[PATCH] mm/memory-failure.c: move refcount only in !MF_COUNT_INCREASED

[Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>]

# Resending due to sending failure. Sorry if you received twice.
---
mce-test detected a test failure when injecting error to a thp tail page.
This is because we take page refcount of the tail page in madvise_hwpoison()
while the fix in commit a3e0f9e47d5e ("mm/memory-failure.c: transfer page
count from head page to tail page after split thp") assumes that we always
take refcount on the head page.

When a real memory error happens we take refcount on the head page where
memory_failure() is called without MF_COUNT_INCREASED set, so it seems to me
that testing memory error on thp tail page using madvise makes little sense.

This patch cancels moving refcount in !MF_COUNT_INCREASED for valid testing.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: stable@vger.kernel.org # 3.9+: a3e0f9e47d5e
---
 mm/memory-failure.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git v3.14-rc1.orig/mm/memory-failure.c v3.14-rc1/mm/memory-failure.c
index ab55d489eb05..16886ddb6ab4 100644
--- v3.14-rc1.orig/mm/memory-failure.c
+++ v3.14-rc1/mm/memory-failure.c
@@ -1042,8 +1042,10 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
 			 * to it. Similarly, page lock is shifted.
 			 */
 			if (hpage != p) {
-				put_page(hpage);
-				get_page(p);
+				if (!(flags && MF_COUNT_INCREASED)) {
+					put_page(hpage);
+					get_page(p);
+				}
 				lock_page(p);
 				unlock_page(hpage);
 				*hpagep = p;
-- 
1.8.5.3

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>