Race in NFS in 6.0-RC1?

[Frank Mayhar]

I've started using NFS in 6.0 a little more heavily lately, as since the
em(4) wedge has been fixed I can actually use it reliably.
Unfortunately there appears to be a problem.  Twice, now, in less than
24 hours the client has paniced under load.  Both times it was building
OpenOffice in an NFS-mounted /usr/ports.  In case it matters, it's a
soft mount from another 6.0 box over an em(4) interface with an MTU of
9000.

Both times it was a panic from vnlru while trying to flush a vnode and
both times it was a null-pointer dereference in nfs_putpages() at
nfs_bio.c:301.  In both cases vp->v_data was null.  The vnode itself
looks fine to my eyes, although there may well be FreeBSD-specific
subtleties that I'm missing.  I've just entered a PR for this problem,
kern/87967.  I'll keep the cores around; if anyone wants more
information from them, let me know.  As may be apparent, I can reproduce
this fairly easily, although it takes a few minutes for it to trigger.

The worrying thing about this is, in fact, its reproducibility.
-- 
Frank Mayhar frank at exit.com     http://www.exit.com/
Exit Consulting                 http://www.gpsclock.com/
                                http://www.exit.com/blog/frank/