Heads Up: NFS server will now use LK_SHARED vnode locks

Hi,

I have just committed r227809 to head/current which enables the
new/default NFS server's use of shared vnode locks for Read,
Readdir, Readlink, Getattr and Access.

Although it is hoped that this will improve performance for these
operations when multiple ones are performed concurrently on the
same file/vnode, I thought I should give a heads up.

Why?
Well it is conceivable that this may have negative issues that I
haven't seen in testing along the lines of overloading a server,
due to the lack of serialization of the above RPCs for the same
file/vnode.

If anyone encounters problems with their NFS server after upgrading
to post-r227809, please email and let me know.

rick