linux-ext4 - Re: [PATCH v2 2/3] fscrypt: Have filesystems handle their d

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Message-ID: <X7QW9aqdF9ivHKBe@sol.localdomain>
Date:   Tue, 17 Nov 2020 10:31:17 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Daniel Rosenberg <drosen@...gle.com>
Cc:     "Theodore Y . Ts'o" <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Chao Yu <chao@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Richard Weinberger <richard@....at>,
        linux-fscrypt@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mtd@...ts.infradead.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel-team@...roid.com
Subject: Re: [PATCH v2 2/3] fscrypt: Have filesystems handle their d_ops

On Tue, Nov 17, 2020 at 04:03:14AM +0000, Daniel Rosenberg wrote:
> diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
> index a8f7a43f031b..df2c66ca370e 100644
> --- a/include/linux/fscrypt.h
> +++ b/include/linux/fscrypt.h
> @@ -741,8 +741,9 @@ static inline int fscrypt_prepare_rename(struct inode *old_dir,
>   * directory's encryption key is available, then the lookup is assumed to be by
>   * plaintext name; otherwise, it is assumed to be by no-key name.
>   *
> - * This also installs a custom ->d_revalidate() method which will invalidate the
> - * dentry if it was created without the key and the key is later added.
> + * After calling this function, a filesystem should ensure that its dentry
> + * operations contain fscrypt_d_revalidate if DCACHE_ENCRYPTED_NAME was set,
> + * so that the dentry can be invalidated if the key is later added.
>   *
>   * Return: 0 on success; -ENOENT if the directory's key is unavailable but the
>   * filename isn't a valid no-key name, so a negative dentry should be created;

This should say DCACHE_NOKEY_NAME, not DCACHE_ENCRYPTED_NAME.

But more importantly, the explanation here isn't very clear.  How about the
following instead:

 * This will set DCACHE_NOKEY_NAME on the dentry if the lookup is by no-key
 * name.  In this case the filesystem must assign the dentry a dentry_operations
 * which contains fscrypt_d_revalidate (or contains a d_revalidate method that
 * calls fscrypt_d_revalidate), so that the dentry will be invalidated if the
 * directory's encryption key is later added.