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=-2.1 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 97203C3A5A9 for ; Mon, 4 May 2020 16:29:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6FEB72075A for ; Mon, 4 May 2020 16:29:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Hh/71gI4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729547AbgEDQ3P (ORCPT ); Mon, 4 May 2020 12:29:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42526 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729425AbgEDQ3O (ORCPT ); Mon, 4 May 2020 12:29:14 -0400 Received: from mail-wm1-x342.google.com (mail-wm1-x342.google.com [IPv6:2a00:1450:4864:20::342]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 46185C061A0E for ; Mon, 4 May 2020 09:29:13 -0700 (PDT) Received: by mail-wm1-x342.google.com with SMTP id k12so170965wmj.3 for ; Mon, 04 May 2020 09:29:13 -0700 (PDT) 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=rJsjfY32fdlazgOtr9f8PulSzUm9PmE64Ox6eErNEn8=; b=Hh/71gI4okTJ1pc4WrJ6eZNptlsrzP6dgrVaUdV9i534BUHUy2DGotQ0s3AkneEHAJ ovSht+CQ56YWMrB6ghlMz6hQhwZ+FJoWTJ+Ej/UX6fQEOnhjtf50C7q0hPsO7u5+Hily kyJw32iGrS/rdu3GWTfuPUVR1Zu5LoVNkwJt2nVfLzxbCKumjlIiPzDyQTZFuF3aiC3m 7CnCpV2jkwmlwbJLx4EwrVe8RAlqM7szSwMdgEgyA37ITjQrE/KhC5iU3go4bd55ObmF GY/Lw/flauXAaAc+zQymW5iyEb6+9maA5DnVPjMnr2CVIAkj0K7UHwjBtX9wGxam4INL F2HA== 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=rJsjfY32fdlazgOtr9f8PulSzUm9PmE64Ox6eErNEn8=; b=tzF54Ma7bPTFYlCXhlyenqbuUN8mKObCjFga4Fsl2ooDvcTG8IpfttW7TDXNRMXua+ WqiCcgG16LczQ4W8B3w1gLoIxMlkua/gj0ODeg35dNqJIeF5tnTqS3XmpTAvbpcHkyNK 14FkZgqGh9HZ7wR3KbU9VRlJnqs/DqsLutwENAO0GN1GWV1vtxy+efzIlWluZvnI65fe 3oCbdl/kBcmd9QfG0OJUgwbJg2g5K5KNxfbWeU8Gfz8Xy4zgA9qhULc7gM2hxfSJxvuA SIkwBOGQwJaI3zXHpfBI3zusZ/Qhv8OaZ2p4lDpFiMDIo1C7wlLOlaIvrW/59EaUOQNt GQKQ== X-Gm-Message-State: AGi0Puarz+hHf4NJ6d1CzJEwlG/bwjbwigEV+bGP0mmZBRG4LubCy55N emQ6lwxg5AFmjugsWyW465vOoPr6 X-Google-Smtp-Source: APiQypJWi7qUHgqvwUX6qjsOx5s1koAtxzLcpTJYkpMPseGyxCCjyekGUGXPSlbT8VZVjHhmXKK2EQ== X-Received: by 2002:a1c:7d90:: with SMTP id y138mr16694497wmc.121.1588609751720; Mon, 04 May 2020 09:29:11 -0700 (PDT) Received: from [192.168.43.158] ([109.126.133.135]) by smtp.gmail.com with ESMTPSA id v10sm20279748wrq.45.2020.05.04.09.29.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 04 May 2020 09:29:11 -0700 (PDT) To: Jens Axboe , Bijan Mottahedeh Cc: io-uring References: <1588207670-65832-1-git-send-email-bijan.mottahedeh@oracle.com> <05997981-047c-a87b-c875-6ea7b229f586@kernel.dk> <07fda8ac-93e4-e488-0575-026b339d2c36@gmail.com> <84554b60-2ec5-9876-79ce-5962ae5580e4@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 1/1] io_uring: use proper references for fallback_req locking Message-ID: Date: Mon, 4 May 2020 19:28:06 +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: <84554b60-2ec5-9876-79ce-5962ae5580e4@kernel.dk> 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 04/05/2020 19:12, Jens Axboe wrote: > On 5/3/20 6:52 AM, Pavel Begunkov wrote: >> On 30/04/2020 17:52, Jens Axboe wrote: >>> On 4/29/20 6:47 PM, Bijan Mottahedeh wrote: >>>> Use ctx->fallback_req address for test_and_set_bit_lock() and >>>> clear_bit_unlock(). >>> >>> Thanks, applied. >>> >> >> How about getting rid of it? As once was fairly noticed, we're screwed in many >> other ways in case of OOM. Otherwise we at least need to make async context >> allocation more resilient. > > Not sure how best to handle it, it really sucks to have things fall apart > under high memory pressure, a condition that isn't that rare in production > systems. But as you say, it's only a half measure currently. We could have > the fallback request have req->io already allocated, though. That would > provide what we need for guaranteed forward progress, even in the presence > of OOM conditions. Good idea. +extend it to work with links as a next step. E.g. for short links (2-3 reqs). -- Pavel Begunkov