Thanks to Bill Irwin for pointing this out.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
 
        if (atomic_inc_and_test(&page->_mapcount)) {
                struct anon_vma *anon_vma = vma->anon_vma;
-               pgoff_t index;
 
                BUG_ON(!anon_vma);
                anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
                page->mapping = (struct address_space *) anon_vma;
 
-               index = (address - vma->vm_start) >> PAGE_SHIFT;
-               index += vma->vm_pgoff;
-               index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
-               page->index = index;
+               page->index = linear_page_index(vma, address);
 
                inc_page_state(nr_mapped);
        }