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    Subject[PATCH v2 2/5] mm: Clear vmf->pte after pte_unmap_same() returns
    Date
    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 <david@redhat.com>
    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
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