mm: split page_type out from _mapcount

We're already using a union of many fields here, so stop abusing the
_mapcount and make page_type its own field.  That implies renaming some of
the machinery that creates PageBuddy, PageBalloon and PageKmemcg; bring
back the PG_buddy, PG_balloon and PG_kmemcg names.

As suggested by Kirill, make page_type a bitmask.  Because it starts out
life as -1 (thanks to sharing the storage with _mapcount), setting a page
flag means clearing the appropriate bit.  This gives us space for probably
twenty or so extra bits (depending how paranoid we want to be about
_mapcount underflow).

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Matthew Wilcox <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Jérôme Glisse <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions