Re: [PATCH v8 1/9] Basic kernel memory functionality for the Memory Controller

On 12/09/2011 12:44 PM, David Laight wrote:

quoted

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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