[PATCH 01/16] mm: Dont assume page-table invariance during faults
From: Laurent Dufour <hidden>
Date: 2017-08-08 14:36:04
Also in:
linuxppc-dev, lkml
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
From: Peter Zijlstra <peterz@infradead.org> 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@infradead.org> --- 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
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