balloon_compaction: update the NR_BALLOON_PAGES state

Update the NR_BALLOON_PAGES counter when pages are added or removed using
the balloon compaction interface.

The virtio, Vmware, and pseries-cmm balloon drivers utilize the
balloon_compaction interface to allocate and free balloon pages.  Other
balloon drivers will have to maintain this counter manually.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Nico Pache <[email protected]>
Cc: Alexander Atanasov <[email protected]>
Cc: Chengming Zhou <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Dexuan Cui <[email protected]>
Cc: Haiyang Zhang <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Juegren Gross <[email protected]>
Cc: Kanchana P Sridhar <[email protected]>
Cc: K. Y. Srinivasan <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Nhat Pham <[email protected]>
Cc: Oleksandr Tyshchenko <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Stefano Stabellini <[email protected]>
Cc: Wei Liu <[email protected]>
Cc: Michael Kelley <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: PacheNico

mm/balloon_compaction.c

@@ -24,6 +24,7 @@ static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info,
 	balloon_page_insert(b_dev_info, page);
 	unlock_page(page);
 	__count_vm_event(BALLOON_INFLATE);
+	inc_node_page_state(page, NR_BALLOON_PAGES);
 }
 
 /**
@@ -103,6 +104,7 @@ size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
 		__count_vm_event(BALLOON_DEFLATE);
 		list_add(&page->lru, pages);
 		unlock_page(page);
+		dec_node_page_state(page, NR_BALLOON_PAGES);
 		n_pages++;
 	}
 	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);