linux-ext4 - Re: [PATCH v8 8/8] f2fs: Handle casefolding with Encryption

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Message-ID: <20200307052424.GB1069@sol.localdomain>
Date:   Fri, 6 Mar 2020 21:24:24 -0800
From:   Eric Biggers <ebiggers@...nel.org>
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,
        linux-fscrypt@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        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 v8 8/8] f2fs: Handle casefolding with Encryption

On Fri, Mar 06, 2020 at 06:36:11PM -0800, Daniel Rosenberg wrote:
>  int f2fs_add_regular_entry(struct inode *dir, const struct qstr *new_name,
>  				const struct qstr *orig_name,
> +				f2fs_hash_t dentry_hash,
>  				struct inode *inode, nid_t ino, umode_t mode)
>  {
>  	unsigned int bit_pos;
>  	unsigned int level;
>  	unsigned int current_depth;
>  	unsigned long bidx, block;
> -	f2fs_hash_t dentry_hash;
>  	unsigned int nbucket, nblock;
>  	struct page *dentry_page = NULL;
>  	struct f2fs_dentry_block *dentry_blk = NULL;
> @@ -632,7 +650,6 @@ int f2fs_add_regular_entry(struct inode *dir, const struct qstr *new_name,
>  
>  	level = 0;
>  	slots = GET_DENTRY_SLOTS(new_name->len);
> -	dentry_hash = f2fs_dentry_hash(dir, new_name, NULL);
>  
>  	current_depth = F2FS_I(dir)->i_current_depth;
>  	if (F2FS_I(dir)->chash == dentry_hash) {
> @@ -718,17 +735,19 @@ int f2fs_add_dentry(struct inode *dir, struct fscrypt_name *fname,
>  				struct inode *inode, nid_t ino, umode_t mode)
>  {
>  	struct qstr new_name;
> +	f2fs_hash_t dentry_hash;
>  	int err = -EAGAIN;
>  
>  	new_name.name = fname_name(fname);
>  	new_name.len = fname_len(fname);
>  
>  	if (f2fs_has_inline_dentry(dir))
> -		err = f2fs_add_inline_entry(dir, &new_name, fname->usr_fname,
> +		err = f2fs_add_inline_entry(dir, &new_name, fname,
>  							inode, ino, mode);
> +	dentry_hash = f2fs_dentry_hash(dir, &new_name, fname);
>  	if (err == -EAGAIN)
>  		err = f2fs_add_regular_entry(dir, &new_name, fname->usr_fname,
> -							inode, ino, mode);
> +						dentry_hash, inode, ino, mode);
>  

Why are the changes to f2fs_add_dentry(), f2fs_add_regular_entry(), and
f2fs_add_inline_entry() being made?  Directories can't be modified through
no-key names, so there's no need to make this part of the code handle grabbing
the dentry hash from the struct fscrypt_name.  And both the on-disk and original
filenames were already passed to these functions.  So what else do we need?

> +static f2fs_hash_t __f2fs_dentry_hash(const struct inode *dir,
> +				const struct qstr *name_info,
> +				const struct fscrypt_name *fname)
>  {
>  	__u32 hash;
>  	f2fs_hash_t f2fs_hash;
> @@ -79,12 +80,17 @@ static f2fs_hash_t __f2fs_dentry_hash(const struct qstr *name_info,
>  	size_t len = name_info->len;
>  
>  	/* encrypted bigname case */
> -	if (fname && !fname->disk_name.name)
> +	if (fname && !fname->is_ciphertext_name)
>  		return cpu_to_le32(fname->hash);

Isn't this check backwards?  The hash is valid if fname->is_ciphertext_name, not
if !fname->is_ciphertext_name.

(Maybe the phrase "ciphertext name" is causing confusion, as we're now calling
them "no-key names" instead?  We could rename it, if that would help.)

- Eric