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=-4.3 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 7F2B8C2BB48 for ; Tue, 15 Dec 2020 11:18:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43C5822286 for ; Tue, 15 Dec 2020 11:18:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728619AbgLOLS2 (ORCPT ); Tue, 15 Dec 2020 06:18:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728609AbgLOLSV (ORCPT ); Tue, 15 Dec 2020 06:18:21 -0500 Received: from mail-wm1-x341.google.com (mail-wm1-x341.google.com [IPv6:2a00:1450:4864:20::341]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C36ACC0617A6; Tue, 15 Dec 2020 03:17:40 -0800 (PST) Received: by mail-wm1-x341.google.com with SMTP id g25so10804695wmh.1; Tue, 15 Dec 2020 03:17:40 -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=NXdRZfQTFz8GJLGwd4lZ+RpQBFd7WkHYcttMRSgrBPQ=; b=G1VcW1G1wT8O9omEXaax0jhFqKQpTrPsMlhnekh5H1ux21lONk30oVuyOADeELZon5 gtQBlPeSyXEtjcIq5xVh6oy7oazPWCu39/3VxDmRiN+TeCegXvCvm5MM7rC+vN7kErk4 FZUY/3ZyC19rAZSDIt430nhQza9bIB1x1iAh1wWxl9gZUGkFfkjIwZKenUuR5H0HzCXu LlKYMYlx6U0vt0FvyLcumYBTBDg3AzzKiSANlp6wmyibx3DvwqMQReeldVav/OFewSx0 1vVk09ok7iQnbIuj2YPsZ1rlCVQJYbhyViaY3aP6dUaMUPpTdjXJPQ/kwKR0nVUAiiAG ksBQ== 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=NXdRZfQTFz8GJLGwd4lZ+RpQBFd7WkHYcttMRSgrBPQ=; b=bu3aX5s6+2Eu0z8ZHhgicowhmcr80d8ftkaob9NF9NV50NDOrmTYOptTLSEU5eZDkW eGAZZHa1xH7OPbjPKxYmUK6WnfSmr57c5Kt3RFo+JuwVpAQaxnVm4qPDK9U6a+zURsNW 8ofKWgLa0IHUb5gchfdt0Gd2mAy/NTcnAx1EvdpT7QAxhSWDh9WQcYDY9beGrKniQZcU Piw4NfdxLoDBr/P9Q8RUoWHqZ8ZUg5LbzOSPi8z127iIGWFKDb51m97fbK48PCbe3cz9 5IogFRMe8cUI+sULj+Ypw3OSrvZ5h+a+sDv39WneVFkwj197cSF2fwWWBmGXwq2sQkYX 5/UA== X-Gm-Message-State: AOAM533Lr07ujv3l28O5MlhEqHrfTj48nQiW4kAE+jjqQq0u3lf27CbO G1ZCFVzbPqnv+OFjvomzYiIdgcJQw4e5OcJE X-Google-Smtp-Source: ABdhPJx/8GaFJx3wgSis9m2GfVpkehqsGkV90VmiK9UU8M4C6LWEDQV4f5dIS7ee5xiJqgimLEauLg== X-Received: by 2002:a05:600c:40ca:: with SMTP id m10mr32057301wmh.54.1608031059314; Tue, 15 Dec 2020 03:17:39 -0800 (PST) Received: from [192.168.8.128] ([185.69.145.6]) by smtp.gmail.com with ESMTPSA id z64sm35195661wme.10.2020.12.15.03.17.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Dec 2020 03:17:38 -0800 (PST) To: Ming Lei Cc: linux-block@vger.kernel.org, Jens Axboe , Christoph Hellwig , 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> 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: <103235c1-e7d0-0b55-65d0-013d1a09304e@gmail.com> Date: Tue, 15 Dec 2020 11:14:20 +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: <20201215014114.GA1777020@T590> 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 15/12/2020 01:41, Ming Lei wrote: > On Tue, Dec 15, 2020 at 12:20:19AM +0000, Pavel Begunkov wrote: >> Instead of creating a full copy of iter->bvec into bio in direct I/O, >> the patchset makes use of the one provided. It changes semantics and >> obliges users of asynchronous kiocb to track bvec lifetime, and [1/6] >> converts the only place that doesn't. > > Just think of one corner case: iov_iter(BVEC) may pass bvec table with zero > length bvec, which may not be supported by block layer or driver, so > this patchset has to address this case first. The easiest for me would be to fallback to copy if there are zero bvecs, e.g. finding such during iov_iter_alignment(), but do we know from where zero bvecs can came? As it's internals we may want to forbid them if there is not too much hassle. > > Please see 7e24969022cb ("block: allow for_each_bvec to support zero len bvec"). -- Pavel Begunkov