A race condition starts to be visible in recent mmotm, where a PG_hwpoison
flag is set on a migration source page *before* it's back in buddy page pool.
This is problematic because no page flag is supposed to be set when freeing
(see __free_one_page().) So the user-visible effect of this race is that it
could trigger the BUG_ON() when soft-offlining is called.
The root cause is that we call lru_add_drain_all() to make sure that the
page is in buddy, but that doesn't work because this function just schedules
a work item and doesn't wait its completion. drain_all_pages() does draining
directly, so simply dropping lru_add_drain_all() solves this problem.
Fixes: commit f15bdfa802bf ("mm/memory-failure.c: fix memory leak in successful soft offlining")
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.11+]
---
mm/memory-failure.c | 2 --
1 file changed, 2 deletions(-)
diff --git mmotm-2015-02-03-16-38.orig/mm/memory-failure.c mmotm-2015-02-03-16-38/mm/memory-failure.c
index b2a68bde8058..fa44054c205f 100644
--- mmotm-2015-02-03-16-38.orig/mm/memory-failure.c
+++ mmotm-2015-02-03-16-38/mm/memory-failure.c
@@ -1647,8 +1647,6 @@ static int __soft_offline_page(struct page *page, int flags)
* setting PG_hwpoison.
*/
if (!is_free_buddy_page(page))
- lru_add_drain_all();
- if (!is_free_buddy_page(page))
drain_all_pages(page_zone(page));
SetPageHWPoison(page);
if (!is_free_buddy_page(page))
--
1.9.3
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