memcpy(hello->greeting, default_greeting, sizeof(default_greeting));
printk("%s\n", hello->greeting);
printk("%p %p %p\n", hello, hello->greeting,
container_of(&hello->greeting, struct hello, greeting));
printk("size %d\n", ARRAY_SIZE(default_greeting));
memcpy(hello->greeting, default_greeting, sizeof(default_greeting));
printk("%s\n", hello->greeting);
printk("%p %p %p\n", hello, hello->greeting,
container_of(&hello->greeting, struct hello, greeting));
printk("size %d\n", ARRAY_SIZE(default_greeting));