[PATCH v8 04/20] cachefiles: notify user daemon when withdrawing cookie

[JeffleXu]

On 4/11/22 9:42 PM, David Howells wrote:
> JeffleXu <jefflexu at linux.alibaba.com> wrote:
> 
>>>
>>>> +	if (fd == 0)
>>>> +		return -ENOENT;
>>>
>>> 0 is a valid fd.
>>
>> Yeah, but IMHO fd 0 is always for stdin? I think the allocated anon_fd
>> won't install at fd 0. Please correct me if I'm wrong.
> 
> If someone has closed 0, then you'll get 0 next, I'm pretty sure.  Try it and
> see.

Good catch.

> 
>> In fact I wanna use "fd == 0" as the initial state as struct
>> cachefiles_object is allocated with kmem_cache_zalloc().
> 
> I would suggest presetting it to something like -2 to avoid confusion.

Okay, as described in the previous email, I'm going to replace @fd to
@object_id. I will define some symbols to make it more readable,
something like

```
struct cachefiles_object {
	...
#ifdef CONFIG_CACHEFILES_ONDEMAND
#define CACHEFILES_OBJECT_ID_DEFAULT -2
#define CACHEFILES_OBJECT_ID_DEAD    -1
	int object_id;
#endif
	...
}
```

Thanks for your time.

-- 
Thanks,
Jeffle