linux-kernel - NFS 4.2 client support broken on 5.10.5

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Date:   Fri, 8 Jan 2021 12:41:01 +0100
From:   Kurt Garloff <kurt@...loff.de>
To:     Neil Brown <NeilB@...e.de>,
        Anna Schumaker <Anna.Schumaker@...app.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: NFS 4.2 client support broken on 5.10.5

Hi Neil, Anna, Trond,

compiling a kernel, I suddenly started getting errors from objtool orc.
(This first occurs on init/main.o.)

I looked at all kind of things, before I noticed that this was not a
toolchain issue (gcc-10.2.1 self compiled), gcc plugins (I use
structleak and stackleak) nor an issue with objtool or libelf,
but that there was an -EIO error.

The kernel tree is on an NFS share, and I run 5.10.5 client kernel
against the kernel NFS (4.2) server, running a 5.10.3 kernel.

The issue does NOT occur on a 5.10.3 client kernel, but is easily
reproducible on 5.10.5. Note that 5.10.5 on a local file system or
against an NFSv3 server does not show the issue.

Test program that reproduces this on the first pwrite64() is attached.
Note that the call to ftruncate() is required to make the problem happen.

I could go on bisecting this to a particular patch, but you'll
probably be able to see right away what's wrong.

Best,

-- 
Kurt Garloff <kurt@...loff.de>
Cologne, Germany

View attachment "testpwrite.c" of type "text/x-csrc" (1507 bytes)