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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 60730C48BE0 for ; Fri, 11 Jun 2021 15:13:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D401613DE for ; Fri, 11 Jun 2021 15:13:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229685AbhFKPPW (ORCPT ); Fri, 11 Jun 2021 11:15:22 -0400 Received: from mail-ej1-f47.google.com ([209.85.218.47]:42604 "EHLO mail-ej1-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229517AbhFKPPV (ORCPT ); Fri, 11 Jun 2021 11:15:21 -0400 Received: by mail-ej1-f47.google.com with SMTP id k25so5052142eja.9 for ; Fri, 11 Jun 2021 08:13:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=mn6jzUsVPHH3R0oXLF1/xAS/lFbxM8x4AAoXhzQmxh4=; b=mcOavaBbARncM2CA6iUipG1isTlgMCbqkMxDfVHQAT/6hHdx/+/hbwO11L/L+E+v7j L72GTk8PEtTS2xJCRkVhoUiN5/ZXZrCWR9+TfXGEN18NyUbM4wRmWCNAz6eG4iA7cZYi wf4oI6H84TxUmw0IPj+oVa8VC7vCUddT4a6m9MuJVfjHpBoB/3jrM1qxBjbB1hGxbdy4 nt57TGcaRr4GqrPSejNKRrq8vVJgHxiVl574pXtgN5T+PKQFl3xW2+VJKeBL0pHDQ9al LHUt9kOQfGt1P2Z9YLVo2fZqsaCDm5rEjkPz1rKwjXuRApQ806mBdz/stgjqqHVz5KzO /WaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=mn6jzUsVPHH3R0oXLF1/xAS/lFbxM8x4AAoXhzQmxh4=; b=ajMLuXbzJTmv3Ac0MD22v/dnpBi6RfqWeDm8sfhcMG1FxIx+JrikOzSUTFXBxA1iLV OTLZfiBB93090ZOrI2Oom9Qg+WRmZ2knFJDv7r82WTOqa183/mV4T3FYDzCHtETLJIKs hTPScf7aBqqhog4TsNFaYc3qX6Alq/kZAVCLj5JRDxutUP3aVCYOKvOTUqj6DYvozm1U BDP3nvddhxYDNICFmeRrMSFSLluBz6uVvOQjulztwE++ekanp/ADBhOd7DHa97wSIUyG oQbGPi8pVK/NIt0jXzpNyhF775iZ/6mEnimuMoC2tbpw2U6yC/1NbEkzcs5BXXLK52k+ j4PQ== X-Gm-Message-State: AOAM533Sg3M3ewS4lcHgdE2vg5Ybc9FmrheF/9qipW4gJXE27k1otSj/ BqSScCYXlKaHZmxdEKALVe2H3OmSHkz1ikn2MMmFtA== X-Google-Smtp-Source: ABdhPJzNE4G469QuiQdFpOpyQD/QeTCYcSWLVr648fmxf26KsPpQElHY212dh4rmJvzFvzkzdBhDcscYNnrfqQveEt4= X-Received: by 2002:a17:906:490:: with SMTP id f16mr4200567eja.541.1623424330299; Fri, 11 Jun 2021 08:12:10 -0700 (PDT) MIME-Version: 1.0 References: <000000000000ae236f05bfde0678@google.com> <1435f266-9f6d-22ef-ba7d-f031c616aede@I-love.SAKURA.ne.jp> <7b8c9eeb-789d-e5e6-04d6-130ee8be7305@i-love.sakura.ne.jp> <20210609164639.GM4910@sequoia> <49e00adb-ccf5-8024-6403-014ca82781dd@i-love.sakura.ne.jp> In-Reply-To: <49e00adb-ccf5-8024-6403-014ca82781dd@i-love.sakura.ne.jp> From: Pavel Tatashin Date: Fri, 11 Jun 2021 11:11:34 -0400 Message-ID: Subject: Re: [syzbot] possible deadlock in del_gendisk To: Tetsuo Handa Cc: Tyler Hicks , Petr Vorel , Christoph Hellwig , Jens Axboe , Stefan Haberland , Jan Hoeppner , linux-block , syzbot , Tejun Heo Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Fri, Jun 11, 2021 at 10:47 AM Tetsuo Handa wrote: > > On 2021/06/10 1:46, Tyler Hicks wrote: > > Thanks for doing this. I haven't had a chance to retry this commit with > > lockdep but I did re-review it and didn't think that it would be the > > cause of this lockdep report since it strictly reduced the usage of the > > loop_ctl_mutex. > > Well, I made commit 310ca162d779efee ("block/loop: Use global lock for ioctl() operation.") > because per device lock was not sufficient. Did commit 6cc8e7430801fa23 ("loop: scale loop > device by introducing per device lock") take this problem into account? This was my intention when I wrote 6cc8e7430801fa23 ("loop: scale loop device by introducing per device lock"). This is why this change does not simply revert 310ca162d779efee ("block/loop: Use global lock for ioctl() operation."), but keeps loop_ctl_mutex to protect the global accesses. loop_control_ioctl() is still locked by global loop_ctl_mutex.