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>

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 59ac18f..89b0391 100644 (file)
--- 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)) {