linux-ext4 - Re: [PATCH 18/20] ext4: Support encoding-aware file name lookups

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Date:   Thu, 12 Jul 2018 14:06:04 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.co.uk>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     linux-ext4@...r.kernel.org, darrick.wong@...cle.com,
        kernel@...labora.com
Subject: Re: [PATCH 18/20] ext4: Support encoding-aware file name lookups

"Theodore Y. Ts'o" <tytso@....edu> writes:

> On Tue, Jul 03, 2018 at 01:06:58PM -0400, Gabriel Krisman Bertazi wrote:
>> +		 * Even if we are doing encodings, an exact-match lookup
>> +		 * could still benefit from DX, so we don't skip it
>> +		 * entirely.  Only if it fails to find a match, we
>> +		 * fallback to linear search.
>
> Why supply the normalized form of the name to ext4_dirhash()?  (Or
> have ext4_dirhash call the normalization function, but that would
> require passing the sbi->encoding to ext4_dirhash)
>
> That way we can do efficient lookups even if the lookup uses a
> different normalized form than what was originally used when the file
> was created.  (We can also use this to do efficient hash lookups once
> we add case folding support.)

Makes total sense. Thanks.  I forgot to address dx when I changed the
design from the mountpoint approach I presented at LSFMM. I will address
this in v2.


-- 
Gabriel Krisman Bertazi