linux-kernel - [PATCH 07/11] thp: Decrement refcount on huge zero page if it is split

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Date:	Tue,  4 Aug 2015 15:58:01 -0400
From:	Matthew Wilcox <matthew.r.wilcox@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	willy@...ux.intel.com
Subject: [PATCH 07/11] thp: Decrement refcount on huge zero page if it is split

From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>

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@...ux.intel.com>
Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>
---
 mm/huge_memory.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 5ffdcaa..326d17e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2951,7 +2951,9 @@ 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 {
-- 
2.1.4

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