On Thu, 30 Jun 2011 10:37:51 -0400
Josef Bacik [off-list ref] wrote:

Can you do sysrq+w when this happens?  The caching kthread should still
be able to make progress, which is what we seem to be waiting on.  Does
it eventually unhang and continue on?  Thanks,

Hello,

Unfortunately I already rebooted that server so can't check SysRq+W.
Before the reboot I waited for about 40 minutes, and the block device seemed to be 100% idle during all this time.
I got an advice on IRC to wait for a couple of hours if this happens again, which I am going to try if it does.

-- 
With respect,
Roman