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

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Date:	Wed, 24 Oct 2012 15:30:46 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Nix <nix@...eri.org.uk>
CC:	"Theodore Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Bryan Schumaker <bjschuma@...app.com>,
	Peng Tao <bergwolf@...il.com>, Trond.Myklebust@...app.com,
	gregkh@...uxfoundation.org,
	Toralf Förster <toralf.foerster@....de>
Subject: Re: Apparent serious progressive ext4 data corruption bug in 3.6.3
 (and other stable branches?)

On 10/24/2012 02:49 PM, Nix wrote:
> On 24 Oct 2012, Theodore Ts'o spake thusly:
>> Toralf, Nix, if you could try applying this patch (at the end of this
>> message), and let me know how and when the WARN_ON triggers, and if it
>> does, please send the empty_bug_workaround plus the WARN_ON(1) report.
>> I know about the case where a file system is mounted and then
>> immediately unmounted, but we don't think that's the problematic case.
>> If you see any other cases where WARN_ON is triggering, it would be
>> really good to know....
> 
> Confirmed, it triggers. Traceback below.
> 

<giant snip>

The warn on triggers, but I can't tell - did the corruption still occur
with Ted's patch?

-Eric

> 
> OK. That umount of local filesystems sprayed your added
> empty bug workaround and WARN_ONs so many times that nearly all of them
> scrolled off the screen -- and because syslogd was dead by now and this
> is where my netconsole logs go, they're lost. I suspect every single
> umounted filesystem sprayed one of these (and this happened long before
> any reboot-before-we're-done).
> 
> But I did the old trick of camera-capturing the last one (which was
> probably /boot, which has never got corrupted because I hardly ever
> write anything to it at all). I hope it's more useful than nothing. (I
> can rearrange things to umount /var last, and try again, if you think
> that a specific warning from an fs known to get corrupted is especially
> likely to be valuable.)
> 
> So I see, for one umount at least (and the chunk of the previous one
> that scrolled offscreen is consistent with this):
> 
> jbd2_mark_journal_empty bug workaround (21218, 21219)
> [obscured by light] at fs/jbd2/journal.c:1364 jbd2_mark_journal_empty+06c/0xbd
> ...
> [addresses omitted for sanity: traceback only]
> warn_slowpath_common+0x83/0x9b
> warn_slowpath_null+0x1a/0x1c
> jbd2_mark_journal_empty+06c/0xbd
> jbd2_journal_destroy+0x183/0x20c
> ? abort_exclusive_wait+0x8e/0x8e
> ext4_put_super+0x6c/0x316
> ? evict_inodes+0xe6/0xf1
> generic_shutdown_super+0x59/0xd1
> ? free_vfsmnt+0x18/0x3c
> kill_block_super+0x27/0x6a
> deactivate_locked_super+0x26/0x57
> deactivate_super+0x3f/0x43
> mntput_no_expire+0x134/0x13c
> sys_umount+0x308/0x33a
> system_call_fastpath+0x16/0x1b

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