On 10/24/2012 02:49 PM, Nix wrote:

On 24 Oct 2012, Theodore Ts'o spake thusly:

quoted

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