linux-kernel - Re: [PATCH v11 2/4] fs: Add standard casefolding support

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Date:   Tue, 7 Jul 2020 21:12:30 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Daniel Rosenberg <drosen@...gle.com>
Cc:     Theodore Ts'o <tytso@....edu>, linux-ext4@...r.kernel.org,
        Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fscrypt@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v11 2/4] fs: Add standard casefolding support

On Tue, Jul 07, 2020 at 08:05:50PM -0700, Daniel Rosenberg wrote:
> +/**
> + * generic_ci_d_compare - generic d_compare implementation for casefolding filesystems
> + * @dentry:	dentry whose name we are checking against
> + * @len:	len of name of dentry
> + * @str:	str pointer to name of dentry
> + * @name:	Name to compare against
> + *
> + * Return: 0 if names match, 1 if mismatch, or -ERRNO
> + */
> +int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
> +			  const char *str, const struct qstr *name)
> +{
> +	const struct dentry *parent = READ_ONCE(dentry->d_parent);
> +	const struct inode *inode = READ_ONCE(parent->d_inode);

How about calling the 'inode' variable 'dir' instead?

That would help avoid confusion about what is the directory and what is a file
in the directory.

Likewise in generic_ci_d_hash().

> +/**
> + * generic_ci_d_hash - generic d_hash implementation for casefolding filesystems
> + * @dentry:	dentry whose name we are hashing

This comment for @dentry needs to be updated.

It's the parent dentry, not the dentry whose name we are hashing.

> + * @str:	qstr of name whose hash we should fill in
> + *
> + * Return: 0 if hash was successful, or -ERRNO

As I mentioned on v9, this can also return 0 if the hashing was not done because
it wants to fallback to the standard hashing.  Can you please fix the comment?

> +int generic_ci_d_hash(const struct dentry *dentry, struct qstr *str)
> +{
> +	const struct inode *inode = READ_ONCE(dentry->d_inode);
> +	struct super_block *sb = dentry->d_sb;
> +	const struct unicode_map *um = sb->s_encoding;
> +	int ret = 0;
> +
> +	if (!inode || !needs_casefold(inode))
> +		return 0;
> +
> +	ret = utf8_casefold_hash(um, dentry, str);
> +	if (ret < 0)
> +		goto err;
> +
> +	return 0;
> +err:
> +	if (sb_has_strict_encoding(sb))
> +		ret = -EINVAL;
> +	else
> +		ret = 0;
> +	return ret;
> +}

On v9, Gabriel suggested simplifying this to:

	ret = utf8_casefold_hash(um, dentry, str);
	if (ret < 0 && sb_has_enc_strict_mode(sb))
		return -EINVAL;
	return 0;

Any reason not to do that?

- Eric