rmap.c: try_to_unmap_file(): VM_LOCKED not respected

[li nux]

My application is using remap_file_pages and mlocks
those pages.
So in the code of  try_to_unmap_file (see below),
I should never reach the call to try_to_unmap_cluster,
because for those pages VM_LOCKED is always set.
But, under heavy load I am seeing try_to_unmap_cluster
is getting called. Stack:
try_to_unmap_cluster
try_to_unmap_file
try_to_unmap
shrink_list
__pagevec_release
shrink_cache
shrink_zone
balance_pgdat
prepare_to_wait
kswapd


Any idea why VM_LOCKED is not being respected ?

   do {
 list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
                                                
shared.vm_set.list) {
     if (vma->vm_flags & (VM_LOCKED|VM_RESERVED))
              continue;
    cursor = (unsigned long) vma->vm_private_data;
while (vma->vm_mm->rss &&
cursor < max_nl_cursor &&                             
   cursor < vma->vm_end - vma->vm_start) {
                                
try_to_unmap_cluster(cursor, &mapcount, vma);
        cursor += CLUSTER_SIZE;
}
.....<snip>
   } while (max_nl_cursor <= max_nl_size);

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