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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 C8268C2BA19 for ; Fri, 10 Apr 2020 02:58:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 91B4320730 for ; Fri, 10 Apr 2020 02:58:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 91B4320730 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=acm.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 249468E002C; Thu, 9 Apr 2020 22:58:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1D2138E0003; Thu, 9 Apr 2020 22:58:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 09B5F8E002C; Thu, 9 Apr 2020 22:58:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0081.hostedemail.com [216.40.44.81]) by kanga.kvack.org (Postfix) with ESMTP id DFE338E0003 for ; Thu, 9 Apr 2020 22:58:17 -0400 (EDT) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 96B4DA8D6 for ; Fri, 10 Apr 2020 02:58:17 +0000 (UTC) X-FDA: 76690436634.19.lock95_485e583ebb936 X-HE-Tag: lock95_485e583ebb936 X-Filterd-Recvd-Size: 5264 Received: from mail-pj1-f68.google.com (mail-pj1-f68.google.com [209.85.216.68]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Fri, 10 Apr 2020 02:58:17 +0000 (UTC) Received: by mail-pj1-f68.google.com with SMTP id l36so295332pjb.3 for ; Thu, 09 Apr 2020 19:58:17 -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=3/zr6sp9cnHWIbeu5mJQjJua9Pc19Fnu4r/08td9UIE=; b=LVSJ9BH2rSgO3GItfExFgTa6PyAoAvHUSgFMyppHKecw6so5WkUsERs6gCGevyk/II umqG+3TD0R5iPBFxiyvtOt2nByy8MKMA/UlmEtZ7FPv+cKA8LiZpi5VDJfOxvwWAT+s2 ypSm9g9VuX8fK6N/rI0F5AiIULtzi/D0mYvp0g57z/b4YIMuB2LcEsOy2MZ/Tk8aj2wZ aTYHAWTlwW5a5memXy/S0OevShv5ld9ZfEtwKKLXryWFX/vD5Lnhe68dPNZ0IUUqzwgB DpwGgsLHGZUk0M5gQGTagjP+NHgSVfe/lg9UXgjW/3mgeVZbaw1gHFRcbb+Q+a91R97A yTFQ== X-Gm-Message-State: AGi0PuaqDTg8AnlQCtrBnskaT/uiacfHbgmCLEyhsJqFkG9si9Xy7tOy tHRIj1+dZ9kf7S6T2EGVjeo= X-Google-Smtp-Source: APiQypITMgw/AlMFWADX+9U8ko5YTL0iHM+x6VLTaZdr633nQqFlHiG0A1Q83kztjT0dA4M+pSaGPg== X-Received: by 2002:a17:902:bf46:: with SMTP id u6mr2700916pls.33.1586487496100; Thu, 09 Apr 2020 19:58:16 -0700 (PDT) Received: from ?IPv6:2601:647:4000:d7:ed4e:1b14:7fc4:cd73? ([2601:647:4000:d7:ed4e:1b14:7fc4:cd73]) by smtp.gmail.com with ESMTPSA id ne16sm470242pjb.11.2020.04.09.19.58.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Apr 2020 19:58:15 -0700 (PDT) Subject: Re: [RFC v2 3/5] blktrace: ref count the request_queue during ioctl To: Luis Chamberlain , axboe@kernel.dk, viro@zeniv.linux.org.uk, gregkh@linuxfoundation.org, rostedt@goodmis.org, mingo@redhat.com, jack@suse.cz, ming.lei@redhat.com, nstange@suse.de, akpm@linux-foundation.org Cc: mhocko@suse.com, yukuai3@huawei.com, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Omar Sandoval , Hannes Reinecke , Michal Hocko References: <20200409214530.2413-1-mcgrof@kernel.org> <20200409214530.2413-4-mcgrof@kernel.org> 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: Date: Thu, 9 Apr 2020 19:58:13 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200409214530.2413-4-mcgrof@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2020-04-09 14:45, Luis Chamberlain wrote: > Ensure that the reqest_queue ref counts the request_queue ^^^^^^^^^^^^ ^^^^^^^^^^ request_queue? refcounts? > during its full ioctl cycle. This avoids possible races against > removal, given blk_get_queue() also checks to ensure the queue > is not dying. > > This small race is possible if you defer removal of the reqest_queue ^^^^^^^^^^^^ request_queue? > and userspace fires off an ioctl for the device in the meantime. Anyway: Reviewed-by: Bart Van Assche