linux-kernel - Re: [PATCH v7 1/8] unicode: Add utf8_casefold

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Date:   Fri, 14 Feb 2020 13:47:37 -0800
From:   Daniel Rosenberg <drosen@...gle.com>
To:     Eric Biggers <ebiggers@...nel.org>,
        Gabriel Krisman Bertazi <krisman@...labora.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,
        kernel-team@...roid.com
Subject: Re: [PATCH v7 1/8] unicode: Add utf8_casefold_iter

On Tue, Feb 11, 2020 at 7:38 PM Eric Biggers <ebiggers@...nel.org> wrote:
>
> Indirect function calls are expensive these days for various reasons, including
> Spectre mitigations and CFI.  Are you sure it's okay from a performance
> perspective to make an indirect call for every byte of the pathname?
>
> > +typedef int (*utf8_itr_actor_t)(struct utf8_itr_context *, int byte, int pos);
>
> The byte argument probably should be 'u8', to avoid confusion about whether it's
> a byte or a Unicode codepoint.
>
> - Eric

Gabriel, what do you think here? I could change it to either exposing
the things necessary to do the hashing in libfs, or instead of the
general purpose iterator, just have a hash function inside of unicode
that will compute the hash given a seed value.
-Daniel