mm: clear vmf->pte after pte_unmap_same() returns

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.

Link: https://lkml.kernel.org/r/20210915181533.11188-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Liam Howlett <liam.howlett@oracle.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index 1b7032a..cf7b059 100644 (file)
--- 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;
 }
 
@@ -3488,7 +3488,7 @@ 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);