Re: drivers/block/rbd.c: atomic_inc_return_safe() & atomic_dec_return_safe()

[Jens Axboe]

On 10/2/20 4:34 PM, Shuah Khan wrote:
> All,
> 
> I came across these atomic_inc_return_safe() & atomic_dec_return_safe()
> functions that hold the counters at safe values.
> 
> atomic_inc_return_safe()
> 
> If the counter is already 0 it will not be incremented.
> If the counter is already at its maximum value returns
> -EINVAL without updating it.
> 
> atomic_dec_return_safe()
> 
> Decrement the counter.  Return the resulting value, or -EINVAL
> 
> These two routines are static and only used in rbd.c.
> 
> Can these become part of atomic_t ops?

I think you just want to use refcount_t for this use case. They
have safe guards for under/overflow.

-- 
Jens Axboe