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,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 96FC2C2BB55 for ; Thu, 16 Apr 2020 03:43:38 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4738020737 for ; Thu, 16 Apr 2020 03:43:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4738020737 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 75A9D8E0078; Wed, 15 Apr 2020 23:43:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 70BD58E0001; Wed, 15 Apr 2020 23:43:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5D39A8E0078; Wed, 15 Apr 2020 23:43:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0085.hostedemail.com [216.40.44.85]) by kanga.kvack.org (Postfix) with ESMTP id 43DA68E0001 for ; Wed, 15 Apr 2020 23:43:37 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id EDB965853 for ; Thu, 16 Apr 2020 03:43:36 +0000 (UTC) X-FDA: 76712323632.14.story79_59ba951c92e10 X-HE-Tag: story79_59ba951c92e10 X-Filterd-Recvd-Size: 5743 Received: from mail-pg1-f196.google.com (mail-pg1-f196.google.com [209.85.215.196]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Thu, 16 Apr 2020 03:43:36 +0000 (UTC) Received: by mail-pg1-f196.google.com with SMTP id d17so1028848pgo.0 for ; Wed, 15 Apr 2020 20:43:36 -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=MF+GTcAP/Qi1eGTnMDQ31INQwaQqeTxesD5C90whNm4=; b=hCzaT+M/3hc0HBBkeutbJe0/hY9hB7d7JzyHxw0Pxf/Oc/kPy1awzb5BA0JlB7iaTV WYPUCcb2hsYIJoFDP5AmrdNjgZ2d9Hf5rgl0NVcm2swlfTQRQQ0/3CFw2GFfvjFEOjBP gGpRE0S3p/ckYcVFUIe9sxRUmawS9tUrlbywulVLRnCoro7Ivxt39opb5WIOmcrVgIl4 RVNszIrRWy1Lx8W4JBM8Oh0YGnfEVwiMGLoPbwO/nPE06+7zkp1eeAzcUeGad3T5dV/q WfniuvhaT13P9LCaRxvr4m1UqzSAYYE39nzDDr+gdK+J/KbTfqHcmz6sQ1xq9e0NINWV bVEw== X-Gm-Message-State: AGi0PuaqyYe77lMpOKqTa2bp0NIFtt+t9KVehoniE54mo4najGxOUuny zerUrSnHVR1S9i+/aAKTFE8= X-Google-Smtp-Source: APiQypJW/DVeigCfIx/tEMJ1u8JJIZm5hJJ9dvGJdqr8k9BoFgyywcE0DNRRh5Kfl5ObHf8rRTRZ/A== X-Received: by 2002:a63:1f0c:: with SMTP id f12mr28638998pgf.245.1587008615446; Wed, 15 Apr 2020 20:43:35 -0700 (PDT) Received: from ?IPv6:2601:647:4000:d7:91ba:7380:46ae:a781? ([2601:647:4000:d7:91ba:7380:46ae:a781]) by smtp.gmail.com with ESMTPSA id u24sm12045079pgo.65.2020.04.15.20.43.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 Apr 2020 20:43:34 -0700 (PDT) Subject: Re: [PATCH 3/5] blktrace: refcount the request_queue during ioctl To: Luis Chamberlain Cc: Christoph Hellwig , 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, 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: <20200414041902.16769-1-mcgrof@kernel.org> <20200414041902.16769-4-mcgrof@kernel.org> <20200414154044.GB25765@infradead.org> <20200415061649.GS11244@42.do-not-panic.com> <20200415071425.GA21099@infradead.org> <20200415123434.GU11244@42.do-not-panic.com> <73332d32-b095-507f-fb2a-68460533eeb7@acm.org> <20200416011247.GB11244@42.do-not-panic.com> 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: Wed, 15 Apr 2020 20:43:32 -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: <20200416011247.GB11244@42.do-not-panic.com> 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 2020-04-15 18:12, Luis Chamberlain wrote: > On Wed, Apr 15, 2020 at 07:18:22AM -0700, Bart Van Assche wrote: >> blk_get_queue() prevents concurrent freeing of struct request_queue but >> does not prevent concurrent blk_cleanup_queue() calls. > > Wouldn't concurrent blk_cleanup_queue() calls be a bug? If so should > I make it clear that it would be or simply prevent it? I think calling blk_cleanup_queue() while the queue refcount > 0 is well established behavior. At least the SCSI core triggers that behavior since a very long time. I prefer not to change that behavior. Regarding patch 3/5: how about dropping that patch? If the queue refcount can drop to zero while blk_trace_ioctl() is in progress I think that should be fixed in the block_device_operations.open callback instead of in blk_trace_ioctl(). Thanks, Bart.