/*把addr开始一块block地址清0*/
#define clear_block(addr) \
__asm__("cld\n\t" \
"rep\n\t" \
"stosl" \
::"a" (0),"c" (BLOCK_SIZE/4),"D" ((long) (addr)):"cx","di")
/*把addr中偏移为nr的位置1*/
#define set_bit(nr,addr) ({\
register int res __asm__("ax"); \
__asm__("btsl %2,%3\n\tsetb %%al":"=a" (res):"0" (0),"r" (nr),"m" (*(addr))); \
res;})
/*把addr中偏移位nr的位清0*/
#define clear_bit(nr,addr) ({\
register int res __asm__("ax"); \
__asm__("btrl %2,%3\n\tsetnb %%al":"=a" (res):"0" (0),"r" (nr),"m" (*(addr))); \
res;})
/*把addr中第一个为0的位偏移返回*/
#define find_first_zero(addr) ({ \
int __res; \
__asm__("cld\n" \
"1:\tlodsl\n\t" \
"notl %
