Re: [PATCH] libfs: Attempt exact-match comparison first during casefold lookup

[Gabriel Krisman Bertazi <krisman@suse.de>]

Al Viro <viro@zeniv.linux.org.uk> writes:

> On Wed, Jan 17, 2024 at 07:28:36PM -0300, Gabriel Krisman Bertazi wrote:
>
>> Note that, for strict mode, generic_ci_d_compare used to reject an
>> invalid UTF-8 string, which would now be considered valid if it
>> exact-matches the disk-name.  But, if that is the case, the filesystem
>> is corrupt.  More than that, it really doesn't matter in practice,
>> because the name-under-lookup will have already been rejected by
>> generic_ci_d_hash and we won't even get here.
>
>> -	if (ret >= 0)
>> -		return ret;
>> -
>> -	if (sb_has_strict_encoding(sb))
>> +	qstr.len = len;
>> +	qstr.name = str;
>> +	ret = utf8_strncasecmp(dentry->d_sb->s_encoding, name, &qstr);
>> +	if (ret < 0)
>>  		return -EINVAL;
>
> Umm...  So why bother with -EINVAL?  The rest looks sane, but
> considering the fact that your string *has* passed ->d_hash(),
> do we need anything beyond
> 	return utf8_strncasecmp(dentry->d_sb->s_encoding, name, &qstr);
> here?

No, you are right.  In fact, it seems d_compare can't propagate errors
anyway as it is only compared against 0, anyway.

I spin the v2 dropping this bit as suggested.

thanks,

-- 
Gabriel Krisman Bertazi