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

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Message-ID: <20180712020649.GF9955@thunk.org>
Date:   Wed, 11 Jul 2018 22:06:49 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Gabriel Krisman Bertazi <krisman@...labora.co.uk>
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

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.)

					- Ted