uma_zalloc_arg complaining about non-sleepable locks

[Marius Strobl]

On Sun, Jan 31, 2010 at 12:06:18PM +1100, Peter Jeremy wrote:
> Sorry for the delay, I was trying to avoid rebooting my server.
> I've setup a similar environment in VirtualBox to test it.
> 
> On 2010-Jan-27 12:52:29 +0100, Marius Strobl <marius at alchemy.franken.de> wrote:
> >Ah, I forgot that using nfsm_aligned() causes nfs_realign() to
> >be a NOP on architectures without strict alignment requirements
> >for performance reasons. That's generally fine but unfortunately
> >that way you don't actually exercise the code which caused the
> >problem before (unfortunately I still don't manage to hit the
> >unaligned case myself).
> 
> >Could you please test with #ifdef __NO_STRICT_ALIGNMENT replaced
> >with #if 0 in sys/nfs/nfs_common.h? The vfs.nfs.realign_count
> >counter should also increase then.
> 
> I'm not sure what triggers the unaligned case either - I tried
> roughly "tar -cf - -C /mnt/usr src | tar -xf - -C /mnt/tmp" and
> that caused some unaligned accesses (but also completely wedged
> the VBox host).  I also tried copying a pile of files off my
> NFS client (FreeBSD-8.x/i386) and that also triggered some
> unaligned accesses without any errors being reported.
> 
> Currently, I have:
> vfs.nfs.realign_count: 12
> vfs.nfs.realign_test: 188817
> 
> I'd say that your patch works.

John, are you okay with that patch?
http://people.freebsd.org/~marius/fha_extract_info_realign2.diff

It's intention is to:
- Move nfs_realign() from the NFS client to the shared NFS code and
  remove the NFS server version in order to reduce code duplication.
  The shared version now uses a second parameter how, which is passed
  on to m_get(9) and m_getcl(9) as the server used M_WAIT while the
  client requires M_DONTWAIT, and replaces the the previously unused
  parameter hsiz.
- Change nfs_realign() to use nfsm_aligned() so as with other NFS code
  the alignment check isn't actually performed on platforms without
  strict alignment requirements for performance reasons because as the
  comment suggests only occasionally occurs with TCP.
- Change fha_extract_info() to use nfs_realign() with M_NOWAIT rather
  than M_DONTWAIT because it's called with the RPC sp_lock held.

The only downside of the shared nfs_realign() are the combined
SYSCTL counters but the fact we incremented them non-atomically
so far I think already indicates that their intention only is a
rough indication rather than exact values for client and server.

Marius