From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.163.com (m16.mail.163.com [117.135.210.4]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D8CB4328B6; Fri, 11 Oct 2024 06:18:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=117.135.210.4 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728627503; cv=none; b=Swqt3JcSpzKgrgdZQzeXJKWCF4Wp+zmVwPuoIbuKDJhHXw4XPcjiI82Y2RqOtLmaiGG5jjvcr5vX18Ul9IEDJERKHpTErTUiZjH3jjHRjr8bJrqtxB23Y79WnWHp05OakGYbLE81LrY+NJI6besxbmQkSW9Ns9ipT/BZQkw2iK8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728627503; c=relaxed/simple; bh=eO3/CiHURI2AIuuoUgMs66MWLroRYMhaRhQD3hiw9CQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KOxyA42T+VTSLtuCyJFHiHRQqO/CjgQcY5oIcj6xsmaq2e/YiC3HXZW3qzpiNtU4r0hBdanW9vpn5Q81k1lXvpXz18blkUJeAA5SySVRzjy0HiEPHGnpI1EebGVusvlSv5kTZ7gxTeK71K1LqY+XkZJhAt+F7RfyhGS68Fj1E4Y= 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=mJm14Gq+; arc=none smtp.client-ip=117.135.210.4 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="mJm14Gq+" 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=RpJz4KKgLgp+St5K7RZyZ9YL3L6T8JAC/gWa6Q+sU1o=; b=mJm14Gq+alijs6afIQltJSEOdyyaxvQ8HQJwP9tNklbSBDGsiB64D1B6bnzj6t r4U4ehrUpmnGYlDhRQPPuQ0bJKD2q3WQomzkCAjroeB6ZjGfoC8zV1OhwGmbGzR4 lsCJ7CbPqX7OXyBRFwRFcfvdx2AmDFEcoqyIyYjfCsXq4= Received: from [192.168.22.184] (unknown [223.70.253.255]) by gzga-smtp-mtada-g0-1 (Coremail) with SMTP id _____wDHr04awwhnriCrAQ--.44184S2; Fri, 11 Oct 2024 14:18:03 +0800 (CST) Message-ID: <2635f3f9-86e1-4d09-ad40-4e02ac4447c5@163.com> Date: Fri, 11 Oct 2024 14:18:01 +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> From: liubaolin In-Reply-To: <20241010092923.r53povuflevzhxrw@quack3> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wDHr04awwhnriCrAQ--.44184S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxZFy3WFWDXFy7GFWftFy3XFb_yoWrCF43pr W5K345KrWqgry29Fs2qF4fXFy0gw18GrW7GrWfKryFy3y5WFn2qryrtrn8AF1qyrZ3uwn5 Zr4UAF9Fk3Wjv37anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07U3-BiUUUUU= X-CM-SenderInfo: xolxutxrol0iasrtmqqrwthudrp/1tbiLgR1ymcIwv0ClgAAsR > 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. > > 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. > bh->b_this_page is a circular list for managing all bh on the same page. > After get_block jumps out of the for loop, then bh->b_this_page is not processed by clear new in the for loop. > So after calling ext4_journalled_zero_new_buffers, > The ext4_journalled_zero_new_buffers function will determine all bh of the same page and call write_end_fn if they are in new state, > get_block returns err's bh->b_this_page and circular list other unhandled bh if the state was previously set to new. > Because bh not get access, the corresponding transaction is not placed in jh->b_transaction, resulting in a crash. > > Therefore, the patch processing method I submit is to make unprocessed bh determines if it is in new state and get access. > There is another way to handle the remaining bh clear_buffer_new that is not processed. > I personally recommend get access this way, the impact is small. > Please guide the two processing methods, which one do you recommend? 在 2024/10/10 17:29, Jan Kara 写道: > On Thu 10-10-24 10:58:55, Baolin Liu wrote: >> From: Baolin Liu >> >> Since the merge of commit 3910b513fcdf ("ext4: persist the new uptodate >> buffers in ext4_journalled_zero_new_buffers"), a new assertion failure >> occurred under a old kernel(ext3, data=journal, pagesize=64k) with >> corresponding ported patches: > ... >> which was caused by bh dirting without calling >> do_journal_get_write_access(). >> >> In the loop for all bhs of a page in ext4_block_write_begin(), >> when a err occurred, it will jump out of loop. >> But that will leaves some bhs being processed and some not, >> which will lead to the asserion failure in calling write_end_fn(). > > Thanks for the patch but I don't understand one thing here: For > ext4_journalled_zero_new_buffers() to call write_end_fn() the buffer must > have buffer_new flag set. That flag can get set only by ext4_get_block() > function when it succeeds in which case we also call > do_journal_get_write_access(). So how is it possible that buffer_new was > set on a buffer on which we didn't call do_journal_get_write_access()? This > indicates there may be some deeper problem hidden. How exactly did you > trigger this problem? > > Honza > >> >> To fixed that, get write access for the rest unprocessed bhs, just >> as what write_end_fn do. >> >> Fixes: 3910b513fcdf ("ext4: persist the new uptodate buffers in ext4_journalled_zero_new_buffers") >> Reported-and-tested-by: Zhi Long >> Suggested-by: Shida Zhang >> Signed-off-by: Baolin Liu >> --- >> fs/ext4/inode.c | 17 ++++++++++++++++- >> 1 file changed, 16 insertions(+), 1 deletion(-) >> >> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c >> index 54bdd4884fe6..a72f951288e4 100644 >> --- a/fs/ext4/inode.c >> +++ b/fs/ext4/inode.c >> @@ -1102,9 +1102,24 @@ int ext4_block_write_begin(handle_t *handle, struct folio *folio, >> err = -EIO; >> } >> if (unlikely(err)) { >> - if (should_journal_data) >> + if (should_journal_data) { >> + if (bh != head || !block_start) { >> + do { >> + block_end = block_start + bh->b_size; >> + >> + if (buffer_new(bh)) >> + if (block_end > from && block_start < to) >> + do_journal_get_write_access(handle, >> + inode, bh); >> + >> + block_start = block_end; >> + bh = bh->b_this_page; >> + } while (bh != head); >> + } >> + >> ext4_journalled_zero_new_buffers(handle, inode, folio, >> from, to); >> + } >> else >> folio_zero_new_buffers(folio, from, to); >> } else if (fscrypt_inode_uses_fs_layer_crypto(inode)) { >> -- >> 2.39.2 >>