Re: [patch 2/8] mm: memcg-aware global reclaim

[Michal Hocko]

On Wed 01-06-11 08:25:13, Johannes Weiner wrote:
[...]

Just a minor thing. I am really slow at reviewing these days due to
other work that has to be done...

> +struct mem_cgroup *mem_cgroup_hierarchy_walk(struct mem_cgroup *root,
> +					     struct mem_cgroup *prev)
> +{
> +	struct mem_cgroup *mem;

You want mem = NULL here because you might end up using it unitialized
AFAICS (css_get_next returns with NULL).

> +
> +	if (mem_cgroup_disabled())
> +		return NULL;
> +
> +	if (!root)
> +		root = root_mem_cgroup;
> +	/*
> +	 * Even without hierarchy explicitely enabled in the root
> +	 * memcg, it is the ultimate parent of all memcgs.
> +	 */
> +	if (!(root == root_mem_cgroup || root->use_hierarchy))
> +		return root;
> +	if (prev && prev != root)
> +		css_put(&prev->css);
> +	do {
> +		int id = root->last_scanned_child;
> +		struct cgroup_subsys_state *css;
> +
> +		rcu_read_lock();
> +		css = css_get_next(&mem_cgroup_subsys, id + 1, &root->css, &id);
> +		if (css && (css == &root->css || css_tryget(css)))
> +			mem = container_of(css, struct mem_cgroup, css);
> +		rcu_read_unlock();
> +		if (!css)
> +			id = 0;
> +		root->last_scanned_child = id;
> +	} while (!mem);
> +	return mem;

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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