linux-kernel - [PATCH] mm/memory-failure: call shake_page() when error hits thp tail page

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Date:	Wed, 15 Apr 2015 07:25:46 +0000
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Dean Nelson <dnelson@...hat.com>, Andi Kleen <andi@...stfloor.org>,
	"Andrea Arcangeli" <aarcange@...hat.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Jin Dongming <jin.dongming@...css.fujitsu.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] mm/memory-failure: call shake_page() when error hits thp
 tail page

Currently memory_failure() calls shake_page() to sweep pages out from pcplists
only when the victim page is 4kB LRU page or thp head page. But we should do
this for a thp tail page too.
Consider that a memory error hits a thp tail page whose head page is on a
pcplist when memory_failure() runs. Then, the current kernel skips shake_pages()
part, so hwpoison_user_mappings() returns without calling split_huge_page() nor
try_to_unmap() because PageLRU of the thp head is still cleared due to the skip
of shake_page().
As a result, me_huge_page() runs for the thp, which is a broken behavior.

This patch fixes this problem by calling shake_page() for thp tail case.

Fixes: 385de35722c9 ("thp: allow a hwpoisoned head page to be put back to LRU")
Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: stable@...r.kernel.org  # v3.4+
---
 mm/memory-failure.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git v4.0.orig/mm/memory-failure.c v4.0/mm/memory-failure.c
index d487f8dc6d39..2cc1d578144b 100644
--- v4.0.orig/mm/memory-failure.c
+++ v4.0/mm/memory-failure.c
@@ -1141,10 +1141,10 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
 	 * The check (unnecessarily) ignores LRU pages being isolated and
 	 * walked by the page reclaim code, however that's not a big loss.
 	 */
-	if (!PageHuge(p) && !PageTransTail(p)) {
-		if (!PageLRU(p))
-			shake_page(p, 0);
-		if (!PageLRU(p)) {
+	if (!PageHuge(p)) {
+		if (!PageLRU(hpage))
+			shake_page(hpage, 0);
+		if (!PageLRU(hpage)) {
 			/*
 			 * shake_page could have turned it free.
 			 */
-- 
2.1.0
--
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