TAKE - narrow down use of GFP_PAGE_IO

[Steve Lord <lord@xxxxxxx>]

We do not need to use GFP_PAGE_IO in as many places as we were.

Date:  Mon Apr  2 12:42:15 PDT 2001
Workarea:  jen.americas.sgi.com:/src/lord/linux-base

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


Modid:  2.4.x-xfs:slinx:91398a
linux/mm/vmscan.c - 1.52
        - Only skip flushing buffers under GFP_PAGE_IO if they are on a delalloc
          page, this is the only case which matters.

linux/fs/xfs/xfs_buf.h - 1.70
        - Define BUF_BUSY to be PBF_DONT_BLOCK rather than zero, we can use the 
info
          in pagebuf.

linux/fs/pagebuf/page_buf.c - 1.68
        - Only use GFP_PAGE_IO flag for allocates when the caller passes in the
          PBF_DONT_BLOCK flag, this corresponds to a call from within the 
transaction
          system.