mem-hotplug: call isolate_lru_page with elevated refcount

isolate_lru_page() must be called only with stable reference to page.  So,
let's grab normal page reference.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 59ac18fefd65..89b0391f14a8 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -706,7 +706,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
                 if (!pfn_valid(pfn))
                         continue;
                 page = pfn_to_page(pfn);
-                if (!page_count(page))
+                if (!get_page_unless_zero(page))
                         continue;
                 /*
                  * We can skip free pages. And we can only deal with pages on
@@ -714,6 +714,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
                  */
                 ret = isolate_lru_page(page);
                 if (!ret) { /* Success */
+                        put_page(page);
                         list_add_tail(&page->lru, &source);
                         move_pages--;
                         inc_zone_page_state(page, NR_ISOLATED_ANON +
@@ -725,6 +726,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
                                pfn);
                         dump_page(page);
 #endif
+                        put_page(page);
                         /* Because we don't have big zone->lock. we should
                            check this again here. */
                         if (page_count(page)) {