TAKE - Make xfs metadata accesses refresh pages

[Steve Lord <lord@sgi.com>]

This makes xfs metadata accesses to pages move the pages in the lru
lists in a similar manner to the buffer cache metadata filesystems.
This tends to make them stick in cache longer and reduce metadata
reads.

Date:  Mon Mar  4 11:12:38 PST 2002
Workarea:  jen.americas.sgi.com:/src/lord/xfs-merge.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:113212a
linux/mm/filemap.c - 1.106
	- export mark_page_accessed to modules

linux/fs/xfs/pagebuf/page_buf.c - 1.10
	- make xfs metadata references bring pages forward in the cache, fix an
	  assert, and count the number of metadata reads we do.

linux/fs/xfs/pagebuf/page_buf.h - 1.6
	- Add read counter to pagebuf stats