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=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 30D29C48BD1 for ; Fri, 11 Jun 2021 17:51:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 16B60613D9 for ; Fri, 11 Jun 2021 17:51:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229985AbhFKRx0 (ORCPT ); Fri, 11 Jun 2021 13:53:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229931AbhFKRxZ (ORCPT ); Fri, 11 Jun 2021 13:53:25 -0400 Received: from mail-pl1-x630.google.com (mail-pl1-x630.google.com [IPv6:2607:f8b0:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2F43DC061574 for ; Fri, 11 Jun 2021 10:51:12 -0700 (PDT) Received: by mail-pl1-x630.google.com with SMTP id x19so3210030pln.2 for ; Fri, 11 Jun 2021 10:51:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=2rxRAiPtIPFYcoD9aLWTaw2AHjyQyQp4ZMkTG0TPS7E=; b=ifTbSpnQJUBSZvLYFwYcfJtqZOUc2F+tqqkx585oVr1NX3yD+zW5vI1uu+m1MY+3XZ RnW7Xf6XlwyGupoo+F0irbqLyd51juu87lwaNAFh8sX8G0VK9AY/uMX6ak5Yc9Lvefd1 gQw8Q86a6EqHDSci1uu0dAmeNkg84vi8Vja2hGim3dMSI4E880mqywQIb7UtsJRKlwGy JjkK9f8nswJgVBObHusdQ9LGMJDNubWkPkxmV+ePzlW4QZMofnO5/unPhO0dG+fhb/w+ S932GbgOkxqEggV2Q9M6MMaClq7q70oYlUgub4umV46DRE2H2EQTBfoAOKGon5c3dCDY Fisg== 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:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=2rxRAiPtIPFYcoD9aLWTaw2AHjyQyQp4ZMkTG0TPS7E=; b=n5xlq/D7AihPIEgXQ3eCih4lH829vgC3MsM4gIfR1CiHxzFc7ZMT4Sat+x45RgN3gU YbxabqXwxaqoT3uebFAb3Nu0My/x+lv6TVSMVJlR3qNm/02MC1/CbS8so996Y+ztkJK3 kMrDSm2Xovho9Nb97FCUTo9+HG/Gg1urjrfnAJfgx98xvtr0qpRylgjFKLRdhZgdyv6N sF+7xVz0oIMadQDEeW+9xHqZQlLsJpgEZR76bH0aIr7q/KZ2YTpGJhQQnIJPfBD4QPRK 1vhfjDMDiwiDwGVD37m2BK0q+0bTK2RdWBbzrjCAVSLn6+4XU9d+3xzDDnctIoync8eb g7sA== X-Gm-Message-State: AOAM531I6WMIRdRr9ziipXx5ILi8J/WlTmI0hsxjCDgyzHrEUlasMSE5 XjMYlsjH502HpOCF7GWkePbmXg== X-Google-Smtp-Source: ABdhPJwaRIfbEQgveMAxoYPgSHlRY9WSJZS0MiMwPMBoczZx23xnZcXY/lu7YkNPDJOJI1JH3i4Evg== X-Received: by 2002:a17:90a:5504:: with SMTP id b4mr5605740pji.208.1623433871462; Fri, 11 Jun 2021 10:51:11 -0700 (PDT) Received: from [192.168.4.41] (cpe-72-132-29-68.dc.res.rr.com. [72.132.29.68]) by smtp.gmail.com with ESMTPSA id c184sm2751867pfa.38.2021.06.11.10.51.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Jun 2021 10:51:10 -0700 (PDT) Subject: Re: [PATCH] block: loop: fix deadlock between open and remove To: Christoph Hellwig Cc: ming.lei@redhat.com, pasha.tatashin@soleen.com, linux-block@vger.kernel.org, Colin Ian King References: <20210605140950.5800-1-hch@lst.de> From: Jens Axboe Message-ID: Date: Fri, 11 Jun 2021 11:51:12 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210605140950.5800-1-hch@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 6/5/21 8:09 AM, Christoph Hellwig wrote: > Commit c76f48eb5c08 ("block: take bd_mutex around delete_partitions in > del_gendisk") adds disk->part0->bd_mutex in del_gendisk(), this way > causes the following AB/BA deadlock between removing loop and opening > loop: > > 1) loop_control_ioctl(LOOP_CTL_REMOVE) > -> mutex_lock(&loop_ctl_mutex) > -> del_gendisk > -> mutex_lock(&disk->part0->bd_mutex) > > 2) blkdev_get_by_dev > -> mutex_lock(&disk->part0->bd_mutex) > -> lo_open > -> mutex_lock(&loop_ctl_mutex) > > Add a new Lo_deleting state to remove the need for clearing > ->private_data and thus holding loop_ctl_mutex in the ioctl > LOOP_CTL_REMOVE path. > > Based on an analysis and earlier patch from > Ming Lei . Applied, thanks. -- Jens Axboe