Re: [PATCH v5 4/8] ext4: Reuse generic_ci_match for ci comparisons

[Eric Biggers <ebiggers@kernel.org>]

On Wed, May 18, 2022 at 01:23:16PM -0400, Gabriel Krisman Bertazi wrote:
> Instead of reimplementing ext4_match_ci, use the new libfs helper.
> 
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
> ---
[...]
>  int ext4_fname_setup_ci_filename(struct inode *dir, const struct qstr *iname,
>  				  struct ext4_filename *name)
>  {
> @@ -1432,20 +1380,25 @@ static bool ext4_match(struct inode *parent,
>  #if IS_ENABLED(CONFIG_UNICODE)
>  	if (parent->i_sb->s_encoding && IS_CASEFOLDED(parent) &&
>  	    (!IS_ENCRYPTED(parent) || fscrypt_has_encryption_key(parent))) {
> -		if (fname->cf_name.name) {
> -			if (IS_ENCRYPTED(parent)) {
> -				if (fname->hinfo.hash != EXT4_DIRENT_HASH(de) ||
> -					fname->hinfo.minor_hash !=
> -						EXT4_DIRENT_MINOR_HASH(de)) {
> +		int ret;
>  
> -					return false;
> -				}
> -			}
> -			return !ext4_ci_compare(parent, &fname->cf_name,
> -						de->name, de->name_len, true);
> +		if (IS_ENCRYPTED(parent) &&
> +		    (fname->hinfo.hash != EXT4_DIRENT_HASH(de) ||
> +		     fname->hinfo.minor_hash != EXT4_DIRENT_MINOR_HASH(de)))
> +			return false;
> +
> +		ret = generic_ci_match(parent, fname->usr_fname,
> +				       &fname->cf_name, de->name,
> +				       de->name_len);
> +		if (ret < 0) {
> +			/*
> +			 * Treat comparison errors as not a match.  The
> +			 * only case where it happens is on a disk
> +			 * corruption or ENOMEM.
> +			 */
> +			return false;
>  		}
> -		return !ext4_ci_compare(parent, fname->usr_fname, de->name,
> -						de->name_len, false);
> +		return ret;
>  	}

This needs an explanation for why it's okay to remove
'fname->cf_name.name != NULL' from the condition for doing the hash comparison
for an encrypted+casefolded directory entry.

- Eric