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Some questions in v6_copy_user_highpage_aliasing
72 /*
 73  * Copy the page, taking account of the cache colour.
 74  */
 75 static void v6_copy_user_highpage_aliasing(struct page *to,
 76         struct page *from, unsigned long vaddr)
 77 {
 78         unsigned int offset = CACHE_COLOUR(vaddr);
 79         unsigned long kfrom, kto;
 80

81         if (test_and_clear_bit(PG_dcache_dirty, &from->flags))
 82                 __flush_dcache_page(page_mapping(from), from);
 83

84         /* FIXME: not highmem safe */
  85         discard_old_kernel_data(page_address(to));
  86
  87         /*
  88          * Now copy the page using the same cache colour as the
  89          * pages ultimate destination.
  90          */
  91         spin_lock(&v6_lock);
  92
  93         set_pte_ext(TOP_PTE(from_address) + offset,
                     pfn_pte(page_to_pfn(from), PAGE_KERNEL), 0);
  94         set_pte_ext(TOP_PTE(to_address) + offset,
                     pfn_pte(page_to_pfn(to), PAGE_KERNEL), 0);
  95
  96         kfrom = from_address + (offset << PAGE_SHIFT);
  97         kto   = to_address + (offset << PAGE_SHIFT);
  98
  99         flush_tlb_kernel_page(kfrom);
 100         flush_tlb_kernel_page(kto);
 101
 102         copy_page((void *)kto, (void *)kfrom);
 103
 104         spin_unlock(&v6_lock);
 105 }