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Date:   Sat, 21 Nov 2020 23:45:41 -0500
From:   Gabriel Krisman Bertazi <krisman@...labora.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, kernel-team@...roid.com,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH v4 2/3] fscrypt: Have filesystems handle their d_ops

Daniel Rosenberg <drosen@...gle.com> writes:

> 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>
> ---
>  fs/crypto/fname.c           | 4 ----
>  fs/crypto/fscrypt_private.h | 1 -
>  fs/crypto/hooks.c           | 1 -
>  fs/ext4/dir.c               | 7 -------
>  fs/ext4/ext4.h              | 4 ----
>  fs/ext4/namei.c             | 1 +
>  fs/ext4/super.c             | 5 -----
>  fs/f2fs/dir.c               | 7 -------
>  fs/f2fs/f2fs.h              | 3 ---
>  fs/f2fs/namei.c             | 1 +
>  fs/f2fs/super.c             | 1 -
>  fs/ubifs/dir.c              | 1 +
>  include/linux/fscrypt.h     | 7 +++++--
>  13 files changed, 8 insertions(+), 35 deletions(-)
>
> diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
> index 1fbe6c24d705..cb3cfa6329ba 100644
> --- a/fs/crypto/fname.c
> +++ b/fs/crypto/fname.c
> @@ -570,7 +570,3 @@ int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
>  	return valid;
>  }
>  EXPORT_SYMBOL_GPL(fscrypt_d_revalidate);
> -
> -const struct dentry_operations fscrypt_d_ops = {
> -	.d_revalidate = fscrypt_d_revalidate,
> -};
> diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
> index 4f5806a3b73d..df9c48c1fbf7 100644
> --- a/fs/crypto/fscrypt_private.h
> +++ b/fs/crypto/fscrypt_private.h
> @@ -294,7 +294,6 @@ int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname,
>  bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
>  				  u32 orig_len, u32 max_len,
>  				  u32 *encrypted_len_ret);
> -extern const struct dentry_operations fscrypt_d_ops;
>  
>  /* hkdf.c */
>  
> diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
> index 20b0df47fe6a..9006fa983335 100644
> --- a/fs/crypto/hooks.c
> +++ b/fs/crypto/hooks.c
> @@ -117,7 +117,6 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry,
>  		spin_lock(&dentry->d_lock);
>  		dentry->d_flags |= DCACHE_NOKEY_NAME;
>  		spin_unlock(&dentry->d_lock);
> -		d_set_d_op(dentry, &fscrypt_d_ops);
>  	}
>  	return err;
>  }
> diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
> index ca50c90adc4c..e757319a4472 100644
> --- a/fs/ext4/dir.c
> +++ b/fs/ext4/dir.c
> @@ -667,10 +667,3 @@ const struct file_operations ext4_dir_operations = {
>  	.open		= ext4_dir_open,
>  	.release	= ext4_release_dir,
>  };
> -
> -#ifdef CONFIG_UNICODE
> -const struct dentry_operations ext4_dentry_ops = {
> -	.d_hash = generic_ci_d_hash,
> -	.d_compare = generic_ci_d_compare,
> -};
> -#endif
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index bf9429484462..ad77f01d9e20 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -3380,10 +3380,6 @@ static inline void ext4_unlock_group(struct super_block *sb,
>  /* dir.c */
>  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);
>  	if (err == -ENOENT)
>  		return NULL;
>  	if (err)
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 6633b20224d5..0288bedf46e1 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4968,11 +4968,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  		goto failed_mount4;
>  	}
>  
> -#ifdef CONFIG_UNICODE
> -	if (sb->s_encoding)
> -		sb->s_d_op = &ext4_dentry_ops;
> -#endif

This change has the side-effect of removing the capability of the root
directory from being case-insensitive.  It is not a backward
incompatible change because there is no way to make the root directory
CI at the moment (it is never empty). But this restriction seems
artificial. Is there a real reason to prevent the root inode from being
case-insensitive?

> -
>  	sb->s_root = d_make_root(root);
>  	if (!sb->s_root) {
>  		ext4_msg(sb, KERN_ERR, "get root dentry failed");
> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> index 4b9ef8bbfa4a..71fdf5076461 100644
> --- a/fs/f2fs/dir.c
> +++ b/fs/f2fs/dir.c
> @@ -1099,10 +1099,3 @@ const struct file_operations f2fs_dir_operations = {
>  	.compat_ioctl   = f2fs_compat_ioctl,
>  #endif
>  };
> -
> -#ifdef CONFIG_UNICODE
> -const struct dentry_operations f2fs_dentry_ops = {
> -	.d_hash = generic_ci_d_hash,
> -	.d_compare = generic_ci_d_compare,
> -};
> -#endif
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index cb700d797296..62b4f31d30e2 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -3767,9 +3767,6 @@ static inline void f2fs_update_sit_info(struct f2fs_sb_info *sbi) {}
>  #endif
>  
>  extern const struct file_operations f2fs_dir_operations;
> -#ifdef CONFIG_UNICODE
> -extern const struct dentry_operations f2fs_dentry_ops;
> -#endif
>  extern const struct file_operations f2fs_file_operations;
>  extern const struct inode_operations f2fs_file_inode_operations;
>  extern const struct address_space_operations f2fs_dblock_aops;
> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> index 8fa37d1434de..6edb1ab579a1 100644
> --- a/fs/f2fs/namei.c
> +++ b/fs/f2fs/namei.c
> @@ -497,6 +497,7 @@ static struct dentry *f2fs_lookup(struct inode *dir, struct dentry *dentry,
>  	}
>  
>  	err = f2fs_prepare_lookup(dir, dentry, &fname);
> +	generic_set_encrypted_ci_d_ops(dentry);
>  	if (err == -ENOENT)
>  		goto out_splice;
>  	if (err)
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 00eff2f51807..f51d52591c99 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -3427,7 +3427,6 @@ static int f2fs_setup_casefold(struct f2fs_sb_info *sbi)
>  
>  		sbi->sb->s_encoding = encoding;
>  		sbi->sb->s_encoding_flags = encoding_flags;
> -		sbi->sb->s_d_op = &f2fs_dentry_ops;
>  	}
>  #else
>  	if (f2fs_sb_has_casefold(sbi)) {
> diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
> index 155521e51ac5..7a920434d741 100644
> --- a/fs/ubifs/dir.c
> +++ b/fs/ubifs/dir.c
> @@ -203,6 +203,7 @@ static struct dentry *ubifs_lookup(struct inode *dir, struct dentry *dentry,
>  	dbg_gen("'%pd' in dir ino %lu", dentry, dir->i_ino);
>  
>  	err = fscrypt_prepare_lookup(dir, dentry, &nm);
> +	generic_set_encrypted_ci_d_ops(dentry);
>  	if (err == -ENOENT)
>  		return d_splice_alias(NULL, dentry);
>  	if (err)
> diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
> index a8f7a43f031b..e72f80482671 100644
> --- a/include/linux/fscrypt.h
> +++ b/include/linux/fscrypt.h
> @@ -741,8 +741,11 @@ 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.
> + * 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.
>   *
>   * 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;

-- 
Gabriel Krisman Bertazi

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