Patch "mm: hwpoison: drop lru_add_drain_all() in __soft_offline_page()" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mm-hwpoison-drop-lru_add_drain_all-in-__soft_offline_page.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Naoya Horiguchi <[email protected]>
Date: Thu, 12 Feb 2015 15:00:25 -0800
Subject: mm: hwpoison: drop lru_add_drain_all() in __soft_offline_page()

From: Naoya Horiguchi <[email protected]>

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.

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

@@ -1645,8 +1645,6 @@ 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();
 			SetPageHWPoison(page);
 			if (!is_free_buddy_page(page))

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/mm-hwpoison-drop-lru_add_drain_all-in-__soft_offline_page.patch