[PATCH 01/16] mm: Dont assume page-table invariance during faults

[Laurent Dufour]

From: Peter Zijlstra 

One of the side effects of speculating on faults (without holding
mmap_sem) is that we can race with free_pgtables() and therefore we
cannot assume the page-tables will stick around.

Remove the reliance on the pte pointer.

Signed-off-by: Peter Zijlstra (Intel) 
---
 mm/memory.c | 27 ---
 1 file changed, 27 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index f65beaad319b..d08f494f1b37 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2103,30 +2103,6 @@ int apply_to_page_range(struct mm_struct *mm, unsigned 
long addr,
 }
 EXPORT_SYMBOL_GPL(apply_to_page_range);
 
-/*
- * handle_pte_fault chooses page fault handler according to an entry which was
- * read non-atomically.  Before making any commitment, on those architectures
- * or configurations (e.g. i386 with PAE) which might give a mix of unmatched
- * parts, do_swap_page must check under lock before unmapping the pte and
- * proceeding (but do_wp_page is only called after already making such a check;
- * and do_anonymous_page can safely check later on).
- */
-static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
-   pte_t *page_table, pte_t orig_pte)
-{
-   int same = 1;
-#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
-   if (sizeof(pte_t) > sizeof(unsigned long)) {
-   spinlock_t *ptl = pte_lockptr(mm, pmd);
-   spin_lock(ptl);
-   same = pte_same(*page_table, orig_pte);
-   spin_unlock(ptl);
-   }
-#endif
-   pte_unmap(page_table);
-   return same;
-}
-
 static inline void cow_user_page(struct page *dst, struct page *src, unsigned 
long va, struct vm_area_struct *vma)
 {
debug_dma_assert_idle(src);
@@ -2683,9 +2659,6 @@ int do_swap_page(struct vm_fault *vmf)
int exclusive = 0;
int ret = 0;
 
-   if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte))
-   goto out;
-
entry = pte_to_swp_entry(vmf->orig_pte);
if (unlikely(non_swap_entry(entry))) {
if (is_migration_entry(entry)) {
-- 
2.7.4

[PATCH 01/16] mm: Dont assume page-table invariance during faults

[Laurent Dufour]

From: Peter Zijlstra 

One of the side effects of speculating on faults (without holding
mmap_sem) is that we can race with free_pgtables() and therefore we
cannot assume the page-tables will stick around.

Remove the reliance on the pte pointer.

Signed-off-by: Peter Zijlstra (Intel) 
---
 mm/memory.c | 27 ---
 1 file changed, 27 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index f65beaad319b..d08f494f1b37 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2103,30 +2103,6 @@ int apply_to_page_range(struct mm_struct *mm, unsigned 
long addr,
 }
 EXPORT_SYMBOL_GPL(apply_to_page_range);
 
-/*
- * handle_pte_fault chooses page fault handler according to an entry which was
- * read non-atomically.  Before making any commitment, on those architectures
- * or configurations (e.g. i386 with PAE) which might give a mix of unmatched
- * parts, do_swap_page must check under lock before unmapping the pte and
- * proceeding (but do_wp_page is only called after already making such a check;
- * and do_anonymous_page can safely check later on).
- */
-static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
-   pte_t *page_table, pte_t orig_pte)
-{
-   int same = 1;
-#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
-   if (sizeof(pte_t) > sizeof(unsigned long)) {
-   spinlock_t *ptl = pte_lockptr(mm, pmd);
-   spin_lock(ptl);
-   same = pte_same(*page_table, orig_pte);
-   spin_unlock(ptl);
-   }
-#endif
-   pte_unmap(page_table);
-   return same;
-}
-
 static inline void cow_user_page(struct page *dst, struct page *src, unsigned 
long va, struct vm_area_struct *vma)
 {
debug_dma_assert_idle(src);
@@ -2683,9 +2659,6 @@ int do_swap_page(struct vm_fault *vmf)
int exclusive = 0;
int ret = 0;
 
-   if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte))
-   goto out;
-
entry = pte_to_swp_entry(vmf->orig_pte);
if (unlikely(non_swap_entry(entry))) {
if (is_migration_entry(entry)) {
-- 
2.7.4