hv_balloon: use generic_online_page()

Let's use the generic onlining function - which will now also take care
of calling kernel_map_pages().

Link: http://lkml.kernel.org/r/20190909114830.662-3-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Oscar Salvador <osalvador@suse.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/hv/hv_balloon.c

@@ -681,8 +681,7 @@ static void hv_page_online_one(struct hv_hotadd_state *has, struct page *pg)
 
 	/* This frame is currently backed; online the page. */
 	__online_page_set_limits(pg);
-	__online_page_increment_counters(pg);
-	__online_page_free(pg);
+	generic_online_page(pg, 0);
 
 	lockdep_assert_held(&dm_device.ha_lock);
 	dm_device.num_pages_onlined++;