Re: [PATCH v2 1/3] blk-cgroup: check for pd_(alloc|free)_fn in blkcg_activate_policy()

[Bart Van Assche]

On 7/18/24 10:29 PM, Christoph Hellwig wrote:
> On Fri, Jul 19, 2024 at 10:34:29AM +0800, Yu Kuai wrote:
> > +	/*
> > +	 * Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs, and policy
> > +	 * without pd_alloc_fn/pd_free_fn can't be activated.
> > +	 */
> >   	if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
> >   		(!pol->pd_alloc_fn ^ !pol->pd_free_fn))
> >   		goto err_unlock;
> > --
>
> I know this is existing code, but can you fix up the incorrect
> indentation while you touch this:
>
>   	if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
>   	    (!pol->pd_alloc_fn ^ !pol->pd_free_fn))

Using xor (^) for booleans seems weird to me. Is there any preference in
Linux kernel code whether to use ^ or != to check whether to booleans
are different?

Thanks,

Bart.