Re: NFS 4.2 client support broken on 5.10.5

[Kurt Garloff]

Hi Trond,

On 08/01/2021 12:58, Trond Myklebust wrote:
> 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.
>>
> 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.
OK, it is turned on in my kernel -- looks like I have not read the
warning in the config option help text carefully enough ...

I'll test what happens if I switch it off and report back.

Thanks for the quick response

---

Kurt Garloff <kurt@xxxxxxxxxx>
Cologne, Germany