[PATCH AUTOSEL for 4.14 101/161] asm-generic: provide generic_pmdp_establish()

[Sasha Levin]

From: "Kirill A. Shutemov" 

[ 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
before set_pmd_at().

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.

Link: 
http://lkml.kernel.org/r/20171213105756.69879-2-kirill.shute...@linux.intel.com
Signed-off-by: Kirill A. Shutemov 
Cc: Vlastimil Babka 
Cc: Andrea Arcangeli 
Cc: Michal Hocko 
Cc: Aneesh Kumar K.V 
Cc: Catalin Marinas 
Cc: David Daney 
Cc: David Miller 
Cc: H. Peter Anvin 
Cc: Hugh Dickins 
Cc: Ingo Molnar 
Cc: Martin Schwidefsky 
Cc: Nitin Gupta 
Cc: Ralf Baechle 
Cc: Thomas Gleixner 
Cc: Vineet Gupta 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin 
---
 include/asm-generic/pgtable.h | 15 +++
 1 file changed, 15 insertions(+)

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 77b891a8f191..2142bceaeb75 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -309,6 +309,21 @@ extern void pgtable_trans_huge_deposit(struct mm_struct 
*mm, pmd_t *pmdp,
 extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t 
*pmdp);
 #endif
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+/*
+ * 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;
+}
+#endif
+
 #ifndef __HAVE_ARCH_PMDP_INVALIDATE
 extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp);
-- 
2.15.1

[PATCH AUTOSEL for 4.14 101/161] asm-generic: provide generic_pmdp_establish()

[Sasha Levin]

From: "Kirill A. Shutemov" 

[ 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
before set_pmd_at().

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.

Link: 
http://lkml.kernel.org/r/20171213105756.69879-2-kirill.shute...@linux.intel.com
Signed-off-by: Kirill A. Shutemov 
Cc: Vlastimil Babka 
Cc: Andrea Arcangeli 
Cc: Michal Hocko 
Cc: Aneesh Kumar K.V 
Cc: Catalin Marinas 
Cc: David Daney 
Cc: David Miller 
Cc: H. Peter Anvin 
Cc: Hugh Dickins 
Cc: Ingo Molnar 
Cc: Martin Schwidefsky 
Cc: Nitin Gupta 
Cc: Ralf Baechle 
Cc: Thomas Gleixner 
Cc: Vineet Gupta 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin 
---
 include/asm-generic/pgtable.h | 15 +++
 1 file changed, 15 insertions(+)

diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 77b891a8f191..2142bceaeb75 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -309,6 +309,21 @@ extern void pgtable_trans_huge_deposit(struct mm_struct 
*mm, pmd_t *pmdp,
 extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t 
*pmdp);
 #endif
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+/*
+ * 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;
+}
+#endif
+
 #ifndef __HAVE_ARCH_PMDP_INVALIDATE
 extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
pmd_t *pmdp);
-- 
2.15.1