From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) (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 30F261AB6F2; Thu, 26 Sep 2024 09:28:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727342898; cv=none; b=PB43eQTwYyn0QFSca1k7Btj8iTlwLg8GqQEFrY//ui0J0ScVgbCSar9sU3RYpsjXPHfd0ENWF1lvlFHLlSRxws8TXu3A3c0sVp64hidu0H38dTKAAJmWRqHxnpYjc4Fcl77xIK1WebNgypM6rq+gjmyrg6OdI6bXU3RvdJxWaU8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727342898; c=relaxed/simple; bh=EDht8aYisYAcI7n+B9DfXTXswUoogYDJgicgfThstww=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=hx0kWE8jXjAEjqdfOId3XGEYK7VRN8a4jwa9OJh/zFruf3OVIj1VMGpBaLppPM6LJNonFbcTYGi42V9mCBN5ZBYJ2QdQlEUwQhKae2vePkxoRZlmBn7haykAVrYZ7jw6uRjA1BKuNQFfT9mGk5yVNSQcbVWundiF1/KzyQtKegg= 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=45.249.212.187 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 [172.19.88.105]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4XDpBs5d7Hz10McL; Thu, 26 Sep 2024 17:26:45 +0800 (CST) Received: from dggpeml100021.china.huawei.com (unknown [7.185.36.148]) by mail.maildlp.com (Postfix) with ESMTPS id 495EF1401F0; Thu, 26 Sep 2024 17:28:12 +0800 (CST) Received: from [127.0.0.1] (10.174.177.174) by dggpeml100021.china.huawei.com (7.185.36.148) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Thu, 26 Sep 2024 17:28:11 +0800 Message-ID: <52f055eb-a828-45cd-a06d-ca2006321926@huawei.com> Date: Thu, 26 Sep 2024 17:28:11 +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 1/1] ext4: fix crash on BUG_ON in ext4_alloc_group_tables To: Aleksandr Mikhalitsyn CC: Jan Kara , , , Andreas Dilger , =?UTF-8?Q?St=C3=A9phane_Graber?= , Christian Brauner , , , , Wesley Hershberger , Yang Erkun References: <20240925143325.518508-1-aleksandr.mikhalitsyn@canonical.com> <20240925143325.518508-2-aleksandr.mikhalitsyn@canonical.com> <20240925155706.zad2euxxuq7h6uja@quack3> <142a28f9-5954-47f6-9c0c-26f7c142dbc1@huawei.com> Content-Language: en-US From: Baokun Li In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpeml100021.china.huawei.com (7.185.36.148) On 2024/9/26 17:16, Aleksandr Mikhalitsyn wrote: > On Thu, Sep 26, 2024 at 10:29 AM Baokun Li wrote: >> On 2024/9/25 23:57, Jan Kara wrote: >>> On Wed 25-09-24 16:33:24, Alexander Mikhalitsyn wrote: >>>> [ 33.882936] EXT4-fs (dm-5): mounted filesystem 8aaf41b2-6ac0-4fa8-b92b-77d10e1d16ca r/w with ordered data mode. Quota mode: none. >>>> [ 33.888365] EXT4-fs (dm-5): resizing filesystem from 7168 to 786432 blocks >>>> [ 33.888740] ------------[ cut here ]------------ >>>> [ 33.888742] kernel BUG at fs/ext4/resize.c:324! >>> Ah, I was staring at this for a while before I understood what's going on >>> (it would be great to explain this in the changelog BTW). As far as I >>> understand commit 665d3e0af4d3 ("ext4: reduce unnecessary memory allocation >>> in alloc_flex_gd()") can actually make flex_gd->resize_bg larger than >>> flexbg_size (for example when ogroup = flexbg_size, ngroup = 2*flexbg_size >>> - 1) which then confuses things. I think that was not really intended and >>> instead of fixing up ext4_alloc_group_tables() we should really change >>> the logic in alloc_flex_gd() to make sure flex_gd->resize_bg never exceeds >>> flexbg size. Baokun? >>> >>> Honza >> Hi Honza, >> >> Your analysis is absolutely correct. It's a bug! >> Thank you for locating this issue！ >> An extra 1 should not be added when calculating resize_bg in >> alloc_flex_gd(). >> >> >> Hi Aleksandr, > Hi Baokun, > >> Could you help test if the following changes work? > I can confirm that this patch helps. > > Tested-by: Alexander Mikhalitsyn > > Kind regards, > Alex Thank you for the test! Cheers, Baokun >> >> Thanks, >> Baokun >> >> --- >> >> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c >> index e04eb08b9060..1f01a7632149 100644 >> --- a/fs/ext4/resize.c >> +++ b/fs/ext4/resize.c >> @@ -253,10 +253,12 @@ static struct ext4_new_flex_group_data >> *alloc_flex_gd(unsigned int flexbg_size, >> /* Avoid allocating large 'groups' array if not needed */ >> last_group = o_group | (flex_gd->resize_bg - 1); >> if (n_group <= last_group) >> - flex_gd->resize_bg = 1 << fls(n_group - o_group + 1); >> + flex_gd->resize_bg = 1 << fls(n_group - o_group); >> else if (n_group - last_group < flex_gd->resize_bg) >> - flex_gd->resize_bg = 1 << max(fls(last_group - o_group + 1), >> + flex_gd->resize_bg = 1 << max(fls(last_group - o_group), >> fls(n_group - last_group)); >> >> flex_gd->groups = kmalloc_array(flex_gd->resize_bg, >> sizeof(struct ext4_new_group_data), >>