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=-6.2 required=3.0 tests=BAYES_00, 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 CEE5BC433DF for ; Sun, 23 Aug 2020 01:58:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B6AF9206DA for ; Sun, 23 Aug 2020 01:58:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726603AbgHWB6L (ORCPT ); Sat, 22 Aug 2020 21:58:11 -0400 Received: from mail-pl1-f195.google.com ([209.85.214.195]:40624 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725821AbgHWB6J (ORCPT ); Sat, 22 Aug 2020 21:58:09 -0400 Received: by mail-pl1-f195.google.com with SMTP id b11so2579947pld.7; Sat, 22 Aug 2020 18:58:08 -0700 (PDT) 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=FUpDqn3GSqZeYvxxsArGtttJRoK3eORe52wIumG4FE8=; b=aY0Jy5RHcwfBtdHh392krsm1iOtzGH30PhwwV5WwO3WVNUUdFg2GwunVAxgdqkTNV1 r0/hk7TBQKHwBXU/cq/+DL8hP5a5JujUrVowYDDBtLSqUhhcam01w2XVQQV66KMm81AZ nLNmV2jPwITqPBOEE3R8w4gJheyyT0bBqbAGNlwYL9qN9/SM2pnrwI/NRqwej1Jx7JdY KGg1X1aDJiIBygoxfMEcOUycUkGT/oLFTvoZA6zCtdqBBdvGiM18UmLudv+TzuIBkxLg 0FNgUHXj4oK1ctUs224OA8PaS+fk/NnWWJZrX6tKsM9MJjUbEJS3KXypzggJFvBXYbrk NSRw== X-Gm-Message-State: AOAM533UOvvJeJKP9epS7KKmIu9KE+QX1RqY28Lb120rkERVelY0w3Q4 RRzMFugL+sDjrdG6uxo9ZJQMbE+gy0c= X-Google-Smtp-Source: ABdhPJwxY/OESBRANK55Fb5iFeAwJIxMeib/AxROR6q//81ET4jq0kJs6pLlQ1ZQ/7OV1bSLjz9JXg== X-Received: by 2002:a17:90a:2e0f:: with SMTP id q15mr4202pjd.49.1598147887514; Sat, 22 Aug 2020 18:58:07 -0700 (PDT) Received: from [192.168.3.217] (c-73-241-217-19.hsd1.ca.comcast.net. [73.241.217.19]) by smtp.gmail.com with ESMTPSA id o192sm7270748pfg.81.2020.08.22.18.58.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 22 Aug 2020 18:58:06 -0700 (PDT) Subject: Re: IOPRIO_CLASS_RT without CAP_SYS_ADMIN? To: Khazhismel Kumykov , axboe@kernel.dk, paolo.valente@linaro.org Cc: linux-block@vger.kernel.org, Linux Kernel Mailing List References: From: Bart Van Assche Autocrypt: addr=bvanassche@acm.org; prefer-encrypt=mutual; keydata= mQENBFSOu4oBCADcRWxVUvkkvRmmwTwIjIJvZOu6wNm+dz5AF4z0FHW2KNZL3oheO3P8UZWr LQOrCfRcK8e/sIs2Y2D3Lg/SL7qqbMehGEYcJptu6mKkywBfoYbtBkVoJ/jQsi2H0vBiiCOy fmxMHIPcYxaJdXxrOG2UO4B60Y/BzE6OrPDT44w4cZA9DH5xialliWU447Bts8TJNa3lZKS1 AvW1ZklbvJfAJJAwzDih35LxU2fcWbmhPa7EO2DCv/LM1B10GBB/oQB5kvlq4aA2PSIWkqz4 3SI5kCPSsygD6wKnbRsvNn2mIACva6VHdm62A7xel5dJRfpQjXj2snd1F/YNoNc66UUTABEB AAG0JEJhcnQgVmFuIEFzc2NoZSA8YnZhbmFzc2NoZUBhY20ub3JnPokBOQQTAQIAIwUCVI67 igIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEHFcPTXFzhAJ8QkH/1AdXblKL65M Y1Zk1bYKnkAb4a98LxCPm/pJBilvci6boefwlBDZ2NZuuYWYgyrehMB5H+q+Kq4P0IBbTqTa jTPAANn62A6jwJ0FnCn6YaM9TZQjM1F7LoDX3v+oAkaoXuq0dQ4hnxQNu792bi6QyVdZUvKc macVFVgfK9n04mL7RzjO3f+X4midKt/s+G+IPr4DGlrq+WH27eDbpUR3aYRk8EgbgGKvQFdD CEBFJi+5ZKOArmJVBSk21RHDpqyz6Vit3rjep7c1SN8s7NhVi9cjkKmMDM7KYhXkWc10lKx2 RTkFI30rkDm4U+JpdAd2+tP3tjGf9AyGGinpzE2XY1K5AQ0EVI67igEIAKiSyd0nECrgz+H5 PcFDGYQpGDMTl8MOPCKw/F3diXPuj2eql4xSbAdbUCJzk2ETif5s3twT2ER8cUTEVOaCEUY3 eOiaFgQ+nGLx4BXqqGewikPJCe+UBjFnH1m2/IFn4T9jPZkV8xlkKmDUqMK5EV9n3eQLkn5g lco+FepTtmbkSCCjd91EfThVbNYpVQ5ZjdBCXN66CKyJDMJ85HVr5rmXG/nqriTh6cv1l1Js T7AFvvPjUPknS6d+BETMhTkbGzoyS+sywEsQAgA+BMCxBH4LvUmHYhpS+W6CiZ3ZMxjO8Hgc ++w1mLeRUvda3i4/U8wDT3SWuHcB3DWlcppECLkAEQEAAYkBHwQYAQIACQUCVI67igIbDAAK CRBxXD01xc4QCZ4dB/0QrnEasxjM0PGeXK5hcZMT9Eo998alUfn5XU0RQDYdwp6/kMEXMdmT oH0F0xB3SQ8WVSXA9rrc4EBvZruWQ+5/zjVrhhfUAx12CzL4oQ9Ro2k45daYaonKTANYG22y //x8dLe2Fv1By4SKGhmzwH87uXxbTJAUxiWIi1np0z3/RDnoVyfmfbbL1DY7zf2hYXLLzsJR mSsED/1nlJ9Oq5fALdNEPgDyPUerqHxcmIub+pF0AzJoYHK5punqpqfGmqPbjxrJLPJfHVKy goMj5DlBMoYqEgpbwdUYkH6QdizJJCur4icy8GUNbisFYABeoJ91pnD4IGei3MTdvINSZI5e Message-ID: <992ed2ed-f644-a5ad-3239-b38ddeafe28b@acm.org> Date: Sat, 22 Aug 2020 18:58:04 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-08-20 17:35, Khazhismel Kumykov wrote: > It'd be nice to allow a process to send RT requests without granting > it the wide capabilities of CAP_SYS_ADMIN, and we already have a > capability which seems to almost fit this priority idea - > CAP_SYS_NICE? Would this fit there? > > Being capable of setting IO priorities on per request or per thread > basis (be it async submission or w/ thread ioprio_set) is useful > especially when the userspace has its own prioritization/scheduling > before hitting the kernel, allowing us to signal to the kernel how to > order certain IOs, and it'd be nice to separate this from ADMIN for > non-root processes, in a way that's less error prone than e.g. having > a trusted launcher ionice the process and then drop priorities for > everything but prio requests. Hi Khazhy, In include/uapi/linux/capability.h I found the following: /* Allow raising priority and setting priority on other (different UID) processes */ /* Allow use of FIFO and round-robin (realtime) scheduling on own processes and setting the scheduling algorithm used by another process. */ /* Allow setting cpu affinity on other processes */ #define CAP_SYS_NICE 23 If it is acceptable that every process that has permission to submit IOPRIO_CLASS_RT I/O also has permission to modify the priority of other processes then extending CAP_SYS_NICE is an option. Another possibility is to extend the block cgroup controller such that the capability to submit IOPRIO_CLASS_RT I/O can be enabled through the cgroup interface. There may be other approaches. I'm not sure what the best approach is. Bart.