mm: convert PG_balloon to PG_offline

PG_balloon was introduced to implement page migration/compaction for
pages inflated in virtio-balloon.  Nowadays, it is only a marker that a
page is part of virtio-balloon and therefore logically offline.

We also want to make use of this flag in other balloon drivers - for
inflated pages or when onlining a section but keeping some pages offline
(e.g.  used right now by XEN and Hyper-V via set_online_page_callback()).

We are going to expose this flag to dump tools like makedumpfile.  But
instead of exposing PG_balloon, let's generalize the concept of marking
pages as logically offline, so it can be reused for other purposes later
on.

Rename PG_balloon to PG_offline.  This is an indicator that the page is
logically offline, the content stale and that it should not be touched
(e.g.  a hypervisor would have to allocate backing storage in order for
the guest to dump an unused page).  We can then e.g.  exclude such pages
from dumps.

We replace and reuse KPF_BALLOON (23), as this shouldn't really harm
(and for now the semantics stay the same).  In following patches, we
will make use of this bit also in other balloon drivers.  While at it,
document PGTABLE.

[[email protected]: fix comment text, per David]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: David Hildenbrand <[email protected]>
Acked-by: Konstantin Khlebnikov <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]>
Acked-by: Pankaj gupta <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Christian Hansen <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Pavel Tatashin <[email protected]>
Cc: Alexander Duyck <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Miles Chen <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Kazuhito Hagio <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Haiyang Zhang <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Julien Freche <[email protected]>
Cc: Kairui Song <[email protected]>
Cc: "K. Y. Srinivasan" <[email protected]>
Cc: Len Brown <[email protected]>
Cc: Lianbo Jiang <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Nadav Amit <[email protected]>
Cc: Omar Sandoval <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Rafael J. Wysocki <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Stefano Stabellini <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Xavier Deguillard <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/uapi/linux/kernel-page-flags.h b/include/uapi/linux/kernel-page-flags.h
index 21b9113c69da..6f2f2720f3ac 100644
--- a/include/uapi/linux/kernel-page-flags.h
+++ b/include/uapi/linux/kernel-page-flags.h
@@ -32,7 +32,7 @@
 
 #define KPF_KSM			21
 #define KPF_THP			22
-#define KPF_BALLOON		23
+#define KPF_OFFLINE		23
 #define KPF_ZERO_PAGE		24
 #define KPF_IDLE		25
 #define KPF_PGTABLE		26