mm: hwpoison: drop lru_add_drain_all() in __soft_offline_page()

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.

[n-horiguchi@ah.jp.nec.com: resolve conflict to apply on v3.11.10]
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>
Cc: <stable@vger.kernel.org>	[3.11+]
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>

1 files changed, 0 insertions, 2 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index a98c7fce470a..ffc7bf0458fb 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1645,8 +1645,6 @@ 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();
 			SetPageHWPoison(page);
 			if (!is_free_buddy_page(page))