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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 3F3A1C433DF for ; Tue, 23 Jun 2020 11:59:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1E25B20738 for ; Tue, 23 Jun 2020 11:59:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="LjLU2uuj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732471AbgFWL7O (ORCPT ); Tue, 23 Jun 2020 07:59:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59406 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732632AbgFWL7M (ORCPT ); Tue, 23 Jun 2020 07:59:12 -0400 Received: from mail-ej1-x644.google.com (mail-ej1-x644.google.com [IPv6:2a00:1450:4864:20::644]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9DB70C061573; Tue, 23 Jun 2020 04:59:11 -0700 (PDT) Received: by mail-ej1-x644.google.com with SMTP id a1so7295128ejg.12; Tue, 23 Jun 2020 04:59:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=to:references:from:autocrypt:subject:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=ctgLWgT+qJoV3tLMYgFeonjqCttgFCowopS2fJ1sPps=; b=LjLU2uujwm6eXjEpvMh68RY15U4r18xH9m28sTB3puy7Hkbt8+bDqGJT8X+7bQbVOS nIWeiYS3W8UALXueJ0zcaYk//8XoqKPbRgymYHIk7TQ+fmO+IUOXoWEOfG8IZ61QHxJk hJ4L7uaDirF7yaaVnNGLULCwEITmxuXuvaoVRWiplCprhBajvAT4PP0cHoAJu38Pt2gY EeMwXYe8cALkOV4OWxRhcZQSZMvqAYi/7KUOLipgJRJp2CohzyFcDCkZH8tPNxxdB7dP 0J6ZIT8CZW9iMVZwaVpdEKNl1XOEMm4lADvY94wQ6EpWG378x60bShj0vsktwAeQqABe b16g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:references:from:autocrypt:subject:message-id :date:user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=ctgLWgT+qJoV3tLMYgFeonjqCttgFCowopS2fJ1sPps=; b=n8w5MsgH7tarkusWTF6MaMWyJz33tRy7jWY4MPxe/BiO2h2SO5azio2n03lPsNw3D9 pwM4RFrhL8sVJ8rk7nez6zzt0eC/Wkn96WWKc0qBUmaGql8FVMh7r2f0zWISfsULVlXx IpwKreAwJR8ftU2LvxOWMvg+fS+WTepyhqpd7MC1nmSZ4R2WYklo70C7pj4Me0rWoVGY GyCGSNXguumuxjPDfUm1U29y7WVtRFfvLgIY/vLS9X5J3aTXYps3Fk4odulS0F6OQZXS BlrlmaKx/l5XVccz/c+VCDBbyk3lApXwiabshLe26+XcYcdKPsB5cINjjX6KQm0dJLB8 ZXWQ== X-Gm-Message-State: AOAM533qcXRVg7nwMshQ/TIxBfSXE2T9HFGoRLl/LgOVuF1gfBMRMhPo LWa8MAZfQvxvr83SXR0FYPrG+qAF X-Google-Smtp-Source: ABdhPJwOVq4OQ9lERc4Yw587Sogi9WdMrUi5WzJF7ce7cBXLh+XcDgCXNBbXyHBoUReaH92g9xvVQg== X-Received: by 2002:a17:906:8401:: with SMTP id n1mr19431926ejx.479.1592913549928; Tue, 23 Jun 2020 04:59:09 -0700 (PDT) Received: from [192.168.43.181] ([5.100.193.85]) by smtp.gmail.com with ESMTPSA id k2sm13699528ejc.20.2020.06.23.04.59.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Jun 2020 04:59:09 -0700 (PDT) To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <0301f35644823a01cbae87e440df7d58ebcf2279.1592863245.git.asml.silence@gmail.com> <95b720a6-926c-a208-e929-1d0203fa8701@kernel.dk> 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 1/4] io_uring: fix hanging iopoll in case of -EAGAIN Message-ID: <6714cb8f-894c-9ff1-7b3a-4f86d7dbe52a@gmail.com> Date: Tue, 23 Jun 2020 14:57:38 +0300 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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 23/06/2020 05:18, Jens Axboe wrote: > On 6/22/20 8:07 PM, Jens Axboe wrote: >> On 6/22/20 4:16 PM, Pavel Begunkov wrote: >>> io_do_iopoll() won't do anything with a request unless >>> req->iopoll_completed is set. So io_complete_rw_iopoll() has to set >>> it, otherwise io_do_iopoll() will poll a file again and again even >>> though the request of interest was completed long ago. >> >> I need to look at this again, because with this change, I previously >> got various use-after-free. I haven't seen any issues with it, but >> I agree, from a quick look that I'm not quite sure how it's currently >> not causing hangs. Yet I haven't seen any, with targeted -EAGAIN >> testing. Can io_complete_rw_iopoll() get -EAGAIN after being successfully enqueued (i.e. EIOCBQUEUED)? It's reliably fails for me, because my hacked nullblk _can_ (i.e. probabilistically returns BLK_STS_AGAIN from ->iopoll()). > > Ah I think I know what it is - if we run into: > > if (req->result == -EAGAIN) > return -EAGAIN > > in io_issue_sqe() and race with it, we'll reissue twice potentially. > So the above isn't quite enough, we'll need something a bit broader. I see, I'll deal with it. -- Pavel Begunkov