From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Subject: mm: hwpoison: drop lru_add_drain_all() in __soft_offline_page()
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
poo= l.
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
schedule= s a work item and doesn't wait its completion.
drain_all_pages() does drainin= g directly, so simply dropping
lru_add_drain_all() solves this problem.
Fixes: f15bdfa802bf ("mm/memory-failure.c: fix memory leak in successful soft offlining")
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Chen Gong <gong.chen@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.11+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory-failure.c | 2 --
1 file changed, 2 deletions(-)
diff -puN mm/memory-failure.c~mm-hwpoison-drop-lru_add_drain_all-in-__soft_offline_page mm/memory-failure.c
--- a/mm/memory-failure.c~mm-hwpoison-drop-lru_add_drain_all-in-__soft_offline_page
+++ a/mm/memory-failure.c
@@ -1647,8 +1647,6 @@ static int __soft_offline_page(struct pa
* 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))
_
--
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