This is a note to let you know that I've just added the patch titled
mm: numa: Do not mark PTEs pte_numa when splitting huge pages
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-numa-do-not-mark-ptes-pte_numa-when-splitting-huge-pages.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From abc40bd2eeb77eb7c2effcaf63154aad929a1d5f Mon Sep 17 00:00:00 2001
From: Mel Gorman <mgorman@xxxxxxx>
Date: Thu, 2 Oct 2014 19:47:42 +0100
Subject: mm: numa: Do not mark PTEs pte_numa when splitting huge pages
From: Mel Gorman <mgorman@xxxxxxx>
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.
VM_RW|VM_PROTNONE
|-----------------|
^
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 <mgorman@xxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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;
BUG_ON(PageCompound(page+i));
+ /*
+ * 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);
BUG_ON(!pte_none(*pte));
set_pte_at(mm, haddr, pte, entry);
Patches currently in stable-queue which might be from mgorman@xxxxxxx are
queue-3.14/mm-thp-move-invariant-bug-check-out-of-loop-in-__split_huge_page_map.patch
queue-3.14/mm-numa-do-not-mark-ptes-pte_numa-when-splitting-huge-pages.patch
queue-3.14/hugetlb-ensure-hugepage-access-is-denied-if-hugepages-are-not-supported.patch
queue-3.14/mm-migrate-close-race-between-migration-completion-and-mprotect.patch
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