linux-kernel - Re: [PATCH v4 2/3] fscrypt: Have filesystems handle their d

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Date:   Sun, 22 Nov 2020 13:12:18 +0800
From:   Gao Xiang <hsiangkao@...hat.com>
To:     Daniel Rosenberg <drosen@...gle.com>
Cc:     "Theodore Y . Ts'o" <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Eric Biggers <ebiggers@...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, Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH v4 2/3] fscrypt: Have filesystems handle their d_ops

Hi all,

On Thu, Nov 19, 2020 at 06:09:03AM +0000, Daniel Rosenberg wrote:
> This shifts the responsibility of setting up dentry operations from
> fscrypt to the individual filesystems, allowing them to have their own
> operations while still setting fscrypt's d_revalidate as appropriate.
> 
> Most filesystems can just use generic_set_encrypted_ci_d_ops, unless
> they have their own specific dentry operations as well. That operation
> will set the minimal d_ops required under the circumstances.
> 
> Since the fscrypt d_ops are set later on, we must set all d_ops there,
> since we cannot adjust those later on. This should not result in any
> change in behavior.
> 
> Signed-off-by: Daniel Rosenberg <drosen@...gle.com>
> Acked-by: Eric Biggers <ebiggers@...gle.com>
> ---

...

>  extern const struct file_operations ext4_dir_operations;
>  
> -#ifdef CONFIG_UNICODE
> -extern const struct dentry_operations ext4_dentry_ops;
> -#endif
> -
>  /* file.c */
>  extern const struct inode_operations ext4_file_inode_operations;
>  extern const struct file_operations ext4_file_operations;
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 33509266f5a0..12a417ff5648 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -1614,6 +1614,7 @@ static struct buffer_head *ext4_lookup_entry(struct inode *dir,
>  	struct buffer_head *bh;
>  
>  	err = ext4_fname_prepare_lookup(dir, dentry, &fname);
> +	generic_set_encrypted_ci_d_ops(dentry);

One thing might be worth noticing is that currently overlayfs might
not work properly when dentry->d_sb->s_encoding is set even only some
subdirs are CI-enabled but the others not, see generic_set_encrypted_ci_d_ops(),
ovl_mount_dir_noesc => ovl_dentry_weird()

For more details, see:
https://android-review.googlesource.com/c/device/linaro/hikey/+/1483316/2#message-2e1f6ab0010a3e35e7d8effea73f60341f84ee4d

Just found it by chance (and not sure if it's vital for now), and
a kind reminder about this.

Thanks,
Gao Xiang