TAKE - fix mix of buffered and direct I/O to a file in parallel

[Steve Lord <lord@xxxxxxx>]

Buffered reads were getting stomped on by direct writes which happened
at the same time. I doubt anyone was doing this outside of test programs.

Date:  Wed Jan  9 13:18:10 PST 2002
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:109311a
linux/fs/xfs/linux/xfs_lrw.c - 1.119
        - Fix parallel direct and buffered I/O on a file, do not allow the page
          invalidate which comes out of a direct write to happen at the same 
time
          as a buffered read.