[PATCH 4.14 113/183] asm-generic: provide generic_pmdp_establish()
From: Greg Kroah-Hartman
Date: Wed Apr 25 2018 - 06:43:36 EST
4.14-stable review patch. If anyone has any objections, please let me know.
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
[ Upstream commit c58f0bb77ed8bf93dfdde762b01cb67eebbdfc29 ]
Patch series "Do not lose dirty bit on THP pages", v4.
Vlastimil noted that pmdp_invalidate() is not atomic and we can lose
dirty and access bits if CPU sets them after pmdp dereference, but
The bug can lead to data loss, but the race window is tiny and I haven't
seen any reports that suggested that it happens in reality. So I don't
think it worth sending it to stable.
Unfortunately, there's no way to address the issue in a generic way. We
need to fix all architectures that support THP one-by-one.
All architectures that have THP supported have to provide atomic
pmdp_invalidate() that returns previous value.
If generic implementation of pmdp_invalidate() is used, architecture
needs to provide atomic pmdp_estabish().
pmdp_estabish() is not used out-side generic implementation of
pmdp_invalidate() so far, but I think this can change in the future.
This patch (of 12):
This is an implementation of pmdp_establish() that is only suitable for
an architecture that doesn't have hardware dirty/accessed bits. In this
case we can't race with CPU which sets these bits and non-atomic
approach is fine.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: David Daney <david.daney@xxxxxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Nitin Gupta <nitin.m.gupta@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
include/asm-generic/pgtable.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)
@@ -309,6 +309,21 @@ extern void pgtable_trans_huge_deposit(s
extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
+ * This is an implementation of pmdp_establish() that is only suitable for an
+ * architecture that doesn't have hardware dirty/accessed bits. In this case we
+ * can't race with CPU which sets these bits and non-atomic aproach is fine.
+static inline pmd_t generic_pmdp_establish(struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmdp, pmd_t pmd)
+ pmd_t old_pmd = *pmdp;
+ set_pmd_at(vma->vm_mm, address, pmdp, pmd);
+ return old_pmd;
extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,