From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E8DAC34022 for ; Mon, 17 Feb 2020 19:02:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14AC120578 for ; Mon, 17 Feb 2020 19:02:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728781AbgBQTCT (ORCPT ); Mon, 17 Feb 2020 14:02:19 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:43516 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728728AbgBQTCT (ORCPT ); Mon, 17 Feb 2020 14:02:19 -0500 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: krisman) with ESMTPSA id A833F292457 From: Gabriel Krisman Bertazi To: Daniel Rosenberg Cc: Eric Biggers , "Theodore Ts'o" , linux-ext4@vger.kernel.org, Jaegeuk Kim , Chao Yu , linux-f2fs-devel@lists.sourceforge.net, linux-fscrypt@vger.kernel.org, Alexander Viro , Richard Weinberger , linux-mtd@lists.infradead.org, Andreas Dilger , Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v7 1/8] unicode: Add utf8_casefold_iter Organization: Collabora References: <20200208013552.241832-1-drosen@google.com> <20200208013552.241832-2-drosen@google.com> <20200212033800.GC870@sol.localdomain> Date: Mon, 17 Feb 2020 14:02:10 -0500 In-Reply-To: (Daniel Rosenberg's message of "Fri, 14 Feb 2020 13:47:37 -0800") Message-ID: <8536b95971.fsf@collabora.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-fscrypt-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fscrypt@vger.kernel.org Daniel Rosenberg writes: > On Tue, Feb 11, 2020 at 7:38 PM Eric Biggers 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. >> just for the record, we use int utf8byte because it can fail error codes, but that is not the case here. It should be u8. > > 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. Sorry for the delay, I'm away on a long vacation and intentionally staying away from my laptop :) Eric has a very good point, if not prohibitively, it is unnecessarily expensive for a hot path. Why not expose utf8ncursor and utf8byte to libfs and implement the hash in libfs? -- Gabriel Krisman Bertazi