Re: Need help debugging NFS issues new to 4.20 kernel

Sasha Levin
2019-01-26T17:59:16Z

On Fri, Jan 25, 2019 at 07:13:27PM +0000, Schumaker, Anna wrote:
>On Thu, 2019-01-24 at 19:58 +0000, Trond Myklebust wrote:
>> On Thu, 2019-01-24 at 11:32 -0600, Jason L Tibbitts III wrote:
>> > I could use some help figuring out the cause of some serious NFS
>> > client
>> > issues I'm having with the 4.20.3 kernel which I did not see under
>> > 4.19.15.
>> >
>> > I have a network of about 130 desktops (plus a bunch of other
>> > machines,
>> > VMs and the like) running Fedora 29 connecting to six NFS servers
>> > running CentOS 7.6 (with the heavily patched vendor kernel
>> > 3.10.0-957.1.3). All machines involved are x86_64. We use
>> > kerberized
>> > NFS4 with generally sec=krb5i. The exports are generally made with
>> > "(rw,async,sec=krb5i:krb5p)".
>> >
>> > Since I booted those clients into 4.20.3 I've started seeing
>> > processes
>> > getting stuck in the D state. The system itself will seem OK (except
>> > for the high load average) as long as I don't touch the hung NFS
>> > mount.
>> > Nothing was logged to dmesg or to the journal. So far booting back
>> > into
>> > the 4.19.15 kernel has cleared up the problem. I cannot yet
>> > reproduce
>> > this on demand; I've tried but it is probably related to some
>> > specific
>> > usage pattern.
>> >
>> > Has anyone else seen issues like this? Can anyone help me to get
>> > more
>> > useful information that might point to the problem? I still haven't
>> > learned how to debug NFS issues properly. And if there's a stress
>> > test
>> > tool I could easily run that might help to reproduce the issue, I'd
>> > be
>> > happy to run it.
>> >
>> > I note that 4.20.4 is out; I see one sunrpc fix which I guess could
>> > be
>> > related (sunrpc: handle ENOMEM in rpcb_getport_async) but the systems
>> > involved have plenty of free memory so I doubt that's it. I'll
>> > certainly try it anyway.
>> >
>> > Various package versions:
>> > kernel-4.20.3-200.fc29.x86_64 (the problematic kernel)
>> > kernel-4.19.15-300.fc29.x86_64 (the functional kernel)
>> > nfs-utils-2.3.3-1.rc2.fc29.x86_64
>> > gssproxy-0.8.0-6.fc29.x86_64
>> > krb5-libs-1.16.1-25.fc29.i686
>> >
>> > Thanks in advance for any help or advice,
>> >
>> > - J<
>>
>> Commit deaa5c96c2f7 ("SUNRPC: Address Kerberos performance/behavior
>> regression") was supposed to be marked for stable as a fix. Chuck &
>> Anna?
>
>Looks like I missed that, sorry!
>
>Stable folks, can you please backport deaa5c96c2f7 ("SUNRPC: Address Kerberos
>performance/behavior regression") to v4.20?

Queued for 4.20, thank you.

--
Thanks,
Sasha