, int len,
	struct fat_slot_info *sinfo)
	{
	struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
	unsigned char msdos_name[MSDOS_NAME];
	int err;

	err = msdos_format_name(name, len, msdos_name, &sbi->options);
	if (err)
	return -ENOENT;

	err = fat_scan(dir, msdos_name, sinfo);
	if (!err && sbi->options.dotsOK) {
	if (name[0] == '.') {
	if (!(sinfo->de->attr & ATTR_HIDDEN))
	err = -ENOENT;
	} else {
	if (sinfo->de->attr & ATTR_HIDDEN)
	err = -ENOENT;
	}
	if (err)
	brelse(sinfo->bh);
	}
	return err;
	}

	/*
	* Compute the hash for the msdos 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 msdos fs routines will
	* return ENOENT or EINVAL as appropriate.
	*/
	static int msdos_hash(const struct dentry dentry, struct qstr qstr)
	{
	struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
	unsigned char msdos_name[MSDOS_NAME];
	int error;

	error = msdos_format_name(qstr->name, qstr->len, msdos_name, options);
	if (!error)
	qstr->hash = full_name_hash(dentry, msdos_name, MSDOS_NAME);
	return 0;
	}

	/*
	* Compare two msdos names. If either of the names are invalid,
	* we fall back to doing the standard name comparison.
	*/
	static int msdos_cmp(const struct dentry *dentry,
	unsigned int len, const char str, const struct qstr name)
	{
	struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
	unsigned char a_msdos_name[MSDOS_NAME], b_msdos_name[MSDOS_NAME];
	int error;

	error = msdos_format_name(name->name, name->len, a_msdos_name, options);
	if (error)
	goto old_compare;
	error = msdos_format_name(str, len, b_msdos_name, options);
	if (error)
	goto old_compare;
	error = memcmp(a_msdos_name, b_msdos_name, MSDOS_NAME);
	out:
	return error;

	old_compare:
	error = 1;
	if (name->len == len)
	error = memcmp(name->name, str, len);
	goto out;
	}

	static const struct dentry_operations msdos_dentry_operations = {
	.d_hash = msdos_hash,
	.d_compare = msdos_cmp,
	};

	/*
	* AV. Wrappers for FAT sb operations. Is it wise?
	*/

	/***** Get inode using directory and name */
	static struct dentry msdos_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;
	int err;

	mutex_lock(&MSDOS_SB(sb)->s_lock);
	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
	switch (err) {
	case -ENOENT:
	inode = NULL;
	break;
	case 0:
	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
	brelse(sinfo.bh);
	break;
	default:
	inode = ERR_PTR(err);
	}
	mutex_unlock(&MSDOS_SB(sb)->s_lock);
	return d_splice_alias(inode, dentry);
	}

	/***** Creates a directory entry (name is already formatted). */
	static int msdos_add_entry(struct inode dir, const unsigned char name,
	int is_dir, int is_hid, int cluster,
	struct timespec ts, struct fat_slot_info sinfo)
	{
	struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
	struct msdos_dir_entry de;
	__le16 time, date;
	int err;

	memcpy(de.name, name, MSDOS_NAME);
	de.attr = is_dir ? ATTR_DIR : ATTR_ARCH;
	if (is_hid)
	de.attr \|= ATTR_HIDDEN;
	de.lcase = 0;
	fat_time_unix2fat(sbi, ts, &time, &date, NULL);
	de.cdate = de.adate = 0;
	de.ctime = 0;
	de.ctime_cs = 0;
	de.time = time;
	de.date = date;
	fat_set_start(&de, cluster);
	de.size = 0;

	err = fat_add_entries(dir, &de, 1, sinfo);
	if (err)
	return err;

	dir->i_ctime = dir->i_mtime = timespec_to_timespec64(*ts);
	if (IS_DIRSYNC(dir))
	(void)fat_sync_inode(dir);
	else
	mark_inode_dirty(dir);

	return 0;
	}

	/***** Create a file */
	static int msdos_create(struct inode dir, struct dentry dentry, umode_t mode,
	bool excl)
	{
	struct super_block *sb = dir->i_sb;
	struct inode *inode = NULL;
	struct fat_slot_info sinfo;
	struct timespec64 ts;
	struct timespec t;
	unsigned char msdos_name[MSDOS_NAME];
	int err, is_hid;

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

	err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
	msdos_name, &MSDOS_SB(sb)->options);
	if (err)
	goto out;
	is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
	/* Have to do it due to foo vs. .foo conflicts */
	if (!fat_scan(dir, msdos_name, &sinfo)) {
	brelse(sinfo.bh);
	err = -EINVAL;
	goto out;
	}

	ts = current_time(dir);
	t = timespec64_to_timespec(ts);
	err = msdos_add_entry(dir, msdos_name, 0, is_hid, 0, &t, &sinfo);
	if (err)
	goto out;
	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_mtime = inode->i_atime = inode->i_ctime = ts;
	/* timestamp is already written, so mark_inode_dirty() is unneeded. */

	d_instantiate(dentry, inode);
	out:
	mutex_unlock(&MSDOS_SB(sb)->s_lock);
	if (!err)
	err = fat_flush_inodes(sb, dir, inode);
	return err;
	}

	/***** Remove a directory */
	static int msdos_rmdir(struct inode dir, struct dentry dentry)
	{
	struct super_block *sb = dir->i_sb;
	struct inode *inode = d_inode(dentry);
	struct fat_slot_info sinfo;
	int err;

	mutex_lock(&MSDOS_SB(sb)->s_lock);
	err = fat_dir_empty(inode);
	if (err)
	goto out;
	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &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_ctime = current_time(inode);
	fat_detach(inode);
	out:
	mutex_unlock(&MSDOS_SB(sb)->s_lock);
	if (!err)
	err = fat_flush_inodes(sb, dir, inode);

	return err;
	}

	/***** Make a directory */
	static int msdos_mkdir(struct inode dir, struct dentry dentry, umode_t mode)
	{
	struct super_block *sb = dir->i_sb;
	struct fat_slot_info sinfo;
	struct inode *inode;
	unsigned char msdos_name[MSDOS_NAME];
	struct timespec64 ts;
	struct timespec t;
	int err, is_hid, cluster;

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

	err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
	msdos_name, &MSDOS_SB(sb)->options);
	if (err)
	goto out;
	is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
	/* foo vs .foo situation */
	if (!fat_scan(dir, msdos_name, &sinfo)) {
	brelse(sinfo.bh);
	err = -EINVAL;
	goto out;
	}

	ts = current_time(dir);
	t = timespec64_to_timespec(ts);
	cluster = fat_alloc_new_dir(dir, &t);
	if (cluster < 0) {
	err = cluster;
	goto out;
	}
	err = msdos_add_entry(dir, msdos_name, 1, is_hid, cluster, &t, &sinfo);
	if (err)
	goto out_free;
	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;
	}
	set_nlink(inode, 2);
	inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
	/* timestamp is already written, so mark_inode_dirty() is unneeded. */

	d_instantiate(dentry, inode);

	mutex_unlock(&MSDOS_SB(sb)->s_lock);
	fat_flush_inodes(sb, dir, inode);
	return 0;

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

	/***** Unlink a file */
	static int msdos_unlink(struct inode dir, struct dentry dentry)
	{
	struct inode *inode = d_inode(dentry);
	struct super_block *sb = inode->i_sb;
	struct fat_slot_info sinfo;
	int err;

	mutex_lock(&MSDOS_SB(sb)->s_lock);
	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
	if (err)
	goto out;

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

	return err;
	}

	static int do_msdos_rename(struct inode old_dir, unsigned char old_name,
	struct dentry *old_dentry,
	struct inode new_dir, unsigned char new_name,
	struct dentry *new_dentry, int is_hid)
	{
	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 timespec64 ts;
	loff_t new_i_pos;
	int err, old_attrs, is_dir, update_dotdot, corrupt = 0;

	old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
	old_inode = d_inode(old_dentry);
	new_inode = d_inode(new_dentry);

	err = fat_scan(old_dir, old_name, &old_sinfo);
	if (err) {
	err = -EIO;
	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;
	}
	}

	old_attrs = MSDOS_I(old_inode)->i_attrs;
	err = fat_scan(new_dir, new_name, &sinfo);
	if (!err) {
	if (!new_inode) {
	/* "foo" -> ".foo" case. just change the ATTR_HIDDEN */
	if (sinfo.de != old_sinfo.de) {
	err = -EINVAL;
	goto out;
	}
	if (is_hid)
	MSDOS_I(old_inode)->i_attrs \|= ATTR_HIDDEN;
	else
	MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
	if (IS_DIRSYNC(old_dir)) {
	err = fat_sync_inode(old_inode);
	if (err) {
	MSDOS_I(old_inode)->i_attrs = old_attrs;
	goto out;
	}
	} else
	mark_inode_dirty(old_inode);

	inode_inc_iversion(old_dir);
	old_dir->i_ctime = old_dir->i_mtime = current_time(old_dir);
	if (IS_DIRSYNC(old_dir))
	(void)fat_sync_inode(old_dir);
	else
	mark_inode_dirty(old_dir);
	goto out;
	}
	}

	ts = current_time(old_inode);
	if (new_inode) {
	if (err)
	goto out;
	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 {
	struct timespec t = timespec64_to_timespec(ts);
	err = msdos_add_entry(new_dir, new_name, is_dir, is_hid, 0,
	&t, &sinfo);
	if (err)
	goto out;
	new_i_pos = sinfo.i_pos;
	}
	inode_inc_iversion(new_dir);

	fat_detach(old_inode);
	fat_attach(old_inode, new_i_pos);
	if (is_hid)
	MSDOS_I(old_inode)->i_attrs \|= ATTR_HIDDEN;
	else
	MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
	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;
	inode_inc_iversion(old_dir);
	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);
	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);
	MSDOS_I(old_inode)->i_attrs = old_attrs;
	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;
	}

	/***** Rename, a wrapper for rename_same_dir & rename_diff_dir */
	static int msdos_rename(struct inode old_dir, struct dentry old_dentry,
	struct inode new_dir, struct dentry new_dentry,
	unsigned int flags)
	{
	struct super_block *sb = old_dir->i_sb;
	unsigned char old_msdos_name[MSDOS_NAME], new_msdos_name[MSDOS_NAME];
	int err, is_hid;

	if (flags & ~RENAME_NOREPLACE)
	return -EINVAL;

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

	err = msdos_format_name(old_dentry->d_name.name,
	old_dentry->d_name.len, old_msdos_name,
	&MSDOS_SB(old_dir->i_sb)->options);
	if (err)
	goto out;
	err = msdos_format_name(new_dentry->d_name.name,
	new_dentry->d_name.len, new_msdos_name,
	&MSDOS_SB(new_dir->i_sb)->options);
	if (err)
	goto out;

	is_hid =
	(new_dentry->d_name.name[0] == '.') && (new_msdos_name[0] != '.');

	err = do_msdos_rename(old_dir, old_msdos_name, old_dentry,
	new_dir, new_msdos_name, new_dentry, is_hid);
	out:
	mutex_unlock(&MSDOS_SB(sb)->s_lock);
	if (!err)
	err = fat_flush_inodes(sb, old_dir, new_dir);
	return err;
	}

	static const struct inode_operations msdos_dir_inode_operations = {
	.create = msdos_create,
	.lookup = msdos_lookup,
	.unlink = msdos_unlink,
	.mkdir = msdos_mkdir,
	.rmdir = msdos_rmdir,
	.rename = msdos_rename,
	.setattr = fat_setattr,
	.getattr = fat_getattr,
	};

	static void setup(struct super_block *sb)
	{
	MSDOS_SB(sb)->dir_ops = &msdos_dir_inode_operations;
	sb->s_d_op = &msdos_dentry_operations;
	sb->s_flags \|= SB_NOATIME;
	}

	static int msdos_fill_super(struct super_block sb, void data, int silent)
	{
	return fat_fill_super(sb, data, silent, 0, setup);
	}

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

	static struct file_system_type msdos_fs_type = {
	.owner = THIS_MODULE,
	.name = "msdos",
	.mount = msdos_mount,
	.kill_sb = kill_block_super,
	.fs_flags = FS_REQUIRES_DEV,
	};
	MODULE_ALIAS_FS("msdos");

	static int __init init_msdos_fs(void)
	{
	return register_filesystem(&msdos_fs_type);
	}

	static void __exit exit_msdos_fs(void)
	{
	unregister_filesystem(&msdos_fs_type);
	}

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Werner Almesberger");
	MODULE_DESCRIPTION("MS-DOS filesystem support");

	module_init(init_msdos_fs)
	module_exit(exit_msdos_fs)