Removing page->index

[Matthew Wilcox <willy@infradead.org>]

I've pushed out a new tree to
git://git.infradead.org/users/willy/pagecache.git shrunk-page
aka
http://git.infradead.org/?p=users/willy/pagecache.git;a=shortlog;h=refs/heads/shrunk-page

The observant will notice that it doesn't actually shrink struct page
yet.  However, we're getting close.  What it does do is rename
page->index to page->__folio_index to prevent new users of page->index
from showing up.

There are (I believe) three build failures in that tree:

 - fb_defio
 - fbtft
 - s390's gmap (and vsie?  is that the same thing?)

Other than that, allmodconfig builds on x86 and I'm convinced the build
bots will tell me about anything else I missed.

Lorenzo is working on fb_defio and fbtft will come along for the ride
(it's a debug printk, so could just be deleted).

s390 is complicated.  I'd really appreciate some help.

The next step is to feed most of the patches through the appropriate
subsystems.  Some have already gone into various maintainer trees
(thanks!)


There are still many more steps to go after this; eliminating memcg_data
is closest to complete, and after that will come (in some order)
eliminating ->lru, ->mapping, ->refcount and ->mapcount.  We also need
to move page_pool out into its own structure.