From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4E6CD23EAA6 for ; Mon, 3 Nov 2025 21:37:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762205869; cv=none; b=ZZOjbz/J/dDUbCTtbb4jOSf1VVmnEFWK8BaR6L3+C739y5psqSAZXRdJFwxwXyq4lYZ6I2TFJ930IZRRzyUYBuMaD45bDuw/CHU5BZAc1NWsmEhs7dlY4iF1vSFAmZ8tFCwyo47TCPs6OsCJOdlk1eilQTjntxoyeb/m0OgWzPg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762205869; c=relaxed/simple; bh=Yp95Cm2/IEal6SUf7o8oFxPKOXWxIABtmRachxH93OU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=A5bsRI1RmIZpmT+VKEQu/gcI60aZhhoVRDqsUGX9xg0FTkrIU7Y3AK5f6ywnHtz2kDf4iCw4mgedKRp0LctS60VXvrht9X3pbXhYeFU4mGba0VRAVSS/I18/cYB4ybX+WkjJiD2BwEON8CxtgJ+Ca4K5KVaH9wxllBjrAArUrfE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HEsRVN4H; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HEsRVN4H" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED149C4CEE7; Mon, 3 Nov 2025 21:37:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762205869; bh=Yp95Cm2/IEal6SUf7o8oFxPKOXWxIABtmRachxH93OU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=HEsRVN4HQghsYTREY4QO1w5dBJ+h91YvLf5nm0yJyLyT4NlhV9L7SSoLvwwgSA1vD KBcCbVxOh5uWdMKXZPzn61jwgyWWqu9c9PuGmOTP/aBfk83IJC4aQcrxbLsNZsg/mh ZYFgHFj1zogc5ItUM2Zif1vTe5V8UO+1d0dnlBcKeG+jigw4u8C15OO5WJz2E8+kNx iYQAuB7E0UJA/Qh7MWoSWkN2IC+PwnvuPa6buE/fQ/aC4LdcrCFX1kSpfrYITVRtMp nVd/5x+7bywSKLurr/JXv2DC1LIbuyMygSyuSk4XeIiGu4g8+/4y8txgiqLZ4uoKE/ 0Et08Kqfm1Rmg== Date: Mon, 3 Nov 2025 13:37:48 -0800 From: "Darrick J. Wong" To: Ye Bin Cc: tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, jack@suse.cz Subject: Re: [PATCH v2] jbd2: fix the inconsistency between checksum and data in memory for journal sb Message-ID: <20251103213748.GA196358@frogsfrogsfrogs> References: <20251103010123.3753631-1-yebin@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251103010123.3753631-1-yebin@huaweicloud.com> On Mon, Nov 03, 2025 at 09:01:23AM +0800, Ye Bin wrote: > From: Ye Bin > > Copying the file system while it is mounted as read-only results in > a mount failure: > [~]# mkfs.ext4 -F /dev/sdc > [~]# mount /dev/sdc -o ro /mnt/test > [~]# dd if=/dev/sdc of=/dev/sda bs=1M > [~]# mount /dev/sda /mnt/test1 > [ 1094.849826] JBD2: journal checksum error > [ 1094.850927] EXT4-fs (sda): Could not load journal inode > mount: mount /dev/sda on /mnt/test1 failed: Bad message > > The process described above is just an abstracted way I came up with to > reproduce the issue. In the actual scenario, the file system was mounted > read-only and then copied while it was still mounted. It was found that > the mount operation failed. The user intended to verify the data or use > it as a backup, and this action was performed during a version upgrade. > Above issue may happen as follows: > ext4_fill_super > set_journal_csum_feature_set(sb) > if (ext4_has_metadata_csum(sb)) > incompat = JBD2_FEATURE_INCOMPAT_CSUM_V3; > if (test_opt(sb, JOURNAL_CHECKSUM) > jbd2_journal_set_features(sbi->s_journal, compat, 0, incompat); > lock_buffer(journal->j_sb_buffer); > sb->s_feature_incompat |= cpu_to_be32(incompat); > //The data in the journal sb was modified, but the checksum was not > updated, so the data remaining in memory has a mismatch between the > data and the checksum. > unlock_buffer(journal->j_sb_buffer); > > In this case, the journal sb copied over is in a state where the checksum > and data are inconsistent, so mounting fails. > To solve the above issue, update the checksum in memory after modifying > the journal sb. > > Fixes: 4fd5ea43bc11 ("jbd2: checksum journal superblock") > Signed-off-by: Ye Bin Looks fine to me, Reviewed-by: "Darrick J. Wong" --D > --- > fs/jbd2/journal.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c > index d480b94117cd..bf255f8b5eeb 100644 > --- a/fs/jbd2/journal.c > +++ b/fs/jbd2/journal.c > @@ -2349,6 +2349,12 @@ int jbd2_journal_set_features(journal_t *journal, unsigned long compat, > sb->s_feature_compat |= cpu_to_be32(compat); > sb->s_feature_ro_compat |= cpu_to_be32(ro); > sb->s_feature_incompat |= cpu_to_be32(incompat); > + /* > + * Update the checksum now so that it is valid even for read-only > + * filesystems where jbd2_write_superblock() doesn't get called. > + */ > + if (jbd2_journal_has_csum_v2or3(journal)) > + sb->s_checksum = jbd2_superblock_csum(sb); > unlock_buffer(journal->j_sb_buffer); > jbd2_journal_init_transaction_limits(journal); > > @@ -2378,9 +2384,17 @@ void jbd2_journal_clear_features(journal_t *journal, unsigned long compat, > > sb = journal->j_superblock; > > + lock_buffer(journal->j_sb_buffer); > sb->s_feature_compat &= ~cpu_to_be32(compat); > sb->s_feature_ro_compat &= ~cpu_to_be32(ro); > sb->s_feature_incompat &= ~cpu_to_be32(incompat); > + /* > + * Update the checksum now so that it is valid even for read-only > + * filesystems where jbd2_write_superblock() doesn't get called. > + */ > + if (jbd2_journal_has_csum_v2or3(journal)) > + sb->s_checksum = jbd2_superblock_csum(sb); > + unlock_buffer(journal->j_sb_buffer); > jbd2_journal_init_transaction_limits(journal); > } > EXPORT_SYMBOL(jbd2_journal_clear_features); > -- > 2.34.1 > >