vfs patch 04 (commit candidate)

[esmith]

Matthew Dillon wrote:
    Ok, here's an updated VFS patch.  I consider this a commit candidate. 
    This patch fixes a number of nullfs issues that came up from various
    people's testing.  The UFS code looks to be quite stable.
Nullfs is well known to be broken on FreeBSD. Could you explain what are nullfs's 
presently known limitations, at this point in the VFS work, and what allows nullfs to 
work properly on DF?