From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
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) <peterz@xxxxxxxxxxxxx>
[Remove only if !CONFIG_SPF]
Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c
index 6632c9b357c9..b7a9baf3df8a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2287,6 +2287,7 @@ int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
}
EXPORT_SYMBOL_GPL(apply_to_page_range);
+#ifndef CONFIG_SPF
/*
* handle_pte_fault chooses page fault handler according to an entry which was
* read non-atomically. Before making any commitment, on those architectures
@@ -2296,7 +2297,7 @@ EXPORT_SYMBOL_GPL(apply_to_page_range);
* 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)
+ pte_t *page_table, pte_t orig_pte)
{
int same = 1;
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
@@ -2310,6 +2311,7 @@ static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
pte_unmap(page_table);
return same;
}
+#endif /* CONFIG_SPF */
static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
{
@@ -2871,11 +2873,14 @@ int do_swap_page(struct vm_fault *vmf)
if (vma_readahead)
page = swap_readahead_detect(vmf, &swap_ra);
+
+#ifndef CONFIG_SPF
if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte)) {
if (page)
put_page(page);
goto out;
}
+#endif
entry = pte_to_swp_entry(vmf->orig_pte);
if (unlikely(non_swap_entry(entry))) {
--
2.7.4
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