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Date: Wed, 27 Mar 2024 16:28:30 -0400
From: Chuck Lever <chuck.lever@oracle.com>
To: Roland Mainz <roland.mainz@nrubsig.org>
Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: "svc_tcp_read_marker nfsd RPC fragment too large" with Linux 6.6
 LTS nfsd ...
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On Fri, Mar 22, 2024 at 12:11:44PM +0100, Roland Mainz wrote:
> Hi!
> 
> ----
> 
> After updating my Debian 11 and RHEL 9 installations with Linux kernel
> 6.6.20-rt25 I start getting the following error messages
> "svc_tcp_read_marker nfsd RPC fragment too large".
> Client side is Linux NFSv4.2 client (Debian&&RHEL, both default kernel
> and Linux 6.6.20-rt25)+ms-nfs41-client HEAD.
> 
> Is this a know issue, and is there a patch for it ?

The "fragment too large" message means the incoming RPC frame has
the high-order bit set in its TCP record marker. It could mean:

1. The client is trying to send an RPC message that is split over
   multiple RPC fragments. The Linux in-kernel RPC server does not
   support that.

2. The TCP byte stream has gotten out of sync with the RPC
   framing. That's a sign of a bug or misconfiguration somewhere,
   though not necessarily on the NFS server.

Wireshark can help you sort it out.

-- 
Chuck Lever