TAKE - xfs iocore rework

[Steve Lord <lord@sgi.com>]

rework iocore infrastructure, remove some code and make it more
orthogonal. In addition, add some of the hooks for unwritten extents.

Date:  Wed Dec 11 09:27:32 PST 2002
Workarea:  jen.americas.sgi.com:/src/lord/xfs-merge.2.4
Author:  lord
Merged by:  lord
Merged mods:  2.4.x-xfs-dev:slinx:134603a

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


Modid:  2.4.x-xfs:slinx:134603a
linux/fs/xfs/xfs_iocore.c - 1.37
	- Merge of 2.4.x-xfs-dev:slinx:134603a by lord.
	  revamped iocore functions 

linux/fs/xfs/xfs_mount.h - 1.165
	- Merge of 2.4.x-xfs-dev:slinx:134603a by lord.
	  revamped iocore vector

linux/fs/xfs/linux/xfs_lrw.h - 1.31
	- Merge of 2.4.x-xfs-dev:slinx:134603a by lord.
	  externs for iocore functions

linux/fs/xfs/linux/xfs_lrw.c - 1.177
	- Merge of 2.4.x-xfs-dev:slinx:134603a by lord.
	  add xfs_bmap as a thin wrapper around xfs_iomap

linux/fs/xfs/linux/xfs_aops.c - 1.16
	- Merge of 2.4.x-xfs-dev:slinx:134603a by lord.
	  some speedups of O_DIRECT and O_SYNC - in terms of allocating
	  larger chunks of space. Also some unwritten extent hooks.

linux/fs/xfs/linux/xfs_iomap.c - 1.3
	- Merge of 2.4.x-xfs-dev:slinx:134603a by lord.
	  rework iocore to be more orthogonal, add an unwritten extent conversion
	  operation.