NFSv4 mounts take longer the fail from ENETUNREACH than NFSv3 mounts.

[Neil Brown <neilb@suse.de>]

If I don't have any network configured (except loop-back), and try an NFSv3
mount, then it fails quickly:


....
mount.nfs: portmap query failed: RPC: Remote system error - Network is unreachable
mount.nfs: Network is unreachable


If I try the same thing with a NFSv4 mount, it times out before it fails,
making a much longer delay.

This is because mount.nfs doesn't do a portmap lookup but just leaves
everything to the kernel.
The kernel does an 'rpc_ping()' which sets RPC_TASK_SOFTCONN.
So at least it doesn't retry after the timeout.  But given that we have a
clear error, we shouldn't timeout at all.

Unfortunately I cannot see an easy way to fix this.

The place where ENETUNREACH is in xs_tcp_setup_socket.  The comment there
says "Retry with the same socket after a delay".  The "delay" bit is correct,
the "retry" isn't.

It would seem that we should just add a 'goto out' there if RPC_TASK_SOFTCONN
was set.  However we cannot see the task at this point - in fact it seems
that there could be a queue of tasks waiting on this connection.  I guess
some could be soft, and some not. ???

So: An suggestions how to get a ENETUNREACH (or ECONNREFUSED or similar) to
fail immediately when  RPC_TASK_SOFTCONN is set ???


This affects people who upgrade from openSUSE11.2 (which didn't support v4
mounts) to openSUSE11.3 (which defaults to v4) and who use network-manager
(which configures networks late) and have NFS mounts in /etc/fstab with
either explicit IP addresses or host names that can be resolved without the
network.
This config will work because when the network comes up, network-manager will
re-run the 'init.d/nfs' script.  However since 11.3 there is an unpleasant
pause before boot completes.

Thanks,
NeilBrown