namei_vfat.c

linux环境下基于FAT的文件系统的通用代码

					ip += charlen;
					i += charlen;
					op += 2;
				}
			}
			if (i < len)
				return -ENAMETOOLONG;
		} else {
			for (i = 0, ip = name, op = outname, *outlen = 0;
			     i < len && *outlen <= 255;
			     i++, *outlen += 1)
			{
				*op++ = *ip++;
				*op++ = 0;
			}
			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;
	de->start = cpu_to_le16(cluster);
	de->starthi = cpu_to_le16(cluster >> 16);
	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);
}

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

	lock_super(sb);

	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 && !(alias->d_flags & DCACHE_DISCONNECTED)) {
		/*
		 * This inode has non 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);
		unlock_super(sb);
		return alias;
	}
out:
	unlock_super(sb);
	dentry->d_op = sb->s_root->d_op;
	dentry->d_time = dentry->d_parent->d_inode->i_version;
	dentry = d_splice_alias(inode, dentry);
	if (dentry) {
		dentry->d_op = sb->s_root->d_op;
		dentry->d_time = dentry->d_parent->d_inode->i_version;
	}
	return dentry;

error:
	unlock_super(sb);
	return ERR_PTR(err);
}

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

	lock_super(sb);

	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:
	unlock_super(sb);
	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;

	lock_super(sb);

	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:
	unlock_super(sb);

	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;

	lock_super(sb);

	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:
	unlock_super(sb);

	return err;
}

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

	lock_super(sb);

	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++;
	inode->i_nlink = 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);

	unlock_super(sb);
	return 0;

out_free:
	fat_free_clusters(dir, cluster);
out:
	unlock_super(sb);
	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 dotdot_i_pos, 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;
	lock_super(sb);
	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,
					 &dotdot_i_pos) < 0) {
			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) {
		int start = MSDOS_I(new_dir)->i_logstart;
		dotdot_de->start = cpu_to_le16(start);
		dotdot_de->starthi = cpu_to_le16(start >> 16);
		mark_buffer_dirty(dotdot_bh);
		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);
	unlock_super(sb);

	return err;

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

	if (update_dotdot) {
		int start = MSDOS_I(old_dir)->i_logstart;
		dotdot_de->start = cpu_to_le16(start);
		dotdot_de->starthi = cpu_to_le16(start >> 16);
		mark_buffer_dirty(dotdot_bh);
		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_panic(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 int vfat_fill_super(struct super_block *sb, void *data, int silent)
{
	int res;

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

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

	return 0;
}

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

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

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

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

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

module_init(init_vfat_fs)
module_exit(exit_vfat_fs)