NFSv4 bug in linux-3.4+

[David Witbrodt <dawitbro@sbcglobal.net>]

This is a heads up for the Debian Kernel Team, though you likely are
aware of the problem already.

There is a bug affecting NFS version 4 server (nfsd), and the patch
has now hit Linus' tree:

commit fffaee365fded09f9ebf2db19066065fa54323c3
Author: Konstantin Khlebnikov <khlebnikov@openvz.org>
Date:   Tue Jun 5 21:36:33 2012 +0400

    radix-tree: fix contiguous iterator
    
    This patch fixes bug in macro radix_tree_for_each_contig().
    
    If radix_tree_next_slot() sees NULL in next slot it returns NULL, but follow
    radix_tree_next_chunk() switches iterating into next chunk. As result iterat
    becomes non-contiguous and breaks vfs "splice" and all its users.
    
    Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
    Reported-and-bisected-by: Hans de Bruin <jmdebruin@xmsnet.nl>
    Reported-and-bisected-by: Ondrej Zary <linux@rainbow-software.org>
    Reported-bisected-and-tested-by: Toralf Förster <toralf.foerster@gmx.de>
    Link: https://lkml.org/lkml/2012/6/5/64
    Cc: stable <stable@vger.kernel.org> # 3.4.x
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

I'm sure this will be included in gregkh's 3.4.2, but I see that Debian kernel
3.4.1-1~experimental.1 has already been uploaded.  I don't see any reference to
the above NFS-related patch, so don't be surprised if you get some bug reports!


FYI,
Dave W.