path: root/mm
diff options
authorMel Gorman <>2014-10-02 19:47:42 +0100
committerLinus Torvalds <>2014-10-02 11:57:18 -0700
commitabc40bd2eeb77eb7c2effcaf63154aad929a1d5f (patch)
treeee3cddc97fad0654fdc36e3052c0598ae370e9fc /mm
parentd3cb8bf6081b8b7a2dabb1264fe968fd870fa595 (diff)
mm: numa: Do not mark PTEs pte_numa when splitting huge pages
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. Cc: Signed-off-by: Mel Gorman <> Acked-by: Rik van Riel <> Acked-by: Kirill A. Shutemov <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm')
1 files changed, 5 insertions, 2 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d9a21d06b862..f8ffd9412ec5 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1795,14 +1795,17 @@ static int __split_huge_page_map(struct page *page,
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);