From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH v3 (resend)] block/loop: Serialize ioctl operations. To: Ming Lei Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Jan Kara , Jens Axboe , syzbot , syzbot References: <1537009136-4839-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> From: Tetsuo Handa Message-ID: <1af79300-cb04-36e3-a650-168a5942161f@i-love.sakura.ne.jp> Date: Sat, 22 Sep 2018 21:39:02 +0900 MIME-Version: 1.0 In-Reply-To: <1537009136-4839-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> Content-Type: text/plain; charset=utf-8 List-ID: Hello, Ming Lei. I'd like to hear your comment on this patch regarding the ordering of stopping kernel thread. > In order to enforce this strategy, this patch inversed > loop_reread_partitions() and loop_unprepare_queue() in loop_clr_fd(). > I don't know whether it breaks something, but I don't have testcases. Until 3.19, kthread_stop(lo->lo_thread) was called before ioctl_by_bdev(bdev, BLKRRPART, 0) is called. During 4.0 to 4.3, the loop module was using "kloopd" workqueue. But since 4.4, loop_reread_partitions(lo, bdev) is called before loop_unprepare_queue(lo) is called. And this patch is trying to change to call loop_unprepare_queue() before loop_reread_partitions() is called. Is there some reason we need to preserve current ordering? Relevant commits: commit b5dd2f6047ca108001328aac0e8588edd15f1778 block: loop: improve performance via blk-mq commit e03a3d7a94e2485b6e2fa3fb630b9b3a30b65718 block: loop: use kthread_work 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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 EAFA1C433F4 for ; Sat, 22 Sep 2018 12:39:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AE06521532 for ; Sat, 22 Sep 2018 12:39:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AE06521532 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731316AbeIVSdA (ORCPT ); Sat, 22 Sep 2018 14:33:00 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:55380 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728164AbeIVSdA (ORCPT ); Sat, 22 Sep 2018 14:33:00 -0400 Received: from fsav405.sakura.ne.jp (fsav405.sakura.ne.jp [133.242.250.104]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id w8MCdC1G052965; Sat, 22 Sep 2018 21:39:12 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav405.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav405.sakura.ne.jp); Sat, 22 Sep 2018 21:39:11 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav405.sakura.ne.jp) Received: from [192.168.1.8] (softbank060157066051.bbtec.net [60.157.66.51]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id w8MCd2OE052724 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sat, 22 Sep 2018 21:39:09 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH v3 (resend)] block/loop: Serialize ioctl operations. To: Ming Lei Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Jan Kara , Jens Axboe , syzbot , syzbot References: <1537009136-4839-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> From: Tetsuo Handa Message-ID: <1af79300-cb04-36e3-a650-168a5942161f@i-love.sakura.ne.jp> Date: Sat, 22 Sep 2018 21:39:02 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <1537009136-4839-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Ming Lei. I'd like to hear your comment on this patch regarding the ordering of stopping kernel thread. > In order to enforce this strategy, this patch inversed > loop_reread_partitions() and loop_unprepare_queue() in loop_clr_fd(). > I don't know whether it breaks something, but I don't have testcases. Until 3.19, kthread_stop(lo->lo_thread) was called before ioctl_by_bdev(bdev, BLKRRPART, 0) is called. During 4.0 to 4.3, the loop module was using "kloopd" workqueue. But since 4.4, loop_reread_partitions(lo, bdev) is called before loop_unprepare_queue(lo) is called. And this patch is trying to change to call loop_unprepare_queue() before loop_reread_partitions() is called. Is there some reason we need to preserve current ordering? Relevant commits: commit b5dd2f6047ca108001328aac0e8588edd15f1778 block: loop: improve performance via blk-mq commit e03a3d7a94e2485b6e2fa3fb630b9b3a30b65718 block: loop: use kthread_work