fuse_log_level
typedef void (*fuse_log_func_t)(enum fuse_log_level level, const char *fmt, va_list ap);
void fuse_log(enum fuse_log_level level, const char *fmt, ...) __printflike(2, 3);
default_log_func(enum fuse_log_level level __attribute__((__unused__)),
fuse_log(enum fuse_log_level level, const char *fmt, ...) {