bd_open
int bd_open; /* reference counter */
static int bd_open(struct open_file *f, ...);
.dv_open = bd_open,
.dv_open = bd_open,
.dv_open = bd_open,
if (bd->bd_open == 0)
bd->bd_open++;
bd->bd_open--;
if (bd->bd_open == 0) {
bd->bd_open--;
if (bd->bd_open == 0) {