Re: BTRFS BUG at insert_inline_extent_backref+0xe3/0xf0 while rebalancing

["Stéphane Lesimple" <stephane_btrfs@lesimple.fr>]

Le 2015-10-22 10:53, Filipe Manana a écrit :
> On Thu, Oct 22, 2015 at 6:32 AM, Erkki Seppala <flux-btrfs@inside.org> 
> wrote:
>> Hello,
>> 
>> Recently I added daily rebalancing to my cron.d (after finding myself 
>> in
>> the no-space-situation), and not long after that, I found my PC had
>> crashed over night. Having no sign in the logs anywhere (not even over
>> network even though there should be) I had nothing to go on, but this
>> night it crashed again after starting the rebalance, and this time 
>> there
>> was some information on the kernel log.
>> 
>> Kernel version: 4.2.3 (package linux-image-4.2.0-1-amd64 version 
>> 4.2.3-1
>> from Debian Unstable)
>> 
>> The dump is available at:
>> 
>>   http://www.modeemi.fi/~flux/btrfs/btrfs-BUG-2015-10-55.txt
>> 
>> The log is available as well (stripped some unrelated USB- and 
>> firewall
>> logging, showing that last evening there was some kernel task hung for
>> 120 seconds; but it's in another btrfs filesystem and is another 
>> story):
>> 
>>   http://www.modeemi.fi/~flux/btrfs/btrfs-2015-10-55.txt
>> 
>> I'm not quite sure which of the btrfs balance commands caused the
>> issue. But there is my script:
>> 
>> #!/bin/sh
>> fs="$1"
>> if [ -z "$fs" ]; then
>>   echo usage: btrfs-balance / 0 1 5 10 20 50
>>   exit 1
>> fi
>> fs="$1"
>> shift
>> for usage in d m; do for a in "$@"; do date; /bin/btrfs balance start
>> "$fs" -v -${usage}usage=$a; done; done
>> 
>> And it was started at 07:30 with:
>> 
>>   /usr/local/sbin/btrfs-balance / 0 1 2 5 10 20 30 50 70
>> 
>> I should add that the filesystem in question is backed by MD RAID10 
>> and
>> that is backed by four SSDs, so it's reasonably fast in IO, if that
>> affects anything. There should have been no much competing IO at the
>> time of the occurrence.
>> 
>> Before Duncan asks ;-), I only have a moderate number of subvolumes 
>> and
>> snapshots, ie. one subvolume for each of /, /var/log/journal and 
>> /home,
>> 24 snapshots of / and /home plus <10 snapshots of /.
>> 
>> Before that balance there was another balance on a another BTRFS 
>> RAID10,
>> but given the time stamp I think I can easily say it wasn't the cause.
>> 
>> I don't really have other 'solutions' than disabling the rebalancing 
>> for
>> the time being, and only use it as-needed as I had earlier done..
> 
> Try this (just sent a few minutes ago):
> https://patchwork.kernel.org/patch/7463161/


Awesome, I'll also try it right now under 4.3.0-rc6. My system is 
currently hit so hard by this bug that it no longer survives a balance 
for longer than a few minutes.

Will keep you posted on the outcome.

Thanks,

-- 
Stéphane.