BM_PAGE_NEED_WRITEOUT
clear_bit(BM_PAGE_NEED_WRITEOUT, &page_private(page));
set_bit(BM_PAGE_NEED_WRITEOUT, &page_private(page));
return (*addr & ((1UL<<BM_PAGE_NEED_WRITEOUT)|(1UL<<BM_PAGE_LAZY_WRITEOUT))) == 0;