linux-kernel - [PATCH 1/3] mm: clearing pte in clear_soft

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Date:	Fri, 16 Oct 2015 14:07:06 +0200
From:	Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org, xemul@...allels.com,
	linuxppc-dev@...ts.ozlabs.org, mpe@...erman.id.au,
	benh@...nel.crashing.org, aneesh.kumar@...ux.vnet.ibm.com,
	paulus@...ba.org
Cc:	criu@...nvz.org
Subject: [PATCH 1/3] mm: clearing pte in clear_soft_dirty()

As mentioned in the commit 56eecdb912b5 ("mm: Use ptep/pmdp_set_numa()
for updating _PAGE_NUMA bit"), architecture like ppc64 doesn't do
tlb flush in set_pte/pmd functions.

So when dealing with existing pte in clear_soft_dirty, the pte must
be cleared before being modified.

Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
CC: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
 fs/proc/task_mmu.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e2d46adb54b4..c9454ee39b28 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -753,19 +753,20 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
 	pte_t ptent = *pte;
 
 	if (pte_present(ptent)) {
+		ptent = ptep_modify_prot_start(vma->vm_mm, addr, pte);
 		ptent = pte_wrprotect(ptent);
 		ptent = pte_clear_flags(ptent, _PAGE_SOFT_DIRTY);
+		ptep_modify_prot_commit(vma->vm_mm, addr, pte, ptent);
 	} else if (is_swap_pte(ptent)) {
 		ptent = pte_swp_clear_soft_dirty(ptent);
+		set_pte_at(vma->vm_mm, addr, pte, ptent);
 	}
-
-	set_pte_at(vma->vm_mm, addr, pte, ptent);
 }
 
 static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
 		unsigned long addr, pmd_t *pmdp)
 {
-	pmd_t pmd = *pmdp;
+	pmd_t pmd = pmdp_huge_get_and_clear(vma->vm_mm, addr, pmdp);
 
 	pmd = pmd_wrprotect(pmd);
 	pmd = pmd_clear_flags(pmd, _PAGE_SOFT_DIRTY);
-- 
1.9.1

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