[PATCH] memory-hotplug: fix a drain pcp bug when offline pages

[qiuxishi]

From: Xishi Qiu <qiuxishi@xxxxxxxxxx>

When offline a section, we move all the free pages and pcp into MIGRATE_ISOLATE list first.
start_isolate_page_range()
	set_migratetype_isolate()
		drain_all_pages(),

Here is a problem, it is not sure that pcp will be moved into MIGRATE_ISOLATE list. They may
be moved into MIGRATE_MOVABLE list because page_private() maybe 2. So when finish migrating
pages, the free pages from pcp may be allocated again, and faild in check_pages_isolated().
drain_all_pages()
	drain_local_pages()
		drain_pages()
			free_pcppages_bulk()
				__free_one_page(page, zone, 0, page_private(page));

If we add move_freepages_block() after drain_all_pages(), it can not sure that all the pcp
will be moved into MIGRATE_ISOLATE list when the system works on high load. The free pages
which from pcp may immediately be allocated again.

I think the similar bug described in http://marc.info/?t=134250882300003&r=1&w=2


Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
---
 mm/page_alloc.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d0723b2..501f6de 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -673,7 +673,8 @@ static void free_pcppages_bulk(struct zone *zone, int count,
 			/* must delete as __free_one_page list manipulates */
 			list_del(&page->lru);
 			/* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
-			__free_one_page(page, zone, 0, page_private(page));
+			__free_one_page(page, zone, 0,
+					get_pageblock_migratetype(page));
 			trace_mm_page_pcpu_drain(page, 0, page_private(page));
 		} while (--to_free && --batch_free && !list_empty(list));
 	}
-- 1.7.6.1 .



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