linux-kernel - Re: Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?)

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Message-ID: <873910xevu.fsf@spindle.srvr.nix>
Date:	Sat, 27 Oct 2012 13:45:25 +0100
From:	Nix <nix@...eri.org.uk>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	Eric Sandeen <sandeen@...hat.com>, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org
Subject: Re: Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?)

[nfs people purged from Cc]

On 27 Oct 2012, Theodore Ts'o verbalised:

> Huh?  It's not turned on by default.  If you mount with no mount
> options, journal checksums are *not* turned on.

?! it's turned on for me, and though I use weird mount options I don't
use that one:

/dev/main/var   /var        ext4        defaults,nobarrier,usrquota,grpquota,nosuid,nodev,relatime,journal_async_commit,commit=30,user_xattr,acl 1  2
Default mount options:    (none)
/dev/mapper/main-var /var ext4 rw,nosuid,nodev,relatime,journal_checksum,journal_async_commit,nobarrier,quota,usrquota,grpquota,commit=30,stripe=16,data=ordered,usrquota,grpquota 0 0

...

Ah! it's turned on by journal_async_commit. OK, that alone argues
against use of journal_async_commit, tested or not, and I'd not have
turned it on if I'd noticed that.

(So, the combinations I'll be trying for effect on this bug are:

 journal_async_commit (as now)
 journal_checksum
 none

Technically to investigate all possibilities we should try
journal_async_commit,no_journal_checksum, but this seems so unlikely to
have ever been tested by anyone that it's not worth looking into...)

-- 
NULL && (void)
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