[PATCH v4 2/4] mm: Clear vmf->pte after pte_unmap_same() returns
From: Peter Xu <peterx@redhat.com>
Date: 2021-09-15 18:15:43
Also in:
lkml
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
pte_unmap_same() will always unmap the pte pointer. After the unmap, vmf->pte will not be valid any more, we should clear it. It was safe only because no one is accessing vmf->pte after pte_unmap_same() returns, since the only caller of pte_unmap_same() (so far) is do_swap_page(), where vmf->pte will in most cases be overwritten very soon. Directly pass in vmf into pte_unmap_same() and then we can also avoid the long parameter list too, which should be a nice cleanup. Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> Reviewed-by: David Hildenbrand <redacted> Reviewed-by: Liam Howlett <redacted> Signed-off-by: Peter Xu <peterx@redhat.com> --- mm/memory.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 25fc46e87214..7b095f07c4ef 100644
--- a/mm/memory.c
+++ b/mm/memory.c@@ -2724,19 +2724,19 @@ EXPORT_SYMBOL_GPL(apply_to_existing_page_range); * 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) +static inline int pte_unmap_same(struct vm_fault *vmf) { int same = 1; #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPTION) if (sizeof(pte_t) > sizeof(unsigned long)) { - spinlock_t *ptl = pte_lockptr(mm, pmd); + spinlock_t *ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd); spin_lock(ptl); - same = pte_same(*page_table, orig_pte); + same = pte_same(*vmf->pte, vmf->orig_pte); spin_unlock(ptl); } #endif - pte_unmap(page_table); + pte_unmap(vmf->pte); + vmf->pte = NULL; return same; }
@@ -3487,7 +3487,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) vm_fault_t ret = 0; void *shadow = NULL; - if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte)) + if (!pte_unmap_same(vmf)) goto out; entry = pte_to_swp_entry(vmf->orig_pte);
--
2.31.1