TAKE - write out large extents with kiobufs

[Ananth Ananthanarayanan <ananth@xxxxxxxxxxxxxxxxxx>]

Enable use of kiobufs for cluster_writes. This
significantly improves (over 100%) the performance
of sequential output when CONFIG_KIOBUF_IO is turned ON.

Date:  Wed Jun 28 18:23:13 PDT 2000
Workarea:  dbear.engr.sgi.com:/build2/ananth/slinx24-xfs

The following file(s) were checked into:
  bonnie.engr.sgi.com:/isms/slinx/2.4.0-test1-xfs


Modid:  2.4.0-test1-xfs:slinx:65443a
linux/include/linux/page_buf.h - 1.50
http://oss.sgi.com/cgi-bin/cvsweb.cgi/linux-2.4-xfs/linux/include/linux/page_buf.h.diff?r1=text&tr1=1.50&r2=text&tr2=1.49&f=h
linux/kdb/modules/kdbm_pg.c - 1.4
http://oss.sgi.com/cgi-bin/cvsweb.cgi/linux-2.4-xfs/linux/kdb/modules/kdbm_pg.c.diff?r1=text&tr1=1.4&r2=text&tr2=1.3&f=h
linux/fs/pagebuf/page_buf.c - 1.9
http://oss.sgi.com/cgi-bin/cvsweb.cgi/linux-2.4-xfs/linux/fs/pagebuf/page_buf.c.diff?r1=text&tr1=1.9&r2=text&tr2=1.8&f=h
linux/fs/pagebuf/page_buf_io.c - 1.6
http://oss.sgi.com/cgi-bin/cvsweb.cgi/linux-2.4-xfs/linux/fs/pagebuf/page_buf_io.c.diff?r1=text&tr1=1.6&r2=text&tr2=1.5&f=h