[PATCH v3 1/4] mm: remove unnecessary smp_wmb() in collapse_huge_page()

[Yu Zhao]

__SetPageUptodate() always has a built-in smp_wmb() to make sure
user data copied to a new page appears before set_pmd_at().

Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
---
 mm/khugepaged.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index ccede2425c3f..70ff98e1414d 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1067,13 +1067,6 @@ static void collapse_huge_page(struct mm_struct *mm,
 	_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);
-- 
2.23.0.351.gc4317032e6-goog