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[70.77.216.213]) by smtp.gmail.com with ESMTPSA id d129sm9409948pfc.168.2019.08.25.20.05.40 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 25 Aug 2019 20:05:40 -0700 (PDT) From: Andreas Dilger Message-Id: Content-Type: multipart/signed; boundary="Apple-Mail=_2D7617C9-7671-4181-8623-2CDE31F792D1"; protocol="application/pgp-signature"; micalg=pgp-sha256 Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) Subject: Re: question about jbd2 checksum v2 and v3 flag Date: Sun, 25 Aug 2019 21:05:36 -0600 In-Reply-To: Cc: linux-ext4@vger.kernel.org To: Shehbaz Jaffer References: X-Mailer: Apple Mail (2.3273) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org --Apple-Mail=_2D7617C9-7671-4181-8623-2CDE31F792D1 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii On Aug 16, 2019, at 5:55 PM, Shehbaz Jaffer = wrote: >=20 > Hello, >=20 > I am trying to understand jbd2 checksumming procedure. I reboot ext4 > in the middle of a metadata intensive operation using echo b> > /proc/sysrq-trigger. I see that the journal gets replayed on next > mount using prinks in jbd2/recovery.c: do_one_pass() function. >=20 > I then corrupt intermediate metadata logged on jbd2 and I still see > the journal being replayed without multiple error messages which > should ideally get printed when one of the two following flags - > JBD2_FEATURE_INCOMPAT_CSUM_V2 or JBD2_FEATURE_INCOMPAT_CSUM_V3 are > set. >=20 > I have 2 questions: >=20 > 1. Are the two flags: JBD2_FEATURE_INCOMPAT_CSUM_V2 and > JBD2_FEATURE_INCOMPAT_CSUM_V3 set by default? If not, how do we set > them so that the journal will detect and respond to injected > corruptions? See set_journal_csum_feature_set() for details on how these flags are = set. > 2. this is very naive question, but what do compat and incompat > options mean? If flag X in incompat is set, does this mean the feature > does not exist? See description of the compat/incompat/ro_compat fields at: https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout#The_Super_Block Cheers, Andreas --Apple-Mail=_2D7617C9-7671-4181-8623-2CDE31F792D1 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iQIzBAEBCAAdFiEEDb73u6ZejP5ZMprvcqXauRfMH+AFAl1jTIAACgkQcqXauRfM H+CSuw/+L6P9LCAX8Ops0SwB3z0BRzmJ1AQAOjexJ0sAbu86uFz8rdSGhrWo32H+ J/sPn75DNkXeZemwIm5luN3Mz17SpVCTzSzicGqmc8c+ULOWAM4fUEmGSPxWNFXC oaUfUHzD1HesI1XsU0kHbFeyJj+dLquKv6JM+V9fx/nPDfiNK2vtqnazqIovV05I 2ylNwn2aYbHoUNszjCHwe15MIjE2iWF1VNFeQ+lKLgBhY76iKA/nVIStx54I8R5B xzpFIrXed+OQRMRYF05n4oQu7WI5tFOCD2v/x1iGmwKJ4q7KnN/RkA/C9VqGyU3d NC6ucr77wzu13EDOviwdku5KSYIu1ezf3WuO9/3puyt8BTeveKVnFeCkr1MYOTW2 IRYE/yIEm0qPIqRlRoLZXq+sGRlv5GpajhkHtG/GxmlZOqPhP8p08bqll3pFi9xW gzNPgKHlWHnTjzVNqq9ElkxBTU8bW8RGypDmF0h+9nBsBH9nG2g76RT766d+2VQU NGIANP6e6D1y2F1XjscKP+lPhkYLv9vF47fewkwrufIz0p6C6zQpnb1OVzfJgcSp /EycehQyzXluN6P29oqKsHppMCHhYgp/z+ds4DOx/tQ2Pqf5692N3vG54tNKeZYK YczribrV7cqtthHiZWyq3mJ3VxT72Pf5S1h97BZVdxsQryzTS0k= =wr7g -----END PGP SIGNATURE----- --Apple-Mail=_2D7617C9-7671-4181-8623-2CDE31F792D1--