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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 73C7EC4743E for ; Mon, 7 Jun 2021 00:11:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4D9DD613C8 for ; Mon, 7 Jun 2021 00:11:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229885AbhFGANS (ORCPT ); Sun, 6 Jun 2021 20:13:18 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:47596 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229884AbhFGANS (ORCPT ); Sun, 6 Jun 2021 20:13:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623024687; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=fDP2maVPmzsGuozqXFpsK6C2uAMCKTA9vT6K9r3ZBa4=; b=A1JAmZGtXZJb7zJIBuOg1ngkdnLJQuCc6UEHDZUsNbduSHwjvafPXwO1GoT0nGaUxubp+D o2bhxTwQUegI9szReSjGIzmmbtvMvLwpyHEMTa2ao7tXGGC4HvRb58rEgi1w6wqE4jCQOk vnnBPyOSEWG3phL+1OQlDjTuYcfcRa8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-21-QhGvJ5_ZPTeWLMp66CRpmQ-1; Sun, 06 Jun 2021 20:11:26 -0400 X-MC-Unique: QhGvJ5_ZPTeWLMp66CRpmQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 34C80800D55; Mon, 7 Jun 2021 00:11:25 +0000 (UTC) Received: from T590 (ovpn-12-62.pek2.redhat.com [10.72.12.62]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4E6B760C04; Mon, 7 Jun 2021 00:11:17 +0000 (UTC) Date: Mon, 7 Jun 2021 08:11:13 +0800 From: Ming Lei To: Christoph Hellwig Cc: axboe@kernel.dk, pasha.tatashin@soleen.com, linux-block@vger.kernel.org, Colin Ian King Subject: Re: [PATCH] block: loop: fix deadlock between open and remove Message-ID: References: <20210605140950.5800-1-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210605140950.5800-1-hch@lst.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sat, Jun 05, 2021 at 05:09:50PM +0300, 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 . > > Reported-by: Colin Ian King > Fixes: c76f48eb5c08 ("block: take bd_mutex around delete_partitions in del_gendisk") > Signed-off-by: Christoph Hellwig Reviewed-by: Ming Lei -- Ming