3e455cf5 Fri Dec 25 00:37:08 CST 2020 Guo Ren <guoren@linux.alibaba.com> csky: Fixup update_mmu_cache called with user io mapping
The function update_mmu_cache could be called by user-io mapping. There is no space of struct page in mem_map for the pte. Just ignore the user-io mmaping in update_mmu_cache.