mm/memory_hotplug: export generic_online_page()

task #29077503
commit 18db149120c106cf2b1a2595f82f3229f9d223b8 upstream

Let's replace the __online_page...() functions by generic_online_page().
Hyper-V only wants to delay the actual onlining of un-backed pages, so
we can simpy re-use the generic function.

This patch (of 3):

Let's expose generic_online_page() so online_page_callback users can
simply fall back to the generic implementation when actually deciding to
online the pages.

Link: http://lkml.kernel.org/r/20190909114830.662-2-david@redhat.comSigned-off-by: NDavid Hildenbrand <david@redhat.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
(cherry picked from ccommit 18db149120c106cf2b1a2595f82f3229f9d223b8)
Signed-off-by: NAlex Shi <alex.shi@linux.alibaba.com>
Reviewed-by: NYang Shi <yang.shi@linux.alibaba.com>

include/linux/memory_hotplug.h

@@ -91,6 +91,7 @@ extern void __offline_isolated_pages(unsigned long, unsigned long);
 
 typedef void (*online_page_callback_t)(struct page *page, unsigned int order);
 
+extern void generic_online_page(struct page *page, unsigned int order);
 extern int set_online_page_callback(online_page_callback_t callback);
 extern int restore_online_page_callback(online_page_callback_t callback);
 

mm/memory_hotplug.c

@@ -48,8 +48,6 @@
  * and restore_online_page_callback() for generic callback restore.
  */
 
-static void generic_online_page(struct page *page, unsigned int order);
-
 static online_page_callback_t online_page_callback = generic_online_page;
 static DEFINE_MUTEX(online_page_callback_lock);
 
@@ -617,7 +615,7 @@ void __online_page_free(struct page *page)
 }
 EXPORT_SYMBOL_GPL(__online_page_free);
 
-static void generic_online_page(struct page *page, unsigned int order)
+void generic_online_page(struct page *page, unsigned int order)
 {
 	__free_pages_core(page, order);
 	totalram_pages += (1UL << order);
@@ -626,6 +624,7 @@ static void generic_online_page(struct page *page, unsigned int order)
 		totalhigh_pages_add(1UL << order);
 #endif
 }
+EXPORT_SYMBOL_GPL(generic_online_page);
 
 static int online_pages_blocks(unsigned long start, unsigned long nr_pages)
 {