Under what circumstances does the new NFS client return EAGAIN?

[Garrett Wollman]

<<On Wed, 29 Feb 2012 19:21:25 -0500 (EST), Rick Macklem <rmacklem at uoguelph.ca> said:

> If you are using the "soft" or "intr" mount options, I'd suggest you
> get rid of them (technically "intr" should result in EINTR, but I wouldn't
> be surprised if an EWOULDBLOCK could pop out, as well). Also, you
> didn't mention whether you were using UDP or TCP mounts, although the
> above comments should apply to both.

mount -t nfs -o ro,hard,tcp,nointr

> You might also want to capture packets and look at them in wireshark,
> to make sure the EWOULDBLOCK isn't coming from the proprietary NAS server.

Unfortunately, I can't capture packets on this machine fast enough to
record a decodeable NFS/TCP stream with the NAS.

Another bug I've noticed: when mounting any remote NFS filesystem, all
of the local exported NFS filesystems briefly give [EPERM] (or maybe
it's [EACCES]) errors to their clients.  This tends to break whatever
is trying to use them at the time.  It doesn't happen when local ZFS
datasets are created and mounted.

-GAWollman