On Mon, Jun 25, 2012 at 11:38:38AM -0600, Stefan Priebe wrote:

Am 25.06.2012 16:48, schrieb Josef Bacik:

quoted

On Mon, Jun 25, 2012 at 08:45:02AM -0600, Stefan Priebe - Profihost AG wrote:

quoted

quoted

Thats weird, sysrq+w should have a bunch of stacktraces but it's empty, so
unless theres a bug theres nothing blocked.  Is the box actually hung or is it
just taking forever?  Maybe try sysrq+w again to see if the one you pasted was
just a fluke?  Thanks,

This one looks better:
http://pastebin.com/raw.php?i=R4pztDRt

Ok looks like you have discard turned on.

Yes

 >  Can you turn that off and see if you

quoted

can still reproduce the deadlock?  If so sysrq+w again, if not then I know where
to look ;).  Thanks,

without discard i can't reproduce but random write speed with ceph 
without discard is a LOT slower (around 8000 iops/s instead of 
13000iops/s). So i don't know if it is discard or if i'm just not able 
to trigger it.

Ouch, what kind of drive goes faster with discard _on_?  Anyway it looks like
we're waiting for the discard to come back, so either its your drive or theres a
bug in the block layer.  Maybe try an older kernel and see if it's broken there,
and then bisect it down?  Thanks,

Josef