Re: hard freezes with 3.9.0 during io-intensive loads

[Kai Krakow <hurikhan77+btrfs@gmail.com>]

Jan Schmidt <list.btrfs@jan-o-sch.net> schrieb:

>>>> Apparently, it's not fixed. The system does not freeze now but it threw
>>>> multiple backtraces right in front of my Xorg session. The backtraces
>>>> look a little bit different now. Here's what I got:
>>>>
>>>> https://gist.github.com/kakra/8a340f006d01e146865d
>>>>
>>>> Occurence while running "bedup dedup --defrag --size-cutoff
>>>> $((1024*1024))" which was currently dedup'ing my backup volume with
>>>> daily snapshots filled by "rsync --inplace" - so I suppose some file
>>>> contents are pretty scattered.
>>>
>>> At least that looks different for now. I'm not certain about all the
>>> fixes in btrfs-next. Can you give it a try and bisect if btrfs-next is
>>> good? That would be really helpful.
>> 
>> I'd prefer to not bisect my production system kernel... That will
>> probably take ages as running the "reproducable test" takes about 30-60
>> minutes before the problem hits my system. At least unless you had a
>> suggestion how to speed up the process... ;-)
> 
> I see, hoped it would be something quicker.
> 
>> I saw the pull request with those fixes, so I supsect it didn't go into
>> 3.9.1 but rather will go into 3.9.2?
> 
> Probably. However, those patches obviously weren't enough to solve your
> problem. We don't submit a lot of things to stable, so they are likely to
> remain the only btrfs related changes in there, which would mean it is
> unlikely to help with your problem.

I turned off autodefrag which fixes these problems. So without bisect I can 
at least say the problem is probably somewhere in the new snapshot-aware 
defragmentation code which came with 3.9.0 or related to the introduction of 
the same.

3.9.2 still does not fix anything. I'll go with autodefrag=off for the 
moment until I hear some news in that regard. With this new information, is 
it still helpful to get a metadata image from me? It should be reproducable 
if you enable autodefrag or defragment cow'ed files.

Regards,
Kai