Re: NFS 4.2 client support broken on 5.10.5

[Trond Myklebust]

On Fri, 2021-01-08 at 12:41 +0100, Kurt Garloff wrote:
> 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,
> 

Hmm... If this is NFSv4.2 do you have READ_PLUS turned on or off in
.config? It really is not safe to enable READ_PLUS on 5.10 kernels
since that can cause random memory corruption.

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx