Message-ID: <20120611091338.1c88e6d0@corrin.poochiereds.net>
Date:	Mon, 11 Jun 2012 09:13:38 -0400
From:	Jeff Layton <jlayton@...hat.com>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	bfields <bfields@...ldses.org>,
	"Myklebust, Trond" <Trond.Myklebust@...app.com>,
	Joerg Platte <jplatte@...sa.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	Hans de Bruin <jmdebruin@...net.nl>
Subject: Re: Kernel 3.4.X NFS server regression

On Mon, 11 Jun 2012 08:39:32 -0400
Jeff Layton <jlayton@...hat.com> wrote:

> On Mon, 11 Jun 2012 08:16:34 -0400
> bfields <bfields@...ldses.org> wrote:
> 
> > On Sun, Jun 10, 2012 at 03:00:42PM +0000, Myklebust, Trond wrote:
> > > Cc: linux-nfs@...r.kernel.org + bfields and changing title to label it
> > > as a server regression since that is what the trace appears to imply.
> > > 
> > > On Sun, 2012-06-10 at 12:56 +0200, Joerg Platte wrote:
> > > > All 3.4 kernels I tried so far (3.4, 3.4.1 and 3.4.2) suffer from the 
> > > > same NFS related problem:
> > > > 
> > > > Jun 10 09:23:36 coco kernel: INFO: task kworker/u:1:8 blocked for more 
> > > > than 120 seconds.
> > > > Jun 10 09:23:36 coco kernel: "echo 0 > 
> > > > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > > > Jun 10 09:23:36 coco kernel: kworker/u:1     D 002ba28c     0     8 
> > > >   2 0x00000000
> > > > Jun 10 09:23:36 coco kernel:  df465ec0 00000046 00000005 002ba28c 
> > > > 00000000 0000000a 00000282 df465e70
> > > > Jun 10 09:23:36 coco kernel:  df465ec0 df44d2b0 ffff6b60 df465e84 
> > > > df44d2b0 e33fa6b3 00000282 de764ae0
> > > > Jun 10 09:23:36 coco kernel:  ffffffff d78bcfb8 df465e8c c012e0f6 
> > > > df465ea4 c013610c 00000000 d78bcf80
> > > > Jun 10 09:23:36 coco kernel: Call Trace:
> > > > Jun 10 09:23:36 coco kernel:  [<c012e0f6>] ? add_timer+0x11/0x17
> > > > Jun 10 09:23:36 coco kernel:  [<c013610c>] ? queue_delayed_work_on+0x74/0xf0
> > > > Jun 10 09:23:36 coco kernel:  [<c0136ba4>] ? queue_delayed_work+0x1b/0x28
> > > > Jun 10 09:23:36 coco kernel:  [<c0350f5b>] schedule+0x1d/0x4c
> > > > Jun 10 09:23:36 coco kernel:  [<e0cda5f1>] cld_pipe_upcall+0x4e/0x75 [nfsd]
> > > > Jun 10 09:23:36 coco kernel:  [<e0cda678>] 
> > > > nfsd4_cld_grace_done+0x60/0x99 [nfsd]
> > > > Jun 10 09:23:36 coco kernel:  [<e0cd9cb5>] 
> > > > nfsd4_record_grace_done+0x10/0x12 [nfsd]
> > > > Jun 10 09:23:36 coco kernel:  [<e0cd6696>] laundromat_main+0x291/0x2d8 
> > > > [nfsd]
> > > > Jun 10 09:23:36 coco kernel:  [<c0136d2f>] process_one_work+0xff/0x325
> > > > Jun 10 09:23:36 coco kernel:  [<c0134bec>] ? start_worker+0x20/0x23
> > > > Jun 10 09:23:36 coco kernel:  [<e0cd6405>] ? 
> > > > nfsd4_process_open1+0x32b/0x32b [nfsd]
> > > > Jun 10 09:23:36 coco kernel:  [<c013727a>] worker_thread+0xf4/0x39a
> > > > Jun 10 09:23:36 coco kernel:  [<c0137186>] ? rescuer_thread+0x231/0x231
> > > > Jun 10 09:23:36 coco kernel:  [<c013a556>] kthread+0x6c/0x6e
> > > > Jun 10 09:23:36 coco kernel:  [<c013a4ea>] ? kthreadd+0xe8/0xe8
> > > > Jun 10 09:23:36 coco kernel:  [<c035263e>] kernel_thread_helper+0x6/0xd
> > > > 
> > > > A kworker task is stuck in D state and nfs mounts from other clients do 
> > > > not work at all. This happens only on one machine, another one with the 
> > > > same kernel (same self compiled Debian package) works. All previous 3.3 
> > > > kernels work as well.
> > > > 
> > > > Since this machine is remote it is not that easy to bisect to find the 
> > > > bad commit. Are there any other things I can try?
> > 
> > If you create a directory named /var/lib/nfs/v4recovery/, does the
> > problem go away?
> > 
> > My guess would be that it's trying to upcall to the new reboot-recovery
> > state daemon, and you don't have that running.
> > 
> > Before the addition of that upcall state was kept in
> > /var/lib/nfs/v4recovery.  So we decide whether to use the old method or
> > the new one by checking for the existance of that path.
> > 
> > But I'm guessing we were wrong to assume that existing setups that
> > people perceived as working would have that path, because the failures
> > in the absence of that path were probably less obvious.
> > 
> > --b.
> 
> This sounds like the same problem that Hans reported as well. I've not
> been able to reproduce that so far. Here's what I get when I start nfsd
> with no v4recoverdir and nfsdcld isn't running:
> 
> [  109.715080] NFSD: starting 90-second grace period
> [  229.984220] NFSD: Unable to end grace period: -110
> 
> What I don't quite understand is why the queue_timeout job isn't
> getting run here. What should happen is that 30s after upcall,
> rpc_timeout_upcall_queue should run. The message will be found to be
> still sitting on the , so it should set its status to -ETIMEDOUT
> and wake up the caller.
> 
> I can only assume that the queue_timeout job isn't getting run for some
> reason, but I'm unclear on why that would be.
> 

Ahh, I think I see the bug. From rpc_timeout_upcall_queue:

-----------------------[snip]--------------------------
        dentry = dget(pipe->dentry);
        spin_unlock(&pipe->lock);
        if (dentry) {
                rpc_purge_list(&RPC_I(dentry->d_inode)->waitq,
                               &free_list, destroy_msg, -ETIMEDOUT);
                dput(dentry);
        }
-----------------------[snip]--------------------------

...when there is no dentry (as there wouldn't be when rpc_pipefs isn't
mounted), then the rpc_purge_list won't run. FWIW, you'd probably see
similar problems if you attempted a sec=krb5 mount without having
rpc_pipefs mounted.

I'm still looking at the code to see what the right fix is. For now,
making sure you have a /var/lib/nfs/v4recoverydir is probably the
easiest workaround.

-- 
Jeff Layton <jlayton@...hat.com>
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