On Tue, Mar 20 2018, J. Bruce Fields wrote:

> On Fri, Mar 16, 2018 at 10:44:23AM +1100, NeilBrown wrote:
>> 
>> nfs4_proc_exchange_id() can return -EINVAL if the server
>> reported NFS4INVAL (which I have seen in a packet trace),
>
> Can you say which server this was?  (One we can fix?)

It was Linux 2.6.32 (on armv5), and presumably anything before
Commit: 357f54d6b382 ("NFS fix the setting of exchange id flag")
which landed in 2.6.38.

These servers return NFS4ERR_INVAL when EXCHGID4_FLAG_BIND_PRINC_STATEID
is set in the exchange_id flags, which Linux has done since
Commit: 4f0b429df104 ("NFSv4.1: Enable state protection")
in 3.11.

Maybe NFS should retry without that flag if it gets EINVAL??  Or it could
just say that NFSv4.1 isn't supported.  I still don't think EIO is justified.

Thanks,
NeilBrown