[PATCH 3.19 040/177] mm: hwpoison: drop lru_add_drain_all() in __soft_offline_page()

Greg Kroah-Hartman
2015-03-16T15:57:03Z

From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

commit 9ab3b598d2dfbdb0153ffa7e4b1456bbff59a25d upstream.

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@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Chen Gong <gong.chen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/memory-failure.c | 2 --
1 file changed, 2 deletions(-)

--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1654,8 +1654,6 @@ 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))