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Date:	Tue,  7 Oct 2014 16:19:30 -0700
From:	Greg Kroah-Hartman <>
Cc:	Greg Kroah-Hartman <>,, Mel Gorman <>,
	Rik van Riel <>,
	"Kirill A. Shutemov" <>,
	Linus Torvalds <>
Subject: [PATCH 3.14 13/37] mm: numa: Do not mark PTEs pte_numa when splitting huge pages

3.14-stable review patch.  If anyone has any objections, please let me know.


From: Mel Gorman <>

commit abc40bd2eeb77eb7c2effcaf63154aad929a1d5f upstream.

This patch reverts 1ba6e0b50b ("mm: numa: split_huge_page: transfer the
NUMA type from the pmd to the pte"). If a huge page is being split due
a protection change and the tail will be in a PROT_NONE vma then NUMA
hinting PTEs are temporarily created in the protected VMA.

      split here

In the specific case above, it should get fixed up by change_pte_range()
but there is a window of opportunity for weirdness to happen. Similarly,
if a huge page is shrunk and split during a protection update but before
pmd_numa is cleared then a pte_numa can be left behind.

Instead of adding complexity trying to deal with the case, this patch
will not mark PTEs NUMA when splitting a huge page. NUMA hinting faults
will not be triggered which is marginal in comparison to the complexity
in dealing with the corner cases during THP split.

Signed-off-by: Mel Gorman <>
Acked-by: Rik van Riel <>
Acked-by: Kirill A. Shutemov <>
Signed-off-by: Linus Torvalds <>
Signed-off-by: Greg Kroah-Hartman <>

 mm/huge_memory.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1826,14 +1826,17 @@ static int __split_huge_page_map(struct
 		for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
 			pte_t *pte, entry;
+			/*
+			 * Note that pmd_numa is not transferred deliberately
+			 * to avoid any possibility that pte_numa leaks to
+			 * a PROT_NONE VMA by accident.
+			 */
 			entry = mk_pte(page + i, vma->vm_page_prot);
 			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
 			if (!pmd_write(*pmd))
 				entry = pte_wrprotect(entry);
 			if (!pmd_young(*pmd))
 				entry = pte_mkold(entry);
-			if (pmd_numa(*pmd))
-				entry = pte_mknuma(entry);
 			pte = pte_offset_map(&_pmd, haddr);
 			set_pte_at(mm, haddr, pte, entry);

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