From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.163.com (m16.mail.163.com [117.135.210.5]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 262A12F46; Fri, 18 Oct 2024 11:34:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=117.135.210.5 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729251300; cv=none; b=doj1nqrG49oRX2yKwvKJJyfuAZREq5fYBBE6NHYC7agVtgLhGZb3sRLV36SEibyBZVwPpbNHd5jkTe12VRLUx3jf46ZufjecB1ok3FJsIz1/yeyJYk6NcaJ9jlXaQI4I0lloPebNn6n1T/AbS6fyPHSdmZrBcfcmIRloYtc2trI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729251300; c=relaxed/simple; bh=vIo6d3z0ZWjVlUbhqsm8NCa8h8VBGEoEX5hD5dHZBWU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jxrImR4WLQ2EI7CCJIPXXo4IfY7IcToXQWrbDGunEjjJPz8S6H4asHfoBn2UjTbZNvZZCm6ihqK+ZNFagsV7JHWQp1ohhg+SpbZs6t5MSlXo0eazCDEIpKrtewgV//X6W0Mw1tb6JYtdwBD3ZAH7bqoov+4PcY8DXPfXz2y19Xo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=j75om5FA; arc=none smtp.client-ip=117.135.210.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="j75om5FA" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=Message-ID:Date:MIME-Version:Subject:From: Content-Type; bh=caUiTptCocfNUoFU8zd6duiK1xNXinI7kyJpdRcGEvs=; b=j75om5FAJKsveEOjLsZpZb+n+xrRc3+swqgTAZ/moXsyoNJcrGlJFSOWFGI/eh O86SdoFqVqiQOxncWSu9Kzgt3B5XNmcvISqGFTq4SEqzao+cftdc63D8Me0hYgh3 H5xpuWn1dVUWdpUXk15POSMN2Fi9XBK3Lfz0N4vhMziek= Received: from [192.168.22.184] (unknown [223.70.253.255]) by gzga-smtp-mtada-g0-2 (Coremail) with SMTP id _____wDXHzbLRxJnWzhPBw--.50533S2; Fri, 18 Oct 2024 19:34:35 +0800 (CST) Message-ID: Date: Fri, 18 Oct 2024 19:34:31 +0800 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] ext4: fix a assertion failure due to ungranted bh dirting To: Jan Kara Cc: tytso@mit.edu, adilger.kernel@dilger.ca, zhangshida@kylinos.cn, longzhi@sangfor.com.cn, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Baolin Liu References: <20241010025855.2632516-1-liubaolin12138@163.com> <20241010092923.r53povuflevzhxrw@quack3> <5dc22111.4718.19279c3f3b7.Coremail.liubaolin12138@163.com> <20241016103301.rl6qngi2fb6yxjin@quack3> <908502d6-cb0c-44ae-8c03-9a22c8c7fbf2@163.com> <8c14e5b0-5229-4611-b8e6-434c6eb34ee9@163.com> <20241018091444.tmzhbj73gvegfmb5@quack3> From: liubaolin In-Reply-To: <20241018091444.tmzhbj73gvegfmb5@quack3> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wDXHzbLRxJnWzhPBw--.50533S2 X-Coremail-Antispam: 1Uf129KBjvJXoW3AF1kZr1DKFW3WF13Jr18Krg_yoWxAryrpr y3Ka17Kr4qyryDArn2qF4UXrWUK34jqr9rWr15Grn7Z390yrn3tF48tr10kFyDCrWkG3WF vr1UAr9rCr1qy37anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07U3-BiUUUUU= X-CM-SenderInfo: xolxutxrol0iasrtmqqrwthudrp/1tbiMR58ymcSPaGuuAAAsm > Sorry, I saw the patch you submitted. > I would like to request a modification to the commit message. > I use the email 'Baolin Liu liubaolin12138@163.com' for community communication. > However, my work email is 'Baolin Liu liubaolin@kylinos.cn'. > > So I would like to ask you to modify the commit message as follows: > From: > Reported-by: Baolin Liu liubaolin12138@163.com > Reported-by: Zhi Long longzhi@sangfor.com.cn > To: > Reported-and-tested-by: Baolin Liu liubaolin@kylinos.cn > Reported-and-tested-by: Zhi Long longzhi@sangfor.com.cn > > Could you please make the modification? Thank you. 在 2024/10/18 17:14, Jan Kara 写道: > On Fri 18-10-24 09:48:17, liubaolin wrote: >>> Hello, I am very sorry. >>> I did not previously understand the approach of your patch to solve the issue. >>> Yesterday, I intentionally injected faults during the quick reproduction >>> test, and indeed, after applying your patch, the crash issue was >>> resolved and did not occur again. >>> I finally understood your approach to solving the problem. Please disregard my previous email. >>> Thank you for helping me solve this crash issue in a better way. >>> I still need to improve my skills in file systems, and I truly appreciate your guidance. > > Great! Thanks for testing. I'll send the patch for inclusion then. > > Honza > >> 在 2024/10/16 21:38, liubaolin 写道: >>>> Hello, >>>> I reviewed the patch attached in your email. The issue you mentioned >>>> about clearing buffer_new(bh) in write_end_fn() is indeed a bug. >>>> However, this patch does not resolve the crash issue we encountered. >>>> >>>> Let me explain my analysis in detail below. >>>> The crash occurs in the function jbd2_journal_dirty_metadata(). >>>> >>>> ext4_block_write_begin() -> ext4_journalled_zero_new_buffers() -> >>>> write_end_fn() >>>>  -> ext4_dirty_journalled_data() -> ext4_handle_dirty_metadata() -> >>>> __ext4_handle_dirty_metadata() >>>>  -> jbd2_journal_dirty_metadata() >>>> >>>> In the function jbd2_journal_dirty_metadata(), there is the >>>> following condition: >>>> —--------------------------------------------------------------------------------------------------- >>>>         if (data_race(jh->b_transaction != transaction && >>>>             jh->b_next_transaction != transaction)) { >>>>                 spin_lock(&jh->b_state_lock); >>>>                 J_ASSERT_JH(jh, jh->b_transaction == transaction || >>>>                                 jh->b_next_transaction == transaction); >>>>                 spin_unlock(&jh->b_state_lock); >>>>         } >>>> ---------------------------------------------------------------------------------------------------- >>>> By analyzing the vmcore, I found that both jh->b_transaction and jh- >>>>> b_next_transaction are NULL. >>>> Through code analysis, I discovered that the >>>> __jbd2_journal_file_buffer() function adds the corresponding >>>> transaction of bh to jh->b_transaction. >>>> Normally, this is accessed through do_journal_get_write_access(), >>>> which can call __jbd2_journal_file_buffer(). >>>> The detailed function call process is as follows: >>>> do_journal_get_write_access() -> ext4_journal_get_write_access() -> >>>> __ext4_journal_get_write_access() >>>>  -> jbd2_journal_get_write_access() -> do_get_write_access() -> >>>> __jbd2_journal_file_buffer() >>>> >>>> >>>> Therefore, resolving the crash issue requires obtaining write access >>>> before calling the jbd2_journal_dirty_metadata() function. >>>> The comment at the definition of the jbd2_journal_dirty_metadata() >>>> function also states:     'The buffer must have previously had >>>> jbd2_journal_get_write_access().' >>>> >>>> In the ext4_block_write_begin() function, if get_block() encounters >>>> an error, then neither bh->b_this_page nor the subsequent bh calls >>>> do_journal_get_write_access(). >>>> If bh->b_this_page and the subsequent bh are in the new state, it >>>> will lead to a crash when reaching the jbd2_journal_dirty_metadata() >>>> function. >>>> >>>> So, there are two ways to resolve this crash issue: >>>> 1、Call do_journal_get_write_access() on bh that is not handled due >>>> to get_block() error. >>>>     The patch modification is in the attachment 0001-ext4-fix-a- >>>> assertion-failure-due-to-ungranted-bh-dir.patch. >>>> >>>> 2、Call clear_buffer_new() on bh that is not handled due to >>>> get_block() error. >>>>     The patch modification is in the attachment 0001-ext4-fix-a- >>>> assertion-failure-due-to-bh-not-clear-new.patch. >>>> >>>> Additionally, I have found a method to quickly reproduce this crash >>>> issue. >>>> For details, please refer to the email I previously sent you: >>>> “https://lore.kernel.org/all/bd41c24b-7325-4584- >>>> a965-392a32e32c74@163.com/”. >>>> I have verified that this quick reproduction method works for both >>>> solutions to resolve the issue. >>>> >>>> Please continue to consider which method is better to resolve this >>>> issue. If you think that using clear_buffer_new() is a better >>>> solution, I can resend the patch via git send-mail. >>> >>> >>> >>> 在 2024/10/16 18:33, Jan Kara 写道: >>>> Hello, >>>> >>>> On Fri 11-10-24 12:08:58, Baolin Liu wrote: >>>>> Greetings， >>>>> >>>>> This problem is reproduced by our customer using their own testing tool >>>>> “run_bug”. When I consulted with a client, the testing tool “run_bug” >>>>> used a variety of background programs to benchmark (including memory >>>>> pressure, cpu pressure, file cycle manipulation, fsstress Stress testing >>>>> tool, postmark program，and so on). >>>>> >>>>> The recurrence probability is relatively low. >>>> >>>> OK, thanks for asking! >>>> >>>>> In response to your query, in ext4_block_write_begin, the new state will >>>>> be clear before get block, and the bh that failed get_block will not be >>>>> set to new. However, when the page size is greater than the >>>>> block size, a >>>>> page will contain multiple bh. >>>> >>>> True. I wanted to argue that the buffer_new bit should be either >>>> cleared in >>>> ext4_block_write_begin() (in case of error) or in >>>> ext4_journalled_write_end() (in case of success) but actually >>>> ext4_journalled_write_end() misses the clearing. So I think the better >>>> solution is like the attached patch. I'll submit it once testing finishes >>>> but it would be great if you could test that it fixes your problems as >>>> well. Thanks! >>>> >>>>                                 Honza >>