From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga06-in.huawei.com (szxga06-in.huawei.com [45.249.212.32]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB37D2F30; Sat, 8 Mar 2025 01:09:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.32 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741396183; cv=none; b=VP7lFLX+47vYv2s4sSpIGyTtcFh4Klt70Y6N5jnAaqdOVI1H2GDYPzdiYRP8Vi63XT0nWy6Ep8pS6OaUWKZP8VxjD9wLW1DS1Wo2+HwIqVWEs2QzV+9HQw/FlNDWA9SBIsgRgNxZFwb7NOuyjfKaNXaWwt8IIc5Cre1B5yYdYc8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741396183; c=relaxed/simple; bh=XoL3MCMqaSyBFiZUsFNBsRSZqQJXhK/OZFNeft7zbI0=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=bSrJhwi5Va9ALj3aOh8f4XlFCBc+qRtyzrDM6mR1JZfb46nNFDy/pbcyj++VlSIGwhloeHEqEr8BrdI41PEcckyCjLXrICVYpqJIYs+xLWL1lyzlf4TW8cNMSLFnJSsHMaAstoe0Zc/su9rmccq1aqNGpmh/ONl37iTUEWVZqtI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.32 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.162.112]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4Z8lSW4jQcz17NTH; Sat, 8 Mar 2025 09:10:03 +0800 (CST) Received: from kwepemg500008.china.huawei.com (unknown [7.202.181.45]) by mail.maildlp.com (Postfix) with ESMTPS id 86E241402CC; Sat, 8 Mar 2025 09:09:29 +0800 (CST) Received: from [127.0.0.1] (10.174.177.71) by kwepemg500008.china.huawei.com (7.202.181.45) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Sat, 8 Mar 2025 09:09:28 +0800 Message-ID: <692ab4aa-ff90-4b6f-980d-bfd6c1ca7619@huawei.com> Date: Sat, 8 Mar 2025 09:09:28 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/3] Fix a BUG_ON crashing the kernel in start_this_handle To: Ojaswin Mujoo CC: , Theodore Ts'o , Jan Kara , , Yang Erkun References: Content-Language: en-US From: Baokun Li In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemg500008.china.huawei.com (7.202.181.45) On 2025/3/6 22:28, Ojaswin Mujoo wrote: > ** Changes since v1 [1] ** > > * Picked up RVBs from Jan and Ritesh > * In patch 2/3, we now use a flag in sbi instead of SB_ACITVE > to determine when to journal sb vs when to commit directly. > * Added a prep patch 1/3 > > [1] https://lore.kernel.org/linux-ext4/cover.1740212945.git.ojaswin@linux.ibm.com/T/#m5e659425b8c8fe2ac01e7242b77fed315ff89db4 > > @Baokun, I didn't get a chance to look into the journal_inode > modifications we were discussing in [2]. I'll try to spend some time and > send that as a separate patch. Hope that's okay > > [2] https://lore.kernel.org/linux-ext4/cover.1740212945.git.ojaswin@linux.ibm.com/T/#mad8feb44d9b6ddadf87830b92caa7b78d902dc05 > That's fine, it's not a priority. And if this patch set makes sure we don't crash when things go wrong, I'm okay with leaving it as is. It's possible that jbd2_journal_commit_transaction() could call ext4_handle_error() in other places as the code evolves. Fixing known problems and protecting against potential ones is always a good thing. Cheers, Baokun > ** Original Cover ** > > When running LTP stress tests on ext4, after a multiday run we seemed to > have hit the following BUG_ON: > > [NIP : start_this_handle+268] > #3 [c000001067c27a40] start_this_handle at c008000004d40f74 [jbd2] (unreliable) > #4 [c000001067c27b60] jbd2__journal_start at c008000004d415cc [jbd2] > #5 [c000001067c27be0] update_super_work at c0080000053f9758 [ext4] > #6 [c000001067c27c70] process_one_work at c000000000188790 > #7 [c000001067c27d20] worker_thread at c00000000018973c > #8 [c000001067c27dc0] kthread at c000000000196c84 > #9 [c000001067c27e10] ret_from_kernel_thread at c00000000000cd64 > > Which comes out to > > 382 repeat: > 383 read_lock(&journal->j_state_lock); > * 384 BUG_ON(journal->j_flags & JBD2_UNMOUNT); > 385 if (is_journal_aborted(journal) || > 386 (journal->j_errno != 0 && !(journal->j_flags & JBD2_ACK_ERR))) { > 387 read_unlock(&journal->j_state_lock); > > > Initially this seemed like it should never happen but upon crash > analysis it seems like it could indeed be hit as described in patch 1/2. > > I would like to add that through the logs we only knew that: > > - ext4_journal_bmap -> ext4_map_blocks is failing with EFSCORRUPTED. > - update_super_work had hit the BUG_ON > > I was not able to hit this bug again (without modifying the kernel to > inject errors) but the above backtrace seems to be one possible paths > where this BUG_ON can be hit. Rest of the analysis and fix is in patch > 2/3. Patch 3 is just a small tweak that i found helpful while debugging. > > That being said, journalling is something I'm not very familiar with and > there might be gaps in my understanding so thoughts and suggestions are > welcome. > > Ojaswin Mujoo (3): > ext4: define ext4_journal_destroy wrapper > ext4: avoid journaling sb update on error if journal is destroying > ext4: Make sb update interval tunable > > fs/ext4/ext4.h | 11 +++++++++++ > fs/ext4/ext4_jbd2.h | 22 ++++++++++++++++++++++ > fs/ext4/super.c | 35 +++++++++++++++++------------------ > fs/ext4/sysfs.c | 4 ++++ > 4 files changed, 54 insertions(+), 18 deletions(-) >