linux-kernel - Re: [PATCH 3/3] fs: fat: add ioctl method in fat filesystem driver

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Date:   Mon, 29 Jan 2018 22:02:43 +0900
From:   OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:     ChenGuanqiao <chen.chenchacha@...mail.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] fs: fat: add ioctl method in fat filesystem driver

ChenGuanqiao <chen.chenchacha@...mail.com> writes:

> +static int fat_check_d_characters(char *label, unsigned long len)
> +{
> +	int i;
> +
> +	for (i = 0; i < len; ++i) {
> +		switch (label[i]) {
> +		case 'a' ... 'z':
> +			label[i] = __toupper(label[i]);
> +		case 'A' ... 'Z':
> +		case '0' ... '9':
> +		case '_':
> +		case 0x20:
> +			continue;
> +		default:
> +			return -EINVAL;
> +		}

Same question with previous though, what windows do if label = "a b c"?
(this is including space other than end of name or extension.)

> +	}
> +
> +	return 0;
> +}

> +static int fat_ioctl_set_volume_label(struct file *file,
> +				      u8 __user *vol_label)
> +{
> +	int err = 0;
> +	u8 label[MSDOS_NAME];
> +	struct timespec ts;
> +	struct buffer_head *boot_bh;
> +	struct buffer_head *vol_bh;
> +	struct msdos_dir_entry *de;
> +	struct fat_boot_sector *b;
> +	struct inode *inode = file_inode(file);
> +	struct super_block *sb = inode->i_sb;
> +	struct msdos_sb_info *sbi = MSDOS_SB(sb);
> +

[...]

> +	err = mnt_want_write_file(file);
> +	if (err)
> +		goto out;
> +
> +	down_write(&sb->s_umount);

Looks like inode_lock() for rootdir is gone. It is necessary to
traverse+modify.

> +	/* Updates root directory's vol_label */
> +	err = fat_get_volume_label_entry(inode, &vol_bh, &de);
> +	ts = current_time(inode);
> +	if (err) {
> +		/* Create volume label entry */
> +		err = fat_add_volume_label_entry(inode, label, &ts);
> +		if (err)
> +			goto out_vol_brelse;
> +	} else {
> +		/* Write to root directory */
> +		memcpy(de->name, label, sizeof(de->name));
> +		inode->i_ctime = inode->i_mtime = inode->i_atime = ts;
> +
> +		mark_buffer_dirty(vol_bh);
> +	}
> +
> +	/* Update sector's vol_label */
> +	boot_bh = sb_bread(sb, 0);
> +	if (boot_bh == NULL) {
> +		fat_msg(sb, KERN_ERR,
> +			"unable to read boot sector to write volume label");
> +		err = -EIO;
> +		goto out_boot_brelse;
> +	}
> +
> +	b = (struct fat_boot_sector *)boot_bh->b_data;
> +	if (sbi->fat_bits == 32)
> +		memcpy(b->fat32.vol_label, label, sizeof(label));
> +	else
> +		memcpy(b->fat16.vol_label, label, sizeof(label));
> +
> +	mark_buffer_dirty(boot_bh);
> +
> +	/* Synchronize the data together */
> +	err = sync_dirty_buffer(boot_bh);
> +	if (err)
> +		goto out_boot_brelse;
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>