linux-kernel - Re: [PATCH v7 2/8] fs: Add standard casefolding support

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Message-ID: <20200208021216.GE23230@ZenIV.linux.org.uk>
Date:   Sat, 8 Feb 2020 02:12:16 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
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,
        Eric Biggers <ebiggers@...nel.org>,
        linux-fscrypt@...r.kernel.org, Richard Weinberger <richard@....at>,
        linux-mtd@...ts.infradead.org,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v7 2/8] fs: Add standard casefolding support

On Fri, Feb 07, 2020 at 05:35:46PM -0800, Daniel Rosenberg wrote:

> +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);
> +	const struct super_block *sb = dentry->d_sb;
> +	const struct unicode_map *um = sb->s_encoding;
> +	struct qstr entry = QSTR_INIT(str, len);
> +	int ret;
> +
> +	if (!inode || !needs_casefold(inode))
> +		goto fallback;
> +
> +	ret = utf8_strncasecmp(um, name, &entry);

Again, is that safe in case when the contents of the string str points to
keeps changing under you?