BITS_PER_PAGE
#ifndef BITS_PER_PAGE
#define BITS_PER_PAGE_MASK (BITS_PER_PAGE - 1)
# if BITS_PER_PAGE != (1UL << (PAGE_SHIFT + 3))
bits += bitmap_weight(p_addr, BITS_PER_PAGE);
unsigned int page_idx = cur_bit / BITS_PER_PAGE;
unsigned int offset = cur_bit % BITS_PER_PAGE;
unsigned int nbits = min(BITS_PER_PAGE - offset,