expand_stack
vma = expand_stack(mm, address);
vma = expand_stack(mm, address);
vma = expand_stack(mm, address);
vma = expand_stack(mm, address);
vma = expand_stack(mm, address);
struct vm_area_struct *expand_stack(struct mm_struct * mm, unsigned long addr);
if (!vma_lookup(mm, addr) && !expand_stack(mm, addr))
vma = expand_stack(mm, addr);