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Wed, 24 Jun 2020 05:57:17 +0000 Received: from sol.localdomain (c-107-3-166-239.hsd1.ca.comcast.net [107.3.166.239]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4DCC22085B; Wed, 24 Jun 2020 05:57:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592978229; bh=2lsFqyU8P0hr8E82YY+KRZpjYFvt+d061bicFKiQlRc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lbxsf9ik4Ybnb1VNbbAkDP+AkNKZAjMqErfEG+Qv5FJjpqdXBrE0v20o6fKaxGDjU 6IbwyTMIIAryhYBDmhFPRgTRIvcrOwKn8x8VQtZkIfd6G07QWTXk8aEvAPsrzSaFLQ hTu4hRjCUpgjrPNmucpIRCRbHtnLrLbiJjgdLxRY= Date: Tue, 23 Jun 2020 22:57:07 -0700 From: Eric Biggers To: Daniel Rosenberg Message-ID: <20200624055707.GG844@sol.localdomain> References: <20200624043341.33364-1-drosen@google.com> <20200624043341.33364-3-drosen@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200624043341.33364-3-drosen@google.com> X-Headers-End: 1jnyPL-00GCdA-62 Subject: Re: [f2fs-dev] [PATCH v9 2/4] fs: Add standard casefolding support X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kernel-team@android.com, Theodore Ts'o , Jonathan Corbet , Richard Weinberger , Andreas Dilger , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fscrypt@vger.kernel.org, linux-mtd@lists.infradead.org, Alexander Viro , linux-fsdevel@vger.kernel.org, Jaegeuk Kim , linux-ext4@vger.kernel.org, Gabriel Krisman Bertazi Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Tue, Jun 23, 2020 at 09:33:39PM -0700, Daniel Rosenberg wrote: > This adds general supporting functions for filesystems that use > utf8 casefolding. It provides standard dentry_operations and adds the > necessary structures in struct super_block to allow this standardization. > > Ext4 and F2fs will switch to these common implementations. > > Signed-off-by: Daniel Rosenberg > --- > fs/libfs.c | 101 +++++++++++++++++++++++++++++++++++++++++++++ > include/linux/fs.h | 22 ++++++++++ > 2 files changed, 123 insertions(+) > > diff --git a/fs/libfs.c b/fs/libfs.c > index 4d08edf19c782..f7345a5ed562f 100644 > --- a/fs/libfs.c > +++ b/fs/libfs.c > @@ -20,6 +20,8 @@ > #include > #include > #include > +#include > +#include > > #include > > @@ -1363,3 +1365,102 @@ bool is_empty_dir_inode(struct inode *inode) > return (inode->i_fop == &empty_dir_operations) && > (inode->i_op == &empty_dir_inode_operations); > } > + > +#ifdef CONFIG_UNICODE > +/** > + * needs_casefold - generic helper to determine if a filename should be casefolded > + * @dir: Parent directory > + * > + * Generic helper for filesystems to use to determine if the name of a dentry > + * should be casefolded. It does not make sense to casefold the no-key token of > + * an encrypted filename. > + * > + * Return: if names will need casefolding > + */ > +bool needs_casefold(const struct inode *dir) > +{ > + return IS_CASEFOLDED(dir) && dir->i_sb->s_encoding && > + (!IS_ENCRYPTED(dir) || fscrypt_has_encryption_key(dir)); > +} > +EXPORT_SYMBOL(needs_casefold); Note that the '!IS_ENCRYPTED(dir) || fscrypt_has_encryption_key(dir)' check can be racy, because a process can be looking up a no-key token in a directory while concurrently another process initializes the directory's ->i_crypt_info, causing fscrypt_has_encryption_key(dir) to suddenly start returning true. In my rework of filename handling in f2fs, I actually ended up removing all calls to needs_casefold(), thus avoiding this race. f2fs now decides whether the name is going to need casefolding early on, in __f2fs_setup_filename(), where it knows in a race-free way whether the filename is a no-key token or not. Perhaps ext4 should work the same way? It did look like there would be some extra complexity due to how the ext4 directory hashing works in comparison to f2fs's, but I haven't had a chance to properly investigate it. - Eric _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel