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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 31902C001B0 for ; Mon, 14 Aug 2023 13:14:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229605AbjHNNOJ (ORCPT ); Mon, 14 Aug 2023 09:14:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230423AbjHNNOE (ORCPT ); Mon, 14 Aug 2023 09:14:04 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B13C9E71 for ; Mon, 14 Aug 2023 06:13:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692018798; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=isiG484zzCuLoyRUFKL6De9VKMSnc0IGGZzsm/pASx8=; b=Gvi2NFBkB2dzc3mhb9hd1TMfh2k2WiPIyc1eUn4dRlgbOOTvlJDxq7OX+SBJ/SmrHPaxHx zS+QLo5pj314NH1tVyDIQGmjFhBD/7BLConm3BE/O91uuOWL7cSO5emH202lBA/IEAbgQs ZtoeMJTTneQTFTyjdYOaSzH8gbTsPSA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-611-ZaxUL9r3NBeKF3Hn7XEVaQ-1; Mon, 14 Aug 2023 09:13:13 -0400 X-MC-Unique: ZaxUL9r3NBeKF3Hn7XEVaQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C4DAB85D063; Mon, 14 Aug 2023 13:13:12 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.42.28.13]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4236D2026D68; Mon, 14 Aug 2023 13:13:10 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <3710261.1691764329@warthog.procyon.org.uk> <3888331.1691773627@warthog.procyon.org.uk> To: Linus Torvalds Cc: dhowells@redhat.com, Alexander Viro , Jens Axboe , Christoph Hellwig , Christian Brauner , Matthew Wilcox , jlayton@kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] iov_iter: Convert iterate*() to inline funcs MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <4032544.1692018789.1@warthog.procyon.org.uk> Date: Mon, 14 Aug 2023 14:13:09 +0100 Message-ID: <4032545.1692018789@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Linus Torvalds wrote: > > So I think you need to remove the changes you did to > memcpy_from_iter(). The old code was an explicit conditional of direct > calls: > > if (iov_iter_is_copy_mc(i)) > return (void *)copy_mc_to_kernel(to, from, size); > return memcpy(to, from, size); > > and now you do that > > iov_iter_is_copy_mc(i) ? > memcpy_from_iter_mc : memcpy_from_iter); > > to pass in a function pointer. > > Not ok. Not ok at all. It may look clever, but function pointers are > bad. Avoid them like the plague. Yeah. I was hoping that the compiler would manage to inline that, but it just does an indirect call. I'm trying to avoid passing the iterator as that makes things bigger. I think I can probably share the extra argument used for passing checksums. David