[patch 06/11] thp: fix MADV_DONTNEED vs clear soft dirty race

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From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: thp: fix MADV_DONTNEED vs clear soft dirty race

Yet another instance of the same race.

Fix is identical to change_huge_pmd().

See "thp: fix MADV_DONTNEED vs. numa balancing race" for more details.

Link: http://lkml.kernel.org/r/20170302151034.27829-5-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 fs/proc/task_mmu.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff -puN fs/proc/task_mmu.c~thp-fix-madv_dontneed-vs-clear-soft-dirty-race fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~thp-fix-madv_dontneed-vs-clear-soft-dirty-race
+++ a/fs/proc/task_mmu.c
@@ -900,7 +900,14 @@ static inline void clear_soft_dirty(stru
 static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
 		unsigned long addr, pmd_t *pmdp)
 {
-	pmd_t pmd = pmdp_huge_get_and_clear(vma->vm_mm, addr, pmdp);
+	pmd_t pmd = *pmdp;
+
+	/* See comment in change_huge_pmd() */
+	pmdp_invalidate(vma, addr, pmdp);
+	if (pmd_dirty(*pmdp))
+		pmd = pmd_mkdirty(pmd);
+	if (pmd_young(*pmdp))
+		pmd = pmd_mkyoung(pmd);
 
 	pmd = pmd_wrprotect(pmd);
 	pmd = pmd_clear_soft_dirty(pmd);
_
--
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