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=-6.8 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,URIBL_BLOCKED,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 E3DEEC433E9 for ; Wed, 23 Dec 2020 12:57:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1BB1224B0 for ; Wed, 23 Dec 2020 12:57:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728625AbgLWM5H (ORCPT ); Wed, 23 Dec 2020 07:57:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728516AbgLWM5F (ORCPT ); Wed, 23 Dec 2020 07:57:05 -0500 Received: from mail-wr1-x42e.google.com (mail-wr1-x42e.google.com [IPv6:2a00:1450:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50784C061793; Wed, 23 Dec 2020 04:56:25 -0800 (PST) Received: by mail-wr1-x42e.google.com with SMTP id d26so18506505wrb.12; Wed, 23 Dec 2020 04:56:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=to:cc:references:from:autocrypt:subject:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=V8yuZe/XKO2JAJAcMHgWSJTvwfutI16LmYdfxTFjPYU=; b=CT2PWH6HL+1/JNMbdoDfgZQu4hleqhfQEH/3Koaq2aoU7FkUWXNDL/iMJ/QAnFlDG6 k7ol75IPDjndCuqNk9cJiqnVenXR4/cdFbhXWcQM2bwzhGRDKqOFCzYN8sKVChecNW2/ 8SIPMgATznDFVBuD9TNGevdiobiauf5OmxRXJw0ilUhqe9xJjkXNGF3yVcv3qHKGfgtv vx9KQiOQ/KrfwjcZTkcd5+phk8JDekky/cxpyiUm6H6Fb0bkFUWzOtGQCnBuLWvxjiDo vB2HCpOKEEIRsfMs2bGpDMLZahEl2tlun1qm2BWQ9BKlNXwuR7rfpFyNtELV2UiONlz9 i+Yw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:autocrypt:subject :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=V8yuZe/XKO2JAJAcMHgWSJTvwfutI16LmYdfxTFjPYU=; b=cwGnE6zMqgJ0uPpYoULr9WIHsJU3Dawa4r6fIz7cFhnJ76+4GHxk797frOs7GtJBGs YgCbwhVg261KKJZ2ozcdpP8UK+FGFaCoYyyaW5msSWdFOu6IP4dAzxWaHuzLAakYd0o4 CzQ3lSQr75IIxU0s/zI0t35mhRDrclhew/7bE0XDk5vy7shdXmNoKWtH6XQBcUAV4MR/ /wgD7kPYkwtYtKf6KJgWVK8Zacm5mzORDUys8bW6EEN5ckZ3F6DGGGbNVC9ptlGj+7hR YtSVuZ4NR32kOIjrXsuAUFa3SzV7nrFRql9jsanZX9CVp7x9ckqJxTwT0P37SEnJgxsq sRHA== X-Gm-Message-State: AOAM531dcV3UUxfEDczxeOnnhDf7ag14GaxZeLI6FwWwC0JkgulVytYl bUdAHKMb6O++iVFdvPKvlCm5z2CwSW1t6+F9 X-Google-Smtp-Source: ABdhPJxWN+ccQniO8c/aQCmYGhKmAtpIj8N5tDRJBhD62JqXgH3Ykk1ZsTy87LQFlHRm4SqDhTtiBw== X-Received: by 2002:adf:9506:: with SMTP id 6mr29080023wrs.172.1608728182837; Wed, 23 Dec 2020 04:56:22 -0800 (PST) Received: from [192.168.8.148] ([85.255.233.85]) by smtp.gmail.com with ESMTPSA id x17sm34973694wro.40.2020.12.23.04.56.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Dec 2020 04:56:22 -0800 (PST) To: Christoph Hellwig Cc: Ming Lei , linux-block@vger.kernel.org, Jens Axboe , Matthew Wilcox , Johannes Weiner , Alexander Viro , "Darrick J . Wong" , "Martin K . Petersen" , Jonathan Corbet , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, target-devel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-doc@vger.kernel.org References: <20201215014114.GA1777020@T590> <103235c1-e7d0-0b55-65d0-013d1a09304e@gmail.com> <20201215120357.GA1798021@T590> <20201222141112.GE13079@infradead.org> 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== Subject: Re: [PATCH v1 0/6] no-copy bvec Message-ID: <933030f0-e428-18fd-4668-68db4f14b976@gmail.com> Date: Wed, 23 Dec 2020 12:52:59 +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: <20201222141112.GE13079@infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 22/12/2020 14:11, Christoph Hellwig wrote: > On Tue, Dec 15, 2020 at 02:05:35PM +0000, Pavel Begunkov wrote: >>> You may find clue from the following link: >>> >>> https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2262077.html >> >> Thanks for the link! >> >> Al, you mentioned "Zero-length segments are not disallowed", do you have >> a strong opinion on that? Apart from already diverged behaviour from the >> block layer and getting in the way of this series, without it we'd also be >> able to remove some extra ifs, e.g. in iterate_bvec() > > I'd prefer not to support zero-length ITER_BVEC and catching them > early, as the block layer can't deal with them either. From a quick > look at iter_file_splice_write it should be pretty trivial to fix there, > although we'll need to audit other callers as well (even if I don't > expect them to submit this degenerate case). Can scatterlist have 0-len entries? Those are directly translated into bvecs, e.g. in nvme/target/io-cmd-file.c and target/target_core_file.c. I've audited most of others by this moment, they're fine. Thanks for other nits, they will go into next version. -- Pavel Begunkov