[3.16.y-ckt stable] Patch "mm: hwpoison: drop lru_add_drain_all() in __soft_offline_page()" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Mon Mar 2 13:37:32 UTC 2015

This is a note to let you know that I have just added a patch titled

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

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:


This patch is scheduled to be released in version 3.16.7-ckt8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see



>From 810f995d7d125db4f806233cd4d6cc71d9c788ce Mon Sep 17 00:00:00 2001
From: Naoya Horiguchi <n-horiguchi at ah.jp.nec.com>
Date: Thu, 12 Feb 2015 15:00:25 -0800
Subject: 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.

Fixes: f15bdfa802bf ("mm/memory-failure.c: fix memory leak in successful soft offlining")
Signed-off-by: Naoya Horiguchi <n-horiguchi at ah.jp.nec.com>
Cc: Andi Kleen <andi at firstfloor.org>
Cc: Tony Luck <tony.luck at intel.com>
Cc: Chen Gong <gong.chen at linux.intel.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 mm/memory-failure.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index a013bc94ebbe..607a6d62bcab 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1649,8 +1649,6 @@ 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))
 			if (!is_free_buddy_page(page))

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