F_UDISABLED
t->flags = F_NODEV|F_UDISABLED;
#define F_DISABLED (F_NODEV|F_UDISABLED)
t->flags |= F_UDISABLED;
t->flags |= F_UDISABLED;
t->flags &= ~(F_UDISABLED|F_RESET);
if (!(t->flags & F_UDISABLED))