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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 166AAC433E1 for ; Thu, 9 Jul 2020 13:26:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EA3B92065D for ; Thu, 9 Jul 2020 13:26:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="CrTKomoc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727822AbgGIN0P (ORCPT ); Thu, 9 Jul 2020 09:26:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36796 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726506AbgGIN0P (ORCPT ); Thu, 9 Jul 2020 09:26:15 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 56479C08C5CE; Thu, 9 Jul 2020 06:26:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=3VK0PPpTgajPRvu6w9TsxcWut69QO/23qhJyuACRUe8=; b=CrTKomocywcnC625URQttrWyQp jrEY1kIYXkOyUapLoHnqwuPYHbKVdz++upCTeYPIEJy8v+GPCC+5TFVDhoa+uKNSJfsENZ6eb0bU9 mWSNsbCasQsNFI7wkb2H9mGlIv5LYNU/aWzcDv7dqTPjxALYgHvNRjbBFWSV2Tv43861WpKM1+DSU jtGt2vhR99n0OXwoCLR95+xhHxWUVM5RiXBFHPGh0vT4Mss0uN1prqQ8XPvJCU0NQlu+echRWZ08m /pcLaJc0eoBlMJX5vsHAl8y7ReqBYLdkrGA9PqDdnGHGu+iWvLsJjTuliiA0E7jn8Mf3a1KcOyfO0 Q+RfNpDw==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jtWZ1-0000Xj-FX; Thu, 09 Jul 2020 13:26:11 +0000 Date: Thu, 9 Jul 2020 14:26:11 +0100 From: Christoph Hellwig To: Matthew Wilcox Cc: Christoph Hellwig , Jens Axboe , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Kanchan Joshi , Javier Gonzalez Subject: Re: [PATCH 0/2] Remove kiocb ki_complete Message-ID: <20200709132611.GA1382@infradead.org> References: <20200708222637.23046-1-willy@infradead.org> <20200709101705.GA2095@infradead.org> <20200709111036.GA12769@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200709111036.GA12769@casper.infradead.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 09, 2020 at 12:10:36PM +0100, Matthew Wilcox wrote: > On Thu, Jul 09, 2020 at 11:17:05AM +0100, Christoph Hellwig wrote: > > I really don't like this series at all. If saves a single pointer > > but introduces a complicated machinery that just doesn't follow any > > natural flow. And there doesn't seem to be any good reason for it to > > start with. > > Jens doesn't want the kiocb to grow beyond a single cacheline, and we > want the ability to set the loff_t in userspace for an appending write, > so the plan was to replace the ki_complete member in kiocb with an > loff_t __user *ki_posp. > > I don't think it's worth worrying about growing kiocb, personally, > but this seemed like the easiest way to make room for a new pointer. The user offset pointer has absolutely no business in the the kiocb itself - it is a io_uring concept which needs to go into the io_kiocb, which has 14 bytes left in the last cache line in my build. It would fit in very well there right next to the result and user pointer.