NFS Mount Hangs

Wed Mar 17 22:17:18 UTC 2021

Thank you for the responses.
The NFS Client does properly negotiate down to 128K for the rsize and wsize.

The client port should be changing as we are using the noresvport option.

On the NFS Client
cat /proc/mounts
nfs-server.domain.com:/data /mnt/data nfs4 rw,relatime,vers=4.1,rsize=131072,wsize=131072,namlen=255,hard,noresvport,proto=tcp,timeo=600,retrans=2,sec=krb5,clientaddr=NFS.Client.IP.X,lookupcache=pos,local_lock=none,addr=NFS.Server.IP.X 0 0

When the issue occurs, this is what I see on the NFS Server.
tcp4       0      0 NFS.Server.IP.X.2049      NFS.Client.IP.X.51550     CLOSE_WAIT  

Capturing packets right before the issue is a great idea, but I am concerned about running tcpdump for such an extended period of time on an active server.
I have gone 9 days with no issue which would be a lot of data and overhead.

I will look into disabling the TSO and LRO options and let the group know how it goes.
Below are the current options on the NFS Server.
lagg0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
	options=e507bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>

Please share other ideas if you have them.

Jason Breitman

On Mar 17, 2021, at 5:58 PM, Rick Macklem <rmacklem at uoguelph.ca> wrote:

Alan Somers wrote:
[stuff snipped]
>Is the 128K limit related to MAXPHYS? If so, it should be greater in 13.0.
For the client, yes. For the server, no.
For the server, it is just a compile time constant NFS_SRVMAXIO.

It's mainly related to the fact that I haven't gotten around to testing larger
sizes yet.
- kern.ipc.maxsockbuf needs to be several times the limit, which means it would
have to increase for 1Mbyte.
- The session code must negotiate a maximum RPC size > 1 Mbyte.
(I think the server code does do this, but it needs to be tested.)
And, yes, the client is limited to MAXPHYS.

Doing this is on my todo list, rick

The client should acquire the attributes that indicate that and set rsize/wsize
to that. "# nfsstat -m" on the client should show you what the client
is actually using. If it is larger than 128K, set both rsize and wsize to 128K.

>Output from the NFS Client when the issue occurs
># netstat -an | grep NFS.Server.IP.X
>tcp 0 0 NFS.Client.IP.X:46896 NFS.Server.IP.X:2049 FIN_WAIT2
I'm no TCP guy. Hopefully others might know why the client would be
stuck in FIN_WAIT2 (I vaguely recall this means it is waiting for a fin/ack,
but could be wrong?)

># cat /sys/kernel/debug/sunrpc/rpc_xprt/*/info
>netid: tcp
>addr: NFS.Server.IP.X
>port: 2049
>state: 0x51
>
>syslog
>Mar 4 10:29:27 hostname kernel: [437414.131978] -pid- flgs status -client- --rqstp- ->timeout ---ops--
>Mar 4 10:29:27 hostname kernel: [437414.133158] 57419 40a1 0 9b723c73 >143cfadf 30000 4ca953b5 nfsv4 OPEN_NOATTR a:call_connect_status [sunrpc] >q:xprt_pending
I don't know what OPEN_NOATTR means, but I assume it is some variant
of NFSv4 Open operation.
[stuff snipped]
>Mar 4 10:29:30 hostname kernel: [437417.110517] RPC: 57419 xprt_connect_status: >connect attempt timed out
>Mar 4 10:29:30 hostname kernel: [437417.112172] RPC: 57419 call_connect_status
>(status -110)
I have no idea what status -110 means?
>Mar 4 10:29:30 hostname kernel: [437417.113337] RPC: 57419 call_timeout (major)
>Mar 4 10:29:30 hostname kernel: [437417.114385] RPC: 57419 call_bind (status 0)
>Mar 4 10:29:30 hostname kernel: [437417.115402] RPC: 57419 call_connect xprt >00000000e061831b is not connected
>Mar 4 10:29:30 hostname kernel: [437417.116547] RPC: 57419 xprt_connect xprt >00000000e061831b is not connected
>Mar 4 10:30:31 hostname kernel: [437478.551090] RPC: 57419 xprt_connect_status: >connect attempt timed out
>Mar 4 10:30:31 hostname kernel: [437478.552396] RPC: 57419 call_connect_status >(status -110)
>Mar 4 10:30:31 hostname kernel: [437478.553417] RPC: 57419 call_timeout (minor)
>Mar 4 10:30:31 hostname kernel: [437478.554327] RPC: 57419 call_bind (status 0)
>Mar 4 10:30:31 hostname kernel: [437478.555220] RPC: 57419 call_connect xprt >00000000e061831b is not connected
>Mar 4 10:30:31 hostname kernel: [437478.556254] RPC: 57419 xprt_connect xprt >00000000e061831b is not connected
Is it possible that the client is trying to (re)connect using the same client port#?
I would normally expect the client to create a new TCP connection using a
different client port# and then retry the outstanding RPCs.
--> Capturing packets when this happens would show us what is going on.

If there is a problem on the FreeBSD end, it is most likely a broken
network device driver.
--> Try disabling TSO , LRO.
--> Try a different driver for the net hardware on the server.
--> Try a different net chip on the server.
If you can capture packets when (not after) the hang
occurs, then you can look at them in wireshark and see
what is actually happening. (Ideally on both client and
server, to check that your network hasn't dropped anything.)
--> I know, if the hangs aren't easily reproducible, this isn't
easily done.
--> Try a newer Linux kernel and see if the problem persists.
The Linux folk will get more interested if you can reproduce
the problem on 5.12. (Recent bakeathon testing of the 5.12
kernel against the FreeBSD server did not find any issues.)

Hopefully the network folk have some insight w.r.t. why
the TCP connection is sitting in FIN_WAIT2.

rick

Jason Breitman

_______________________________________________
freebsd-net at freebsd.org<mailto:freebsd-net at freebsd.org> mailing list
https://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "freebsd-net-unsubscribe at freebsd.org<mailto:freebsd-net-unsubscribe at freebsd.org>"

_______________________________________________
freebsd-net at freebsd.org<mailto:freebsd-net at freebsd.org> mailing list
https://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "freebsd-net-unsubscribe at freebsd.org<mailto:freebsd-net-unsubscribe at freebsd.org>"