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Date:   Thu, 10 Jan 2019 07:00:02 -0500
To:     Nikolay Borisov <nborisov@suse.com>
Cc:     "Scott E. Blomquist" <sb@techsquare.com>, Jojo <jojo@automatix.de>,
        linux-btrfs@vger.kernel.org
Subject: Re: btrfs hang on nfs?
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Nikolay Borisov writes:
 > > 
 > > Unfortunately the cfq scheduler did not help.  The system wedged.
 > > 
 > > I did notice this for the first time...
 > > 
 > >     [Wed Jan  9 06:03:41 2019] BTRFS info (device sda1): the free space cache file (83320273633280) is invalid, skip it
 > 
 > What you could do is mount btrfs with -o clear_cache to make btrfs
 > rebuild the freespace cache.
 > 
 > > 
 > > anything I should do about that?
 > > 
 > > The messages were similar...
 > > 
 > >     [Wed Jan  9 23:52:04 2019] INFO: task nfsd:2997 blocked for more than 120 seconds.
 > >     [Wed Jan  9 23:52:04 2019]       Not tainted 4.17.14-custom #1
 > >     [Wed Jan  9 23:52:04 2019] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 > >     [stuff deleted]
 > >     [Wed Jan  9 23:54:07 2019] RBP: 00007f0c3f348c60 R08: 00000000000000ff R09: 0000000000001000
 > >     [Wed Jan  9 23:54:07 2019] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000a6672f
 > >     [Wed Jan  9 23:54:07 2019] R13: 00007f0c918affe0 R14: 0000000000000000 R15: 00007f0c918affb0
 > > 
 > 
 > These don't tell the full story, what seems to be happening is that
 > stuff is waiting for transaction to finish but it's not evident which
 > thread is holding the transaction. Please, paste the output of
 > "echo w > /proc/sysrq-trigger" so we have full picture of what's blocked
 > where.
 > 

Thanks.  I have not seen the free space cache message with the new
kernel.

Next time the hang pops up I'll echo w > /proc/sysrq-trigger and send
it along.

I am hoping that the new kernel will magically fix the problem.

Thanks again,

sb. Scott Blomquist