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=-4.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 5E957C433DB for ; Thu, 28 Jan 2021 11:44:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 175C564DDA for ; Thu, 28 Jan 2021 11:44:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231363AbhA1LoF (ORCPT ); Thu, 28 Jan 2021 06:44:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35608 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229667AbhA1Lnj (ORCPT ); Thu, 28 Jan 2021 06:43:39 -0500 Received: from mail-wm1-x331.google.com (mail-wm1-x331.google.com [IPv6:2a00:1450:4864:20::331]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1B678C061574; Thu, 28 Jan 2021 03:42:59 -0800 (PST) Received: by mail-wm1-x331.google.com with SMTP id u14so4045032wml.4; Thu, 28 Jan 2021 03:42:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:autocrypt:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=p5ruvM3Pi2TwZL/KAf2g8R8ehK0uJHZDo1/BwXoSTqM=; b=PoweDyPOoq5w4h8ke1eXu7ZpkY9b+VEeYHSkn64n+gEfrI5nxeXycdK8vMlOJDIXzE 3uJZkLfkS5Ln1qHhLTZu1O8ultXfrqNpGNwaBa/2YvzOHb0jIl1Pp4wwcW7F9sKM/2C9 sjvM0n7mdfGKve0oQwLU8bRIw6oU3NB+21XSrHbD9jabto4/4/RFRCI3KDuoPilYSRt3 NK2RHEyXSaHaEB0vCzKWvnT8nycZWZOYg6n4VXEsKTo+vxRqmnsdJdOgzA1eItjyn/FP c6Dd8FFyPMYSBKTI6W4az1jdGAcy4Ns3/zhjqdD3V8ipI3X9wfQbPUFfKELELQNBc9Nz YEoQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=p5ruvM3Pi2TwZL/KAf2g8R8ehK0uJHZDo1/BwXoSTqM=; b=BcpT+Vg8cOcxqD37k1bNCLJbhdhaC/LxxX+bC/VAQa4LO+rE72/1uaJD9DSeuT7PKC wmvGHyjbDYMXC/SsGMN/wc0YNpmqh3LuoAqlJwhIHfPAHAhgqa4fYSoC3mB1ttYsCMDc oMmqkyP75izxtYjwQt/pHe5lq0ADUCB7BTYpF3T9Qm3kGSvBgF9sFD7otcP1NHzQLrod zp7WwRjRAKJugcfyJZEH8ygRjgO9fNdz1CzvYscRLZaVr0rr5NfJgDfg4jJxAYQC9Xqd lYrVKADFPP6rBaHiLluRqYYbjD7pju2HprVHU/EKZG18Y79zJ9xQ8DwXTyZg6XnOrt12 AB1w== X-Gm-Message-State: AOAM532eF6ONDmPFJhK9E3Ar0WepLIDBMAtNY+BdWdr9CfLo7qph7Lht z8GlrWRCyyRE60Oo5GYtpUTVzcKy3kQ= X-Google-Smtp-Source: ABdhPJw+0u+6NvKGOp5YbUibO+/KUDdk0GXChzlYTyhRGWutrdddJlrVUVv1liWEX+tN3hxZ0rij+w== X-Received: by 2002:a05:600c:2a47:: with SMTP id x7mr8219554wme.145.1611834177646; Thu, 28 Jan 2021 03:42:57 -0800 (PST) Received: from [192.168.8.160] ([148.252.132.131]) by smtp.gmail.com with ESMTPSA id v4sm7454860wrw.42.2021.01.28.03.42.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 28 Jan 2021 03:42:56 -0800 (PST) Subject: Re: [PATCH] iov_iter: optimise iter type checking To: Al Viro Cc: David Laight , "linux-fsdevel@vger.kernel.org" , Jens Axboe , "linux-kernel@vger.kernel.org" References: <6e795064-fdbd-d354-4b01-a4f7409debf5@gmail.com> <54cd4d1b-d7ec-a74c-8be0-e48780609d56@gmail.com> <20210109170359.GT3579531@ZenIV.linux.org.uk> <1783c58f-1016-0c6b-be7f-a93bc2f8f2a4@gmail.com> <20210116051818.GF3579531@ZenIV.linux.org.uk> <20210127183152.GP740243@zeniv-ca> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: Date: Thu, 28 Jan 2021 11:39:15 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <20210127183152.GP740243@zeniv-ca> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 27/01/2021 18:31, Al Viro wrote: > On Wed, Jan 27, 2021 at 03:48:10PM +0000, Pavel Begunkov wrote: >> On 16/01/2021 05:18, Al Viro wrote: >>> On Sat, Jan 09, 2021 at 10:11:09PM +0000, Pavel Begunkov wrote: >>> >>>>> Does any code actually look at the fields as a pair? >>>>> Would it even be better to use separate bytes? >>>>> Even growing the on-stack structure by a word won't really matter. >>>> >>>> u8 type, rw; >>>> >>>> That won't bloat the struct. I like the idea. If used together compilers >>>> can treat it as u16. >>> >>> Reasonable, and from what I remember from looking through the users, >>> no readers will bother with looking at both at the same time. >> >> Al, are you going turn it into a patch, or prefer me to take over? > > I'll massage that a bit and put into #work.iov_iter - just need to dig my > way from under the pile of ->d_revalidate() review... Perfect, thanks -- Pavel Begunkov