TAKE - nfs reference cache version 2

[Steve Lord <lord@xxxxxxx>]

OK, this actually should fix the performance of writes, I will think
some more about ways to do this without all the code this adds, there
is probably a simpler way.

Date:  Tue Mar  6 13:05:35 PST 2001
Workarea:  jen.americas.sgi.com:/src/lord/xfs-linux.2.4

The following file(s) were checked into:
  bonnie.engr.sgi.com:/isms/slinx/2.4.x-xfs


Modid:  2.4.x-xfs:slinx:89070a
linux/fs/xfs/xfs_rw.c - 1.332
        - Change reference cache to do a VOP_RELEASE on removal from cache,
          this will truncate out space allocated beyond end of file.

linux/fs/xfs/xfs_vnodeops.c - 1.491
        - Change release code to do nothing if an inode is in the reference 
cache