From: Andreas Dilger <adilger@dilger.ca>
To: Shehbaz Jaffer <shehbazjaffer007@gmail.com>
Cc: linux-ext4@vger.kernel.org
Subject: Re: question about jbd2 checksum v2 and v3 flag
Date: Sun, 25 Aug 2019 21:05:36 -0600 [thread overview]
Message-ID: <FF31C738-6B87-434B-9736-76286ED0F8E3@dilger.ca> (raw)
In-Reply-To: <CAPLK-i8xE4n8BJ-Beu0f80PC2W6b-A30nwcz+V_bCb_iAyB++Q@mail.gmail.com>
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On Aug 16, 2019, at 5:55 PM, Shehbaz Jaffer <shehbazjaffer007@gmail.com> wrote:
>
> Hello,
>
> 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.
>
> 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.
>
> I have 2 questions:
>
> 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
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next prev parent reply other threads:[~2019-08-26 3:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-16 23:55 question about jbd2 checksum v2 and v3 flag Shehbaz Jaffer
2019-08-26 3:05 ` Andreas Dilger [this message]
2019-08-26 16:51 ` Theodore Y. Ts'o
2019-08-26 18:31 ` Darrick J. Wong
2019-08-26 18:56 ` Theodore Y. Ts'o
2019-08-27 20:06 ` Andreas Dilger
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