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SubjectRe: [PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller
On 12/09/2011 12:44 PM, David Laight wrote:
>
>> How about this?
>>
>> val = !!val;
>>
>> /*
>> * This follows the same hierarchy restrictions than
>> * mem_cgroup_hierarchy_write()
>> */
>> if (!parent || !parent->use_hierarchy) {
>> if (list_empty(&cgroup->children))
>> memcg->kmem_independent_accounting = val;
>> else
>> return -EBUSY;
>> }
>> else
>> return -EINVAL;
>>
>> return 0;
>
> Inverting the tests gives easier to read code:
>
> if (parent&& parent->user_hierarchy)
> return -EINVAL;
> if (!list_empty(&cgroup->children))
> return -EBUSY;
> memcg->kmem_independent_accounting = val != 0;
> return 0;

On the other hand, inconsistent with mem_cgroup_hierarchy_write(), which
applies the logic in the same way I did here.

> NFI about the logic...
> On the face of it the tests don't seem related to each other
> or to the assignment!

How so?

If parent's use_hierarchy is set, we can't set this value (we need to
have a parent for that to even matter).

We also can't set it if we already have any children - otherwise all the
on-the-fly adjustments become hell-on-earth.

As for = val != 0, sorry, but I completely disagree this is easier than
!!val. Not to mention the !!val notation is already pretty widespread in
the kernel.

> David
>
>
>
>
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