TAKE - fix unmount of xfs filesystem after nfs export

[Steve Lord <lord@xxxxxxx>]

Recent changes this week introduced some optimizations for nfs exporting
xfs, and this bug - unmounts would report a busy inode. This should 
fix it.

Date:  Fri Mar  9 15:41:04 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:89479a
linux/fs/xfs/linux/xfs_lrw.c - 1.82
        - Fix xfs_write to correctly cleanup after reference cache overflow, 
fixes
          unmount of xfs on nfs server.