Re: "nfs server not responding, timed out" with Linux client and 13.0-RELEASE server

From: Rick Macklem <>
Date: Wed, 02 Jun 2021 01:09:17 UTC
Alan Somers wrote:
>I have several Linux NFS clients (Debian, with various 4.9 kernels)
>mounting NFS 4.0 from both Solaris and FreeBSD (mostly 12.2-RELEASE)
>servers.  I frequently see kernel messages in the clients about "nfs:
>server <HOSTNAME> not responding, timed out" for both the FreeBSD and
>Solaris servers.  It usually recovers after a few seconds.  However, on the
>sole 13.0-RELEASE server, the hangs last for minutes to hours.
>tcpdump/wireshark shows the NFS client sending a "V4 Call SEQUENCE" packet
>every 5-10 seconds, all with the same sessionid.  The server responds with
>a TCP ACK, but sends no NFS-level response.  I've seen this with both NFS
>4.0 and 4.2.
>NFS delegations are disabled, and nfsdumpstate shows that the client has
>callbacks enabled, with 2-4 opens, openowners, locks, and lockowners.
>Can anybody suggest how to fix or further debug this problem?
See PR#256280 for the ways to fix this, rick