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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0386C77B73 for ; Thu, 27 Apr 2023 06:37:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 18C9F6B0071; Thu, 27 Apr 2023 02:37:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 116FC6B0072; Thu, 27 Apr 2023 02:37:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F1F6D6B0074; Thu, 27 Apr 2023 02:37:17 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id DE5116B0071 for ; Thu, 27 Apr 2023 02:37:17 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 9AC8E401C2 for ; Thu, 27 Apr 2023 06:37:17 +0000 (UTC) X-FDA: 80726214114.23.9ED067C Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf26.hostedemail.com (Postfix) with ESMTP id D2206140003 for ; Thu, 27 Apr 2023 06:37:13 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=none; spf=pass (imf26.hostedemail.com: domain of libaokun1@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=libaokun1@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1682577435; a=rsa-sha256; cv=none; b=xuUyxHDsda4idRT2vywdntFKrkgD1DUIwvFMSCPsfImOvY2pcna++4eNu8GmmIPUCBRipj Ws/N2MlS/4FRrVu3WnXPpmKi5l7pNWtZ0KD0Qgwp30nkGcHC8AJOSXM/ZCn5VZKxkORgyE ceRH9/+rxyrszsd5+CDLrIiaePYgaZ0= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=none; spf=pass (imf26.hostedemail.com: domain of libaokun1@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=libaokun1@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1682577435; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=STE9iEnnciq3qDv8yxQ1IqC/LwCrMjfX1Z4OjH7UdmY=; b=Zxkuf/r50GyZ8MHip8IJQO3/7DboJH34pPxsnw99c4CpT8PisRxJXm9Lq8kxsXToqM5rjZ aqsQP/e0T84Prj9wzRki7ZTRPMyTjnnfdGXp/HN6/sJf6qc92uFySYg5nxTBI5vClEJ5IK qXxvtTkU+y/uVRtbDEGNq/W9HBnh0ZY= Received: from dggpeml500021.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Q6QwJ0kWnzsR8d; Thu, 27 Apr 2023 14:35:28 +0800 (CST) Received: from [10.174.177.174] (10.174.177.174) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Thu, 27 Apr 2023 14:37:06 +0800 Message-ID: Date: Thu, 27 Apr 2023 14:36:51 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.1.2 Subject: Re: [ext4 io hang] buffered write io hang in balance_dirty_pages To: Ming Lei , Matthew Wilcox CC: Theodore Ts'o , , Andreas Dilger , , Andrew Morton , , , Dave Chinner , Eric Sandeen , Christoph Hellwig , Zhang Yi , yangerkun , Baokun Li References: Content-Language: en-US From: Baokun Li In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.174] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml500021.china.huawei.com (7.185.36.21) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Queue-Id: D2206140003 X-Rspamd-Server: rspam01 X-Stat-Signature: 678qhj1zkgo7kkik8xske93mqrukhang X-HE-Tag: 1682577433-564540 X-HE-Meta: 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 QJMGyRxm odZqvCHmZD0WmKF5nTzKEIJXZjEeFXUYuTQTyigmMl5eitQR+SMFZxcmkf7+ehZKcOUwgVopXF/Wh0cA/zT9gl20bhEAc+2wMyIkkrIP7kbFciwiVvh+7euX409zvQD8s5cz9VE7SJTfuBL4VLZOVTWK3pfWbAktdDzpus3fulb2qTZp2DgOdGYFopw== 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 2023/4/27 12:50, Ming Lei wrote: > Hello Matthew, > > On Thu, Apr 27, 2023 at 04:58:36AM +0100, Matthew Wilcox wrote: >> On Thu, Apr 27, 2023 at 10:20:28AM +0800, Ming Lei wrote: >>> Hello Guys, >>> >>> I got one report in which buffered write IO hangs in balance_dirty_pages, >>> after one nvme block device is unplugged physically, then umount can't >>> succeed. >> That's a feature, not a bug ... the dd should continue indefinitely? > Can you explain what the feature is? And not see such 'issue' or 'feature' > on xfs. > > The device has been gone, so IMO it is reasonable to see FS buffered write IO > failed. Actually dmesg has shown that 'EXT4-fs (nvme0n1): Remounting > filesystem read-only'. Seems these things may confuse user. The reason for this difference is that ext4 and xfs handle errors differently. ext4 remounts the filesystem as read-only or even just continues, vfs_write does not check for these. xfs shuts down the filesystem, so it returns a failure at xfs_file_write_iter when it finds an error. ``` ext4 ksys_write  vfs_write   ext4_file_write_iter    ext4_buffered_write_iter     ext4_write_checks      file_modified       file_modified_flags        __file_update_time         inode_update_time          generic_update_time           __mark_inode_dirty            ext4_dirty_inode ---> 2. void func, No propagating errors out             __ext4_journal_start_sb              ext4_journal_check_start ---> 1. Error found, remount-ro     generic_perform_write ---> 3. No error sensed, continue      balance_dirty_pages_ratelimited       balance_dirty_pages_ratelimited_flags        balance_dirty_pages         // 4. Sleeping waiting for dirty pages to be freed         __set_current_state(TASK_KILLABLE)         io_schedule_timeout(pause); ``` ``` xfs ksys_write  vfs_write   xfs_file_write_iter    if (xfs_is_shutdown(ip->i_mount))      return -EIO;    ---> dd fail ``` >> balance_dirty_pages() is sleeping in KILLABLE state, so kill -9 of >> the dd process should succeed. > Yeah, dd can be killed, however it may be any application(s), :-) > > Fortunately it won't cause trouble during reboot/power off, given > userspace will be killed at that time. > > > > Thanks, > Ming > Don't worry about that, we always set the current thread to TASK_KILLABLE while waiting in balance_dirty_pages(). -- With Best Regards, Baokun Li .