From: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Date: Tue, 8 Sep 2015 21:59:28 +0000 (-0700)
Subject: thp: decrement refcount on huge zero page if it is split
X-Git-Tag: v4.1.12-92~18^2^2~100
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=7647606ad4bc81c18eab82d5474751b45fb412ef;p=users%2Fjedix%2Flinux-maple.git

thp: decrement refcount on huge zero page if it is split

Orabug: 22913653

The DAX code neglected to put the refcount on the huge zero page.
Also we must notify on splits.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 5b701b846aad7909d20693bcced2522d0ce8d1bc)
Signed-off-by: Dan Duval <dan.duval@oracle.com>
---

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9f9a536465900..116e8fce6050b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2954,7 +2954,9 @@ again:
 	if (unlikely(!pmd_trans_huge(*pmd)))
 		goto unlock;
 	if (vma_is_dax(vma)) {
-		pmdp_huge_clear_flush(vma, haddr, pmd);
+		pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
+		if (is_huge_zero_pmd(_pmd))
+			put_huge_zero_page();
 	} else if (is_huge_zero_pmd(*pmd)) {
 		__split_huge_zero_page_pmd(vma, haddr, pmd);
 	} else {