smp_wmb() is needed to avoid the copy_huge_page writes to become visible
after the set_pmd_at() write here. But we can reuse the smp_wmb() inside
__SetPageUptodate() to remove this redundant one.
Signed-off-by: Miaohe Lin <linmia...@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
---
mm/khugepaged.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index d43812c5ce16..287e7ecf978c 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1183,19 +1183,18 @@ static void collapse_huge_page(struct mm_struct *mm,
__collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl,
&compound_pagelist);
pte_unmap(pte);
+ /*
+ * spin_lock() below is not the equivalent of smp_wmb(), but
+ * the smp_wmb() inside __SetPageUptodate() can be reused to
+ * avoid the copy_huge_page writes to become visible after
+ * the set_pmd_at() write.
+ */
__SetPageUptodate(new_page);
pgtable = pmd_pgtable(_pmd);
_pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
_pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
- /*
- * spin_lock() below is not the equivalent of smp_wmb(), so
- * this is needed to avoid the copy_huge_page writes to become
- * visible after the set_pmd_at() write.
- */
- smp_wmb();
-
spin_lock(pmd_ptl);
BUG_ON(!pmd_none(*pmd));
page_add_new_anon_rmap(new_page, vma, address, true);
--
2.19.1
